Limited Slip problem?

[Don in Missouri]

I took a long road trip this weekend. When I come off the interstate with the gear oil good and warmed up, I feel a resistance when turning into parking lots. It goes away after a few turns. Could the Trak-Lock be sticking or binding? I figure I would try a gear oil change with Lucas synthetic.



Does this diagnosis sound reasonable?



At first it felt like a front tire was rubbing on the body or frame when I turned sharp. After making sure nothing was wrong up front, I started wondering if it could be the Trak Lock. My next guess would be something in the transmission, but I hope not, becasue the NV4500 hasn't been in there very long.

 

[cerberusiam]

Do you have the DC limited slip additive in the diff? Mine still does it even with the additive and its worse when its warm. The Lucas gear oil made it a lot worse. Went back to the Valvoline and it is better.



The LSD's get worn after a while and tend to pop and bind even if everything is good. If you drop the rear cover and look at the spiders you can see wear starting on the bushings that will cause a pop and bind.



Unless it is really bad I wouldn't worry.

 

[Don in Missouri]

I don't know what's in it now. The previous owner was pretty consciencientious about those kind of things, but I don't know that he ever added anything.



At $15 a quart, I don't want to use the Lucas if it will make things worse.



So you recommend Valvoline synthetic and Daimler Chrysler additive?

 

[BJMarshall]

Mine does this every time I hop off the Interstate after a long run. Seems to be worse when I am towing. It stops after a few minutes of low speed driving. It was really bad before I changed the oil. Pick your own gear oil, but definitely go with the DC additive.

 

[cerberusiam]

Whether yours would do what mine does is unknown. The LSD in my truck has 275k and is showing definite wear in the spiders and bushings. With the Lucas oil and the DC additive it popped and bound constantly. I pulled it apart to see if it had spit some parts but everything was still in one piece. Instead of the expensive Lucas I put the cheap Valvoline 80-90 and 1 bottle of additive back in it. Problem solved.



Either the syn oil cleaned things up real well or its getting ready to puke its guts the next time I pour the coal to it.



FWIW, some will swear there are cheaper additives than the DC stuff that will work just as well. Thy might given there is little or no wear on the LSD. I tried several cheaper types that claim to work in the Dana 70 LSD. They didn't. I just buy 2 bottles of additive from the dealer and a decent dino oil and call it good.

 

[bgilbert]

I don't know what's in it now. The previous owner was pretty consciencientious about those kind of things, but I don't know that he ever added anything.

Drop the rear cover, drain gear oil, add 8 ounces of limited slip additive, also known as a 'friction modifier'. Then fill it the rest of the way with gear oil.

I put the cheap Valvoline 80-90 and 1 bottle of additive back in it. Problem solved.

What he said. Stop by your favorite parts store, I prefer Napa gear oils, buy the correct amount of dino -non-synthetic- gear oil and LS additive, it usually comes in a 7 or 8 oz bottle. Most folk either don't add the additive or not enough and thats why they have issues. Some think that since its 'synthetic' they don't need a friction modifier. FWIW, I always check/drain/replace everything lubes/fluids on all vehicles I buy cause you never know if the PO added the correct stuff, or was cheap on that extra $$ for the LS add or had a bunch of gasser 10W30 and used it for motor oil in his Cummins.

 

[Greenleaf]

After I change my diff oil the first time, I added one bottle of the modifyer. Worked well, untill I began Interstate travels. It would pop and bind when truning untill the oil cooled a tad.



The next change-out I added two bottles of the friction modifyer and it worked real well during the trip to Florida.





I have only used the Golf brand 80w-90 and NAPA modifyer. My oil is changed yearly cause it's so easy to do when the truck is over the pit. You'd be good for years I suppose.



-S

 

["Mad Max"]

We also had a similar issue while on the road. Diff was REAL hot, and all we could find at Wally World was Mobil 1 synthetic and Valvoline, so we tossed in one full quart of Mobil 1 and topped off with regular 80-90. Was good to go after that, but still occasionally pops. The regular lube with the required DC additives I think would be the best choice.



I asked the Mobil 1 tech line folks about running straight Mobil 1 in diffs and manual trannys, and they told me that the 'friction modifiers' recommended actually mean friction reducers, not enhancers, which allow the clutches to slip when going around corners... . and that Mobil 1 is great for that purpose. But they also said the Mobil 1 is so slick that it doesn't adhear to the gear teeth nearly as well as regular 80-90, especially when hot, but they recommend it for racing as the lube usually doesn't really even get hot.

When used as engine oil it's great as the system is always pressurized, but IMO it's not great on startup. Plus, if there is a hairline leak in the gasket/seal... Mobil 1 will find it... whereas 80-90 usually won't.



Based on my experience, I have only used regular old dependable oil in my engines or lube in my diffs/manual transmission's, with either Mobil 1 or applicable additive as the friction modifier.

- Sam