: Driveshaft Vibrations after installing rebuilt transmission and new clutch



raguncajn
06-25-12, 10:57 PM
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.
7.) Installed Killernoodle trailing arms and Turn In Concepts bushings

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.



http://www.youtube.com/watch?v=N7W_vOf6CdY


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.

FuzzyLogic
06-25-12, 11:12 PM
Did you remember to index the propeller flange where the driveshaft connects to the transmission?

Since it sounds like you didn't mess with the differential, the process of elimination indicates that the problem must reside with the driveshaft bearing or the connections to the differential or tranmission. Since the only drivetrain component that can really move is the differential (you should probably buy the Creative Steel differential bushing and block), that's where the vibration is going to manifest regardless of the location of the actual source.

raguncajn
06-25-12, 11:28 PM
Did you remember to index the propeller flange where the driveshaft connects to the transmission?

I did index it, but during the transmission rebuild they blasted the propeller flange and removed my marks. I will try rotating it when I get some time.


Edit #1: You might also want to check and see if you torqued all of the rear flange bolts where the driveshaft connects to the differential equally.

Edit #2: Another dumb observation: have you noticed how the driveshaft floats upward as you increase speed? It's almost as if the driveshaft joint is being allowed to sag in the middle and doesn't really straighten out and stabilize until it's forced to by sheer speed. Did you tighten up that mount enough?

I made sure to follow the pattern in the manual which is basicially a star pattern when tightening the 6 bolts on diff. I didn't use a torque wrench, but they are correct according to my calibrated forearms ;)

The bearing mount is fully seated against the bottom of the car, there is no where for it to go. Also I do have the Creative Steel Diff bushing, but I do not have the block. The previous owner installed it about 3 years ago now. I have not inspected it, so I will see if it is worn. Also I want to make two more videos. One looking at the diff, an a second looking from the diff to the carrier bearing.

FuzzyLogic
06-25-12, 11:32 PM
I did index it, but during the transmission rebuild they blasted the propeller flange and removed my marks. I will try rotating it when I get some time.

That's where I'd put my money. Check out the "Speed Related Vibrations" section (bottom of the 2nd page):

http://www.hurst-drivelines.com/files/Driveline-Vibration-FAQ.pdf

raguncajn
06-25-12, 11:48 PM
That's where I'd put my money. Check out the "Speed Related Vibrations" section (bottom of the 2nd page):

http://www.hurst-drivelines.com/files/Driveline-Vibration-FAQ.pdf

I did forget to mention that I installed killernoodle's trailing arms. I have edited the first post to say this.

The pdf talks about where you feel the vibration, either in the shifter, or through the floor. It's hard for me to say because with with billet guibo installed it is more pronounced in the shifter, but still felt through the floor. With the rubber installed, you don't feel it in the shifter as much. Maybe I just don't notice it as much since the entire car is shaking more? The vibration is so strong you cannot make out anything in the rear view mirror, very similar to 2 subs hitting hard.

I hope the problem is just the propeller flange, but it's hard for me to believe it can make a vibration this strong.

FuzzyLogic
06-26-12, 12:02 AM
I just installed the RevShift transmission block insert, and I can definitely feel more vibration through the shifter than before. Based on what I've heard about the hardness of the Creative Steel transmission mount, you're probably fine there.

Dug up this old thread:

http://ls1tech.com/forums/cadillac-cts-v/1404338-help-driveshaft-vibration-no-speedo-after-cluch-change.html

If you poke around the internet, you'll find stories about people forgetting to index their driveshafts and having to rotate them once or twice (120 or 240 degrees) before the vibration went away. Hope that's the issue.

By the way, are you associated with Thunder Racing? Shane over there has a 2005 LS6 CTS-V that apparently makes some pretty serious power. We've been talking about various modifications to our cars over the phone for the last 6 months or so. He's got the TRuTorq Level 5 cam in his car, and I've got the TRuTorq Level 3 cam sitting beside me here (didn't want the nasty cammed sound that the Level 5 is known for). Hoping to make 450 RWHP with it when I find a free weekend. Knowing me, I'll have the Extreme Composites hood, B-Quiet sound dampening material, and Forgestar F14 wheels installed before that happens. Gotta get my priorities straight. ;)

raguncajn
06-26-12, 12:26 AM
Dug up this old thread:

http://ls1tech.com/forums/cadillac-cts-v/1404338-help-driveshaft-vibration-no-speedo-after-cluch-change.html



I found this one also
http://ls1tech.com/forums/cadillac-cts-v/1331414-driveshaft-vibration-after-short-shifter-install-help.html




By the way, are you associated with Thunder Racing? Shane over there has a 2005 LS6 CTS-V that apparently makes some pretty serious power. We've been talking about various modifications to our cars over the phone for the last 6 months or so. He's got the TRuTorq Level 5 cam in his car, and I've got the TRuTorq Level 3 cam sitting beside me here (didn't want the nasty cammed sound that the Level 5 is known for). Hoping to make 450 RWHP with it when I find a free weekend. Knowing me, I'll have the Extreme Composites hood, B-Quiet sound dampening material, and Forgestar F14 wheels installed before that happens. Gotta get my priorities straight. ;)

No I'm not associated, but I need to talk to them about tuning my car once I break in the clutch. I"m either going to them or the corvette guru over in Hammond, Darren Blanchard.

I know about the priorities, before my shifting issue KW3 was going to be my first major mod. Now i've got headers and a new clutch, plus a stage III rebuild on the tranny ;)

yooper
06-26-12, 12:47 AM
What does the service manual say the maximum angle allowed on the center bearing while removing the driveshaft?

darkman
06-26-12, 07:59 AM
What does the service manual say the maximum angle allowed on the center bearing while removing the driveshaft?

8 degrees - see attached.

raguncajn
06-26-12, 09:25 AM
8 degrees - see attached.

Thanks again Darkman for your attachments! The manual says 8 degrees, but only references CV boot damage, which could lead to CV joint failure. The way that I raised and lowered the shaft, all the deflection was in the middle by the carrier bearing. The CV was not articulated much, just when the middle of the shaft was lowered to help with getting it removed from the differential. I was not able to simply move the driveshaft forward and remove it. The shaft would not collapse enough, it needed maybe 1/16" more. I dropped the carrier bearing bracket, supported the shaft in the middle, and let it droop until I had the clearance to remove it from the differential.

raguncajn
07-21-12, 11:01 PM
--- 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!:banghead: