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Need help with two problems that may be same problem

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Whenever i make a right hand turn or also when accelerating sometimes there is a clunking noise in the trans tunnel which i've discovered is the transmission banging against the 'L' shaped bracket that holds up the transmission. There is only about 1/8 of an inch clearance and when the rubber mounts flexes more than 1/8 of an inch to the drivers side, it bangs. I've adjusted everything i can see under there that would move it over a bit more but no luck, any suggestions? It is a 5 speed.

The other issue occurs only when you get up to about 55 mph or so and it is a vibration that you can hear and feel in the gear stick. when you get on the gas it seems to lessen and then come back when you are off the gas. It happens whether you are in gear or not.

The car has all new urethane suspension bushings front and rear, all new rubber motor and tranny mounts and all new guibo.

Any suggestions for either of these problems would be appreciatted.

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First issue possibilities

1) Shifter plate mount bushings are bad.

2) Support arm bushings are bad (top rubber bushing is molded in the arm, bottom bushing is removable and replaceable).

Second issue possibilities

1) You mentioned 5-speed which opens up issue possibilities. Was the driveshaft rebuilt with new bmw u-joints, center bearing, and then balanced as a complete unit? IF not (or not sure) check the U-joints, center bearing, and where the weld for the shortened driveshaft was made.

Here's what a bad u-joint looks like

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Thanks for the info, but i'm not familiar with the shifter plate mount bushings and i'm not exactly sure what you're referring to as the support arm bushings as well. Can you further explain where/what they are or show a pic?

The 5 speed conversion was done before i bought the car and i have replaced the guibo but not the center support bearing. i'll have to check that and then the u joint as well.

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The support rod is the piece at the bottom supporting the plate, it has a bushing on either end. The caveat is IF this is missing with the 5-speed swap, check that the plate is not hanging via a rubber mount from the transmission tunnel (like the Ireland Eng. 5-speed plate does).

shifter_02_diagram_zps82a38b87.jpg

** EDIT jgerock is swift to the punch!

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I am not fond of that support rod, it is the way of working on so much under the car. I just drill a hole through the platform, towards the rear of it, and run a bolt through the transmission tunnel through the hole drilled in the platform. Someone actually welds a washer onto the rear of the platform for such a connection. If you want to get real sexy, use a bushing instead of a bolt.

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I jacked it up today and checked things out. I found a little more adjustment on the bottom of the trans mount and was able to move it over just enough to more or less solve problem number 1. All of the shift and shift support bushings seemed ok, looked ok and no play.

I checked over the u joints and they didn't have any play and the drive shaft itself seemed fine, but the high speed noise/vibration that starts around 50 to 55 is still there. It does seem related to the drive shaft. I'm going to change out the center support bearing when i get a chance since it hasn't been replaced.

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If and when you separate your driveshaft, remember to index it so you can put it back together the way it came apart.

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Depending on who did the driveshaft, there is a very real possibility its out of balance (part of why I asked to see the shortening welds and where they're located). If you have the chance at least take the driveshaft to a shop and see if its close enough to be balanced.

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