New Posi grinds during turns

[dkm004 11]

Just had a new Yukon rear end installed and its making severe rubbing/grinding noises from the clutches during slow turns, it really sounds like something is ready to break off back there. No issues in a straight line.

Im taking it back to the shop that did the work tomorrow and Im assuming from what Ive found online that they neglected to put in friction additive. Can anyone recommend a particular brand to me?

[Wycked69 20]

I prefer the Motorcraft friction modifier you get from your local Ford Dealership. You can also get it from Amazon.

 

http://www.amazon.com/Ford-XL-3-Friction-Modifier-Additive/dp/B000NU5LP6/ref=sr_1_1?s=automotive&ie=UTF8&qid=1403530650&sr=1-1&keywords=friction+modifier+additive

[LoneWolf2U 136]

+1 on Fords modifer,even with it added you will still have some noise when tight turning slowly.

[stangnet33 88]

I like Red Line's modifier/break-in on new installs/rebuild's and then go to Royal Purples Max Gear after break-in (had modifier already). All of the domestic's modifier's are Ok also (save some money) but use a synthetic gear oil.

[stangnet33 88]

True unless to much modifier is added. 4-5 % modifier on broke-in diff's.

 

+1 on Fords modifer,even with it added you will still have some noise when tight turning slowly.

[dkm004 11]

Thanks fella's, however it looks like it could be a bigger issue, they claim that the friction additive was added, if thats the case then something is very wrong back there. As a reference, just how much noise is acceptable and to be expected while turning with a clutched posi?

They cant see it till Wednesday, my concern is that there has been some damage done to the clutches or gears.

Edited June 24, 2014 by dkm004

[fredfordguy 16]

On the same lines, I recently had a trac loc installed, when turning slowly tight to the left only, there is a bit of a shudder, slight. Is that normal??? Thanks

[SA69mach 39]

Tru trac is quiet.

 

Detroit or Yukon posi are both noisy. Totally different systems. You will not break anything, and it can be very disconcerting if you are not familiar with the very noisy clicking on almost all turns.

Don't worry until the shop tell you to.

[SA69mach 39]

On the same lines, I recently had a trac loc installed, when turning slowly tight to the left only, there is a bit of a shudder, slight. Is that normal??? Thanks

 

Yes that is normal. You have a series of 'springs' instead of clutches (in simple terms) to lock your diff, and it can be felt and heard on very tight turns, but not noticeable reversing or in normal turns.

 

Dont sweat it. It is the ability of the unit to unlock that is the key. At some point, and with plenty of space, you should get on it hard and see how the lock affects your control with spinning tires and in hard power turns. these things are pretty cool, and very strong.

[dkm004 11]

It turned out to be the synthetic lubricant. They changed it out and tried a few different types with the additive and now its all quiet back there...Pheeew!