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68 Chevelle, 454, ST10 (iron 904 main case if it matters) w/ ~15k since full rebuild (previous owner had it done, ~13k of those have been in this car/motor setup), Hurst Super Comp shifter, brand new when the trans was rebuilt.

About a month ago, out for a spirited Drive, turn left from a stop, 1-2 shifted fine, then 3-4 horrible angry grinding noise going into gear and the motor stalled out... Rolling, clutch in tried to change gears, couldn't get it out of gear, finally with effort got it into neutral, but then wouldn't go into any other gear. Car had to be towed home/rolled back into the garage.

Initially the trans wouldn't shift into gear at all... I drained the gear oil because i suspected it may have been low (it wasn't)
didn't see any significant chunks or sparkly stuff come out. refilled new 1.5quarts till it came out the fill hole.

With fresh oil (and no other changes), it now goes into all gears just fine (with the car not running).
Initially it wouldn't go into reverse but after working it a bit reverse freed up as well. Again this is all with the car not running.

A friend suggested I fire it up and go through the gears under power with the rear tires in the air...

Clutch in, motor fires up fine... stick in neutral- release the clutch and angry gear noise right at the transmission and the engine stalls out.
Tried the same thing in each gear, tried feathering the gas giving it more, going faster and slower with clutch release- but same result each time- trans/gear noise and engine stalls.

Seems like input shaft must be jammed or something, since the engine runs fine with the clutch pushed in, but won't allow the engine to turn even in neutral... but yet the car rolled just fine when we needed to push it.

A friend suggested taking all the shift linkages loose to ensure its not jammed trying to go into 2 gears at once... figure i have to do that anyway before i remove the shifter so will do that...

Any other suggestions to try before i start taking things apart to pull this out of the car?

Thanks in advance, sorry for the novel! LOL
 

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When I bought my daughters 75 vette. The shifting was horrible trying to get it in gear. After I tore it down, the clutch fork was broken off the pivot ball? Maybe pull the bell housing boot and inspect the fork function and bearing?
 

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It's stuck in 2 gears. When this happens 2 gears are engaged with the countershaft and both gears are trying to turn the countershaft at different speeds. The countershaft says nope! I can't explain why you could move the car. The output shaft is locked to the 2 gears it's stuck in, so moving should have been an issue.

It's usually caused by sloppy shifter linkage or there is a lockout on the shift forks that is supposed to keep this from happening that may be bad. If you get it free, have someone go through the gears after you reset your neutral adjustment, while you are looking at the shift rods/shifter. You may notice rod interference with another, or the adjustment and lockout allow the movement into third gear before you are completely out of second. Often happens on the 2 to 3 shift because you are crossing gates. The Hurst pit pass steel bushing kit can help tighten your shifter rods along with new clips.

You're probably still in second and partway into third. Move the shift levers on the trans by hand to the center position. It could also be stuck in reverse, so check that lever and make sure it is moved forward. I think forward is the correct movement of the lever to be out of reverse.

You can watch this video from the beginning, it should be cued to the shift interlock.
SUPER T10 DISASSEMBLY

I guess it's possible to have a broken shift fork too. The side cover needs to come off for inspection if you can't get it free. Watch the video so you don't lose the springs and parts for the lockout. Leave the levers on the shafts of the side cover until you get it on the bench so the sector shafts don't fall out and the spring and parts go flying into the trans or that lost in space place all lost parts end up in.

Could also be something busted and not allowing movement in the trans.

I think the angry noise might be the clutch slipping???? or the marcel springs chattering.

I think the clutch is fine. Sounds like it's working. The trans is locked up for some reason.
 

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Being able to push it in neutral means the trans is not in 2 gears at the same time.

Dragging the engine to a stall with the clutch out and in neutral says the input shaft is not moving....I would suspect the input roller bearing has exploded, or the input to cluster gear teeth..
This would play along with the difficulty or no go on putting it in 3rd or 4th, since that syncro slider is at the front of the main shaft directly at the rear face of the input shaft gear.

It will roll in neutral with the input blown up and seized because the 3rd, 2nd, and 1st gears are uncoupled from the main shaft when in neutral, so nothing is trying to turn the cluster gear from the output side.....but the cluster can't turn now because of the wedged/exploded/unmeshed input gear at the front of the case prevents the cluster from turning.

Put it in 1st or 2nd so the main output shaft and a 1st or 2nd speed gear is then connected to the cluster gear, engine off, step down on the clutch, and have a buddy try to push it....if it won't move, or hard to move while making crunchy noises it confirms the diagnosis.
 
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