Hearing a clonk on and off throttle low speeds
04-03-2019, 06:32 AM
#1
Hearing a clonk on and off throttle low speeds
Hi all ,i can hear a clonk on my 928 s Euro 1983 Auto . It happens when im on and off light low speed throttle probably mainly on . It sounds hollow. The cars been on a ramp and the mechanic had a quick look and said that there was some play where the torque shaft goes into the torque converter . Im just wondering if there is anything in that area that could be the root of the problem .. Ive researched the pinch bolt but people describe that as a rattle not a clonk . I havent had the bolt checked yet . Regards to all .
04-03-2019, 07:35 AM
#2
Team Owner
First thing to check crank end play
make sure the engine bell housing bolts all 4 of them are tight
retorque both of the drive shaft bolts look and see if the damper if you have one is sliding back and forth at the rear of the TT
Also consider taking the car to a 928 mechanic that has experience
make sure the engine bell housing bolts all 4 of them are tight
retorque both of the drive shaft bolts look and see if the damper if you have one is sliding back and forth at the rear of the TT
Also consider taking the car to a 928 mechanic that has experience
Last edited by Mrmerlin; 04-03-2019 at 09:35 AM.
04-03-2019, 12:14 PM
#3
Thanks for your suggestions First thing to check crank end play yep done that all ok
make sure the engine bell housing bolts all 4 of them are tight yep tight
retorque both of the drive shaft bolts not yet done , but the issue and play seems to be more of a turning of the shaft into the torque converter that causes it not the forward action .also it does it on the ramp look and see if the damper if you have one is sliding back and forth at the rear of the TT , does same on the ramp when there is no forward movement of the car .
Also consider taking the car to a 928 mechanic that has experience, yes i agree , unfortuantely they are a bit thin on the ground in my area in the UK .
make sure the engine bell housing bolts all 4 of them are tight yep tight
retorque both of the drive shaft bolts not yet done , but the issue and play seems to be more of a turning of the shaft into the torque converter that causes it not the forward action .also it does it on the ramp look and see if the damper if you have one is sliding back and forth at the rear of the TT , does same on the ramp when there is no forward movement of the car .
Also consider taking the car to a 928 mechanic that has experience, yes i agree , unfortuantely they are a bit thin on the ground in my area in the UK .
04-03-2019, 05:38 PM
#4
Rennlist Member
I had two issues with clunks which were sequentially resolved...
1- Check that all the exhaust suspension rubber is in place... loose exhaust will make that sound as it move and hits metal around it.
2- Check your rear axles... one of my was worn and would perform partial free rotation and make a noise at low speeds. Solved by a rebuilt axle from 928 International.
Just items you would never think of that cause irritating noises!
1- Check that all the exhaust suspension rubber is in place... loose exhaust will make that sound as it move and hits metal around it.
2- Check your rear axles... one of my was worn and would perform partial free rotation and make a noise at low speeds. Solved by a rebuilt axle from 928 International.
Just items you would never think of that cause irritating noises!
04-03-2019, 07:45 PM
#5
Rennlist Member
I had two issues with clunks which were sequentially resolved...
1- Check that all the exhaust suspension rubber is in place... loose exhaust will make that sound as it move and hits metal around it.
2- Check your rear axles... one of my was worn and would perform partial free rotation and make a noise at low speeds. Solved by a rebuilt axle from 928 International.
Just items you would never think of that cause irritating noises!
1- Check that all the exhaust suspension rubber is in place... loose exhaust will make that sound as it move and hits metal around it.
2- Check your rear axles... one of my was worn and would perform partial free rotation and make a noise at low speeds. Solved by a rebuilt axle from 928 International.
Just items you would never think of that cause irritating noises!
04-04-2019, 03:20 PM
#6
Chronic Tool Dropper
Lifetime Rennlist
Member
Lifetime Rennlist
Member
The connections between the drive shaft in the torque tube and the torque converter itself include the clamp where the drive flange receives the end of the driveshaft. There's a splined connection there, with a clamp bolt that must be indexed to the driveshaft correctly, and must be tightened correctly. There's a relief slot in the splined end of the driveshaft that the bolt needs to pass through. If the driveshaft isn't lined up correctly in the clamped end of the drive flange, the clamping force may not be sufficient.
The rear drive flange includes the clamped end around the shaft, a section that passes through ball bearings in the torque converter housing, then a three-legged plate that bolts to the torque converter itself. That three-legged plate is attached to the end of the support tube with rivets that are know to get tired with age and use/abuse. As they loosen, the holes in the connecting pieces also enlarge, allowing some play and the clunk you hear when swapping between leading and trailing throttle. The fix is to remove the rivets and replace them with hardened bolts.
