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4.56 swap

10K views 82 replies 15 participants last post by  HEMI SPORT 
#1 ·
Well my engine isn't even broken in yet and I'm already planning my next mod. I've had a lot of people suggest 4.56 gears so I'm planning on doing it. I have two things holding me back, installation and highway mileage. I know, someone is gonna say "if you're worried about mileage buy a Prius" and that's very true. I just tend to drive a good bit of highway for my work, I'm a union electrical apprentice so I truly never know where my next job will be located. Also I don't like paying a shop an arm and a leg to install things I can handle. But I would also not enjoy screwing up my rear end. So my plan is buying a used rear end off a parts truck and changing the gears on the bench. I'll put that rear end in to see how I like the gears, and how bad my mileage gets. If I ultimately decide it's not worth it for me (which probably won't happen) or if I mess up terribly, I will still have my intact 3.92 rear end to put back in. If I end up loving it, I'll order another set of gears for my front end and tackle that. I plan on doing the rear first to be sure I like it, then the front. I did some calling around on a bunch of Craigslist posts and saw prices from $500-$800, but finally found a guy who said $100. So if it works out this weekend I'll try to drive out and pull it out. So any input? Will going from 3.92 to 4.56 be that big of a difference?
 
#2 ·
What size tire do you run?
 
#5 ·
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BEST single mod ever IMO is 4:56's:thumb:. I'm using the Detroit Tru-Trac with the Motive 4:56 gears in a 4x2 running SRT10 / 22's with a circumference height of 33". It completely woke the heavy Quad Cab up and also allowed it to get into the most efficient cruising RPM range - contrary to popular belief the Hemi is a turd at low RPM's and needs to get into it's power band to perform :dance:.
My 2 cents worth :D,

:GoodLuck1:
 
#6 ·
Ok that's what's been confusing in my research. Most people ASSUME you will tank your mileage on the highway just because it's a low ratio, but don't take into account the hemi powerband. That's why I couldn't decide for sure. But now I'm realizing the rear end I would be buying probably isn't a limited slip like mine. So I would probably have to buy a locker right? That would be another exspense
 
#7 ·
The 4:56 gears made a huge difference. I could easily do a nice burn out with my 35's now.
 
#8 ·
Well short of the supercharger your is a pretty identical build to mine so I'm sure you would know. What gears did you have originally?

And to be fair, I could do a pretty sweet burnout before haha
 
#9 ·
Mine came with 3:92 gears.
 
#11 ·
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...as did mine - 3.92 LSD - the recall along with all of the reported horror stories about the differential going off like a grenade is what initially started my desire to make the changes...glad I did :D.
 
#10 ·
Is there a way to visually see if the gears are open end or limited slip? If it's an open diff, you you have to install something else?
 
#12 ·
I'm sure there is but I'll let one of the more knowledgeable guys answer that one..

Look up your build sheet if you haven't already. I'll try and find the link someone had posted that got me all the info on my truck.
 
#15 ·
building the spare rear is the best way to go, this way if you don't like the 56's you can sell the rear, make back at least 50% of the investment and you still have your 3t.92 rear to put back in the truck.
to change from open end to trac lok(LSD, POSI What ever you want to call it) all you need is the LSD unit.
you can see if your truck has an open rear, jack up the rear both tires off the ground, and spin a wheel. if it spins with trans in park you have an open rear.
 
#16 ·
Awesome that's exactly what I was looking for. I know my truck is a lsd, I've used that vin decoder before. I just don't know if the donor truck was or not and no vin was available. The guy I was buying from was being difficult so I just told him to forget it, I'm just gonna swap it out on my truck now. I think I have enough positive reviews on the gears to be comfortable living with it, I keep thinking how nice the extra in town acceleration will be. So I found a brand new front gear and master instal kit on another forum, should be having the guy ship it to me soon. Me and my wife are doing a big evening job for a few weeks so I'm tied up, but should have some extra truck funds soon :) so after this is done I'll start the swap. Thanks for all the help!
 
