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Proud Canadian
120 Posts
Discussion Starter · #1 ·
A few members have reached out to me with questions about swapping in an 8HP70 so I figured I would do a bit of a writeup on it, hopefully this helps simplify things for any of you thinking of doing this swap. I have to do this in a few parts because of the limit on the number of images.

The first thing that you need to understand is that this is going to be expensive. I can't give you a ballpark because I don't know what you will be paying for parts and there are a lot of variables, but I can give you a breakdown of basically everything that you are going to need.

First off are the transmission itself and the shifter. 4WD truck transmissions are a dime a dozen, but I pulled my front diff, driveshaft, and half shafts a long time ago so I would rather not lug around and turn a transfer case that I am not using. If you are going 2WD, get a transmission from a car. Car transmissions are fairly easy to come by and will be far easier than finding a 2WD truck transmission. There were no clearance issues at all with the headers or the starter.

2WD transmissions, whether from a truck or a car, have a flanged output so you will need a slip joint in your driveshaft to account for the change in driveshaft length as the suspension cycles up and down. You will also need to bolt up to the flange, and Sonnax makes flange adapters. They are billet aluminum and made for a 1350 series u-joint. The adapters are different depending on which transmission you are using. This is the link for the adapter I used to mate up to the output on the transmission I have, which was from a Challenger. Sonnax Flange Adapter

Here is the driveshaft with the slip joint

You will also need to figure out a rear mount, but that is fairly simple. I used the factory rear mount from my truck as well as the car bracket that bolts to the transmission, and I made a simple adapter out of ¼” plate to join the two. Here is a picture of the car brackets and crossmember.

You could make brackets that come in from the frame and adapt this to make it work, but it is simpler to use what bolts to the truck and what bolts to the transmission, and then just bridge the gap. The notch in the crossmember is from when I was using more of the car parts and needed the space for bolt heads.

For the electronics, I used the Sound German harness and controller. It is a fairly basic and straightforward install, all you need are a TPS signal, brake switch input, RPM input, and there is an output to ground a relay to control your reverse lights. Those 4 plus a 12v constant, 12v switched, and a ground and you will be up and running. There are other things that you can hook up, but that is the minimum to get you up and running. There is supposedly another company offering a standalone for the 8HP, but I don't know anything about them. However I can tell you that the Sound German kit works, and it works well. The only problems that I ever had were due to me, not due to the kit or controller. Also, they don't forget about you after you spend your money. They had a new firmware update with the shift cut (torque management request) perfected, and Russell spent an hour and 15 minutes on the phone with me and remotely connected to my laptop via Teamviewer so he could update my controller. And he did it on a Saturday. Plus, this was more than a year after I bought the kit. He provides phenomenal customer service. Below are the instructions that Sound German provides with the kit.

8hp kit installation instructions.

The 8hp kit is as close to plug n play as possible. The required inputs for the transmission to work with this kit are RPM, TPS, Torque, Brake switch or Brake lamp input. All other wiring is optional and for your use as needed. We provide Neutral safety output and Reverse light output to ground only. Speedometer output is a programmable and should work with any modern electronic speedometer or a speedometer driver such as Speedhut Speedbox. The harness is made to receive inputs via CAN or discrete wiring. Both are not needed. One or the other. This allows easy installation and no calibration requirements for supported CAN based ECUs. Also wiring with aftermarket ECUs and even a Carb engine or diesel with a TPS sensor and RPM sensor. The discrete inputs are programmable for virtually any sensor.

Note: After calibration the Save Cal Command button at the top must be pressed and then the control module must be powered down and then disconnected from Battery power for 5-10 seconds for the changes to take effect.

Some adjustments of setup are available in the PCS control module. All Calibration of the transmission is done via OBD to the 8hp control unit as it would be done in the factory vehicle. Aftermarket tuning devices will be required. The PCS software and cable will not make adjustments to the 8hp TCM calibration.

Mopar Crate or other factory Mopar ECUs with Star connector:

Power and Ground:

There are two power inputs. A switched 12vlts to be wired to power when the key is on and a constant 12vlt battery input. Ground to chassis or battery ground. These all must be secure and reliable. Power must not drop during cranking and check that ground differential during cranking or other high loads is not high. Either of these scenarios can cause the Control module to lose power or drop to a critical level momentarily and turn off. This can cause starting issues when using the N/S output and others.

Plug C4

Connect from PCS harness to Mopar Star connector any position.

Plug C1

Plug into rear passenger side of the transmission.

Plug C5

Plug into the 8hp shifter.

Unterminated wires:

Brake input Gry/Blk to brake switch. It is calibrated to 12vlt input for the switch by default but can be calibrated to a ground contact as well.

Neutral Safety output from PCS harness Pink/Blk to Mopar harness N – Color: DG/OG – Gauge: 18 – Clutch Interlock:

Reverse lights output to ground side control of a relay for activating reverse lights.

Speedometer output:

This is a signal output to run and electronic speedometer. The Orange/wht wire will go to signal input of the speedometer. If the speedometer instructions show a 3 wire sensor diagram. 5vlt Ref and Signal ground are not required. These two wires are for operating an independent sensor. Power and ground to the Speedometer is required and this signal wire.

PCS software for monitoring data:

Please download the PCS tuning software at this address. https://www.powertraincontrolsolutions.com//functions/download.php?dir=Software&file=TCM2800_Tuning-Install.exe

Install the software and Read the calibration from the control unit using the Read CAL tab at the top; with the Eyeball. Save this file on your computer. Go to Software Setup select Tuning Mode / Advanced. Your screen should look like this after this is done.

After this open the Monitor Screen using the Monitor tab which looks like a speedometer at the top it will open the lightweight monitor by default. Change this to TCM 2600/2800 Datastream in the Selected Monitor pull down in the window and you should be able to see RPM, TPS, Turbine Speed, Lever position, Current Gear and vehicle speed. (See below) As well s other input output functions. With the engine running you should see RPM and Turbine speed and if your foot is on the brake digital input 1 and Cancel TCC should be on. You should be able to remove the shifter from Park if these conditions are met. If you override your shifter then it will not go into gear. The transmission will not come out of park if the engine is not running unless you use the manual override lever on the driver’s side of the transmission.

Aftermarket ECUs with TPS and RPM:

If using and aftermarket ECU or any unsupported CAN ECU TPS and RPM signals can be shared between control units.

TPS signal Yel/Blk will go to sensor input at the ECU. The 5vlt Ref. Red/wht and sensor ground BLK/wht should not be used. The ECU is already providing these to operate the sensor.

RPM input Orn/Blk will go to the tachometer output on an aftermarket ECU. This can also be shared with the Tachometer. Again, sensor ground is not needed.

Both of these signals need to be calibrated in the software under the Hardware Setup Folder.

TPS is under Analog inputs (x) TPS Calibration. Read the voltage using the Monitor in the box labeled Voltages Set the 0% voltage value and then press the pedal to full throttle and set the 100% throttle value. Hit enter after entering these values.

RPM is in the folder labeled SPEEDS. Set speed input pulses per RPM for Speed 1.

Applications with no other Computers:

Calibrate sensor inputs as per the instructions above after they are wired correctly.


Wire a TPS sensor to 5vlt ref. Signal ground and TPS input wires on unterminated harness as instructed on the TPS sensor instructions.

Note: After calibration the Save Cal Command button at the top must be pressed and then the control module must be powered down and then disconnected from Battery power for 5-10 seconds for the changes to take effect.


Magnetic 2 wire sensors can be wired directly to RPM input and Sensor ground.

Hall Effect 3 wire sensors should be wired to 5vlt Ref. Sensor ground and RPM input per Sensor instructions. Some sensors may also require 12vlt input or a pull up resistor to read the sensor.

