1995 z28 4 speed automatic. Off the line near the top end of first gear my car had an audible “thunk” noise. I thought maybe it was a bump in the road I didn’t see so I did a pull from 45 mph and it downshifted to what I’m guessing was 3rd or 2nd and yet again there was a loud “thunk”, I could physically feel it and it seemed to have come from under the the center console. I drove it the rest of the way home without heavy acceleration and it seemed fine. No dash lights came on, and all the gauges were in their ideal ranges. I laid some cardboard under it and I’ll check it for any fluids in the morning, but it all looked dry.

from the threads I’ve seen here it seems the tranny mount is a pretty common issue. Kinda bummed as I just fixed the AC today and not even 6 hours later this happened. Any help is much appreciated. Thank you!

 

Sounds like the transmission mount may have broken. Not an unusual occurrence.

http://shbox.com/1/trans_mount.jpg

 

thank you! Where can I find the poly mount to hopefully avoid a future issue?

 

Energy Suspension makes a polyurethane mount that is relatively unbreakable. I put one under the T56 in my formula a couple years after I bought the car new. 25 years later it’s still intact having survived behind an 800 HP/800 #-ft build. Stood up under the T56 with 5,000+ RPM clutch dumps, the conversion to a TH400 to harness the power, and then under the TH400 with a Gear Vendors overdrive unit. Sold the car 2 years ago, and the new owner has been making 9-second passes with a 200 shot of nitrous, pulling the front wheels and 1.2-second 60-foots.

Some people find the ES mount increases shifter vibration with both the T56 and the 4L60E, but I never found it to be a problem. Eliminating the “pre-load” plate is supposed to minimize vibration. But ES says it shouldn’t be eliminated.

This is the ES part listing. Should be a bit cheaper at Amazon.

https://www.energysuspensionparts.com/3.1142

Check yours first. Simply try to lift the tailshaft of the trans. If it’s broken the rubber will separate, allowing the trans to lift.

 

I’ll try lifting the trans after work today to check the mount. The cardboard I left under the car last night was dry this morning, but I’ll still probably check the trans fluid to be safe.

thank you for all your help, you’ve saved my *** at least a few times in the last year. Happy New Year!

 

Thanks for the positive feedback. And a Happy New Year to you!