#20 ·
I have Trutrac in both red and the qc. The qc uses the 11.5 unit and wieghs about the same as a pallet of bricks. I think there ought be a law that all 4x4 be equiped with a locking rear axle. Whats the point of having a 4x4 if you cant lock it all in?
 
#21 ·
So what exactly is different about a trutrac versus the factory "anti slip differential"? That's what I have in my truck, and I thought I have a 9.25 rear end. Am I missing something?
 
#22 ·
the tru trac is a different type of rear locker, the factory uses clutches to engage both wheels where as a tru trac is a mechanical locker using gears, works better and locks both wheels together stronger. 9.25 is the size of your rear end
 
#23 ·
Sorry for the confusion, my qc is a diesel and uses a larger differential than our 1500. The factory limited slip uses clutches where as the DTT uses gears. Ive beat on mine for something over 10 years and it still operates like new.
 
#24 ·
Sorry for the confusion, my qc is a diesel and uses a larger differential than our 1500. The factory limited slip uses clutches where as the DTT uses gears. Ive beat on mine for something over 10 years and it still operates like new.
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:exactly: - Look at an exploded view of each one and you will quickly see the simplicity and durability associated with the DTT :thumb:.
 
#25 ·
Any special tools required to remove the gears/bearings? Just starting to read up on how the whole installation goes. Does the differential housing need "spread"? I'm not afraid to do the work, just want to know what special tools need bought/rented so I don't get any unwanted surprises
 
#26 ·
Couple special tools are needed along with the standard stuff.
The carrier bearing tool, slips into the axle housing. And i found a pinion yoke tool. Bolts to the yoke with a long handle to hold the pinion while loading the crush sleeve.
https://m.summitracing.com/parts/otc-6602
 
#27 ·
The Spanner wrench(carrier bearing tool) is definitely worth it and a must tool, pinion tool, I have one but in a pinch a large pipe wrench will work.
As for a case spreader, depends I've had a few 9.25s that needed to be spread for assembly. the 2010 rear I built for my 2014 , that literally fell in to place. The last one I built for the Lil Red, I had to spread that thing like it was a Dana60.
 
#28 ·
I just did the rear of my 2004 1500 QC 2 weeks ago. It had 3.92's and I'm now running 35" tyres. I went with the Motive 4.56's. I paid $800 for front & rear gears and all the bearings, seals, crush-washers and the LSD clutch pack. No problems installing the rears, though I did have to "shave" a tooth on the ring-gear to get the center pin in & out. Special tools needed were a dial-gauge indicator and a rotational torque gauge that I borrowed from a friend. I bought a flat steel bar from Home Depot that I drilled to fit the pinion plate to hold it while I set the crush-washer. The wind-in & out shims that secure the carrier can be reached with a flat-blade screwdriver through a hole either side of the housing.
The installation went perfectly and the gears are silent. Because the Hemi is now in a more powerful rev band, the motor pulls easier. My gas mileage went from a 10.1 mpg average, up to an 11.6 mpg average. That's about a 15% improvement.
I'll be installing the front gears tomorrow. I need to get it done before I forget myself and engage 4WD! I believe it's pretty much the same as the rear, except I now have to deal with shims. I just got my micrometer to measure them.
 
#29 ·
Well done, altough I recommend using the special tool to set carrier bearings load.
As for the front I'm no help having not done one. With this last snow storm I had to engage 4wd to get out to the road. First time since around this time last year... I don't use it often, but when needed it's there.
 
#30 ·
Awesome, thanks for the info! I still need to get around to doing mine, I have the fronts purchased, just not the rear yet. Couple questions-

I drove a guys 4.7 ram 1500 with 4.56 and 35” tires. When I let off the gas to coast, I could really feel the gears “dragging”. Is that normal or did that guy just have the gears set wrong? I really didn’t like how it felt.

When you do the front ones, is there enough room to do it on the truck? Or do you need to drop the front differential? I thought I read you might need a case spreader as well.
 
#31 ·
I don't feel any significant difference on the overrun now I'm running 4.56's, compared to the 3.92's.

Looking at the front diff, I think I have plenty of room, but then again, my differential is 5" lower than standard, thanks to the lift kit.
 
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