Torque Map:

The torque map is used in these applications. It is TPS vs RPM and can be found in the Calibration/Tuning folder Main Torque Map. The break points can be changed to represent your engines operating range. This map must be representative of the actual torque, both positive and negative, being generated by the engine at the flywheel. If it is not the transmission may fail prematurely or simply not work at all. Reporting higher than actual torque is more desirable than reporting to little. See example map below.

Speedometer output:

Speedometer output setup pulses per mile is done under Hardware Setup / Speeds / (x) Speedo Output Settings Set the pulses per mile to match your speedometer to the speedometer in the PCS Software monitor.

Gear ratio and Tire size:

Set gear ratio and tire size under Setup Info / (x) Gear Ratios and Tire Size.

The transmission ratios are not necessary. Only final drive ratio and driven tire diameter.

If you are using the Mopar instrument cluster via CAN; the scaling is incorrect for this and you must adjust tire size to correct for this. I recommend setting it correctly, so the PCS software reads correctly on the Monitor screen. Get the vehicle to 60mph steady state and then adjust the tire size so that the instrument cluster reads 60mph while maintaining a constant speed.

Option connector and other CAN connectors:

In an effort to provide optional input setups and future expansion the harness is made with additional connectors for CAN. The option connector is used for items such as Gear indicators and Paddle shifters.

The additional 2 pin CAN connectors are not required for any particular installation and can just be stored in the harness if not used.

Sport and Track Modes:

Note: Modes are only supported if the Calibration in the 8hp TCM inside the transmission is set for these. This kit cannot activate modes that are not in the factory transmission calibration. ie a truck calibration does not have Sport and Track modes.

Sport mode and Track mode can be activated via the software and kept that way without wiring in or an additional wire can be added to the Main PCS 56 pin connector. Sport mode is set to digital input 2 (pin 3) and Track Mode is set to digital input 4 (pin 5). Nothing is required in the software if adding a wire to a switch. Simply add the wire to the correct pin and ground the wire and the mode will activate.

To activate either via the software without wiring got to Hardware setup / Digital Inputs / Invert button logic. Invert either digital input 2 for Sport or digital input 4 for Track.

Note: After calibration the Save Cal Command button at the top must be pressed and then the control module must be powered down and then disconnected from Battery power for 5-10 seconds for the changes to take effect.

If you have any questions about your installation or problems with the product or software. Please contact me.

Sound German Automotive

Russell Drake

[email protected]


You will also need to source a flexplate and a starter, and of course a torque converter if for some reason it isn't included with the transmission. You will also need the starter locator plate, which is the stamped piece of sheetmetal that goes between the engine and transmission to locate your starter. For the car transmissions, the parts catalog at the dealership has an error in it and lists the wrong part number, which made finding the correct part extremely difficult. Regardless of if you go in there with a car VIN, you will still get the wrong part. The picture is correct but you will end up with a small sheetmetal plate (part number 4792978AC) that is used as a cover for accessing the torque converter bolts. The starter locator plate is different for the cars, the trucks, and the Hellcats, because the lower half of the transmission bellhousing is different on each of them. The top (where it bolts to the block) is the same on all the transmissions, but the lower half is not. For the car 8HP70's the part number that you need is 4591910AA which is the starter locator plate for the NAG1 transmission. Finding this was absolute hell, and the way that I happened to stumble across it was by noticing that the oil pan for the NAG1 cars and the 8HP70 cars was the same part number. The oil pan on these cars is a front sump and the rear of the pan also bolts to the transmission, same as the structural dust cover on the 545RFE. So, common sense told me that since the pan bolts up to both transmissions then obviously both transmissions must have the same bolt pattern, and that ended a lengthy search for the correct part.

Another part that you may or may not need is a pilot bushing to locate the converter in the crank. It is listed as a Crank Shaft Pilot Sleeve, part number 4736283AA.

The reason I say that you may or may not need this is because the earlier 8HP70s had a smaller converter pilot, in which case you would need to install this bushing to center the converter pilot in the crank. Later 8HP70s have a larger pilot which is the same size as the converter pilot on the 545RFE, so the bushing is not needed. Truck cranks and all aftermarket cranks will need this bushing with an earlier 8HP70 converter, car cranks came with them installed from the factory, obviously. Do not attempt to simply bolt the converter to the flexplate and hope for the best because it will not be centered and you will just end up destroying your transmission. The bushing was backordered at the end of 2019 when I installed mine and held me at a standstill for a month and a half. These are photos of the pilot on a 545RFE converter and a 2020 8HP70 converter. The first 8HP70 I installed was from a 2016 Challenger, so I needed the bushing, the second transmission was from a 2020 Challenger so the bushing was not needed but pulling it can be a pain in the ass so I just used the 2016 converter with the new transmission. Here is a photo of a 545RFE converter and a later model (2020) 8HP70 converter with the larger snout which does not require the crank bushing.

This is the valve body and solenoids, and then underneath the valve body. The tcm is underneath the valve body. I’m not sure where the tcm for this transmission wandered off to, I hope it is somewhere in the garage but for now it is MIA.

The install is straightforward, it is a simple transmission swap. On these trucks it is far easier to pull the motor along with the transmission rather than working from underneath, as I am sure most of you know. Once you have the transmission in the truck set to the proper angle with your rear mount fabricated and installed, you can grab your flange-to-flange measurement and get a driveshaft made. As I said, a slip joint is necessary so be sure not to omit that.

When installing your shifter you will need to fabricate some sort of platform and enclosure for it, the style of which will be up to you. If your truck already has a console shifter or you are swapping in a console, you’re good that way as well.

For the transmission cooler lines, on the car transmissions they are on the driver’s side, top is fluid out and bottom is fluid in. You need to pay some attention to doing this properly, because you want the transmission fluid to be pretty warm, around 180 degrees Fahrenheit. ZF mentions 176 degrees, and depending on who you ask, you will hear anything from 175 to 195 degrees as the desired operating temperature. If you just run the lines to and from a cooler, the transmission will never reach operating temperature unless you live somewhere with a pretty hot climate.

For a cooler, you can do this a couple of different ways. You can get ahold of a factory cooler and bypass valve, you can install your own cooler with a 3-position valve and run a temperature sensor to bypass the cooler below a certain fluid temperature, or you can figure something else out. When I was having difficulty getting the fluid up to temperature, I bought a marine oil cooler and used it as a heat exchanger. It is made by Seakamp and the part number is 63832A1.

I tapped into the supply line from the water pump to the heater core and diverted it through the oil cooler and then onto the heater core for its normal circuit. I then ran the transmission cooler lines to the oil cooler, so I am using the coolant to heat up the transmission fluid. I thought about using a radiator with a built-in transmission cooler, but this was far simpler and so far has proven to be very effective. My rad fan on/off temps are 195/180, and I haven’t had any problems with the transmission fluid getting too hot. It warms up quickly and I maintain 160-190 degrees, depending on speed. 160 if it is a bit of a cooler night and I am on the freeway, and 180 to 190 for street driving. Once it is warmed up, it stays within 10 degrees or so of the coolant temperature. I don’t drive the truck very much when it is 85+ outside because I removed the a/c system (well, everything except for the evaporator) a couple years ago and I am not a fan of hot weather. I am Canadian, after all. I also don’t drive the truck long distances, so having no a/c doesn’t bother me. I don’t have a bypass valve on the oil cooler/heater/whatever and it works great to get the fluid up to temp and doesn’t get it too hot. I do have a 180 degree thermostat in the motor, forgot to mention that as well.

You will want to run a transmission temp gauge as well, but since the factory pan is plastic, drilling and tapping it is not going to be something that would be feasible. I swapped out the drain plug with one that has a 1/8” NPT port on it, so my temp sensor threads into the plug, and it works great. You can view the transmission temperature via the PCS software, but I don’t imagine anyone is going to drive around looking at their laptop. The filler plug is an M18x1.5, I found the M18 to 1/8” NPT adapter plug here. Torque Solution Oil Galley Plug Subaru EJ Engines M18-1.5 to 1/8 NPT Adapter | TS-SU-609


Proud Canadian
120 Posts
Discussion Starter · #2 · (Edited)
Another thing that you will have to figure out a solution to is torque management. If you run this transmission without torque management, you’re going to drastically shorten the life of it. High rpm, full throttle shifting with no torque management will kill this transmission. There are guys running Chargers/Challengers in the 9s on the stock transmission, it is well built, you just need to do the right stuff.

The Sound German kit has programmable PWM outputs, and one can be set up to give a ground pulse when the TCM inside the transmission is requesting a torque reduction. I was using a 2-step when I was running the factory PCM on the motor, and it worked pretty decent. I was using the N2MB wot box. The 12v supply to the coils gets run through the box and when it is triggered by the ground pulse, it cuts the power to the coils. I was cutting 7 cylinders, cylinder 1 stayed active all the time because it was being used to run the Autometer tach signal generator to give an rpm signal to the transmission. A disadvantage is that the box is programmed for a set duration, so I had to set it a bit longer than the longest shift in order to keep the power from coming back in before the end of the shift. I have since switched to a Holley Terminator X standalone, and it is so much better than band-aids on the factory pcm.

When you have your transmission programmed to shift quickly, torque management is not a detriment to performance, and it does not make your acceleration slower. My transmission tune has no reduction in the factory torque management, but with the tune the shifts are very fast, and the torque management kicks in for such a brief amount of time that it isn’t even noticeable. Even running on the factory tune, although the torque management is a bit more noticeable it is not in a bad way. The truck doesn’t fall on its face during shifts even with the factory tune, I just hear the timing retard for a bit longer. But any transmission will shift significantly faster when the oncoming clutch isn’t fighting to slow down a motor running wide open.

With the custom tune I have seen wot shifts below 100 milliseconds, and part throttle shifts can sometimes be faster than that. Below is a log showing a wot 4-5 at 0.159 seconds, and a 40% throttle 2-3 at 0.097 seconds. The shift times vary, but at wot the shifts are always sub-200 milliseconds. These datalogs are with 32 degrees of timing retard during the shifts. I never beat on it until the fluid has some heat in it, I generally don’t start going wot until the transmission temp hits around 160 or so, and preferably not until around 180. The shifts get noticeably smoother and faster as the fluid gets hotter. 180-190 seems to be when the shifts feel best.

On the factory tune, they were around 250-300 milliseconds at wot, and some at part throttle were pretty long. The custom tune took care of that. Here is what the timing cut looks like in the Holley datalog. This is 2-5 at wot with the factory transmission tune, the only change being the shift points were set at 6300rpm. 20 degrees of timing retard was being used at this time. You can see that the torque management request is perfectly in sync with the shift, no more and no less on either end of it.

The output on the tcm is wired to an input on the ecm, and when active it triggers a timing offset table. I pull 32 degrees of timing during shifts. I started at 20 degrees of timing retard during shifts, and increasing it to 32 degrees decreased my wot shift times by around 30 milliseconds with the tune I have in the tcm right now. I have gone as high as 40 degrees but found that it is more than what is necessary. 32 degrees seems to be the sweet spot for me but of course this will vary for each combination.

Part throttle shifts are ridiculously quick, but not jarring because of the torque reduction. Sometimes I don’t even feel the shifts at part throttle, and that is certainly saying something considering they are usually around 100-150 milliseconds. My desire for this transmission to live is stronger than my desire for it to kick me in the ass every time it shifts, plus it shifts faster this way, so it’s a no brainer. With a good tune there is absolutely no need to reduce the torque management from the factory settings, I really can’t stress this enough.

