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2013-2018 General Discussion General Chit Chat About the 2013 model year differences 6.7L 4th generation Cummins - NO ADVERTISING - Sponsored by: StarLite Diesel

Thread: Rear diff oil? Reply to Thread
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  Topic Review (Newest First)
08-24-2019 10:00 AM
Jared Herzog I also had the shudder and chatter by 8811 miles. I used Valvoline and Amsoil and the issue went away. When my Amsoil is used up, it was left over from long ago, i will just use a good GL-5, most likely the Valvoline thats easy to get nearby.
I had the chatter when turning tight. What i have noticed, on my last five trucks with two piece driveshafts, is that they have a bit of movement in the center carrier. This sort of launch vibration happens while starting out with too much throttle while turning or going straight. To feel this you must have added throttle.
The diff fluid going bad does not get felt while going straight. Only when turning. To feel the chatter you don’t have to be adding throttle like with the carrier wobble. All i had to do was slowly roll while turning in any direction in forward or reverse. The hotter the fluid the worse it is felt. Also, my 15 dually felt it more easily than my 14 SRW. This could be due to the extra difference between the outer and inner most tire ,while turning tight, causing the outer tire to have to make up more distance than the inner on a SRW truck.
The factory fluid should be good but many have issues that disappear forever with another brand of oil.
08-24-2019 07:16 AM
1ton
Quote:
Originally Posted by Ltngdrvr View Post
I always order mine from amazon, usually get the mobil1 about as cheap or less than locally sourced lesser brands.

Shudder? When?

Many with the limited slip, like mine, have a grinding, tightness after they get hot, during low speed tight turns.

Many, like mine, have been cured by the addition of the limited slip friction modifier additive, either as a separate tube of it added to the lube, or using the lube with the additive already in it. The limited slip in these trucks is a gear type, and normally don't require the additive, but it seems to help with this issue.
Yep same here with the "shudder". First rear end service... added the limited slip additive and the shudder was gone. I pull a 25,000 rated goose neck 95% of the time and the shudder was there almost immediately from new.
08-24-2019 02:32 AM
Mud yapster I've always use Valvoline or Mobil 1 which ever is cheapest when I change my diff oil. I heard this issue once on my truck when it had about 1200 to 1400 miles on it and just getting to town after towing my 10 ton 43' RV 7 hours non stop. I already had the diff oil and had planned on changing it to get the break in wear metals out it. Any how i changed the rear diff oil and have never heard it again. Now at 38,000 miles and still haven't heard it. Nope no extra friction modifier most all rear diff oil has the modifier in it anyway. Look at the bottle it's in there. I think you would have to purposely buy rear diff oil without the modifier.
As far as Lucas oils and additives go I say it's all a scam don't use it.
All the tests I've read on Lucas oil have been bad, their poisonous snake oils, but hey it is your money.
08-24-2019 02:32 AM
Mud yapster I've always use Valvoline or Mobil 1 which ever is cheapest when I change my diff oil. I heard this issue once on my truck when it had about 1200 to 1400 miles on it and just getting to town after towing my 10 ton 43' RV 7 hours non stop. I already had the diff oil and had planned on changing it to get the break in wear metals out it. Any how i changed the rear diff oil and have never heard it again. Now at 38,000 miles and still haven't heard it. Nope no extra friction modifier most all rear diff oil has the modifier in it anyway. Look at the bottle it's in there. I think you would have to purposely buy rear diff oil without the modifier.
As far as Lucas oils and additives go I say it's all a scam don't use it.
08-23-2019 08:23 PM
Ltngdrvr
Quote:
Originally Posted by KATOOM View Post
If a torsion differential requires friction modifier to work properly then I'd be questioning the lubricity of the fluid being used. There is no reason to need anything else since friction modifier is designed to change the properties of carbon based clutches found in clutch type LS carrier, but hey whatever works.
Maybe I'll try rubbing some friction modifier on the sore joints since it seems to cure all...
As I stated, not REQUIRED for the gear type diff, but apparently the AAM gear type diff is built with very tight tolerances, that on some units become too tight when they get hot. The friction modifier seems to change the properties of the lube enough to alleviate this issue.

Friction modifier is just that, it modifies the friction properties of the oil film, this is what keeps the friction clutch plates in diffs of that type from sticking too much to the steel separator plates during differential action. This same modification to the friction properties of the oil, apparently helps the helical gears in the AAM diff from binding against each other too much, alleviating the noise.
08-23-2019 07:18 PM
KATOOM If a torsion differential requires friction modifier to work properly then I'd be questioning the lubricity of the fluid being used. There is no reason to need anything else since friction modifier is designed to change the properties of carbon based clutches found in clutch type LS carrier, but hey whatever works.
Maybe I'll try rubbing some friction modifier on the sore joints since it seems to cure all...
08-23-2019 07:10 PM
lilbxl [QUOTE=Ltngdrvr;29068929]You did get the synthetic fluid, right?[/QUOTE

Yes. Synpower for limited slip.
08-23-2019 07:07 PM
Ltngdrvr You did get the synthetic fluid, right?
08-23-2019 07:03 PM
lilbxl If it does it again, I will definitely put in the additive.
08-23-2019 07:02 PM
Ltngdrvr
Quote:
Originally Posted by lilbxl View Post
I read the bottle of the valvoline and it states it has “special additives” for limited slip🏼
Some brands have more than others, try the valvoline without adding any more to it, if it still has the issue, you can always add a tube to it, only takes a few minutes.

And, if you fill the axle correctly, to just about 1/4"-3/8" below the fill plug, you will still have plenty of room to put the additive in.
08-23-2019 06:59 PM
Ltngdrvr
Quote:
Originally Posted by KATOOM View Post
I'm confused... I thought the 4th gen trucks have torsion differentials. Friction modifier does nothing for those.
Quote:
Originally Posted by KATOOM View Post
How can it help? There's nothing but gears in there. No clutches for the friction modifier...
Required for the gear type diff? No.

Does it help the grinding sticking issue in the gear type diff? Absolutely.

I had this issue with my truck, and after doing some research, came across a thread where someone else had this issue, believe it was on another forum. So, I tried it and it completely eliminated the issue.

So, if something that easy to do fixes the issue, I won't complain.
08-23-2019 06:56 PM
lilbxl
Quote:
Originally Posted by Ltngdrvr View Post
Quote:
Originally Posted by lilbxl View Post
Is there a certain brand/type I need to use?
No, it's all the same, just needs to be limited slip differential additive.

I use K&W because the local autozone has it about as cheap as anyplace.

https://www.crcindustries.com/produc...oz-402508.html
I read the bottle of the valvoline and it states it has “special additives” for limited slip🏼
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