I've posted about this before, but this time I'm really worried.

First, the full history (at least everything I know. Never met original owner)

4 speed muncie (85GT)... Guy named Jack owned it. Took me for a ride one day and I liked the car. I ended up buying an auto 86GT because of him.

Jack sold it to Dusty, who promptly (idk how) broke the shift fork and ruined the transmission. My step brother picked up the car cheap and paid someone to swap in another used 4 speed from a local scrap yard. After being stranded twice because of a fuel pump (his fault) he got angry and sold the car to me. I fixed the pump and drove it several thousand miles without issues (still stock 2.8L)

Started having issues with what I'm guessing what 3rd gear syncro. After long (1hr+) highway trips, it wouldn't want to shift into or out of 3rd gear and would make terrible metallic grinding noises if you left it in 3rd and drove it. I was gentle enough to make it til summer and swapped in a 3800SC and yet another muncie 4 speed, this time 'tested' by FieroFactory. I adjusted the shift/select cables as per the haynes manual... there was always some side-to-side play in the shifter, even before the swap, no matter what gear it was in or how the cables were adjusted.

Now about 5 months later (about the same length of time before running into problems with the 1st muncie replacement) I'm hearing the same nasty grinding noise, with a few differences.
-I've heard it in 1st, but the exhaust is so damn loud I can never tell when it's really grinding. Happens mainly under acceleration in 2nd and 3rd gears. 4th never makes a noise that I've heard over the muffler.
-Shifting in and out of any gear isn't really any more difficult now that it's grinding than before
-Noise starts in 2nd and progresses to 3rd the hotter the transmission gets. No noise pulling out of my driveway; slight noise in 2nd after a mile or so in town; 2nd and 3rd scraping and loud under acceleration by the time engine is fully warmed up.

Transmission fluid is royal purple syncromax. Wasn't more than a cm or two low, but on the way home I topped it off with 5-30 oil just to see if it would stop grinding (this was at a tiny gas station in the middle of amish country. I didn't have much to work with)

I've got a brand new F40 6 speed that I can not wait to swap in and be done with used trannys all together. But until I have enough $$ for the swap parts, what do you guys think? What exactly is going on? How long til I can't drive my car at all?

.up

have you all ways run synthetic in these or is this something recent.

Its sometimes hard to pin-point a tranny gear noise. On my old 86GT 4 speed, I had a problem with noise once I was coasting with-out giving throttle. Once I was accellerating there was no noise. IIRC, if I was coasting with the clutch pedal in, no noise eithier. The problem was the differential gears in the tranny. The gears (4 of them) that rotate all together had slack in them. The ends of the teeth were worn very bad and that's the growling pitch noise I was experiancing.

Do you know if your tranny has had a rough life, or was luberficated / maintaned well??

My main problem was the owner that put a rebuilt engine in and clutch used an inpact gun to the tranny mount on the the tranny casing. He must of used or mis-used / mixed up the mounting bolts and drove the bolt right through the tranny casing. That wasn't to smart. The final result was the tranny oil was slowly leaking out of this area. I checked to oil level but it was to late. It wasn't my fault, but I wasn't aware of this at all. I found myself in need of a differential gear set. It wasn't until we split the tranny to discover what was the reason for this failure.

Anyways, once we cleaned the tranny and found a spare casing we put it together. Put the engine & tranny on the cradle and installed everything.

The problem was solved and the tranny noise was gone.

I use manual sycrhomesh fluid in my 88GT getrag tranny and that's the best I've used and many folks here would agree. At the time, I had 5W30 in my 86GT tranny. It was good for a substitute oil, but GM sychromesh it the best / recommended oil for fiero transmissions.

To my knowledge today, my old 86GT is still on the road after 7 years since.

Hope this may keep an eye opener...

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fierogt28

88 GT, loaded, 5-speed

[This message has been edited by fierogt28 (edited 12-31-2008).]

quote Originally posted by currie68: have you all ways run synthetic in these or is this something recent.

No idea about previous history on this one. Used from fierofactory. But I've ran synthetic since I installed the tranny in august.

I guess my problem stems from the fact that I don't/won't throw a ton of money into a rebuilt 4 speed knowing full well that I will be swapping in a 6 speed eventually and that the 4 speed wont hold up to the 3800 if I really race it (which I haven't done. I've been slow and easy on just about every shift except 3rd->4th when I was racing a Z28)

I expect that a fresh muncie wouldn't be giving me problems so soon... it's that I keep buying junkyard trannys that I keep having problems.

well... look what I found (cell phone camera, pardon the lack of image quality)



Drained transmission yesterday, poured in about half a court of 5w30 oil and spun the drivers side hub by hand in neutral. Got a bunch more metal out. Finished up by refilling with 3 quarts of penzoil syncromesh. I drove back to toledo today (173 miles) with no gear noise, although I was very easy shifting the whole way.

The dark spot in the second pic is a small rare earth magnet I stuck under the pan. It immediately started pulling the metallic powder and holding it... there didn't seem to be any large chunks really. Unless they flushed out into the bottom of the litter pan.

BTW- that was royal purple synchromax. Pretty purple going in... purple and silver coming out (the silver pan shot was mostly 5w30 oil I used to kidna flush what I could out, that's why it's gold lol) I don't blame the fluid- it could have got up to half a quart low sometime over the last 5 months. Axle seals don't look to be leaking... but it's hard to tell with the little light I had.

Anyways, it's working OK for now... but bring on the 6 speed. I'm talking to archie and should have parts ordered by the end of next week. Once the swap is finished I'll post pics.