If (unfortunately like myself) you have had to junk the crappy stock LSD in the Ram 1500 diff, and replaced it with a Detoit TruTrac.
There is an issue with the DTT not being able to run synthetics.
I e-mailed the tech division at Eaton Corporation who make the DTT's and they stated :

"The Truetrac requirements are as follows - No

synthetics oils, and no additives. Most (not all) synthetic oils cause

excessive slippage causing a reduction in torque loads. I would say that

if you are not having any traction issues after installation, not to

worry."

I have been running with the stock MOPAR synthetic 75W 140 oil since the new DTT instalation as I didn't read fully the instructions that came with it warning of the "no synthetics" advice.
I've had no problems to date however, but my service for the diff is due and I was concerned about what oil I should put in to service the diff correctly?

Anyhow, after looking for a mineral 75W 140 and finding none existed, I e-mailed Royal Purple about their stance on this.
Here's the reply which if I may say, was incredibly fast in under 30 minutes to me here in England and which I'm very impressed with. They also replied to a question about Autotransmission fluids which I have also left in place to read, which I think is useful.

My 1st e-mail to Royal Purple :

Dear sirs,
Firstly, warm regards from England.

I have tried using your FAQ pages but cannot find the answers to my questions.

I have a 2003 Dodge Ram 1500 4x4 SLT QC short box 5.7ltr Hemi.

I have recently, replaced the stock clutch type LSD for a Detroit TruTrac.

The stock LSD requires Mopar synthetic gear lubricant 75W 140 with an addition of a 4oz bottle of friction modifiers.

The newly installed Detroit TruTrac after enquiring with their technical department, requires no synthetic gear oils or additives as to quote them :

"The Truetrac requirements are as follows - No

Synthetics oils, and no additives. Most (not all) synthetic oils cause

Excessive slippage causing a reduction in torque loads."

Unfortunately I did not realise this at the time of my new Detroit TruTrac installation and kept with the stock LSD recommended fluids by Dodge. Namely, the Mopar synthetic 75W 140.

I have been running with that fluid for nearly 12000 miles, with no apparent ill effects.

However the technical department at Detroit state:

"If you are not having any traction issues after installation, not to

Worry."

I'm now coming up to a differential service interval and am somewhat confused about what to use and wondered if any of your Royal Purple gear oils would be specifically suitable, for the Detroit TruTrac LSD?

I also wish to ask, about the fluid recommendations for my auto transmission as well.

Dodge specifically state only to use their propriety brand of ATF, namely Mopar ATF+4 and also no derivative of Dextron II.

Do Royal Purple recommend any products which comply with my Dodge 545RFE automatic transmission specifications?

Many thanks for your help in this.

Here's Royal Purples VERY promt reply :

Allan,

I have a 2007 Dodge Ram 3500 with the Cummins Diesel and it comes from the factory with what is called an AAM 11.50 TrakLok differential – which looks to be a copy or an actual Eaton TruTrac limited slip – which is a gear driven limited slip similar to a Thorsen.







I’ve used the RP MaxGear 75W90 for the last two years and I have no problems getting traction with the duel rear wheel setup. I disagree with TruTrac’s recommendation not to use a synthetic oil. Why would not want to use a higher performing product that handles more heat, more cold and gives a more stable oil film over the lubricated parts? Synthetic is just a general statement meaning made from man-made components or an ‘engineered’ lubricant.

I have contacted Eaton in the past but get a run around on this question as to why they have these archaic lubrication specifications.



Your personal experience using the Mopar 75W140 ‘synthetic’ just proves my point. This gear driven unit will benefit from a better lubricant – not be hurt in any manner. For your change out of the 9.25 AAM with the TruTrak, I recommend the RP MaxGear 75W90. If you installed the Eaton TruTrak in the other differential offered, ie the factory limited slip, then stay with the RP MaxGear 75W140. Either one will work.



We recommend the RP MaxATF MultiSpec ATF fluid part # 01320 for the 545RFE automatic transmission in your 2003 Dodge Ram Hemi. The RP MaxATF is fully compatible with the factory ATF+4 fluid and will mix if you choose to change out just the fluid in the transmission pan rather than the entire system (take 14.8 quarts total with 6.6 quarts in the pan).

Anyhow, I will be going with the Royal Purple and giving it a try and thought I'd post this up to help anyone who has done the crappy stock LSD out......to the instalation of the far superior Detroit TruTrac in.

Hope this helps and sorry for the long post.
Al.

 

After sending a few emails and talking with a VERY unknowledgeable representative at their booth at a truck show, I really never got a firm answer on why you can't use a synthetic with an Auburn LSD either.
Just kept getting told "you can't do it" and "it'll void the units warranty".

I ended up using Lucas Heavy Duty conventional gear lube in the rear differential, figuring that even though I never could get a solid answer as to why, the manufacturer of the unit should know what's best for it.

I do however have RP in the front differential.

I figure I'll change the rear every 15k miles since it's conventional oil and the front every 30k.

So far, so good with this plan, I did the rear about 4k miles ago for the first time since the 4.56 gear break-in and they still looked perfect. Everything sounds fine up front as well and they will both get done in about 11k miles.

I think I'm just going to go ahead and do the same thing. I'm not convinced that synthetic will make my LSD perform any less reliably, but the Lucas is a good product...

 

I do remember reading an article awhile back about Synthetic oils create less friction than conventional oil which in turn would cause some loading issue's inside a differential if spec'd out from the Manufacturer to be used with conventional oil.
While i don't think Synthetic oil will hurt the interior components, I think it may limit the full function of the unit as intended.
I'll try and find something to back this statement up.
At best i could see maybe a shudder while turning and that's about it, but shudder means internal vibrations and potential wear.

 

It's all very confusing isn't it.
So not only does Eaton hedge around why/why not to use synthtics, apparently so do Aurburn???
Hmmmmmmm.
Think I might go the Lucas route. What weight did you find that in HammerZ71?
Al.

 

I don't see how it makes a difference in a gear driven LSD, there are no clutches to slip, it's all positively engaged gears.

FWIW in my Powertrax No-Slip (which is completely different, mind you), the synchros in the side gears don't like synthetic and it will cause harsh and unpredictable engagement.

 

My local auto parts store carries the conventional in 85/140 and 80/90 weights. I got the 85/140...

 

I've read that "no synthetics" for the DTT on a few forums, but it's nowhere in the paperwork that came w/ mine and if it doesn't void the warranty I'm gonna run syn when mine is put in. I think it's a bunch of BS and if you don't have any ill effects or erratic operation/engadgement of the DTT I wouldn't sweat it.