5th gear vibration issue
 

Ok, so I have been having this problem with the car, and I think Kevin at CAR figured out that where the car is in motion in 5th gear, it will vibrate at higher speeds. It will do it down low a bit, but it's more pronounced at 85mph and higher. The tranny came from Keisler, and they told Kevin it was out of warranty, but they didn't shut the idea of them fixing it either. Don't know about that yet. My question is, do they have to rebuild the tranny for this, and what could be causing the issue? It's a TKO-600 in case you anyone was wondering.

First thing that comes to mind is driveshaft.

I second that! My problem was pinion angle.

Pinion angle was good, brought the car up too 85 in forth gear with no vibration, 5th had the vibration at the same speed. I also thought the driveshaft as well.

Can you feel it through the shifter?

I have not really noticed, or tried to notice if the shifter is vibrating more then normal. Maybe I should.

I have the same problem only at 65ish and I feel in the shifter. I'm thinking drive line but could it be the pinion angle?

I think the pinion angle is 2-3 degrees, the way it's should be. They made sure and checked it.

Several things come to mind to check...

mismatched front to rear u-joint working angles

excessive u-joint working angles (this is the cause of my high speed vibration, I need to raise my entire tranny tunnel for more driveshaft clearance so I can raise both the tranny angle and rear end angle to minimize the total u-joint working angles.)

runout issues on either slip yoke or pinion yoke

worn & loose output shaft bushing in transmission

driveshaft runout / balance problem

If it's speed related and not RPM related as you said (the vibe occurs at a given speed no matter what the gear) that pretty rules out the clutch & flywheel as the problem and points to the driveshaft on back as the source of the problem.

It could also be a wheel, axle, or bearing problem too.

It's not speed related. in 4th gear at 85mph it doesn't vibrate at all. In 5th at the same speed it does vibrate. I have new wheels and I did watch them being balanced and they are lazer straight. Does the drive shaft spin more in 5th gear at the same speed as it would be in forth gear at the same given speed? I don't think that's the case, but I don't know.