Prop Shaft Bearing

Rek

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I have recently had some work done on my car and noticed that under heavy acceleration the prop shaft bearing mount (made of rubber) means that the transmission 'tramps' or oscillates quite heavily. Has this happened to anyone else and if so, is there a solution?

My bearing is in good condition and suffers from heating from the exhaust softening the rubber so that once warm there is excess movement. This tramping is from cold. I have a 256bhp engine pushing through a Getrag 265/6.

Any help gratefully received.
 

ChrisWrench

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It could not be the actual bearing it could be worn rubber around the bearing. Inspect carefully. It could be a warn drive shaft coupler (the rubber disk right off the back of the transmission between the transmission and the driveshaft). I could be a warn or sticky universal joint (the joint at the very back of the drive shaft that connects to the differential). It could be that the driveshaft has become unbalanced. Look very closely, the slightest tear in the rubber or slight catching u joint could be the cause.
 

Mike Goble

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I have recently had some work done on my car and noticed that under heavy acceleration the prop shaft bearing mount (made of rubber) means that the transmission 'tramps' or oscillates quite heavily. Has this happened to anyone else and if so, is there a solution?

My bearing is in good condition and suffers from heating from the exhaust softening the rubber so that once warm there is excess movement. This tramping is from cold. I have a 256bhp engine pushing through a Getrag 265/6.

Any help gratefully received.
Are your transmission mounts in good condition? Are the driveshaft angles correct?
 

inovermyhead

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I had a very similar problem with my car, hot or cold under anything more than gentle off the line acceleration the propshaft would thump pretty violently, after checking everything more than once I replaced the transmission mount with a gearbox mount from a 2002 and a couple of washers, problem solved. FYI my car started life as an auto cs but now runs a 3.5 with a 265 o/d box with rebuilt shaft. Hope this might help, mount is pretty cheap and easy to replace.
Cheers. John
 

Rek

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Everything is new in terms of mounts, but the alignment issue is the next thing I will look for, as well as a heat shield.

The 5 speed has been fitted using a Coupe King fitting kit so it should be OK but I will check it out.

Thanks for the advice.
 

CallumNicklin

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Everything is new in terms of mounts, but the alignment issue is the next thing I will look for, as well as a heat shield.

The 5 speed has been fitted using a Coupe King fitting kit so it should be OK but I will check it out.

Thanks for the advice.
How did you get on with this? I have exactly the same symptoms and have gone to great lengths to investigate this!
 

Rek

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The mounts from Coupe King meant the box was hotting the cross support making a huge noise, but the realignment to cure that has gone some way to solving the juddering from the prop. It is now very short and rapid but higher up the rev range it disappears.
 

gazzol

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Are your transmission mounts in good condition? Are the driveshaft angles correct?
What Mike Goble said is the most likely culprit.

A banging only under the heaviest acceleration is usually the prop shaft (drive shaft) out of line. The cause of this is either a misaligned centre bearing or worn out transmission/ engine mounts. The easiest way to check is to undo the 3 bolts that hold the prop to the rubber coupling and slide the prop back so there is a gap between them, now measure the gap it may be easier to use a nut as a feeler guage and then measure the gap at the other 2 points on the yoke, turning the shaft and the coupling a bit and then measure again. The gap should always be the same, if not there's your problem
 

CallumNicklin

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The mounts from Coupe King meant the box was hotting the cross support making a huge noise, but the realignment to cure that has gone some way to solving the juddering from the prop. It is now very short and rapid but higher up the rev range it disappears.
This is interesting. I'm not using the coupe king mount, but have a custom made one and alignment is good. Still have the issue.

All signs point to a heat deformation thing.
 

Rek

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I hopefully have a solution to the intermittant juddering of the prop shaft when the engine torque is high. One solution would be to have stronger engine mounts to stop the torque turning the engine. I wanted to find a stronger prop shaft bearing though.
The cheapest one I found was £250!

I was told however of liquid polyeurathane. I developed a cunning plan.
 

Rek

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This is the Febi bearing and holder fresh from the box. It suspends the bearing in a sheath of rubber but is easily pushed out of true in cases where the prop shaft does not align temporarily as the engine moves on it's mounts.
IMG_8889.JPG
IMG_8891.JPG
 

Rek

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I bought new mount and bearing for £23 and some liquid ply for £13. After doing some research the rigidity of cured polyeurathane is on a scale called the Shore scale. A80 is racing grade and A60 road going grade. Because I already had the existing rubber sheath I decided upon A50.
IMG_8892.JPG
 

Rek

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It takes 2 days to fully cure and I have yet to fit it to see whether it works. The polyeurathane should bond with the existing rubber or so I am told.

This happens with cars where the engine powser has been increased beyond the capacity of the standard engine mounts. I wanted to try the prop shaft holder and bearing first to minimise on harshness and vibration.

I will keep you posted.
 

Ives

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Rek,
I just pulled my engine and tranny out of my Coupe. I dropped it out the bottom and that necessitated taking out the drive shaft and center bearing. An experienced mechanic was in my shop and advised me the two drive shafts have to match up perfectly with the U joints being in a straight line or there will be a lot of imbalance and vibration. I thought this might be of help. The joints need to be lined up to mirror one another.
Regards, Jon
 

Rek

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Thanks Jon. Mine is straight as I checked it with lasers, but the torque of the engine induces it to turn agaist the engine and gearbox mounts resulting in mis- alighnment albeit for only a secind or two but that is when the juddering happens.
 

tochi

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The result after a pouring which took less than 5 minutes is as per the following images.
View attachment 158477
I am not challenging this fix, especially if it works - and considering that I have previously used urethane to stiffen motor mounts. That said, in my limited experience the center bearing and support are quite forgiving - unless the rubber and/or bearing have been compromised by heat, dirt, solvents or wear. You are probably aware that most sources recommend the bearing be “preloaded” by 2mm. While this may not seem like much, it obviously has some impact on drive line function.

As noted in the Autobook manual, “when installing the central bearing support bracket, refer to FIG8:4 and press the assembly 2mm in the direction of the arrows and hold in this position while firmly tightening the mounting nuts.”


https://e9coupe.com/forum/threads/centre-bearing-carrier.18744/
 

Rek

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I remain confident but cautious. I take your point on pre-loading and that was done. The mount is also new. I have 256bhp as opposed to 170bhp standard so 50% additional power means something is necessary. Either engine mounts or propshaft bearing holder, and the propshaft bearing holder was easier.
 
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