T56 problems, harsh driving or just too much power?
Thread Starter
6th Gear
Joined: Nov 2008
Posts: 6
Likes: 0
T56 problems, harsh driving or just too much power?
Hi, I'm going to be getting a C5 Vette soon God willing ( within the next two months ) and was wondering something.
I read a lot of the T56 owners complaining about failures but they seem to all be shift fork failures. Granted, I understand that GM may have screwed up on the shift fork design but what if you granny shift the car? What seems to fail next? How much power can the tranny hold assuming no abusive shifts?
I read a lot of the T56 owners complaining about failures but they seem to all be shift fork failures. Granted, I understand that GM may have screwed up on the shift fork design but what if you granny shift the car? What seems to fail next? How much power can the tranny hold assuming no abusive shifts?
Team Owner
Joined: Sep 2003
Posts: 43,084
Likes: 33
From: Raleigh / Rolesville NC
Not really. Most owners just dont change their trans and diff fluids enough.
the T56 is not designed to power shift, so most guys who complain, just may not know how to shift a T56 properly. Nice an smooth, not a quick jerk motion
the T56 is not designed to power shift, so most guys who complain, just may not know how to shift a T56 properly. Nice an smooth, not a quick jerk motion
Racer
Joined: May 2013
Posts: 360
Likes: 6
From: Panama City, FL
My understanding is that the biggest killer of these trans is shifting when the clutch isn't fully disengaged which is easy to do with the stock hydraulic setup. Tick adjustable master solves that. Of course missed shifts won't help anything, either.
Thread Starter
6th Gear
Joined: Nov 2008
Posts: 6
Likes: 0
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
You are getting some wrong info.
The shift forks usually don't fail "unless your are shifting with your feet" or abnormally forcing the car into gear!!
The small plastic shift fork pads can and do fail as the trans wears. Under NORMAL usage, they last a long time.
The synchro blocker rings also wear as mileage gets high. Changing the ATF inside the trans helps prevent excessive wear.
Drive it and see how it feels cold and hot. If its difficult to shift or grinds under normal driving, something mechanical is wrong. See how it shifts under spirited driving.
I agree on proper clutch operation. If the clutch isn't properly or fully disengaging, it will cause trans wear and damage.
Here is a poet for you:
- C5 ragtopws6, T-56 Build (whats in my tranny?) : http://forums.corvetteforum.com/nort...-smoother.html
BC
The shift forks usually don't fail "unless your are shifting with your feet" or abnormally forcing the car into gear!!
The small plastic shift fork pads can and do fail as the trans wears. Under NORMAL usage, they last a long time.
The synchro blocker rings also wear as mileage gets high. Changing the ATF inside the trans helps prevent excessive wear.
Drive it and see how it feels cold and hot. If its difficult to shift or grinds under normal driving, something mechanical is wrong. See how it shifts under spirited driving.
I agree on proper clutch operation. If the clutch isn't properly or fully disengaging, it will cause trans wear and damage.
Here is a poet for you:
- C5 ragtopws6, T-56 Build (whats in my tranny?) : http://forums.corvetteforum.com/nort...-smoother.html
BC
Thread Starter
6th Gear
Joined: Nov 2008
Posts: 6
Likes: 0
You are getting some wrong info.
The shift forks usually don't fail "unless your are shifting with your feet" or abnormally forcing the car into gear!!
The small plastic shift fork pads can and do fail as the trans wears. Under NORMAL usage, they last a long time.
The synchro blocker rings also wear as mileage gets high. Changing the ATF inside the trans helps prevent excessive wear.
Drive it and see how it feels cold and hot. If its difficult to shift or grinds under normal driving, something mechanical is wrong. See how it shifts under spirited driving.
I agree on proper clutch operation. If the clutch isn't properly or fully disengaging, it will cause trans wear and damage.
Here is a poet for you:
- C5 ragtopws6, T-56 Build (whats in my tranny?) : http://forums.corvetteforum.com/nort...-smoother.html
BC
The shift forks usually don't fail "unless your are shifting with your feet" or abnormally forcing the car into gear!!
