diesel737

I recently changed my diffs over to Mobil 1 75-90. I immediately noticed a shudder in takeoffs from a stop that was never there before. Been two weeks now, and I am more aware of it mainly because I don't know what it is. Yesterday in stop and go traffic, the bucking(or shudder) was so bad between 5 and 10 MPH that I diverted off the highway just to go faster on side roads.
I have pored all over this great Web site, and found two possible problems. The first one and the one I'm leaning towards, is simply adding the Mopar friction modifier. The timing is too coincidental IMO with the diff change. The other problem I have read about is the carrier bearing issue. I have a 05 2500 QC,LB,SRW, with the 6 speed 373 rear end, which qualifies my truck to have this issue.
Of course, any feedback is appreciated.
Oh, I also read about changing out U-joints for ones with zerks, which I think makes great sense.
Thanks again,
Chris

jdh

Chris;

My first step would be to take it for a run and then check the u-joints. You may not be able to tell by trying to move them - they have a tendancy to get seized up. If you drive it for a while you can then feel the joints. If it is hot, it is no good. I don't have the carrier bearing as mine is a SB but I would suspect that would get hot as well if it was bad. Good luck and let us know what you find out.

woodrep

First you need to check that the Mobil has the Limited slip friction modifier in it. How many miles do you have on those ujoints? If you have a drive train shop near you, you can probably have new ones put in with zerks, and the shaft balanced for under $100.00 if you take it to them. Good luck.

livingez_123

The 3rd gen's don't use a friction modifier because the anti spin doesn't use friction plates anymore, it's all gears.
also the the new trucks like to spit out the center u-joint because the driveline angel's are not where they should be causing the center joint not to lubricate properly

CD in NM

The 3rd gens are not SUPPOSED to need the friction modifier, but many have solved the problem by using it.

The center u-joint IS the most frequently replaced part in the driveline, according to how many here report problems, some have solved the shudder by shimming it.

No brainer to installing the better quality replacement u-joints that can be lubricated, might be worth just changing them before they die and you have bigger problems.

jdh's suggestion IS a good one for you to do also. A thermal heat tester will give you very accurate readings, you hand is like feeling for a fever, works too.

A good driveline shop can diagnose and fix it for you too.

CD

nriver

try reading this and see if it is what you have.

http://dodgeram.info/tsb/2004/03-003-04.htm

tonyiii1

I had the exact same problem. Mobil 1 differential fluid change after I swapped gears. I couldn't figure out what was going on. Took it to local dodge dealership and the mechanic noticed my mobile 1 sticker and asked if I recently had my diff fluid serviced. Long story short, I went back to the mobil 1 center and had them add a bottle of the limited slip/positraction? fluid and the problem went away.

diesel737

Well, I have only driven the truck twice since my original post, and now the shudder is very evident in decel through 25mph. Also hearing a 'roaring' type noise at highway speed. I have read all the responses and yes the U-joints are quite warm to the touch. Contacted the dealer and the truck is in there as I write this getting new U-joints. I explained the symptoms and the guy just nodded and said, "yup, sounds just like all the other complaints with these issues."
Again, I'm still suspicious about the Mobil 1 I just put in the diffs. Their website acknowledges that they have a friction modifier in the oil. Still, if I have any shudder or vibration in the new U-joints, the first thing I will do is get the Mopar Friction Modifier that was mentioned in this thread.
Wow, what timing!! Dealer just called and truck is done. They said 'center U-joint on the two-piece driveshaft' was shot. That was the one that felt warm when I checked them, but didn't tell them that. Nice to know that we came to the same conclusion.
Wish me luck!
Chris

diesel737

I'm back, and back to normal!! I don't always get the warm fuzzy's when I deal with the local dealer, so I crawled underneath before I left just to prove that they did indeed actually change out the U-joint. And like I mentioned before it was the forward U-joint of the long drive shaft. Did a twenty mile route to get home, and it is like new.
Lessons learned:
1) 26,000 miles on U-joints is nothing, so in my mind they are crap, and I don't pull anything.(Yet)
2) Mobil 1 LS 75W-90 does indeed have a friction modifier in it, as the LS in the name is in fact for limited slip axles
3) Let Dodge replace them until the warranty runs out. Sure the aftermarket zerk equipped ones are better, but these are free for now.
4) This website and my fellow CTD brethren are a goldmine of knowledge. Thanks for the replies.

Chris

PourinDiesel

U joints....what a surprise!

Wild04.5

i get a light shudder at 3-5mph that wasnt their until i changed Shocks..

i love the ride of the Bilstein 5100's but the shudder is a little noticable..

i also have a 4.5" suspension lift in the truck as well and up until this point not a shudder at all..

jdh

Glad you got it taken care of