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I have a 97' T56 that I pulled out to fix my issue of not being able to go into 6th.
I completed a T56 swap about 4 years ago and added a manual reverse lockout switch. One night I forgot to hit the switch after I was done reversing. When I was going to shift into 5th gear, I instead went into Reverse. I slowly let out on the clutch and once I heard the grinding noise, I immediately pressed the clutch in again. I never fully had the clutch out while it was in reverse, but I was positive the damage was already done.
After the incident, I did not have any issues with reverse. When I would try to shift into 6th gear, there was a light grinding noise and it would not engage 6th. The only gear I have had issues with is 6th gear.
4 years later after not having 6th gear, I finally decided to pull the transmission and tear into it. I now have everything removed from inside the extension housing portion. I did not really notice anything obvious that was damaged. Shift fork doesn't look bent. The gears aren't chipped. The teeth on the reverse synchro look like they may have some wear on it, but I'm not sure. This is the first time I've dug into a transmission, so any ideas would be appreciated. I can send whatever pictures are needed.
Does the blocker ( black part ) feel as if it has any friction at all if you push it into the gear and try and turn it ? There's usually measurements via feeler blades as to how close this can be to the gear to determine if the blockers friction material is worn or not.
Does the blocker ( black part ) feel as if it has any friction at all if you push it into the gear and try and turn it ? There's usually measurements via feeler blades as to how close this can be to the gear to determine if the blockers friction material is worn or not.
Thanks for the response. What could be the issue with the slider hub keys? You’re talking about the three keys that are in the synchro assemblies?
I will check those and the blocker when I get home from work tomorrow morning. Thanks again.
You'd need to look at them and see..I cant see them from here lol.
Just in general condition, operation of any of those moving parts etc. But if it is purely one gear, then blocker sounds more likely. Although odd for it to be so bad yet the gear itself look so good.
5th working and 6th not points to fork pads first.
You can set you countershaft extension cluster back in place with all parts (not the fork) and operate the synchro up and down. If it positively locks in 6th, you have narrowed it down to shift linkage. Check the fork for looseness on the shift rail and zero play between it and the retaining ring for it. It is also highly suggested to check the 5-6 shift rail which interacts with the forward interlock selection pin. Smooth the teeth on 6th with the goal of little to no material removal.
Based on the description, shifts aren't reaching the slide to the gear; blocker ring, key or strut failure is less likely but they should be inspected, and make sure the retaining rings for the keys are started at the same key and wind in opposite directions when you reassemble.
I like having reverse lockout set up like stock, even if the electric isn't hooked up. Good luck.
Thanks for the responses so far guys. The fork pads appear to be in good shape.
While checking some of the other things you guys mentioned, I came upon something. I was attempting to remove the lock ring that sits underneath the 5/6 synchro on the countershaft. I am not able to get this lock ring removed from the countershaft. It almost seems as if the lock ring is jammed or seized in there. As you can see in the picture, there is a small gap in the right side of the ring where it will open up with the lock ring pliers. However, the left side of the ring is not budging. I'm wondering how this happens and if it could have this have anything to do with my 6th gear issue. Maybe it's unrelated, but I just figured I'd run it by you guys for your opinions. Thanks
The lock ring is clearly not in correct there, it is half way out.
As above, tap down the hub to take a little pressure off the lockring and it should come out easily. And good/correct pliers make removal of these easy
Your lock ring pliers may suck. tap the hub down on two sides with a punch so the ring is a little easier to remove.
Originally Posted by stevieturbo
The lock ring is clearly not in correct there, it is half way out.
As above, tap down the hub to take a little pressure off the lockring and it should come out easily. And good/correct pliers make removal of these easy
Ok, I did get the lock ring removed by tapping down on the hub, so thanks for that. Sorry to sound like a noob, I’ve just never been inside a transmission before and I’m just looking for any possible thing that could be causing issues.
Another thing I noticed upon disassembly was that the 5/6 driven gear just lifted off the mainshaft without any effort. The manual shows that it’s supposed to be pressed on and that it takes a puller to get it off.
That isnt really a problem as such. The first one of mine I took apart was the same....made life easier anyway lol.
Some will say it can be a cause of some noises in 5th/6th, but who knows.
A new 5/6 gear will likely be a much tighter fit, if not the shaft itself might be slightly worn. Is it really worth tearing the whole damn thing apart to replace the shaft ? That's up to you.
Replacing the 5/6 gear would be easier of course, but OEM gears are quite expensive and would a cheap copy be better/worse than what you have, even if it might fit a little tighter ?
Just wanted to give an update on this problem I was having. Before winter I had the rear portion of the transmission tore down, but didn’t figure out the issue. The transmission sat on my bench all winter and I never got around to digging further into the transmission.
Today I pulled the main housing off to take a look at the 5-6 shift lever. This is what I found
07-19-2018, 07:10 PM
T56 - 6th Gear Issue 
tap the hub down on two sides with a punch so the ring is a little easier to remove.
