clunk shifting into 3rd when cold
02-23-2014, 11:58 AM
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clunk shifting into 3rd when cold I pulled a fbody t56 out of my track car that has always had a problem with the first shift into 3rd gear after start up where it makes a moderately loud clunk and feels like it wants to pop out. It's very consistent and it's only ever the first shift. I plan on selling it after it's fixed up and won't be able to test it on a car before that. Was hoping someone could help guess what the problem is so if nothing obvious looks bad I know what to swap.
I've rebuilt 4 other t56s, but none of them had a problem like this. Maybe a fork/rail position problem? Any ideas or suggestions?
I've rebuilt 4 other t56s, but none of them had a problem like this. Maybe a fork/rail position problem? Any ideas or suggestions?
03-02-2014, 12:35 PM
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I pulled it apart today. Nothing obviously wrong with it, but I saw some interesting things:
- Missing 3rd gear needle bearing spacer. There are no signs of it. Unless it disintegrated it must have been forgotten by whoever touched it last.
- Worn 3/4 blocker rings that should be replaced. No surprise as that's where the synchros are doing the most work on the tracks I go to.
- 3rd gear is part # 13-86-083-06. Tick lists it as -007. Is the 06 just an earlier revision? It has 2 grooves machined in it between the synchro teeth and gear teeth. One of those grooves goes all the way through to where the bearing sits. Is this normal? I've only looked at m12 3rd gears before and I don't remember them having this.
Seems a waste to replace 3rd gear unless there is something known to be bad with this revision. The teeth look pretty good.
I'm thinking new 3/4 blocker rings and a metal spacer. Hopefully that fixes the problem. Any thoughts?
- Missing 3rd gear needle bearing spacer. There are no signs of it. Unless it disintegrated it must have been forgotten by whoever touched it last.
- Worn 3/4 blocker rings that should be replaced. No surprise as that's where the synchros are doing the most work on the tracks I go to.
- 3rd gear is part # 13-86-083-06. Tick lists it as -007. Is the 06 just an earlier revision? It has 2 grooves machined in it between the synchro teeth and gear teeth. One of those grooves goes all the way through to where the bearing sits. Is this normal? I've only looked at m12 3rd gears before and I don't remember them having this.
Seems a waste to replace 3rd gear unless there is something known to be bad with this revision. The teeth look pretty good.
I'm thinking new 3/4 blocker rings and a metal spacer. Hopefully that fixes the problem. Any thoughts?
03-15-2014, 09:01 PM
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Put it back together today with new 3/4 synchro, 3/4 billet keys, 3/4 blocker rings, and the missing needle bearing spacer. I checked the shims and the countershaft had about .005" of end play with the old shim so I'm thinking that caused the clunk into 3rd while it was warming up and the metal was expanding.
03-21-2014, 04:06 PM
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I know I'm probably talking to myself here, but what are the symptoms and side effects of a transmission that is shimmed incorrectly (too loose and too tight)?
Presumably, too tight is noisier and can cause premature tapered bearing wear. What else? What about too loose?
Presumably, too tight is noisier and can cause premature tapered bearing wear. What else? What about too loose?
