T56/ drivetrain slack & clunk diagnosis
03-03-2015, 08:28 PM
#1
T56/ drivetrain slack & clunk diagnosis The t56 is known to be a notchy transmission. But its not really as notchy as you'd think...
The real cause of the notchiness particularly in GTOs, 5th Gen Corvettes and F-Bodies is a result of drivetrain backlash. Our cars have a lot of excess drivetrain slop; at the diff, which over time can cause clunking when getting on and off the clutch, getting on and off the gas, and shifting between gears.
This phenomenon occurs because there is freeplay in the driveline, it makes the syncros work to make up for the gears bouncing back and fourth between each other.
That's my theory anyways...
Bushings play a big roll in this too. They are designed to soften the effect of the backlash and reduce its clunky noises. as they get older and worn out they don't absorb the impact as well. It causes the backlash clunking noises to become more pronounced because the bushings cant cushion the the driveline play. Switching to stiffer polyurethane drivetrain/suspension bushings will cause the same effect and make drivetrain clunky noises more prevalent.
Axles also may contribute to the problem. Cv joint's axle bar splines over time and abuse can wear down inbetween the splines causing slack to develop. This slack is particularly responsible for clunks when getting on and off the gas, especially at lower speeds.
IMHO...
The real cause of the notchiness particularly in GTOs, 5th Gen Corvettes and F-Bodies is a result of drivetrain backlash. Our cars have a lot of excess drivetrain slop; at the diff, which over time can cause clunking when getting on and off the clutch, getting on and off the gas, and shifting between gears.
This phenomenon occurs because there is freeplay in the driveline, it makes the syncros work to make up for the gears bouncing back and fourth between each other.
That's my theory anyways...
Bushings play a big roll in this too. They are designed to soften the effect of the backlash and reduce its clunky noises. as they get older and worn out they don't absorb the impact as well. It causes the backlash clunking noises to become more pronounced because the bushings cant cushion the the driveline play. Switching to stiffer polyurethane drivetrain/suspension bushings will cause the same effect and make drivetrain clunky noises more prevalent.
Axles also may contribute to the problem. Cv joint's axle bar splines over time and abuse can wear down inbetween the splines causing slack to develop. This slack is particularly responsible for clunks when getting on and off the gas, especially at lower speeds.
IMHO...
03-04-2015, 09:37 PM
#2
What are you getting at? Slack and clucks are not normal despite a manual gearbox driving differently than a auto. Gear assemblies by design have backlash but we're talking very small. it's the same in all vehicles. A notchy transmission could be related to fluid viscosity and gear teeth angle.
03-05-2015, 08:29 AM
#3
Just an informative post...
The reason being i was always trying to fix the extra backlash from my gto and after it all, not to mention comparing it to other gtos and
f bodies that have come through the shop, its the conclusion I came too.
This is just a list of ways to address the issue. for people who coming looking on the forum who don't know where to start
The reason being i was always trying to fix the extra backlash from my gto and after it all, not to mention comparing it to other gtos and
f bodies that have come through the shop, its the conclusion I came too.
This is just a list of ways to address the issue. for people who coming looking on the forum who don't know where to start
01-08-2023, 02:18 PM
#5
Registered User
Join Date: Jan 2023
Posts: 1
Likes: 0
Received 0 Likes
on
0 Posts
T56/LS7 clunk Seems to me a lot of this is pointing to the LS7 clutch in my 2000 SLP 125k. Luke LS7 clutch kit and Tick master installed same time. Right out the gate noticed the clunking and slop in the transmission. New OE Engine mounts trans mount, driveshaft balance new UJoints , rear end rebuilt, clunking slapping drivetrain when releasing clutch fast/ sloppy at low rpm. Car did nothing funky prior to clutch replacement. May switch to Centerforce have had great luck with them in past (3rd gen applications).