Pardon what may be a beginner question.

2002 2500 4WD auto with 4.10's. The truck doesn't get driven much anymore other than the occasional weekend desert trip or Home Depot run, but spent half of it's first 80k miles towing a 15K pound 5th wheel.

About a year ago I had a local quick lube replace the diff oil, and now I'm not sure they used the proper stuff even though they said I wouldn't need to add any additives.

Symptom is that when I make a slow hard turn on pavement, wheel turned all the way to the stops, the truck feels like it's lurching forward, or binding then releasing and binding again. It actually makes the entire truck sort of jump and stall until I straighten the wheel. When I do the same in the dirt, the inside rear wheel will alternate between spinning the same speed as the truck and then spin out real fast.

So is this a typical symptom of needing to add the additive ? If so, what's the easiest way to add it ?

I gotta go to the dealer today to get some brake piston dust seals anyway, so figured I'd pick up the factory stuff when I'm there if I need it.

 

They probably didn't put the friction modifier in it. If the replacement fluid doesn't come with it you have to add it.

 

Thanks for the reply nkennedy.

I do understand that I might need the additive if the fluid was not synthetic like RP, but what I'm really looking for is someone to validate that the symptoms I'm seeing actually match what would be expected if the modifier were left out.

 

Stay away from the Lsd. Ive had bad experience with it and besides .... it illegal.

 

Yes your description is exactly what you would expect if you need friction modifier. Also, I have found out through experience that many synthetic gear oils still require it to be added. The Dodge part number is 4318060AB.

 

I used Mobil 1 synthetic gear oil and still had to add the some modifier. I am going to use Amsoil next time and see how that works. But yes, do some slow figure eights and if it is binding, or lugging forward you need to add some friction modifier. The stuff I purchased from the dealer was expensive but it worked well.

 

Amsoil 75w90 would need the additive as well, at least a yr ago when I did mine it did

 

I did buy a bottle of the modifier from Dodge, figured for $9 it was worth the gamble. Before adding it I took the truck up the street and from a stop I cranked the wheel and pulled a slow u-turn with the expected results. The truck jumped and binded up and that inside rear wheel was spinning and grabbing intermittently.

Drove home and added half the bottle (2 ounces) using a syringe, and then drove 1 mile and repeated the test. It was perfectly smooth !

So as torquefan mention, yes that was a symptom of lack of modifier and was a cheap easy fix.

thanks for the help guys !