ImBatman

Thanks to lakebumm and gkull for posting about slotting the trannie mount!!! The first set of pictures are the drive shaft angles. The second set is where I beleive the problem is after looking at the tailshaft centering

Tail shaft angle reading is -2
I used the yoke side flat



Driveshaft center reading is +2


Rear Pinion is between 0 and +1
I used the point on the pinion for centering



This is where I beleive the problem is. The tailshaft is pointing to the left rear tire. I measured the center of the tailshaft to the inside frame rail. The driverside measured at 24 1/4" the passenger side measured at 22 3/4". Do you guys see the angle in the pics? Am I own to something???

Dirtbuster1

The 1st & 4th picture concern me. It appears to me that the universal joint is cocked to 1 side. Not the angle, but the postion of it? Is the u-joint centered in the yoke?

Ben Lurkin

The engines in these cars are offset to the passenger side a bit so you will see a difference measuring from the yoke to the frame rails. I don't recall what the offset is off hand.

While you have it in the air. Throw a dial indicator on the drive shaft at both ends to check if it is running true.

Z-man

I agree w/Ben. The engine is offset towards the passenger side, so I think you are just seeing that difference when measuring between the framerails. My drive shaft is pretty much offset like that, but it's extremely smooth.

Are you sure it's the driveshaft? IIRC 2 degrees is within normal tolerance for the angles of the shaft. Do the angles offset each other?

V-Twin

The engine is offset 1" to the passenger side.

read this:

Drivetrain alignment

rj8806

As others have already stated, the factory offset the engines to the passenger side to make clearance for the steering box among other things. With the Muncie in there, it wasn't as noticeable because the Munice didn't extend as far into the driveshaft tunnel as the TKO does. It is not uncommon for the corvette guys to slot the holes on the cross member east to west to try and center it up some. Usually it is only done to make clearance for the slip yoke.
Also, because the engine is offset, the factory uses this offset to play a part in the driveline angles as well. Not only is the angle from side to side but also up and down.

Based on these readings, your front working angle is 0* and the back working angle is 1*. In a perfect setup, you want the working angles equal but opposite. In your case, you are so close, that I don't think this is the problem. All of your angles are well below the 5* max limit so that's not it either.
I sent you a PM and will get back to you shortly.


Richard
Tech Support

hugie82

How is your pinion bushing and the angle of the diff. I used to big of a bushing on my pinion and it gave me a vib. Pulled it out and cut it down. The vib went away.

ImBatman

Thanks guys for the input. I don't think the pics are coveying what I am seeing. I realize that the motor and trans are offset however it looks like there is a slight "V" where the tail shaft yoke and the drive shaft meet. In other words it appears that the front of the driveshaft is pointing slightly left towards the front tire and the tail shaft is pointing slightly left to the rear wheel thus crating a "V". The last 2 pics show this best but unfortunately not as clearly as it would if you were actually looking at the connection. If this is normal then I guess I will keep looking for the problem.

V-Twin - Thanks I have that diagram printed and have been using it as a reference. The driveshaft according to the diagram is in a perfectly straight line with the rear end. Again mine "appears" to have a slight V in it at the tail shaft to dive shaft connection.

hugie82 - I am running a poly pinion bushing but my angles "seem" to be fine.


Thanks for all the input. I am about ready to ask for prayers.....

Wade

Dirtbuster1

Have you modified the drive shaft in any way. If so was it balanced, & have you checked for missing weights. I feel sure if you take it to a machine shop and have it checked you will find your problem. The poly bushing in the differential could possibly to stiff and setting up a resonance, causing the vibration. You can use something soft or stiff at the diff to move the vibation to excite at a different frequency.

Does anyone live around you that you could swap drive shafts with to see what would happen.

ImBatman

Thanks Dirtbuster1! I have made no modifications as this is a complete kit and the DS and yoke were balanced as a unit from Keisler when I purchased it. There is knowone near me that I could swap with and they would have to have a tremec tranie installed anyway as the DS is shorter. I have been thinking about getting a rubber bushing and replace the poly one. But I still am wondering if it has to do with the "V" I was describing.

