Shuddering in 5th and 6th—Diff? Tranny?

[Fresh1179]

So I recently replaced my clutch and all attendant components because I believed I had an issue with the clutch slipping based off some symptoms from 5th and 6th gear to wit shuddering under full throttle in 5th and 6th.

I had my shop change out the clutch and parts noted in an earlier post (I will find the link, I don’t mess with removing the tranny on jack stands) and thought everything should be good to go.

Here is the problem I am still having. Only in 5th or 6th gear, if I apply full throttle, the rear (and the whole) car shakes like it is an earthquake.

Anyone have some ideas as to what is going on? Bad diff? Bad tranny? Head gasket.....? I’m certain that it is not a misfire. Regardless it smells like $$$

Thanks!


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[Speed Monkey]

On and off shuddering... this has the tell tale signature of the part shown below that’s located on the prop shaft‘s nose, which suggests it has come to the end of its useful service life. My sled exhibited this same symptom; it’s a PITA to fix in ones garage, but it’s possible with basic tools. Fix this soon otherwise it will destroy the rubber parts in the prop shaft’s center support bearing. If your sled has seen a fair amount of miles with the prop shaft vigorously exercising the support bearing, it would be a good preventive move to replace it due to the beating it’s taken. Good luck!

[Fresh1179]

On and off shuddering... this has the tell tale signature of the part shown below that’s located on the prop shaft‘s nose, which suggests it has come to the end of its useful service life. My sled exhibited this same symptom; it’s a PITA to fix in ones garage, but it’s possible with basic tools. Fix this soon otherwise it will destroy the rubber parts in the prop shaft’s center support bearing. If your sled has seen a fair amount of miles with the prop shaft vigorously exercising the support bearing, it would be a good preventive move to replace it due to the beating it’s taken. Good luck!

I replaced this part as a part of my clutch overhaul. Center support bearing was replaced less than 1000 miles ago. Any other ideas?


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[Speed Monkey]

Since you asked for the peanut gallery’s opinion, I do... 🤪

For starters and to state the obvious, all prop shafts are balanced, and because it is a high speed rotating component, it needs to be. The M3’s prop shaft splits, meaning there is a splined male end that inserts into a matching female end, that makes it possible to replace the center support bearing. This makes the prop shaft balanced at only a single position when it’s married. When I split my prop shaft, I first marked it with a soapstone mark; this wore off easily so I used a whiteout pen so I would be reminded of the exact positioning of each segment; this worked much better. If your shop split the prop shaft, and did not re-insert it into its exact in situ position making it balanced, this will cause an unbalanced prop shaft. This is one possible explanation for your problem.

If the bearing races are worn out in any drive line CV joint, this has the potential to cause an imbalance. Good luck.

[Fresh1179]

I appreciate the help. I will take it to the shop and have them check it out. Thanks for the help!


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[FBloggs]

Was the propeller shaft guibo replaced?

[Fresh1179]

Was the propeller shaft guibo replaced?

It was replaced.

All parts in this post were replaced.

https://nam3forum.com/forums/forum/m...i-do-my-clutch

[Fresh1179]

.

If the bearing races are worn out in any drive line CV joint, this has the potential to cause an imbalance. Good luck.

Are you thinking that this guy, replacement of the center support bearing, and a firm reminder that the shaft needs to be balanced may do the trick?

https://www.ecstuning.com/b-genuine-...iABEgLpqvD_BwE

[Rich022]

Did you find a resolution to this? I'm about to pull the trigger on the same LUX clutch...

[Fresh1179]

Did you find a resolution to this? I'm about to pull the trigger on the same LUX clutch...

I have not yet. I do not think it is the clutch, and I wouldn't hesitate about it as it is the original equipment on the car. I haven't had a chance to take the car back to the shop to check on the driveshaft, but I agree with the posts above that this is the most likely issue.