Re: gearbox/transmission noise
 

All injectors, fuel lines, filter, etc. are brand new. Oil and filter are new, and I just finished replacing all coolant hoses, water pump and tensioner. Trans is up next, and I'll probably do the rear end while I'm in there. From the sound of it, my bet right now is the old (likely original) trans oil is the main culprit. I'll get that done this week and we'll see how it goes.

I'll also clean up the sticky throttle body butterflies - confirmed that's mostly the source of a (really) high idle. When I do get it to idle around 800 it wants to surge a bit. So once this noise is abated and goo is gone from the TB, vacuum troubleshooting begins. I have to admit it's fun having a project to work on again...been a while.

Re: gearbox/transmission noise
 

Spend some time (considerable time) "REASEARCHING" the cleaning of the "throttle body butterflies" - not just a passing glance at maybe a couple threads but thoroughly research! Actually Marc's comments might be all that's needed:

http://www.zr1specialist.com/HAT%20W...tle%20body.htm

Re: gearbox/transmission noise
 

Thanks, appreciate the link. I believe my problem is with the primary because a light tap brings the idle down, sometimes a couple taps to get it all the way down. The plan is cleaning the primary and very light grease on the edges of the plate. I will also look at the secondaries and clean any issues there, without disturbing the factory coating.

Re: gearbox/transmission noise
 

Mark,

I would still check the Prom to be sure it was updated to the latest GM prom. Just takes a 10mm to remove 2 nuts from the ECM turn over and remove the cover to check. A lot of unmolested 90's have been found to have the original proms.

http://zr1specialist.com/HAT%20Web/p...librations.pdf

http://zr1netregistry.com/Portals/0/...s/476503-1.jpg

http://www.zr1.net/forum/showthread....ht=prom+change

Re: gearbox/transmission noise
 

Yep it's the latest prom, confirmed by Marc. With that set, I'm left with gummy primary and vacuum. Once I get the TB working smoothly, I'll be able to look into vacuum although I don't think it's too bad. The idle surge is very minor, less than a hundred rpm. I did get a little instrument flicker once while idling that low, have to check out the alternator too.

And I have to say, after spending years with Porsches and Ferraris, I LOVE the parts prices on Corvettes! Even the LT5 water pump is cheap compared to a 928 pump, and you would not believe what a 928 radiator costs! I won't even mention a Ferrari alternator....