Another stuck-in-3rd issue, not forks or keys
05-05-2013, 10:49 PM
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Another stuck-in-3rd issue, not forks or keys Backstory: This is a 98 Trans Am with the LS1 and a T56. Bought it a couple of years ago with ~150k miles on it then, closer to 190 now. Bought the car cheap because it had a transmission issue - it popped out of 4th (immediately). Very quickly you get used to shifting 1-2-3-5, so not a big deal; otherwise, shifted fine. Drove it as a DD until it got stuck in third a couple of times... as in just wouldn't come out of gear. PO didn't know what had or hadn't been done to the car so my assumption was that nothing had ever been rebuilt.
Research on the internet reflected that this was a worn 3/4 shift fork, and/or the synchro keys for 3/4.. since I had these in the spares pile, should be simple enough to replace these - just time-consuming to pull and reinstall the tranny in the driveway.
So once I got the tranny out and opened it up, it looks like I'm not the first one in here -- case is sealed with RTV, all of the blocker rings look pretty fresh, and the fork pads look new.
The 3/4 keys were all broken in half and stuck to the magnets. Replaced those and their spring, and swapped the 3/4 fork for a low-mileage stock one (I don't think the fork was "worn" as there was close to no wobble on the shaft with either the old or the replacement, and no obvious bend on either). Put it all back together last week and back in the car, and enjoyed having a fully functional transmission.
Until last night, with ~40 miles on the rebuild, when it stuck in third again. Additionally, it now pops out of 2nd occasionally on engine braking; it didn't do that before and I didn't pull the 1/2 synchro apart.
I'm sure the 3/4 keys are toast again and I'm going to have to pull it back out... but I'm not sure what the cause is so I'm turning to you, Internet. I'm going to want to order parts before I take over the driveway again but money is always tight so don't want to just throw parts at it.
Could the rebuild have included new bearings, and they didn't shim it (would that cause this?)
What about worn 3/4 slider or hub?
Any other areas that I'm not picturing?
Research on the internet reflected that this was a worn 3/4 shift fork, and/or the synchro keys for 3/4.. since I had these in the spares pile, should be simple enough to replace these - just time-consuming to pull and reinstall the tranny in the driveway.
So once I got the tranny out and opened it up, it looks like I'm not the first one in here -- case is sealed with RTV, all of the blocker rings look pretty fresh, and the fork pads look new.
The 3/4 keys were all broken in half and stuck to the magnets. Replaced those and their spring, and swapped the 3/4 fork for a low-mileage stock one (I don't think the fork was "worn" as there was close to no wobble on the shaft with either the old or the replacement, and no obvious bend on either). Put it all back together last week and back in the car, and enjoyed having a fully functional transmission.
Until last night, with ~40 miles on the rebuild, when it stuck in third again. Additionally, it now pops out of 2nd occasionally on engine braking; it didn't do that before and I didn't pull the 1/2 synchro apart.
I'm sure the 3/4 keys are toast again and I'm going to have to pull it back out... but I'm not sure what the cause is so I'm turning to you, Internet. I'm going to want to order parts before I take over the driveway again but money is always tight so don't want to just throw parts at it.
Could the rebuild have included new bearings, and they didn't shim it (would that cause this?)
What about worn 3/4 slider or hub?
Any other areas that I'm not picturing?
