Diff change

[DaveyB]

Having taken a stock truck off the lot, I didn't get a rear axle with a locking diff (termed the 'High Traction Diff' on the build sheet). The recent snow has shown me how useful the AAM geared LSD in my last truck, a Ram 2500, really was - without me realising.

I'm looking into getting the diff changed and I'm wondering if it's a straight-forward task (like a Land Rover - prop off, shafts out, 10 bolts, and reverse) or if it's a specialist job (needing factory tools like case stretchers and the need to blue the gears after install).

Also if anyone knows the similarity between 4th gen and 4.5 gen diffs, that would be useful too. The half shafts are apparently different (not confirmed, yet, the differences but I think they have different splines). Any links or suggestions for specialists would be welcomed - or ideas other than the factory spec LSD. Definitely not going the Positraction or TrueTrac route but might look at air or cable lockers.

Thanks

 

[Lary0071]

It will need the gears set up again with the carrier needing shimmed (left/right) for proper seating and the case does need stretched like a Dana housing. The pinion depth will remain as it is.

 

[DaveyB]

Thanks for the info, Lary, I feared it would be Dana-like.

 

[ConstablePD]

Thanks for the info, Lary, I feared it would be Dana-like.

Did you ever get a locking rear? I was wanting to do this to my 2500

I noticed you have a 3500. I was under the impression all 3500's have auto locking rear ends

 

[boatdude1]

Did you ever get a locking rear? I was wanting to do this to my 2500

I noticed you have a 3500. I was under the impression all 3500's have auto locking rear ends

My understanding is the LSD is listed as standard equipment on 3500’s. On mine it is.

 

[Squatch]

Yeah, all 3500 have a rear LSD

 

[DaveyB]

I went to the dealer and confirmed the rear diff is a locker. It's weak and adversely affected by the traction control, but mechanically, it's there. It appears the issue is that the newer generation traction controls cut in more progressively and far earlier than previous incarnations, meaning the spin rate for the LSD locking is not reached very easily. I have asked the dealership to see if there is alternative electronic profile, but no answer yet - I'm not hopeful as they were not 'able' to help with lighting settings in the ECU

 

[Lary0071]

I went to the dealer and confirmed the rear diff is a locker. It's weak and adversely affected by the traction control, but mechanically, it's there. It appears the issue is that the newer generation traction controls cut in more progressively and far earlier than previous incarnations, meaning the spin rate for the LSD locking is not reached very easily. I have asked the dealership to see if there is alternative electronic profile, but no answer yet - I'm not hopeful as they were not 'able' to help with lighting settings in the ECU

Your post confuses me a bit. You start off saying that the dealer claims a locker. Then you go on to talk about limited slip, the traction control and asking about modified traction control programming.

With a locker, traction control doesn't work. It's locked, totally... or it's open... totally.

LSD doesn't lock. Never. It applies some amount of pressure/torque to the wheel with traction, but not locked. With this the traction control can still actively assist.

So your believing that you have an auto locker in your rear axle? Like a Detroit.... could be true, but I highly doubt it.

It's common to use an electronic locker so that you switch it on, the computers in the truck know it, and it stops trying to activate traction control on that axle. An auto locker plays hell with traction control on Jeeps after 2012 and puts them into limp mode often.

Sent from my SM-N986U1 using Tapatalk

 

[Rockcrawlindude]

I went to the dealer and confirmed the rear diff is a locker. It's weak and adversely affected by the traction control, but mechanically, it's there. It appears the issue is that the newer generation traction controls cut in more progressively and far earlier than previous incarnations, meaning the spin rate for the LSD locking is not reached very easily. I have asked the dealership to see if there is alternative electronic profile, but no answer yet - I'm not hopeful as they were not 'able' to help with lighting settings in the ECU

I think you’re confusing “locker” and “LSD”. They’re not the same

Anyway, for normal driving leave your traction control on. If you get stuck, turn your traction control off.

Also, read your window sticker and the Manual

 

[DaveyB]

The manual is a joke!!! The LSD is part of a package, so not listed on the window sticker. It is referred to as th e'High Traction Differential' when seen as an option on the 2500, that was listed separately on my old truck

I don't know what type of locker it is, other than it is an AAM 11.5 inch Trac Rite. It's not a locker like a TruTrac or Detroit where there are ramps and notches (which are actually locked most of the time and unlock to allow differential rated of axle twist), neither does it have clutches as in a standard PosiTraction LSD. The only pic I've found is this one, https://www.demandaam.com/technical-support/aam-diferrentials : it looks like a Torsen, worm and roller type.

Anyway, the traction control cuts in way earlier on the new truck than it ever did on the 2018 2500. I doubt as a Canadian dealer, they will be able to amend any settings in the electronics, as that would be against there national approvals.

 

[H3LZSN1P3R]

Hit the traction control button then it allows you to get the wheel spin required to have the clutches grab.... it is listed as “anti spin rear differential” i have it it works pretty decent for a factory LSD.

 

[DaveyB]

Yes, that does seem to work. The point is that it doesn't move off like the 2500 used to and particularly when on snow and ice, trying to pull away from a junction. I suspect it will be fine in true off road driving.

 

[H3LZSN1P3R]

Yes, that does seem to work. The point is that it doesn't move off like the 2500 used to and particularly when on snow and ice, trying to pull away from a junction. I suspect it will be fine in true off road driving.

Mine grabs for almost everything i barely tap the throttle on ice and both grab infact the lsd on my truck works so well i hardly use 4x4 when plowing

 

[DaveyB]

You see? there is my issue! I'm almost always needing 4wd to pull away in the snow and ice. Something needs adjusting, clearly!