Driveshaft Vibrations after installing rebuilt transmission and new clutch
06-25-2012, 09:05 PM
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Driveshaft Vibrations after installing rebuilt transmission and new clutch Guys I am having a major problem with my driveshaft now that I have put the car back together. Here is some background of what was done.
1.) Had the transmission rebuilt by Texas Drivetrain Performance for two reasons. I could not get out of first gear unless the vehicle was not moving, and I had the infamous 6th gear vibrations.
2.) Replaced the dual-mass turd with a LS7 setup including the slave and remote bleeder from East Coast Corvettes.
3.) Installed new RevShift motor mounts, the red ones.
4.) Installed a new Creative Steel Trans mount because I snapped one of the bolts protruding from the mount when trying to re-install the old Creative Steel mount.
5.) Installed a Revshift billet guibo disc. ---More on this later---
6.) Kooks 1 7/8 headers w/ off-road pipes.
When I removed the drive shaft I made sure to mark the differential end for proper re-installation. Most of my installation went rather smoothly, so I will just touch on the problems I ran into.
First, it is not the best idea to change the motor mounts with the transmission out of the car. I was able to get the old motor mounts out, but I could not get the new mount to line up, since nothing was left to keep the engine from moving. I ended up having to use an engine hoist to pickup on the front of the block to the motor mounts to line up, and also to be able to stab the transmission in to the pilot bearing. The engine wanted to nose dive without the extra weight of the transmission so I could not get the tail housing high enough for the proper entry angle.
Second when removing the drive shaft, the rear CV joint end cap came off releasing the ball bearings onto the garage floor. I was able to clean the bearings, add a little more grease and reassemble the CV joint. I do not think this is causing my vibrations, but I am not sure. At one point in the install I left the driveshaft connected to the transmission, the carrier bearing secured to the chassis, but the rear of the driveshaft hanging unsupported for a week. I think I may have damaged the carrier bearing during this time.
After installing the Revshift guibo, I was expecting to have vibrations and possibly have to shim the transmission mount for the proper vertical alignment. Revshift recommends shimming the transmission mount upwards to account for the sagging of old mounts. Since I have new mounts, I did not think this was my problem. I went ahead and shimmed the cross member down one washer at a time. I found the sweet spot to be 2, 3/8 fender washers. I went as far as 4 washers down on the crossmember and 2 washers up under the transmission mount. In the sweet spot the vibrations come on strong at 25 - 35 mph in any gear. You can control the amplitude of the vibrations by how much throttle you apply. The more throttle, the more amplitude of the vibration. After this speed range, at cruising load the vibrations are very minimal. However, when accelerating the vibrations return. I was not going to live with the vibrations so I removed the Revshift guibo and installed the factor rubber guibo. The vibrations were intensified! Then I got out the contour camera and shot this video.
You can clearly see the shaft moving wildly inside the carrier bearing mount. The shaft is not moving in the bearing, but in the rubber doughnut between the bearing and the mounting bracket.
Any ideas guys? Do I need a new driveshaft, or do I have something out of alignment causing this? I had no vibrations before the install except the 6th gear vibes at 70mph.
1.) Had the transmission rebuilt by Texas Drivetrain Performance for two reasons. I could not get out of first gear unless the vehicle was not moving, and I had the infamous 6th gear vibrations.
2.) Replaced the dual-mass turd with a LS7 setup including the slave and remote bleeder from East Coast Corvettes.
3.) Installed new RevShift motor mounts, the red ones.
4.) Installed a new Creative Steel Trans mount because I snapped one of the bolts protruding from the mount when trying to re-install the old Creative Steel mount.
5.) Installed a Revshift billet guibo disc. ---More on this later---
6.) Kooks 1 7/8 headers w/ off-road pipes.
When I removed the drive shaft I made sure to mark the differential end for proper re-installation. Most of my installation went rather smoothly, so I will just touch on the problems I ran into.
First, it is not the best idea to change the motor mounts with the transmission out of the car. I was able to get the old motor mounts out, but I could not get the new mount to line up, since nothing was left to keep the engine from moving. I ended up having to use an engine hoist to pickup on the front of the block to the motor mounts to line up, and also to be able to stab the transmission in to the pilot bearing. The engine wanted to nose dive without the extra weight of the transmission so I could not get the tail housing high enough for the proper entry angle.
Second when removing the drive shaft, the rear CV joint end cap came off releasing the ball bearings onto the garage floor. I was able to clean the bearings, add a little more grease and reassemble the CV joint. I do not think this is causing my vibrations, but I am not sure. At one point in the install I left the driveshaft connected to the transmission, the carrier bearing secured to the chassis, but the rear of the driveshaft hanging unsupported for a week. I think I may have damaged the carrier bearing during this time.
After installing the Revshift guibo, I was expecting to have vibrations and possibly have to shim the transmission mount for the proper vertical alignment. Revshift recommends shimming the transmission mount upwards to account for the sagging of old mounts. Since I have new mounts, I did not think this was my problem. I went ahead and shimmed the cross member down one washer at a time. I found the sweet spot to be 2, 3/8 fender washers. I went as far as 4 washers down on the crossmember and 2 washers up under the transmission mount. In the sweet spot the vibrations come on strong at 25 - 35 mph in any gear. You can control the amplitude of the vibrations by how much throttle you apply. The more throttle, the more amplitude of the vibration. After this speed range, at cruising load the vibrations are very minimal. However, when accelerating the vibrations return. I was not going to live with the vibrations so I removed the Revshift guibo and installed the factor rubber guibo. The vibrations were intensified! Then I got out the contour camera and shot this video.
You can clearly see the shaft moving wildly inside the carrier bearing mount. The shaft is not moving in the bearing, but in the rubber doughnut between the bearing and the mounting bracket.
Any ideas guys? Do I need a new driveshaft, or do I have something out of alignment causing this? I had no vibrations before the install except the 6th gear vibes at 70mph.
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07-21-2012, 09:04 PM
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--- UPDATE ---
So today I installed a new CS diff bushing and support block. When I bought the car the owner said he had just installed a new diff bushing. Since he had already installed CS motor and trans mounts I assumed he meant a CS diff bushing too.
Well i found a stocker when I lowered the diff today. I installed the new CS bushing and support block without much trouble. It's MUCH easier to work on once you drop the exhaust.
The vibrations went away about 70%. It still isn't right, but it is driveable again. I only get vibrations now at 30-35 mph under lite throttle, and up to 50 or so under hard throttle. Some of what I am feeling could be due to the open headers though. I am going to try reindexing the shaft again before I hang the exhaust and hopefully get all most of the vibrations out.
So the morale of this story is DO NOT support the car by the differential when moving jack stands!
So today I installed a new CS diff bushing and support block. When I bought the car the owner said he had just installed a new diff bushing. Since he had already installed CS motor and trans mounts I assumed he meant a CS diff bushing too.
Well i found a stocker when I lowered the diff today. I installed the new CS bushing and support block without much trouble. It's MUCH easier to work on once you drop the exhaust.
The vibrations went away about 70%. It still isn't right, but it is driveable again. I only get vibrations now at 30-35 mph under lite throttle, and up to 50 or so under hard throttle. Some of what I am feeling could be due to the open headers though. I am going to try reindexing the shaft again before I hang the exhaust and hopefully get all most of the vibrations out.
So the morale of this story is DO NOT support the car by the differential when moving jack stands!
