LS T56 5-6 gear issue
09-29-2018, 06:40 AM
#1
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Car: 1991 Z28 1LE
Engine: LS1
Transmission: T56
Axle/Gears: 3.42
LS T56 5-6 gear issue
Hello, I just wanted to get some feedback from some others that may have dealt with this issue also.
I bought a T56 for 200 Euros a couple years ago with the condition that it pops out of reverse. After a little online research I found that it's somewhat common, and relatively easy to fix (remove material from reverse fork and shim with a washer). Anyways, I recently had the transmission removed and decided to do that. While I had it apart I checked the 5-6 cluster to make sure that it was still tight. Well, I could just remove it by hand. I just went through this with a LT T56 that actually sheared the splines off of the main shaft, and ended up replacing the main shaft and 5-6 cluster. I have that trans on a table at work, so I figured I'll just hang on to it until this one breaks and I'll just swap the front plate and input shaft.
I've seen a few other posts and videos where other people had the same issue during disassembly. My question is for those of you who just put it back together, and how long did it last like that haha? I'm always thinking about it anytime I'm accelerating in OD and I know it's only a matter of time until I hear a loud bang and lose 5-6th completely.
I bought a T56 for 200 Euros a couple years ago with the condition that it pops out of reverse. After a little online research I found that it's somewhat common, and relatively easy to fix (remove material from reverse fork and shim with a washer). Anyways, I recently had the transmission removed and decided to do that. While I had it apart I checked the 5-6 cluster to make sure that it was still tight. Well, I could just remove it by hand. I just went through this with a LT T56 that actually sheared the splines off of the main shaft, and ended up replacing the main shaft and 5-6 cluster. I have that trans on a table at work, so I figured I'll just hang on to it until this one breaks and I'll just swap the front plate and input shaft.
I've seen a few other posts and videos where other people had the same issue during disassembly. My question is for those of you who just put it back together, and how long did it last like that haha? I'm always thinking about it anytime I'm accelerating in OD and I know it's only a matter of time until I hear a loud bang and lose 5-6th completely.
09-29-2018, 04:28 PM
#2
Re: LS T56 5-6 gear issue
The 5-6 issue can sometimes be fixed for a long time by welding and rebuilding the smooth press-fit journal of the mainshaft inside 6th gear. The factory 0.002" interference fit wears away with vibration from 5th and 6th use, and destruction of the splines under 5th happen. Depending on how badly worn your mainshaft is, a repaired mainshaft and the same gear can be used. If it fails, it will push reverse aft on the mainshaft and will destroy far more parts than just a mainshaft and 5-6 gear.
09-30-2018, 09:31 AM
#3
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Car: 1991 Z28 1LE
Engine: LS1
Transmission: T56
Axle/Gears: 3.42
Re: LS T56 5-6 gear issue
The 5-6 issue can sometimes be fixed for a long time by welding and rebuilding the smooth press-fit journal of the mainshaft inside 6th gear. The factory 0.002" interference fit wears away with vibration from 5th and 6th use, and destruction of the splines under 5th happen. Depending on how badly worn your mainshaft is, a repaired mainshaft and the same gear can be used. If it fails, it will push reverse aft on the mainshaft and will destroy far more parts than just a mainshaft and 5-6 gear.
I'm getting the car ready for winter storage and there's a lift at the garage its going to so maybe I'll drop the trans back out and fix it right over winter...
Thanks, Ken
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