Limited Slip Friction Modifiers

[kmcdonough]

In reading the TDReSource in issue 58, I took interest in TSB 03-003-06, Axle Fluid Level. There is a note at the end of the TSB the reads no friction modifiers are required in the limited slip rears. I own a 2003 CTD 3500 4WD QC (purchased 12/02)with a limited slip rear. During my first fluid change (30k), I did not add the friction modifier as it was my understanding it was not required. Shortly thereafter I began to feel a "grinding" in the rear of the truck, typically when starting from a stop while turning. I stopped at the local dealer and was told as a matter of routine, they always add friction modifiers to the limited slip rears. I added the friction modifier, which fixed the problem. I have added the modifier on every fluid chage since, with no problems. Has anyone else had this problem? Was this an early make issue that was corrected. I used Amsoil on that first change and was wondering if that had something to do with it. Just curious.

Kevin McD.

 

[Alan Reagan]

I switched to synthetic lube at 30K and did not add the modifiers and had no problem.



I did the same with my previous truck and with the synthetic, I didn't add modifiers and didn't have a problem.

 

[JHardwick]

I used Amsoil on that first change and was wondering if that had something to do with it.

I've used 3 different fluids, and Mobile1 is the only fluid that doesn't chatter in my truck. No limited-slip additive here, we don't have limited slip rears.

 

[BHolm]

I've had five of these third gens now. Only one, the 2003 dually, benefitted from the friction modifier. All had been changed to Amsoil. The srw trucks were fine, the dually did just as you describe and the additive cured it. This has been reported here several times. It isn't hurting anything and if it fixes the issue, why look a gift horse in the mouth?



BTW, our trucks do in fact use a limited slip differential. They do not use the clutch type limited slip that typically requires the friction modifier additive, but they are limited slip. Personally, having owned two d-max trucks using a similar rear axle but a G80 locking rear, I find that set up superior to what Dodge offers us but I can't drive on of those just for the locker. I prefer pretty much everything else on the Dodge

 

[CDonaldson]

When I changed out the factory fluids I went with the synthetic Amsoil Severe Gear and did not use a friction modifier because my dealer and manual said it was not neccessary. I have had no problems.



Having said that, there ARE threads that discuss people having added the friction modifier because they did have the need as in the symptoms that seem to dictate it's use. Since it is a relatively easy fix and also very inexpensive proposition, it certainly is worth using - like BHolm says "why look a gift horse in the mouth?" It's an easy solution to the problem.



Must be some little torque thing on the DRW's that causes the need? The extra ground contact must create some kind of a difference?



CD

 

[BHolm]

Must be some little torque thing on the DRW's that causes the need? The extra ground contact must create some kind of a difference?



CD

I was wondering about that as well. The grinding was worse with a big load on.

 

[oneshotkyle]

i am at the point to do my first diff change also and read about not adding the modifyer. but still don't understand what diff weight to run. some say 75-90 and some say 75-140. what gives?

 

[BNH4221]

The grinding was worse with a big load on.

You or the truck?:-laf



Steve

 

[Wayne M.]

I used AMZOIL series 2000 lube and yes, I needed a modifier. I bought some K&W stuff and it worked. Yes the grinding gets worse with the more torque. I climb a steep ramp to park at my building, and it ends in a helix (to make a u turn) and as I climbed around the helix, it would do it bad,and if I got off the throttle, or when going down, it wouldn't do it.

 

[JHardwick]

i am at the point to do my first diff change also and read about not adding the modifyer. but still don't understand what diff weight to run. some say 75-90 and some say 75-140. what gives?

I run the 140 variety in the rear ... ... ... ... 90 in the front.

 

[DPKetchum]

80w90 Amsoil Severe Gear in mine. After towing 10k at interstate speeds got the most awful grind out of the rear. Stop and let it cool off it was ok until the next few hundered miles. Added the additive it dosen't need and all is ok now.

 

[kmcdonough]

thanks for the input. It is an easy fix.

Kevin McD.

 

[BHolm]

i am at the point to do my first diff change also and read about not adding the modifyer. but still don't understand what diff weight to run. some say 75-90 and some say 75-140. what gives?

For heavy towing or power like you are trying to put down I would run 140 rear and the 90 in front. That is what I did on the trucks I used for lots of towing.

 

[steved]

I have over 139k on my truck, granted the RP 85w140 might have the additive in it, but I have never added it myself.

I agree with BHolm, and I do run the differing fluids front/rear.

I run 75w90 in the front. Especially since I run the DT kit, the front diff hardly ever sees significant load, and usually that is in the winter months when you need to worry less about heat.

I am very happy with 85w140 in the rear... saw an increase in mileage and the diff runs cooler.

steved

 

[DPKetchum]

Wht kind of temp reduction in the rear diff did you see with the 75w140?

 

[steved]

Wht kind of temp reduction in the rear diff did you see with the 75w140?

If you are referring to me, I'm running 85w140.



I have nothing scientific, but I went from not being able to touch the diff after my typical commute home 53 miles; to the diff being luke warm after the same drive... it was done back to back days at the same ambient temps.



Again, nothing scientific, but it was night and day difference for having the same commute and ambient temps.



steved