Can't shift from 6th to 5th
Thread Starter
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Joined: Dec 2001
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From: So cal.
Can't shift from 6th to 5th I thought it was the master, so i installed a new Mcloud and still it will not go from 6th to 5th, unless i put the clutch in and go to 4th then to 5th. What is going on? It does not grind. It just stops before going into 5th. Upshifting from 4th to 5th seems just fine.
Teching In
Joined: Jan 2002
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From: Upper Marlboro, MD
Originally Posted by mjf454
I thought it was the master, so i installed a new Mcloud and still it will not go from 6th to 5th, unless i put the clutch in and go to 4th then to 5th. What is going on? It does not grind. It just stops before going into 5th. Upshifting from 4th to 5th seems just fine.
I have the exact same problem. Weird. I think it's the syncros.
Originally Posted by mjf454
I thought it was the master, so i installed a new Mcloud and still it will not go from 6th to 5th, unless i put the clutch in and go to 4th then to 5th. What is going on? It does not grind. It just stops before going into 5th. Upshifting from 4th to 5th seems just fine.
Before I sell it (converting to TH400) I plan on fixing it.. wouldn't want to sell something that is not 100%
Thread Starter
TECH Regular
Joined: Dec 2001
Posts: 426
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From: So cal.
Well i just converted from a 4l60 to this t-56. I think this thing is a notchy shifting mess. Having never had a t-56 before, i have nothing to compare it to. It shifts like a Muncie. I thought a new car would shift better. Maybe it is in need of a rebuild.
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Teching In
Joined: Jan 2002
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From: Upper Marlboro, MD
mjf454
Sure glad you posted this question. We would have never known it to be a somewhat common problem. I bought my C5 new and to date it has only 18K miles. I've only drag raced it maybe 10 times and never got beyond 4th gear so this 6th-5th problem is not a factor. Sounds like a recall in the making. Hopefully more will chime in.
Sure glad you posted this question. We would have never known it to be a somewhat common problem. I bought my C5 new and to date it has only 18K miles. I've only drag raced it maybe 10 times and never got beyond 4th gear so this 6th-5th problem is not a factor. Sounds like a recall in the making. Hopefully more will chime in.
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HOLLY SHIZNIT!!! I have the same problem. I don't have an answer, but I can tell you that I have had nothing but problems with my trans since I got the car. GM rebuilt it at 6K becouse the 3-4 synchros went to sh*t. Now, 14k later I am having 5-6 issues.
Well, I repaired a tranny this weekend that had a problem going in to 5th. You really CANNOT diagnose this over the internet, the tranny needs to come apart and inspected.
Here's what I saw on my buddy's tranny...
The 5-6 driven gear is a press fit on the main shaft. The teeth that hold this gear in place had become chewed, and this gear that isn't supposed to move - was moving. This made the reverse slider gear move when it shouldn't have, which wore down the main shaft snap ring above the slider. The end effect was that the whole 5-6 portion of the tranny became 'loose' inside. There were parts slipping, sliding, and wallowing around everywhere.
We ended up replacing the main shaft, the 5-6 driven gear, 5th gear, the 5-6 synchro assembly, the reverse synchro assembly, all the snap rings, the rest of the blocker rings (commonly called 'the synchros'), and probably a couple other parts I'm forgetting.
The bill was almost $1200 in parts alone. But, that's for this one specific trans. You may not have this problem.
It could be as simple as a broken slider key, or as complicated as the mess we had here.
Notchy shifting is indicative of a synchro ring problem.
These trannies aren't that difficult to work on. With a good pair of ring pliers (from Snap On, about $40), access to a press / bearing splitter, and possibly a long puller for the 5-6 driven gear, and a T40 Torx bit (and a torch ), you can take one of these trannies apart in about 3 hours, diagnose the problem, and have it completely reassembled in about 5 hours, including cleaning time.
I have done 6 trannies so far, and I'm sure will do more. They're fun to work on.
-Andrew
Here's what I saw on my buddy's tranny...
The 5-6 driven gear is a press fit on the main shaft. The teeth that hold this gear in place had become chewed, and this gear that isn't supposed to move - was moving. This made the reverse slider gear move when it shouldn't have, which wore down the main shaft snap ring above the slider. The end effect was that the whole 5-6 portion of the tranny became 'loose' inside. There were parts slipping, sliding, and wallowing around everywhere.
We ended up replacing the main shaft, the 5-6 driven gear, 5th gear, the 5-6 synchro assembly, the reverse synchro assembly, all the snap rings, the rest of the blocker rings (commonly called 'the synchros'), and probably a couple other parts I'm forgetting.
The bill was almost $1200 in parts alone. But, that's for this one specific trans. You may not have this problem.It could be as simple as a broken slider key, or as complicated as the mess we had here.
Notchy shifting is indicative of a synchro ring problem.
These trannies aren't that difficult to work on. With a good pair of ring pliers (from Snap On, about $40), access to a press / bearing splitter, and possibly a long puller for the 5-6 driven gear, and a T40 Torx bit (and a torch
), you can take one of these trannies apart in about 3 hours, diagnose the problem, and have it completely reassembled in about 5 hours, including cleaning time.I have done 6 trannies so far, and I'm sure will do more.
They're fun to work on.-Andrew
My trans stop going from 6th to 5th at about 14,000 miles. Like you said, it went 4th to 5th no problem, but wouldn't go from 6th to 5th. I just had it rebuilt, the 5th gear syncros were shot (among other things!).
Anyway, before I got it fixed I was living with it by double-clutching from 6th to 5th. When you double clutch, you match the speeds of the gear sets so they will mesh without needing syncros. Get cruising in 6th gear, push in clutch, put stick in neutral, let out clutch, blip throttle to speed up the engine a little, push in clutch, shift into 5th gear. Give it a try, see if you can live with it. I went another 4,000 miles like that until all my syncros were blown from powershifting, then had the whole thing rebuilt.
Anyway, before I got it fixed I was living with it by double-clutching from 6th to 5th. When you double clutch, you match the speeds of the gear sets so they will mesh without needing syncros. Get cruising in 6th gear, push in clutch, put stick in neutral, let out clutch, blip throttle to speed up the engine a little, push in clutch, shift into 5th gear. Give it a try, see if you can live with it. I went another 4,000 miles like that until all my syncros were blown from powershifting, then had the whole thing rebuilt.
Staging Lane
Joined: Sep 2002
Posts: 96
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From: Cerritos, CA
Do you guys rev match when you go from 6th into 5th? I'm just wondering if your trouble is caused by the added wear on the synchros because you don't rev match or if it is something else?
Last edited by miner_49; Nov 4, 2003 at 11:51 PM.
I rev match my downshifts. I think I read on this forum that there was a service bulletin out for 5th gear syncro failure. I didn't bother pursuing it, I don't know of a dealer that would cover me!
same thing I had the same problem after I checked the fluid level in my master cylinder. I removed some of the fluid and my problem went away. Later I had the updated slave and a z06 clutch installed and I had the same problem. I changed the fluid level in my master cylinder and again the problem went away(an ounce one way or another). Hope this helps someone else.
mine won't shift from 6th to 5th and its freshly rebuilt. even if i rev match, it won't slide in. it finally slides in when my speed falls under 50 mph. it works good going from 4th to 5th. can the reverse lockout mechanism be affecting this?
My fresh trans is doing the same thing. I am going to be taking it apart again soon and seeing what's up with that. I can't go from 6th to 5th, but 4th to 5th works just fine.
-Andrew
-Andrew
Even my newly rebuilt trans is a little harder getting into 5th then all other gears and it has all new parts for 5th gear. The single cone syncronizer in 3-6 really has a hard time stopping the mainshaft from rotating especially when the clutch doesnt disengage 100%.
Just about every one of these cars I have driven has never been really smooth going into 5th gear from 6th and I have had two brand new M6 LS1 f-bodies - be happy it doesnt do that AND pop out of 3rd like the two new cars I bought
Just about every one of these cars I have driven has never been really smooth going into 5th gear from 6th and I have had two brand new M6 LS1 f-bodies - be happy it doesnt do that AND pop out of 3rd like the two new cars I bought