Rear End Vibration Shudder Rumble When Turning and Acclerating From a Stop

[Monkeybird747]

97 EB 4x4

Shuddering during turning acceleration from a stop. I've read some similar issues on this forum regarding the limited slip rear end so I drained the diff and refilled with 3 quarts royal purple synthetic 75w140 and 4oz friction modifier. Still there, maybe even a little worse? Rear tires are the same size. Is my rear end just shot? I've read about some clutches in the rear but I dont know much about the inner workings of the trans/diff/transfer case. What should be my next step? Could it be something else entirely?

 

[Erich Zeppelin]

Take's 8 oz. of friction modifier.

 

[qcksnake]

Yeap go by local parts store and grab some friction modifier and it. When you refill rears like these that need the friction modifier you have to take them to a parking lot and circle clockwise and counterclockwise to work the new fluid and friction modifier in the clutches. You probably just dont have enough in it either as stated above.

 

[Monkeybird747]

Take's 8 oz. of friction modifier.

The owners manual says 4oz of friction modifier, are you saying add some more above what is recommended? If its not going to hurt anything I'll certainly add some more, that would be an easy fix.

I'll do some parking lot circles, I didn't think about that. I've only driven it 30 miles or so, maybe it hasn't worked its way around yet.

Thanks for the replies.

 

[Monkeybird747]

Update:

After driving it for a few days I notice that the shudder is not there when it is cold, only after driving for a while. Does this line up with needing more friction modifier? I just want to be sure before I add more to the diff seeing as how once it's in I cant get it back out

 

[silverbackexpo]

Hey guys I have a question about this as well. Does the same thing apply for the front differential

 

[Monkeybird747]

Hey guys I have a question about this as well. Does the same thing apply for the front differential

The owners manual does not specify friction modifier for the front, only the rear. For the front "Thermally Stable" 75w90, it does specifically mention synthetic for the front either like it does for the rear.

 

[04Excursion]

I have this same problem, i always thought it was my front because it usually does it when im accelerating and making a turn, guess ill add friction stuff to the rear, and oil to the front

 

[FordandPolaris]

For the front, CV joints will cause vibrations sometimes when they go bad. Especially when turning.

 

[04Excursion]

But i havent noticed it lately, i think because ive been easy on the throttle, so i guess that would make it the rear since i only notice it when i give it some gas... from a stop that is

 

[dcarr]

my fire dept expy did this and we thought it was the trans at first since it did it mostly after leaving the station, but it was a turn up a hill. took it to shop and had to replace the diff. always cheaper to try the friction modifier first i suppose but it may only be a band aid.

 

[silverbackexpo]

Thanks guys the reason I asked about the front diff is because when I turn on my 4x4 hi the truck doesn't want to move and when I give it gas I feel this friction. I also feel it when I make any turns.

 

[Monkeybird747]

For the front, CV joints will cause vibrations sometimes when they go bad. Especially when turning.

True but in my case I've replace both front axles. I'll try some more friction modifier and hopefully that helps but I think dcarr is right about it being a bandaid. I guessing some new clutch packs might be in order or do I change the entire diff?

 

[Monkeybird747]

Update:

Added another 4oz of friction modifier, no change. Still only does it once the rear end has warmed up.

 

[dcarr]

im not sure about just the clutch packs or not but since you have the rear end torn down imo you may as well do the whole differential. i think we did because the gears were blued for the clutches making heat. i would say if you have the coin just drop in a whole diff.

 

[Bamfster]

Make sure the inner pinion bearing isn't hammered .... I've seen more than a few of these fail, seems to be on the trucks that tow frequently. The other culprit is the clutches/steels in the 3rd member wear excessively. Fairly easy to replace, but there are some specialty tools required.

 

[ydopen]

Hmm, Ive been wondering about this and saw this thread, Where I ususally go the terrain is flat, but on one main road I have the cruise set and it has to down shift when going up a hill, It has a 1 second shudder when down shifting from the rear end, I thought it mite be u joints? but really dont know?

 

[hammerg26]

I have this same question... I just had the rear diff fluid changed and the rear end was checked out at the same time, mechanic (2 of them actually) said it looked good. I was wondering if it was a u-joint or something similar.

 

[Monkeybird747]

I actually just had this fixed a few days ago. In my case it turned out to be bad clutches in the pumpkin. They were completely smooth and some were even broken. about $600 to replace everything and problem solved. According to the transmission guy you absolutely must use the motorcraft friction modifier additive that i think you have to get from ford. Hope this helps.