I'm getting a noise from my rear when I'm turning and giving it gas from a stop. Even more pronounced when on a slight hill. I was told to change out my Rear Differential fluid and add some NEW friction modifier and the problem should go away. From what I'm told my LS clutches are slipping.

Couple questions:

1. What kind & how much Friction Modifier goes in rear ?

2. Should I buy a gasket or just use some good silicon sealer?

3. How much fluid goes in the rear ? 3 quarts ?

Thanks guy's !!

 

1. 4 Oz.s friction modifier
2. 75w.-140 GL5 Synthetic
3. 5.7 pints or until fluid comes up to fill hole( put modifier in first)
4. go with the RTV

 

Just what TexfordD stated above. I would only add to use the high temp RTV (orange) and insure you put a 1/4" bead around the cover as well as going around the bolt holes, after you put the RTV on bolt on the cover.

 

dont forget the threads of the center bolts,01,they are prone to leaking past from the exposed inside threads

 

Appreciate the quick response from you guy's.

I'll be going out either tomorrow or Saturday to buy my materials. I tried to buy the oil today but 2 different auto stores did not carry 75w140 weight, and they only had GM brand friction modifier. Dont want to go to Ford for the oil cause they told me $20.00 a quart. ****** will screw you for everything I tell ya. I just might have to go to them to buy the Friction modifier.

I have a 1997 5.4L 4x4

74000 miles ! Thinking about having the plugs changed out soon. Hasn't been done yet, but runs good.

 

Valvaline makes a good oil in the syth brand ..also look in the area that the rear is displayed and you,ll see the frition modifier...if you still can't find it go by a gear shop

 

I just replaced my rear diff. with Amsoil 74w-140 4000 miles ago and now I am getting LS slipage. I am not saying the Amsoil caused the problem but I never noticed it prior to changing the fluid Now What Truck has 48000. Fluid changed at 44000

 

Part of the problem with the amsoil is its too good of an oil. My quad has a wet clutch and if i use amsoil my clutch will slip beacuse it works too well. You may be having the same problem with your limited slip clutches.

 

TexfordD,

Should I add Ford's friction modifier to the Valvoline Full Synth oil? Valvo's website says their synth gear oil "contains special additives to reduce chattering in limited-slip differentials." Isn't that basicaaly what the friction modifier does?

I was considering swapping the rear diff oil fairly soon with Valvoline (I can get it a lot cheaper than Motorcraft, and from what I've read on other posts, the Ford product isn't that great anyway) but I don't want to either add an unnecessary additive if the stuff has already got the friction mod in it, or not put the mod in and risk screwing up my rear end.

Any info is much appreciated

 

The answer is YES add Ford's as well. I bought Royal Purple 75W-140 for mine and I asked Mike (Superchips distrib) about it. The Royal Purple also states it has the friction modifier in it and he told me they use that and still add the Ford friction modifier.

I should have added I changed mine out at approx. 20,000 miles and I am now at 36,800 miles with no problems at all, and no leaks.

 

Did you also add the Ford Friction Modifier?? I too used the 75w140 Amsoil, but added Fords stuff too....... Did that about 7000 miles ago and tow a trailer regularly.

 

No I did not add the Ford friction modifier with the Amsoil. I had My mechanic switch back to the ford oil with the ford Modifier The shuddering is gone. I suspect if you use the Amsoil with the ford modifier you would be fine.
Now the Question is did I damage the rear end. I Did not tow or do any off roading while the Modifier was not in the rear end
Doug