GASGZLR

I recently installed a Prothane poly trans mount and a poly torque arm mount and poly panhard bar ( non adjustable) and now my car starts to vibrate at 70 mph a bit and gets a little worse at 80. It is not a constant vibration, more of a pulse of vibrations like............vIBe................vIBe...
If I push the clutch in and pull it out of gear at that speed it gets less but conststant until the car slow to 65 then all is smooth. At slow speeds it is not noticable. I am going outside right now to check these things:

New poly mount height vs. stock mount height
crossmember location
rear suspension bolts for tightness

It never used to do this until I started putting poly bushings and I figured that it was due to the stiffer bushings transmitting more shock to the drivetrain. It was manage able until these last parts. What is every ones experience with complete poly-bushed suspensions?? Are they smooth or REAL rough? Thanks

xpndbl3

iTrader: (5)

they can add some vibration or show you that other things may be adding vibration that was not as noticable before with all those mushy bushings

cam-

Every single bushing in my car is poly and the most noticable one was the trans mount. As soon as I put it on it felt as if my but was sitting on the driveshaft but... After breaking appart many rubber crappo's I would rather have a little more NVH than have to replace it every other month.

88TPI406GTA

Is the trans mount installed with or without the spacer plate? I thought I read somewhere else on the board that you could leave out the spacer plate to help avoid this very issue...something about changing the driveline angle a bit more...could be just anecdotal though.

cc 82Z-28

iTrader: (7)

How are your u-joints? When I switched to the poly mounts in the torque arm as well as the complete suspension I found my u-joints were getting bad and the poly made it visible to me. Did you by chance take the drive shaft out? If so, did you get back into the same position. If not, it will be out of phase and cause vibration. Last but not least, you may need to have the drive shaft balance checked. GM is notorious for using junk tubes for drive shafts as pointed out by the company that made me a new one. I chased my vibration around for some time before finally taking the shaft out and finding it was so badly out of balance that they I had new shaft made. Hope you find it..

GASGZLR

Thanks everyone for the replies. First off I switched back to the stock rubber mount and all vibrations gone. As a precaution I took my wheels off and cleaned the surface of the rear rotors since I have been changing to my DR's quite often. I also found a lot of corrosion on the mounting surface of the wheel and scraped it flat again.

My u joints are the stockers with 211,000 miles on them and they may be going. They have to hold out a little longer til I can afford to get an LS1 driveshaft.

I also checked my trans mount height and it was a noticably higher than the stocker. I checked the alignment of the crossmember and set it exactly where it goes.

BTW: I have the prothane mount and it came with no plate on it like the ES one. I got the prothane cause everyone said it was the same height as the stocker. It wasn't, unless you account for the settling of the stocker.

cam-

I have a t56 so when I welded the crossmember up I set the height using the poly mount so its at "stock" height and angle. I also switched to an aluminum shaft and new U joints and this made a very noticable improvement. Not perfect however... I still feel quite a bit of engine vibration through the poly trans mount but at least it doesn't break

Petes 84Z28

I used some spacers between the crossmember and frame to lower the crossmember by about %frac14;" after installing an ES poly trans mount. This reduced the vibrations at higher speeds. The existing bolts should be long enough to handle the extra length, but I used the next size longer M10X1.5 bolt just to be sure. Almost 3 years now with no problems.

OneBadZ4U

Hey guys, just got caught up on this thread. You all raise some good suggestions. I have two Camaro's. My '86 is all urethane except the engine mounts. I do not have any vibrations period. My '92, a few months back, installed a turethane trans mount. This thing vibrates badly @ 80 MPH and up. I replaced the driveshaft(LS1) I replaced the control arm bushings, one was bad. I found I had a bent axle, I replaced it. I balanced the tires, checked the tires for roundness and checked for a bent rim. Yes the car improved, but there is still that anoying vibration. I hate vibrations. I am going to try to remove the bracket as suggested. I'll let you all know what my results are. Here's hoping it works.

Rob

kenbob

I had the same issue it turns out they advertise the GM 3.1108 as GM transmission mount it doesn't work for 82-02 F-body the es 3.1142 is for 82-02 F-body but it still causes a vibration I'm going to try the prothane mount I have all brand new U-joints and urethane mounts with the 1108 it shook my car like crazy the 1142 still shook my car but not bad when I took the plate out I'm also going to put a 1/8th inch spacer to drop the crossmember to see if it helps the es mount

QwkTrip

iTrader: (22)

I have solid engine mounts and you wouldn't know. I have solid rear suspension and you wouldn't know. I have solid torque arm mount to frame and you wouldn't know. But I still have rubber trans mount because you would really know.

Drew

iTrader: (58)

I've run the old semi-universal Energy Suspension trans mount in 3 thirdgens. Only one exhibited any additional vibes, they went away after adjusting the crossmember during a later service. My 86 TA had ES motor mounts and trans mount, drove smooth as can be. I'm not saying it can't and doesn't happen, but it's never been much of an issue for me.

mikeceli

iTrader: (2)

There is a reason the OE bushings, except sometimes Anti Sway Bar END LINK BUSHINGS are rubber. Can't Out-Engineer the Factories engineers.

kenbob

I'm sure I can give it a try I have a Masters degree in mechanical engineering I got rid of the annoying vibration at 65-80 mph. Keep in mind I have an angle finder and all the proper tools for getting the proper angle. This worked for the energy suspension trans mount 3.1142 I believe this should be the specific trans mount for 82-02 F-body i removed the preload plate then added a 7mm thick washers between the frame and the crossmember to drop the crossmember to the proper height giving me the proper driveline angle. This got rid of all driveline vibration but nothing cures the vibration caused by the stiffness of the polyurethane mount itself. But no more vibration under my butt. I just purchased the prothane mount I'll update yall if it's as bad as the es mount.

cam-

Im full poly and half solid and have worked the vibrations down to none by setting my pinion angle to zero. I played and played with the rear suspension set up to get it to hook the way I want and the zero'd pinion angle works just fine. The car is still very shaky from the engine thumping away but no hwy vibrations. Hwy is where its smootheset. For anyone unsure how to set your angle this vid is solid

mikeceli

iTrader: (2)

OE's spend a lot of money tuning suspension bushings and go w/ rubber. I know poly poly bushings cause LOTS of problems on street cars and that is why OE's don't use them.

Drew

iTrader: (58)

But the OE endlink bushings on FE2 (Most Z28s and WS6 Firebirds) were poly right from GM.

A lot of the bushings on higher end thirdgens are harder rubber or poly from the factory. Harder bushings trade off some noise isolation and comfort for performance. GM was willing to accept the trade off on some thirdgens but not others. By now the effects of age have likely taken enough of a toll on most thirdgens that a few bushings being changed, aren't going to make a significant difference. Anyone that is looking for Cadillac comfort in a thirdgen is delusional. They're not supposed to be a luxury vehicle.

A large part of the problems people run into have more to do with their unrealistic expectations, and poor decision making. Generic Moog coil springs or lowering springs, 18" wheels with O-ring tires, gutting all the emissions equipment and climate control, a lumpy cam and loud exhaust makes for an uncomfortable car that shakes, rattles, rides and drives rough, and is noisy. You can blame the bushings, or accept a little responsibility for poorly considered modifications.

Another problem is backyard mechanics that don't know what they're doing. You can get the transmission and driveline out of whack pretty easily jacking under the trans to change the mount. The floor jack can pull the transmission to the left or the right, and when reassembling the bolts can be tightened with the drivetrain misaligned. Likewise, people will skip the step of lubricating their poly bushings during the install. Or they'll over-torque the fasteners while the car is on stands with the control arms hanging, then wonder why the bushings squeak. Knew a guy once that set his wheel bearing preload with a torque wrench. The spec in the book said inch pounds, he mistakenly thought foot pounds. I'm not saying that's exactly what's happening here. But there are variables. There are reasons why this car can be perfectly fine with poly or solid mounts, and that car shakes the fillings out of your teeth. It's not always just because an entire industry dedicated to supplying polyurethane bushings has got it ALL WRONG.

Changing trans mounts is easy in the grand scheme of things. If you value quiet ride over durability, go for the stock replacement mount and be prepared to change it periodically. If you're willing to sacrifice a bit of comfort for durability, go poly. Fortunately a person can TRY the poly mount, and if it causes all kinds of objectionable conditions, it's just as simple to change it back to rubber as it would be to replace a busted rubber mount. They're cheap too... It's not a big deal.

mikeceli

iTrader: (2)

In my 25+ years of experience and training in the Auto Repair business and a lifetime of hobby automotive work, I have come to the conclusions;;

1 Aftermarket suppliers do not have the testing programs vehicle manufacturers have. Not even close.
2 Aftermarket exists for the express purpose of coming up with something DIFFERENT to sell. Matters little that it is not an improvement on street vehicles. They only need to convince folks there stuff is "better", so they buy it.
3 Aftermarket sells LOTS of items with trade-offs and compromises that are NOT revealed to the buyer until they purchase the item and begin installation.

Colt

This is totally a u-joint angle problem unless the u-joints are worn out (which i doubt since it started with the new bushings). I had this same issue and it took me forever to figure out. I have the spohn t56 mount with the adjustable torque arm. I found that i had to raise the tail of the trans by putting washers under it and adjust the torque arm to get the right drive line angle.

If your car is lowered or the the tail of the trans has been raised/lowered due to a new trans x-member or mount, you are going to get a vibration.

Its also hard to set the correct drive line angle with an angle finder since, even though we have a torque arm rear, we do get a slight amount of axle wind-up. If you have the spohn torque arm, you will get even more wind-up since they have huge tolerances and are sloppy. I used the angle finder to get my angles in the in the ball park, then made manual adjustments after test drives. If I aim the input of the diff down to far, it will be smooth on the gas but vibrate when coasting. The opposite happens when the diff input is too high.
The system is very sensitive to adjustment.

kenbob

I had found that you were correct in driveline angle I used an angle finder and seen I only had .5 degree instead of the factory 2 degree preset my car is stock height but we're the torque arm hits the transmission was way to low I loosened it up and it popped up into place there is still a slight vibration but I believe that the driveshaft is out of balance as well. But I'm going to deal with it because I am getting ready to do my T56 swap as well