Finally got my newly rebuilt and slightly upgraded t56 swapped into my car. Spec 1 clutch, machines flywheel, new master and slave. Got everything bled good and took it for a drive.

All gears work fine except for 3rd. The shifter goes in but as soon as the clutch is released it grinds and pops out of gear. Is this a tranny issue?
The clutch releases very close to the floor. Could a slave spacer help anything?

 

Since its only one gear its most likely the trans. Tough to say whats going on without pulling it back out. Could be something amiss with 3rd gear or that side of the slider. Could also be keys or fork pads.

When I rebuilt mine I replaced all the normal stuff but when I put it back together I could upshift to 3rd easily but downshifting would grind or pop out. Took it all back apart and nothing was phyically wrong, I replaced the 3-4 slider even though it looked good and when I got to the gear I noticed the cone on the gear was worn way down. What I think was happening with mine was the cone of the gear was too worn and the synchro couldnt do its job. After that all was well

 

I think the slave needs a shim, and the trans needs to be gone back through. I think you are right about the cone being worn because the friction ring was replaced

 

Is there any way the clutch not disengaging would cause a problem with the 3rd gear syncro? No other gear has a problem. I know it needs a shim I'm just trying to not have to pull the trans twice, once for the shim and if it doesn't then pull it again to rebuild.

Is there any linkage with the shifter to be adjusted?

What does a 'misaligned' bell housing do, I didn't think it could be aligned.

 

Could also be a bent shift fork so you're never fully engaging 3rd gear. Also you may want to consider getting a Tick M/C, stock ones don't mover enough fluid to fully disengage your clutch which can cause several problems including premature syncro failure.

 

The whole synchro assembly is new, friction ring, slider and hub, and blocking ring.

 

ya sounds like the gear friction cone may be worn. a clutch issue will cause issues in every gear its not specific to one gear. so if all the others go in smooth and trouble free its a trans problem. it could also be as fry said a bent fork. Did you replace the aluminum one with an iron fork

 

This was just a thought but not sure what shifter your using is the stops on the shifter set right. Perhaps it's hitting the stop before it's all the way in gear you could try backing them off see if that changes it all it's a shot in the dark.

 

The stops in the shifter were backed all the way out, and it's not hitting anything else. The shifter itself is a knock-off cheap one that I will replace soon. Any other way that could be a problem?

What is the cone that presses on the friction ring connected to? What hard parts would be replaced if I replaced the cone?

 

the cone on 3rd gear is cast into the steel itself. Theres a spec chart in the service manual about how to test the cone. The cone on mine was right on the edge of the good side but still had problems.

Seen in the pic below is 3rd gear. If the cone smooth part on the back of the gear is worn thin and will cause your issues. If it is bad 3rd gear will have to be replaced.

 

You should really read this...
https://ls1tech.com/forums/manual-tr...ift-forks.html

 

I've read that previously thank you. The builder said the trans was working fine before the rebuild. But it's on the way back to him to see what he finds. If he doesn't see anything I will tell him to replace things for piece of mind.

 

Thought it could have been a disengagement problem in my monster clutch when my reverse popped and grinded randomly. Spoke to steve at snl and he specifically said, if it pops/grinds in a specific gear then its never a clutch issue, its more than likely your clutch pedal adjustment or t56 (which, unfortunately, i think is the culprit).

 

Turned out the 3rd gear hub was pressed on too tight. It took heat to pull it off. A new one was installed and hopefully that's all it was.

 

I see, well good luck to ya. These types of problems are always tricky

 

Put it back in, with a .115 shim. Clutch is perfect. Third still grinds, if I SHOVE it in, and SLOWLY release the clutch it will stay in after a few pops. But normal shifting grinds and stays in, like continues to grind until I move it out.

 

The builder said to only use dextron VI, that's what they soaked the synchros in. And that could cause a problem. But all I've heard is that t56 uses dex III like I have been running.

 

I don't think your builder knows what he's doing bro... T56's prior to 2006 were using dextron iii, then after started using dextron vi, which later on had a TSB recall. Somewhere down the line they stopped using the name dextron iii, and changed it to gm syncromesh (or recently acdelco syncromesh) for what i believe was licensing purposes.

There's a thread that's not on ls1tech that i can PM you giving specific facts to this if you'd like...

 

Better yet, for the greater good of anyone who is still confused about what oil to use in their T56, I'll post the link. Lol hopefully the mods dont delete it..

http://www.ls1gto.com/forums/showthr.../283117?page=1

Page 3 post #25 has your answer.

Dextron vi basically wasn't a great choice for t56 transmissions and GM then advised people to go back to using dextron iii (which is acdelco/gm syncromesh) part #88861800

I recently veered away from gm syncromesh and used royal purple. Shifts were smooth until about a month gears started grinding in high revs. Turns out royal purple chews up the blocker rings which was proved by a vendor on here by testing royal purple and mobil 1 atf on the same type of blocker rings.

Long story short my t56 took a dump, and while i had no problems with the 3 years prior using gm syncromesh, i just went back to using it with no issues to date...

Moral of the story, DONT USE DEXTRON VI. That may just be your problem, lol and/or your builder doesnt know what he's doing..

 

Sent the trans back and they gave me a whole new similarly built unit. Using dex 3, NO SHIM, and the same clutch, master and slave, the car runs perfectly.

The rails in the trans could have been giving me the problems I had getting into reverse and the notchy feel in love other gears.