Poly urethane mounts

[e30newbie1212]

So I recently installed polyurethane transmission mounts, and I have a question. I know that they were supposed to be rougher, and are suggested for track use only, so i expected the vibrations, but i cant help but be paranoid that i did something wrong and the driveshaft CSB is making noise. When in neutral though if i rev it up, i can feel what is surely the added vibrations from the mounts. Is it normal to feel vibrations in lower gears and at higher load?

[jlevie]

If you are getting vibration from under the car in the lowest gears the cause is usually a failed center support bearing (CSB). The vibration will be worse the more rapidly you accelerate. And in almost all cases a failure of the CSB will be caused by binding u-joints in the drive shaft. You can replace just the CSB, but until the drive shaft is replaced the new CSB will have a short life. A reman drive shaft can be had for about $450 and it usually comes with the CSB installed.

[e30newbie1212]

Oh should have mentioned I have a brand new unit from driveshaft services of portland with serviceable u-joints. Been there, done that! :)

[E30Gus]

I just put mine in last night and having the same paranoia. I notice though that the exhaust/engine speed seems to be transmitting a lot of the vibrations. I can be sitting still and rev the car and it shakes. Coasting at any speed it is smooth as it was before so this leads me to believe that a lot of it comes from rpm's.

[e30newbie1212]

Yeah thats exactly the case with mine, i honestly just think its paranoia. Not something I'll be giving up the mounts for, there not as bad as there worked up to be. Mine shakes when reving under no load as well. I think its all good.

[e30newbie1212]

thought it would be interesting to note that i got another ECU with a Dinan chip, and no longer have any roughness when reving with no load. You might want to try picking up a cheap known working ECU and see if that cleans up the problem, because mine is smooth as butter now. Hope this helps

[ROLLingKING]

you shoulda talked to andy at AKG.lol

he talked me away from poly tranny mounts. He said, "dont plan on listening to the radio"
he suggeste i get some e21 mounts and I looove em. just enough vibrations but not too much. i got the akg poly motor mounts and those vibrate quite a bit. otherwise i think u got what u paid for. poly tranny mounts vibrate a shit load though

[bmwstudent]

Hey Rollingking i looked the e21 versus e30 tranny mounts up on reAL OEM and they indeed are a different part #. What is different and why do you like them over the e30 parts. Im putting new seals and selector rod stuff in my trans now and would like to know if this is something i should consider when putting it back together. Thanks

[mRodiek]

Ohh great. Im installing mine tomorrow

[ROLLingKING]

E21 tranny mounts. everyone go get em

Hey Rollingking i looked the e21 versus e30 tranny mounts up on reAL OEM and they indeed are a different part #. What is different and why do you like them over the e30 parts. Im putting new seals and selector rod stuff in my trans now and would like to know if this is something i should consider when putting it back together. Thanks

Yea man. Im trying to get people to give em a try. My tranny mounts were messed up and my motor mounts were broken at the same time so I called AKG. I was planning on ordering the poly motor&tranny mounts but he insisted that was not what i wanted. He said poly tranny mounts will be to loud and vibrate/rattle everything. I said well what about when I go drifting. He said well, go with the e21 oem mounts. He said they used to use those.

HERE IS THE THING HE FORGOT TO TELL ME. the e30 tranny mount threads are 8mm. so the hole on the tranny brace and the slots in the transmission are 8mm. The e21 ones are firmer rubber/stronger and are 10mm thick threads.

So when I got the mounts and went to put em on the bracket it immediately didnt fit. I had to go find then buy a drill bit and make it fit. I also got the aluminum caps for the tranny mounts. you could check out the pics on my build thread i have in my sig but ill post a few quick pictures from the install. Definitely worth it. The actual mount is stronger which gives smoother shifts, and it gives it that nice sports car rumble without it being the poly overkill! i will say tho. ive never been in a car with poly tranny mounts. im just going by akg's word. now if he turned down my money on his own product, it may have actually been for my benifit. and i am happy with the cheaper mounts! akg polyurethane motor mounts were $55. and the E21 mounts are like $14 each i believe. So its a great price.

Old weak 8mm tranny mount. mine were shifted waay over cause my motor mounts ripped apart. i could squish the mount with my fingers


New AKG motor mount and aluminum caps. these tranny mounts are very stiff and have thicker straight through bolts


The bit size you need. It took me driving around to 4 hardware stoors before finding it.

[bmwstudent]

That looks real sweet, I'm gonna try it. Thanks for your input. I was gonna go with poly mounts all around but have decided against it. I was looking for something stiffer and this looks like a nice compromise, I'm headed for your build thread now

[kikkoman]

I just broke one of the bolt on the stock trans mount trying to reinstall it so I'm searching around for best options and found this thread. Although I'm trying out the AKG poly RTAB and subframe bushings on my car I didn't like so many people expressing dislike after installing poly trans mounts so this E21 mount sound like a good upgrade over stock w/o the negatives of going full poly. However, is the installation of those AKG aluminum caps really necessary (althought it looks real nice)? Also, Autohauz site lists these mounts as "for Federal non-CA models" and even BMA doesn't publish the price (must request a quote) so it's like a top secret part or what?.

[mRodiek]

I got my trans mounts in & there is a slight vibration in 1st but at speed with the windows down its not noticeable

[kikkoman]

Are you running this exact setup with E21 mounts (where did you source them from?) and AKG caps? Again, are those caps really necessary or adds that much more to the setup? Both sites I've already mentioned says the E21 mounts they sell are for non-CA cars and I have a CA car so I don't know what to make of this.

[SkiFree]

Sorry but the E21 mount trick originated as a trick with the 2002 guys a long time ago, no secret involved.

for example ... http://www.iemotorsport.com/bmw/2002...2hdtransm.html