Wade

Dirtbuster1

I would try the rubber bushing 1st. If that does not work, see if you can send the driveshaft back to have the balanced checked since it was custom made.

norvalwilhelm

I definitely found mine to be the same, the tranny pointed to the passenger rear tire and the pinion pointed to the passenger front tire. I made gages to measure this.
I loosened the tranny mount, and modified it so I could get perfect alignment by running the string down the centerline of the crank and pinion, I then aligned everything and modified the tranny mount AND DRIVERS MOTOR MOUNT.
I use solid mounts, rubber mounts get twisted and eventually break.
I use a stock solid passenger mount, align the tranny where I want with a poly mount and lock it down and then cut and reweld a drivers solid mount so it slips in and out without putting torque on the drivetrain.
I went from a annoying vibration to absolute vibration free by stringing the drivetrain and then aligning everything.
Good luck and it worked for me

hugie82

Blackrat, I would try loosening the bolt on the poly pinion bushing and go for a test drive. If the vib changes then you know you're in the right place. It worked for me! I know it's a PIA to keep jumping under the car but this test is pretty easy (1 bolt) compared to the alternative

Dirtbuster1

I'm with V-Twin on this one. Leave the feelings in the past. Marck has tons of knowledge that is missing from here.

ImBatman

Norval, Thanks!! Does the angle look funny to you in the last 2 pics like I described?

good idea hugie82 I will try that too. Yeah my back and knees are killing me at this point. Now I know why people buy garage lifts. Not sure the wife will go for that though.....

Wade

TopGunn

I've seen this statement several times regarding alignment, just how are you able to move the tailshaft east and west without enlarging the holes in the motormounts and even then the fit will not be correct? Then how about the fan hitting the shroud, it doesn't take much movement on the tailshaft to make a big difference way up front at the fan.

sly vette

When this topic came up in the past and used norval's method for aligning the driveline and all is perfect!
Thanks Norval

427Hotrod

First Norval....I guess I missed some drama.........I knew you hadn't been around in awhile...but didn't know why. I for one miss you buddy....hope you consider hanging around again!

Blackrat- If I understand you correctly....you are seeing the driveshaft going at a *sideways angle* just like you would normally expect to see going *vertical*. Now that even sounds confusing to me! Anyway, for an example...the Dana 60 IRS in my car has the pinion centerline offset differently than a Vette normally does. When I put it all in there I could have centered it dead on...but I would have had 2 different length halfshafts. I wanted them the same. So my driveshaft goes at a pretty good *sideways* angle too. It doesn't hurt anything on mine...140+ mph regularly. U-joints don't care if they are going up and down or sideways. It's all the same to them. As long as angles are close to cancelling out....they work fine.

You're in the ballpark. I know most Tremec guys end up shimming trans as high as they can up to floorboards and then using washer on rear to get angles to work out.

The trans is the one thing that changed...so it's got to be there.

The motor IS smooth when you rev it right? You haven't changed pulleys or anything up front that could be an issue did you?


JIM

ImBatman

Thanks Jim! Nothing else has changed. I used the same balancer, pulleys, flywheel, pressure plate. Only three things have changed.
1. Clutch disk which is still a centerforce but a 26 spline now.
2. Transmission.
3. Driveshaft.

Last night I ran through the gears with the car on jack stands. Now here is the funny thing. The violent vibration is not there with the weight of the car. Now it does still vibrate the shifter but not nearly as bad as when the weight of the car is on the suspension and you are going down the road.

I can rev the motor with the clutch engaged and disengaged all the way to 4k with no vibration uh, other than that KICK *** cam you helped me with!!!

So my thinking is what changes when the car is on the ground? That leads me back to drive shaft angle again. Thoughts, ideas, suggestions, prayers????

Thanks
Wade

Dirtbuster1

Not to be a know it all, but with the car up on blocks, it has know load. With no load it changes all of the geometry of the car.

I have 27 years of vibration analysis background. I have seen a lot of weird that things, but changing the stiffness of the car changes everything. To prove this the car should react different to a speed increase, as well is a decrease in speed. Load verses no load. What ever your problem is, I feel it is driveshaft related. Balance or a u-joint that is binding.

Hope this input is welcome!