Swapping in an 8HP70

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.



TPS



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.







RPM



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]



425-503-9233





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