I have a 94 6 speed coupe LT-1 and I awoke it from its hybernation to find out that sometimes when I up-shift into 3rd gear it gives a nasty grind, but it never grinds when I down-shift into 3rd. What could this be are my 3rd gear syncro toast and do I need a new tranny. To my knowledge the car has never had the tranny fluid replaced. Should I start there before I do anything else.

 

It certainly can't hurt to change the fluid. I changed my clutch fluid and transmission fluid on my '96 last year, both were original. Could've been my imagination, but it seemed a bit smoother.

 

But because it ground a handfull of times going into third Gear is the tranny shott and now I need a rebuild or is it possible a lube change would fix it.

 

What kind of fluid does this thing take

 

Per the FAQ at the top of this forum:

ZF 6spd - The GM oil (available from GM with part number 1052931; superceded by GM part number 12345349) and the Castrol Synthetic Formula TWS 10W60 (available from BMW with part number 0751009420). Other types have been used/suggest/recommended, including ATF, but the Forum concensus is that the two listed above are the SAFEST solutions.

I strongly suggest you read/reread it. For starters I wouldn't panic just yet. When I bought mine (90 6sp) it would grind if you tried to shift into second quickly. Trans guy told me it was a syncro going bad, but it was still perfectly drivable, as long as it didn't start doing that constantly. Was it good advice? No clue. But he had to know more than me. Change your fluid, drive it a while and maybe it will stop. It may just be mad at you.

Oh, and they are on ebay for around $1400. I bought one with new flywheel and clutch, shipped to my door for $2200. If you want more info do a search for ZFdoc and email him. He's the real pro.

 

I have heard Synthetics are bad in these trans is that true. and WHat ever happened to your tranny... did it eventually blow up and you replaced it. How many miles did you get out of it. Mine isnt really grinding in a quick shift. It does it intermediately and it could be from a slow cruise shift. I have never had it happen on quick shift.

 

Sorry. I realize I left out some detail. From what I can tell I got an honest 132K miles out of my original transmission. It never actually failed. I just found a new one for less than the cost of fixing my original one, so now I have TWO working transmissions. I will probably send the other off to ZFdoc for a primo build. Oh, and the original motor was blown up by someone before me. Didn't find that until after I got the car. When I read up, called, and researched the ZF trans most people say they are hella durable. I believe a version of it is currently used in the full sized fords, gms, and maybe dodge trucks behind their diesels. Heavy dual mass flywheels don't really matter in those cases.

I replaced my black tag unit (pre 1993?) transmission with a new blue tag unit. The guy who installed it didn't mention any issues at all. I stuck with the original clutch set up. The hydraulics suck, but that is a constant thing and a lot of guys simply take the brand new ones apart for inspection and deburring.

I am tempted to be optimistic in your case and say you probably just got some sludge not letting the syncros work too well. I would use the GM fluid, change it, drive it for 3000 miles to work out some guu, then change it again. It may just need to get cleaned out a little. That is the cheapest way to go.

Oh, and my original trans was still silky smooth, except that second gear syncro. Just don't panic and do something expensive first. I hope it works out for you. 6spds are more fun than autos anyways!

 

Thanks for you advice and vote of confidence. I just ordered up the LT's and all the exhaust stuff and now I am facing possible tranny probs and I am just kind of pannicing now. I am going to have everything flushed out. Coolant, Tranny, and rear end. I bought this thing used with 70k on it and I dont know what has been done as far as maintenance so I guess i got to do it for cheap insurance. It should be going in the shop tomarrow. So ill keep you all posted.

 

I had the thing Drained and refilled... It shifts way better now. no grind. However I was told that the thing definately has some wear on it now and the mechanic says because of it rattling when its in neutral that he thinks the input shaft has some play. But from what Ive heard that is perfectly normal for the ZF6 if you have put a different flywheel (other than the stock Dual Mass Flywheel). So I am going to run with it now and deal with it later if this problem resurfaces.