LOUD rumble noise

I was driving home last night, and drove around a hard left turn at about 40 MPH. As I exited the curve I put the hammer down, expecting a downshift and some oompfh, but to my suprise, all I got was a loud rumbling noise, similar to what you hear and feel driving over the shoulder rumble strips on the interstate. Naturally, I immediately let off the gas, and the sound went away. A little further down the road, I started playing with the car to see what was causing the noise. I found the noise and vibration was only produced in 3rd or overdrive gears when the transmission is locked, and enough throttle is applied to normally cause the car to downshift. I suspect what is happening is the transmission is not unlocking itself before it tries to shift. Has anyone had any experiance with this issue, and what did you do about it?

This is a 1988 Z31 2+2 with the automatic transmission.

Thanks!

sounds like you're in for a rebuild... you could start with checking your fluid level and all that, but it sounds like something isn't disengaugeing like you said... i don't know my auto trannies tho, perhaps george will come back from the dead to help you out

you could also check out 88hybrid.com or z31performance.com for knowledgeable z31 owners

Don't say the R word. I can't afford to have the car out of service that long. . . .

I'm thinking the issue is a glitch in the AOD controller unit. The car has not repeated this episode since last friday, and I could force the car to downshift while it was happening by using the overdrive on/off switch or manually downshifting to 2nd.

This thing tends to be quirky anyway-- Cruise control bypasses the temp sensor on most occasions and shifts to overdrive with the transmission cold, cruise control won't allow overdrive above 70+ (on the interstate), but only sometimes, engine RPMs rev up when upshifting between shifts, again on occasion.

I wish it was a 5 speed. . . ..