Tony89GTA

iTrader: (7)

After seeing many people with the same reverse problems as me I figured I might as well do a little write up on how I fixed mine. So if your t-56 tranny pops out of reverse or you have to hold it in gear to back up or all it does is grinds then this could be something you might want to look into.

I have been fighting this reverse problem ever since I bought this tranny, so this last time when I pulled the tranny out I decided to do a rebuild and figure out what's causing this problem. When I had the thing apart I was shifting the gears and seeing how the synchronizers would slide over and lock the gears in and I would notice that there was no space in between the gear and synchronizer and it gave a nice feel as it went in. I did the same for reverse and I could see there was a gap, it never did push the synchronizer over enough to give that good locking feel so when the clutch teeth on both gear and synchronizer started to get worn it would pop out of gear.

The fix.

I took the reverse shift fork over to the lathe and with a 3 jaw chuck I could get her to sit in solid ready for cutting, if you don't have access to a lathe you might be able to get away with using a grinder if your careful. Now judging by the gap that I seen between the reverse synchronizer and gear I figured that if I took about 1/8" off the end of the fork this would be enough to give me that good lockup. Basically all this is doing is is moving the synchronizer closer to the gear to start with so when you go to shift it in reverse the synchronizer will be push all the way into the gear just like when you shift to any of the other 6 gears. So after lathing 1/8" off the end of the fork all that's left to do is find a washer about the same thickness that has a big enough hole(or drill it bigger) to slide the shift rail through it and reassemble starting with washer first then fork, also make sure there is no play when you put it together, if there is try to take it out with a thicker washer. Well that's pretty much it, I'll post some pic's I found over the net and some of my own to kind of show what I mean.

Fist pic is the back housing cover comming off and second is it fully off. So what happens here is when you shift into reverse the shift fork pushes the synchronizer assembley up (see second pic) into the reverse gear, this is how they lock together. Third pic shows the reverse fork and where you should lathe the 1/8" material off. On reassembly you put the washer in first then fork then lock it down with the snap ring, pretty easy stuff.

Tony89GTA

iTrader: (7)

In these pic's just showing the gear and synchronizer out of the car that I have replaced. If you look close you can see how the reverse gear and synchronizer clutch teeth mesh together to lock the gear in.

Tony89GTA

iTrader: (7)

Ok in this last few pic's I want to kind of show you how far out the reverse synchronizer would stick out when the shifter was all the way into reverse, this is how it looked on the tranny at the time. As you can see there was a little gap, then on the next pic you will see how it looks all the way in locked up.


This fix has worked for me for 2 summers so far just wish I took some pic's when I was doing it at the time and made some proper measurements but hey that's hotroding

License2Ill

Tony thanks a million.
This is an excellent fix. And a cool afternoon's work.

My reverse and synchro plus slider are new and this was still a problem after the rebuild.

I think their may have been something off when they casted the reverse forks.

And im positive you don't need to go into first before hitting reverse or anything. After this fix.

Thanks again, i'm Definitely gonna make use of this if not this coming weekend then the next. This should be a sticky.

A true proffessional rigger, you get the McGuyver award!

Tony89GTA

iTrader: (7)

Hey thanks! Me personally, think they just put the fork in the wrong spot on the rail, should have been moved up more but hopefully this will work out for you. About the puting into a forward gear then into reverse I don't think is a bad idea, does stop the clunking.

onebad82z

iTrader: (7)

Hey Tony89GTA, how has this fix held up over time?Any side effects, problems, etc?Or is all well?

Tony89GTA

iTrader: (7)

All is well

Praetorian27

iTrader: (1)

Resurrecting a VERY old thread here...but was wondering how this repair is holding up? I have this problem with my '99 Corvette.

jmd

iTrader: (4)

then pull it and inspect reverse yourself.

License2Ill

I applied this fix way back when as I said that I would. It cured the problem...I since sold the vehicle and the engine and tranny went to another car. His tranny rebuilt by me is still running champ behind a 400hp+ LT1.
The reverse problem was one of the PRIMARY reasons I chose to rebuild and upgrade that tranny. Even though it was my first T56 rebuild(t22 long ago)I took many precautions to make certain I did it right. And I also replaced truly bad gears and syncho's needless to say when I STILL had the Reverse THUNK. I was FUMING....and I knew I just knew it was a manuf. defect and NOT my rebuild. Esp with all the other gears rowing just fine.

