elesquan

iTrader: (1)

I have a LS1/T56 in a '67 el Camino. I was accelerating at a little over half throttle running though the gears when the rear axle blew up. I think I was in third or fourth when it blew up. Pinion gear blew through bottom of case. It was a violent event... Replaced the axle assembly and went for a very timid first drive. Under very mild acceleration (around 5% throttle), the trans felt like it let go, and made a very slight clattering noise. I think it came out of gear. Was able to put it back in gear and drive just fine. Trans sounds quiet and no ugly noises other than that. I did not dare drive it much for fear of further damage to trans, but for sure it will do this in first and second, and I think it did it in third once too.
I got the T56 service manual printed and read that awesome stickied thread on rebuilding the trans. My first time inside one of these, but have rebuilt old saginaw and muncie before.
Tore down the trans last night, and did not find anything too terrible inside.
So now I am wondering what I am overlooking. Worst damage is 1/2 shift fork missing a small piece of the plastic pad on one fork, and second gear is missing 5 or 6 of the syncro teeth. I will try to include pictures if i can figure it out.
Syncro keys are not very worn or broke. Trans worked fine before the axle blew up other than grinding into second sometimes (Found the cause of that problem I think..), and sometimes would not shift into third completely and would come out if you were not paying attention.

I have not removed the clutch, but looking at it through the bellhousing opening nothing looks abnormal.

Any suggestions on what to look for?

MeangreenHD

iTrader: (6)

is the 3/4 shift fork bent?

elesquan

iTrader: (1)

I did not look. The fork looks like it is that pot metal stuff, so I assumed it would break before it bent. I will look at that closer. Thanks MeanGreen.

dgcustomz

iTrader: (127)

They don't bend....

elesquan

iTrader: (1)

Had a chance to look over the parts more carefully last night.
No other damage was found.
Shift forks are not bent or cracked.
Anyone have some suggestions of what to look for?

ToxicT56

If you have teeth missing off the synchronizer, than the synchro is bad. It's also possible the engagement teeth on the gear itself is bad.

The forks for 1/2 and 3/4 are aluminum...wont bend, but they can break. The plastic pads are known problem. They make bronze upgrades for fork pads.
If it's popping out of 3rd gear, then keys could be bad on 3rd gear, engagement teeth on 3rd gear could be bad, and/or synchro and or/spring for keys are bad.

elesquan

iTrader: (1)

Thanks Toxic,

I have examined the syncro keys and springs, they don't look worn out.
The 1/2 fork is missing about half of the pad on one of the forks.
There are 4 or 5 missing engagement teeth on 2nd gear, and the same for the 2nd gear blocking ring. I suspect these were damaged prior to me getting the trans however as 2nd gear was prone to grinding once in a while.

I wondered if the case could have stretched when the rear axle bound and then blew up. This would increase the end play, could that maybe cause this problem? The case looks pretty damn stout, but why would shim kits be needed for rebuilds if this is not a potential problem.
Also the plastic isolator cup is not attached to the rear offset lever, but it is not cracked or anything.

I am going to take out the clutch to be able to examine the disk better, but I very much doubt that is the issue.

Guess I will clean each part and look very closely at each and order replacements for anything found along with a new 2nd gear, 2nd syncro, snap ring kit, shim kit, brass isolator cup, and brass pads for 1/2 and 3/4 forks and put it together again.

Thanks to all of you who gave this some thought.

jmd

iTrader: (4)

One time? You may have simply not put it fully in gear. If you found 2nd gear teeth on the magnets, maybe that was what happened.

Popping out of 2nd and having the stock early 2nd gear with teeth busted off go hand in hand.
Put a magnet on the 3-4 fork. A stock aluminum fork wallows at the shift rail so it can't put you completely into 3rd or 4th and will pop out. I might have an iron one, NIB.

You're overreacting; The tailhousing will crack if too violent a driveline situation happens.

You should get your mainshaft on v-blocks or in a lathe to verify it's not bent. Not because I think your pinion problem caused it; just good to verify on a trans., with miles.

The 4-gates wide T56 will eventually shear the cup. The 3-gates wide T5 and T45 do not.

Sent you a PM.

elesquan

iTrader: (1)

Thank you Matthew.

Whatever was happening, (I assume it must be the trans coming out of gear) happened several times the first drive around the block after the rear end swap.
The next morning I drove it around again, and made sure I had it all the way into first, and it happened again under very minimal acceleration.
The Car has been together and on the road as my daily driver for many years now, and as far as I can remember I have only had occasional issues with it coming out of 3rd gear, and grinding going into 2nd.

It has stock shift forks, I will check them for wallowing on the shaft, and for cracks by the shift rail.

It does not make sense that the case would have stretched, but I wonder why the shim kits are needed if this was not a possibility.

I will check roll out on the main shaft just to be sure, thanks for that suggestion!

PM you about the parts.

elesquan

iTrader: (1)

Broken clutch disk! Steel part inside that is part of the spring dampening broke, and that is connected to the splined hub. Could not see a problem until I put an input shaft in vise, and then twisted the clutch disk on the shaft. With enough twist, the disk gave way and made a click noise..

Thanks for all your input!