The small plastic shift fork pads can and do fail as the trans wears. Under NORMAL usage, they last a long time.
The synchro blocker rings also wear as mileage gets high. Changing the ATF inside the trans helps prevent excessive wear.
Drive it and see how it feels cold and hot. If its difficult to shift or grinds under normal driving, something mechanical is wrong. See how it shifts under spirited driving.
I agree on proper clutch operation. If the clutch isn't properly or fully disengaging, it will cause trans wear and damage.
Here is a poet for you:
- C5 ragtopws6, T-56 Build (whats in my tranny?) : http://forums.corvetteforum.com/nort...-smoother.html
BC
How much can these trannys hold assuming no shift fork/syncro issues?
Instructor
Joined: Nov 2006
Posts: 233
Likes: 2
It's hard to answer that question directly regarding any transmission. A stock T56 is rated at 450 ft-lbs. However, there are obviously people pushing them way beyond that. If you're on slicks, in a heavy car, and you power shift, your tranny is not going to be reliable at nearly the same amount of torque that it would be in a light granny-shifted car on street tires.
In short there are just too many factors to give you a straight up answer. That said, I personally wouldn't hesitate to go upwards of 600 ft-lbs with a stocker. Of course, there are people who push the envelope a LOT further than that.
In short there are just too many factors to give you a straight up answer. That said, I personally wouldn't hesitate to go upwards of 600 ft-lbs with a stocker. Of course, there are people who push the envelope a LOT further than that.
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Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
It's hard to answer that question directly regarding any transmission. A stock T56 is rated at 450 ft-lbs. However, there are obviously people pushing them way beyond that. If you're on slicks, in a heavy car, and you power shift, your tranny is not going to be reliable at nearly the same amount of torque that it would be in a light granny-shifted car on street tires.
In short there are just too many factors to give you a straight up answer. That said, I personally wouldn't hesitate to go upwards of 600 ft-lbs with a stocker. Of course, there are people who push the envelope a LOT further than that.
In short there are just too many factors to give you a straight up answer. That said, I personally wouldn't hesitate to go upwards of 600 ft-lbs with a stocker. Of course, there are people who push the envelope a LOT further than that.
Excellent answer and I agree!
I run 450 RWHP /420 Tq an I had zero problems with my stock MN12 T56.
I have since up graded to a TRANSZILLA T60/60 just cause i could.
Your problems wont really be the trans and more likely the rear-end.. The Stock C5 rear is weak unless you beef it up.
Here are several post that will get you into sync with some of the C5 drive-train.
- C6 T-60/60 Tear Down & Rebuild http://forums.corvetteforum.com/c6-t...post1584119748
- C5 ragtopws6, T-56 Build (whats in my tranny?) : http://forums.corvetteforum.com/nort...-smoother.html
- C5, ragtopws6 , Upgrading your C5 rear with C6 Z06 guts, : http://forums.corvetteforum.com/c5-g...-z06-guts.html
-
- C5, Its_Go_Time, Output Shaft Install - Left and Right: http://forums.corvetteforum.com/c5-t...post1573407966
- C5 Differential Seal replacement: http://forums.corvetteforum.com/c5-g...on-photos.html
Beef up the rear and you will have less chance breaking things.
Bill
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Rick Kim RKT56 
RKT56
http://rkt56.com
Phone number: 301-257-0930
205 Bucheimer Road, #C
Frederick, MD 21701
RKT56
http://rkt56.com
Phone number: 301-257-0930
205 Bucheimer Road, #C
Frederick, MD 21701
Thread Starter
6th Gear
Joined: Nov 2008
Posts: 6
Likes: 0
Thank for the links, love the info. I understand that you can't put a definitive figure on power holding but an average is doable. If it can hold 600whp granny shifting it for a decent amount of time then that's good enough for me.
Race Director
Joined: Dec 2004
Posts: 13,760
Likes: 75
From: Haymarket VA
I just remembered speaking with Rodney at RPM 5 or 6 years ago when I built the 403 engine and asking him when I should think about upgrading my transmission. His response was...he would never go into a transmission that is working fine and that an aggressive 18 year old would kill one of his transmissions faster than a reasonable driver would break a stocker.