You will need to purchase 4 credits from HP tuners to tune the transmission, as well as their MPVI interface. There is an OBD-II port on the PCS harness that is used for diagnostics and to tune the transmission. The tuning is pretty in-depth, and not for the novice tuner at all. I had Satera Tuning do it for me, they’re pricey ($350) for the trans tune but worth every cent. The shifting is incredible and I just tweaked the shift points until I got them right where I wanted them to be, but I rarely have it in D when I am driving around, I prefer to upshift and downshift manually and I pretty much only ever put it in D when I am going wot. I have my 1-2 wot set at 6500 and the other gears at 6800. My engine rev limiter is set to 7000 and the shifts are very consistent so I could bring them up a little but 6800 is high enough.

You can adjust the lockup characteristics of the torque converter as well. Mine were modified, but the factory settings are actually pretty good. The converter clutch is locked up almost all the time, basically any time that you are moving. This is for efficiency, but it obviously makes the engine braking fairly substantial, usually I only use the brakes to come to a complete stop during normal driving around town. Seeing as though the converter is almost always locked I am not sure how much of a difference a higher stall converter would make. Apparently all but one aftermarket converter is just a factory converter with a different stator, but they are manufactured and people buy them, so I assume there is a benefit. The one true aftermarket converter is a beautiful piece of work, it is made by Hellraiser and is a bolt-together billet unit with extra clutch capacity allowing the converter clutch to hold 2,000 horsepower, and it also costs $3,000.


Another thing to consider is that the fluid for this transmission is extremely expensive, I think American prices are around $30-$35 per quart, and here after taxes it is $45 per quart. I am sure the price is in the “because we can” category, but at the end of the day it is cheaper than a new transmission. I don’t know the chemistry behind this fluid, but I do know that it has a very specific additive package, it was designed for this transmission, and the programming in the transmission is based on the characteristics of that specific fluid. It has a relatively low viscosity, it is noticeably thinner than the transmission fluids that most of us are used to. Valvoline Maxlife is a multi-vehicle ATF and Valvoline lists their fluid as an approved replacement for the ZF Lifeguard 8 fluid, but I wouldn’t advise it. It is a lot cheaper, 5 quarts is the same price as one quart of the ZF fluid, and you need around 12 quarts for this transmission depending on the capacity of your cooler and lines. I tried this fluid with my first 8 speed and I am sure that it would be fine for the basic hydraulic functions of a transmission for the average driver who doesn’t beat on their vehicle, but it is not a perfect match and I found that out the hard way. I learned that this transmission is very finely tuned, and it expects the fluid to have specific characteristics that are unique to the ZF fluid. High rpm WOT shifts did not agree with the Valvoline fluid at all and it makes sense because it is more viscous and the transmission expects a certain viscosity at a certain temperature and a certain fill/empty time for the clutches. If you give it something that is different than what it thinks is in there, you are going to have problems. I ended up just grabbing a different transmission and swapping it in because another transmission was almost the same cost as the amount of fluid I would have needed for 2 or 3 fluid replacements in order to completely flush out all of the Valvoline ATF, and I wasn’t about to open the transmission to empty it that way. Long story short, fluid = $ but transmission = more $. The other transmission might still be okay, I am not sure.

Another thing that I can assure you that you want to do is to get an aftermarket shifter handle. The only one that I could find was a Hurst (part number 5380437). Yes you will get hit over the head for more than $250, but it should be considered a necessity. It is like having an entirely different shifter and although I had to grit my teeth when I forked over the money for it, all of that went away instantly the first time I drove it. The factory shifter handle is plastic (obviously) and if the set screw starts to beat up the plastic in the handle (which will happen when the handle is removed and reinstalled several times), the handle will start to get sloppy and twist a bit, which beats up the plastic more, and the problem gets worse and worse. The Hurst handle is a massive upgrade and worth every dollar that they crank you for it. The instructions for the shifter handle from Hurst say to leave the factory shift handle connected and tuck it into the console, but that is so it doesn’t throw a code and turn on a dash light in the cars. For our application it isn’t something we need to be concerned about.

