ok last year i totally destored a t56 i mean when the tail shaft housing came off, a ball of metal big as your fist came with it. well i could not for the life of me figure out what it was that cuased it to happen. so i bought another one and about a year later this one is trashed as well.

but i figured out why this time.

i put a ES tranny mount in that raised the tranny up a little bit, well i never changed my motor mount, well last night i changed the motor mounts and it raised the engine up 7/16 of a inch. well now the motor is straight and all the drive trian is in line agian. before changing the mounts i could not run the car over 85 mph becasue it shook so much. well i changed the motor mounts and the car will cruise at a 110 115. no shaking at all.

but at 120 it scary the noise and vibration that come from underneath the car just like the last tranny.

ok the problem and fix: well with the ES tranny mount having the tranny where its supose to be was ok, but the engine was a different story. the front of the engine was sitting way down, so where the tranny mount, mounts on the tranny it acted as a pivot point. the wore out motor mounts pivoted the tail shaft of the tranny up. so the drive shaft and tail shft of the tranny was not in striaght anylonger. and caused the tail shaft bearing to go and then it broke all the teeth off the gears in the tranny.

so i go to the local performance shop L&B PERFORMANCE and talk to him about it. since they only work on vettes, fbodys and mustangs, they deal with alot of t56s, to see if he had any idea about my problem. and i told him my theory, and he said he had talk to a guy who had the same problem and also tore up two trannys, changed his motor mounts and bought another tranny and never had a problem since.


so if you have any vibration in your car and your sure its not the drive shaft and tires, or bad wheel bearings, then maybe you should look at changing your motor mounts.

 

So what motor mounts fixed it for you?

 

Did you say that you replaced both the transmission mount and the motor mounts and it still shakes at 120? Do you know why? (I replaced both motor mounts and the tranny mount when I put on the headers. The passenger side mount was annihilated and the transmission mount was broken.)

 

the es motor mounts fixed the engine problem for me. the the performance shaop said he has had better luck with the 99 or 20 stock mounts.


the reason its still vibrates at 120 is because the bearing on the tail shaft is gone and it related to speed and not a gear selection and 120 in fifth in shakes and bucks real bad and also in 5th but only at 120.

 

Good info... thanks for the heads-up.

Looks like these Poly Tranny bushings from ES are a crap-shoot. I've got the Prothane one, and have had no vibe issues at all related to the tranny since it went in 5 years ago.

I will say the driveshaft still can cause some nasty vibes at 80+ mph speeds; even a "Balanced" stocker or LS1 shaft.

 

Thanks for the info, My car has had that kinda vibration since I have owned it. I could never figure out what it was, I will have to see about it. Was it a PITA to change the motor mounts? Did you use stock ones? I go through a stock tranny mount about every month. But the vibration has always been there, but only about 75-80mph. Thanks again.

 

...Sounds to me your motor mounts were shot anyways, it shouldn't have stressed the tranny or driveshaft to that extent, especially with all the people here who use those tranny mounts as a cheap but rough riding upgrade from stock or 1LE. I have run my '95Z hard since owning it, and I've had that tranny mount in since like 1998, no real problems, but does vibrate at higher speeds, which could also be a number of things...

I would still say your motor mount(s) were cashed. Which could indeed cause some problems, same as if the tranny mount is shot, imo.

Good info though, I will try it when I put the Kook's in and let you know if I have no more vibration.