This is one of the best kept secret fixes of all time...I pulled this off without having to knock back down the whole tranny. But since the rear tailshaft of it can get knocked off while on the car...I went for it. I applied the fix just as written above within a few hours. I was thankful that I did not need to take it all apart and reset the forks and clutch assemblies due to this chit defect. As well as finding this repair which should have been made a sticky.

If it turns out your Reverse synchro and gear are fine and your apply this fix correctly. This will cure the problem. 5 years strong now! I talk to the new owner ALL the time. Mine was a 1993..im pretty sure they likely did not change anything all the way up to 1998 which is when the LS1 tranny debut...not too different internally but I would imagine they may have corrected this crap by then....but i would not be suprised if it carrys all the way to 2002 T56's.

Yes I do recommend you try it without pulling the whole tranny down if you dont want to...it is entirely possible to do...not easy but with some patience possible. Also I did not ever have to shift into First before Rev....ever the fugg again.

Peace.

Praetorian27

iTrader: (1)

Great post...thanks! Do you know if this repair is also possible in a C5 Corvette since it is mounted in the rear, without removing it from the car?

jmd

iTrader: (4)

It's not possible in a 97-up Vette trans.

The trans. has to be removed from the differential in order to remove the tailhousing casting.

Praetorian27

iTrader: (1)

Thanks...time to learn how to do that!

firechicken_3

iTrader: (4)

just got done doing this on mine, works like a charm now. thanks for the info

Chris Arnold

Just wanted to add a BIG THANK YOU to the OP. I did this about 6 months ago and for the first time in the 6 years I've owned my vette, I'm happy with the transmission. The fix is holding up great! Thank you so much!

Tony89GTA

iTrader: (7)

Wow I haven't seen this thread in a long time lol! I'm thrilled its been helping people fix this stupid annoying problem! Just to update, I still have the tranny in my car and never had a problem with the reverse after all this time

Anyways thanks guys!

Chris Arnold

Yeah man, and my T56 is the transaxle tranny for my C5.

Tony89GTA

iTrader: (7)

Right on, would never have guessed other t56's have this problem too lol.

Edit: So I just did a search on the net and surprisingly this problem affects a lot of the t-56's. The Fix seems to work for those that do it and gives them that positive shift.

Chris Arnold

Yep. After reading this article early this year, I could literally feel how the reverse synchros weren't fully engaging, and I knew immediately that you were right.

You're also right about it being throughout the T56 community. It's actually amazing to me how many guys on the corvette forums ask for help with the reverse gear popping out, and everyone tells them it's the blocker solenoid or their shifter. I just sent this to one such guy, and it took a while to find this thread again. I'm curious to see if he chimes back in.

InfernalVortex

iTrader: (4)

Mine never pops out. Guess I got lucky. It makes a lot of terrible noises and is super clunky at this point, but it always works...

mikeoguz

iTrader: (3)

I have the problem with my t56 popping out of reverse.

I need to get better at mechanics to try this 0_0

do you happen to have a video of "how to"

firechicken_3

iTrader: (4)

Still rocking and rolling here!

The worst part about this fix was all the stupid snap rings... Which were enough reason for me to decide that if the thing ever has to be truely gone through someone else is doing it.

Tony89GTA

iTrader: (7)

I never thought at the time 10 years ago to make a video though I probably should have lol. I imagine if you tried to get a tranny guy to do this he look at you and think your crazy... Haha!

TFS355S10

iTrader: (2)

This sounds like a very good idea to me. I've had a t56 tore down for a while now, upgrading some stuff, and I'll be doing this reverse mod before I put it back together.
I got some small OD washers a couple days ago to use for the spacers. lol

Thanks for taking the time to think this out Tony. I wonder why GM engineers couldn't figure this out to begin with.

Rider Harrison

Just wanted to give this post a +1, just did this to my t56 and no more grinding and slipping out of gear! Thanks alot for the great post.