You can also use the PCS paddle shifters, or you can wire your own. I hijacked a couple of wires in the clockspring and installed buttons on the back of the steering wheel by the audio controls that I use for shifting, but I don't use them very often, I prefer using the shifter.

If you use a car transmission then you will also need to fabricate something to take the place of the structural dust cover (the cover for the lower half of the bellhousing). The truck transmissions have a different bellhousing so the truck cover won’t fit, and the cover for the car transmissions is integrated into the oil pan. The car oil pan is a front sump, so it will not fit in a truck. How you fabricate this will be up to you.

I also installed a gear indicator display which I purchased from Sound German. It fits in a 2 1/16” hole, same as an aftermarket gauge. I mounted mine where the factory cigarette lighter was. The display is very nice to have. It displays P/R/N/1-8.

You will get quite a few transmission DTCs because the transmission doesn’t see the ABS module, BCM, etc, but the codes can all be turned off in the HP Tuners software.

The factory pcm isn’t quite as agreeable to everything.

One other thing I should mention is gearing. I had 4.56’s which worked great with the 545RFE, but I ended up switching to 3.55’s. My main concern was driveshaft speed, but the truck is quicker with 3.55’s anyways. The reason for this is because first gear was pretty much unusable, it was like being in 4LO. I almost always started out in 2nd because the overall drive ratio in 1st with 4.56’s is 21.47:1 and 2nd gear is 14.31:1 (you can shift to 2nd when stopped). 3rd was 9.57:1 and 4th was 7.61:1. With the 3.55’s I can use first so I basically have an extra underdrive gear because I always skipped it with the 4.56’s. The overall drive ratio in 1st with 3.55’s is 16.72:1 which is actually usable, 2nd is 11.14:1, 3rd is 7.45:1. So now I am accelerating through 1st and 2nd with a deeper overall ratio than the first two gears (2 & 3) that I could use with 4.56’s, and then 3rd gear with the 3.55’s and 4th gear with 4.56’s are basically the same, as is 4th with 3.55’s (5.92:1) and 5th with 4.56’s (5.88:1). So with the taller axle ratio my first two gears are deeper than 4.56’s and the next two gears are almost the exact same. I was tempted to go with 3.92’s, but I have no regrets going with 3.55’s.

As I said before, this swap ends up being expensive, things really add up. But obviously nobody who does this swap is doing it to save money. Just be prepared for it to cost more than you initially anticipate. The tuning alone will end up tacking about a grand onto the cost by the time you buy the HP Tuners interface, 4 credits @ $50 each, and then pay for the cost of a tune. And you can’t exactly skip tuning, either. The factory tcm rev limiter is set at 6,380rpm and when you exceed that, it goes into limp mode and locks you into 5th gear until the next key cycle. Also, the factory shift points are around 6000rpm, and that is just no fun at all.

All in all, it is worthwhile to do if you feel like spending the money. It is a massive improvement over the 545RFE and it is a 100% improvement in driveability.

Proud Canadian
120 Posts
Discussion Starter · #3 · (Edited)
If you want to tune this transmission without any tuning experience, here is what you are up against.

There are 102 shift maps

This isn't even close to everything, each of the buttons you see has its own table that can be adjusted. It is worth paying someone to do the tuning, they will know what needs to be messed with and how to mess with it, and what can be left alone.

Proud Canadian
120 Posts
Discussion Starter · #4 ·
I forgot to post the proper fill procedure for the transmission. Having the transmission filled cold with the engine off (the engine had ran and the trans had been through all 8 gears with the truck on stands), when I did the fill procedure with the motor running and the fluid at the proper temp, it took another half gallon of fluid to get it to the proper level. If you don't follow the steps that ZF lays out, prepare to have some major issues. Read the chart carefully, don't just skim over it and see where it says 'fill until fluid runs out' (ask me how I know).

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