I think there was a Tech Service Bulletin that covered this, including the bolts nuts fittings you'll replace them with. For sure our favorite parts vendors will have that info for you, and will also guide you to replacement bearings for the converter housing and replacement bolts for the clamps at either end of the torque tube driveshaft.
Fortunately or unfortunately, the service typically includes dropping the transmission for access, and that opens a floodgate of while-you-are-in-there activities that might include half-shaft and CV joint maintenance, transmission mounts replacement, and fixing any dribbles and seepage sources that you notice.
Good luck in your quest!
The rear drive flange includes the clamped end around the shaft, a section that passes through ball bearings in the torque converter housing, then a three-legged plate that bolts to the torque converter itself. That three-legged plate is attached to the end of the support tube with rivets that are know to get tired with age and use/abuse. As they loosen, the holes in the connecting pieces also enlarge, allowing some play and the clunk you hear when swapping between leading and trailing throttle. The fix is to remove the rivets and replace them with hardened bolts.
I think there was a Tech Service Bulletin that covered this, including the bolts nuts fittings you'll replace them with. For sure our favorite parts vendors will have that info for you, and will also guide you to replacement bearings for the converter housing and replacement bolts for the clamps at either end of the torque tube driveshaft.
Fortunately or unfortunately, the service typically includes dropping the transmission for access, and that opens a floodgate of while-you-are-in-there activities that might include half-shaft and CV joint maintenance, transmission mounts replacement, and fixing any dribbles and seepage sources that you notice.
Good luck in your quest!
The following users liked this post:
imanadguy (06-18-2020)
04-04-2019, 03:56 PM
#7
Administrator - "Tyson"
Lifetime Rennlist
Member
Lifetime Rennlist
Member
We had a local 928 with the most random "clunk" that mostly happened when accelerating from a complete stop.
Long story short, one of the large rear bumper bolts was missing and the sound was the metal cross bumper hitting the inside of the shock it should have been bolted to.
Literally kicking the rear bumper pad is how we discovered it.
Long story short, one of the large rear bumper bolts was missing and the sound was the metal cross bumper hitting the inside of the shock it should have been bolted to.
Literally kicking the rear bumper pad is how we discovered it.
Trending Topics
04-04-2019, 04:33 PM
#8
Thankyou very much for such a comprehensive answer to my problem I’ll investigate .
The connections between the drive shaft in the torque tube and the torque converter itself include the clamp where the drive flange receives the end of the driveshaft. There's a splined connection there, with a clamp bolt that must be indexed to the driveshaft correctly, and must be tightened correctly. There's a relief slot in the splined end of the driveshaft that the bolt needs to pass through. If the driveshaft isn't lined up correctly in the clamped end of the drive flange, the clamping force may not be sufficient.
The rear drive flange includes the clamped end around the shaft, a section that passes through ball bearings in the torque converter housing, then a three-legged plate that bolts to the torque converter itself. That three-legged plate is attached to the end of the support tube with rivets that are know to get tired with age and use/abuse. As they loosen, the holes in the connecting pieces also enlarge, allowing some play and the clunk you hear when swapping between leading and trailing throttle. The fix is to remove the rivets and replace them with hardened bolts.
I think there was a Tech Service Bulletin that covered this, including the bolts nuts fittings you'll replace them with. For sure our favorite parts vendors will have that info for you, and will also guide you to replacement bearings for the converter housing and replacement bolts for the clamps at either end of the torque tube driveshaft.
Fortunately or unfortunately, the service typically includes dropping the transmission for access, and that opens a floodgate of while-you-are-in-there activities that might include half-shaft and CV joint maintenance, transmission mounts replacement, and fixing any dribbles and seepage sources that you notice.
Good luck in your quest!
The rear drive flange includes the clamped end around the shaft, a section that passes through ball bearings in the torque converter housing, then a three-legged plate that bolts to the torque converter itself. That three-legged plate is attached to the end of the support tube with rivets that are know to get tired with age and use/abuse. As they loosen, the holes in the connecting pieces also enlarge, allowing some play and the clunk you hear when swapping between leading and trailing throttle. The fix is to remove the rivets and replace them with hardened bolts.
I think there was a Tech Service Bulletin that covered this, including the bolts nuts fittings you'll replace them with. For sure our favorite parts vendors will have that info for you, and will also guide you to replacement bearings for the converter housing and replacement bolts for the clamps at either end of the torque tube driveshaft.
Fortunately or unfortunately, the service typically includes dropping the transmission for access, and that opens a floodgate of while-you-are-in-there activities that might include half-shaft and CV joint maintenance, transmission mounts replacement, and fixing any dribbles and seepage sources that you notice.
Good luck in your quest!