When doing the TH400 to TKO transition, I measured the vertical distance difference between the mounting tabs to the shaft centerlines on each, and massaged to cross member to get the exact same dimension with the TKO as I had with the TH400. In theory then, the driveline systems should be and behave the same before and after.

I got a digital angle meter, which shows the transmission was/is down 5.1 degrees. My pinion angle was up 1.1 degrees. I never noticed any vibration as it was with that large difference... but then again I never expected this car car to be very refined and smooth.

Anyway, I got some Edelbrock adjustable upper A arms and dialed the pinion up to 5.1, so the two shaft centerlines are exactly, exactly parallel. Man, that was EASY. The driveshaft is down 1.1 degrees, for effective u-joint angles of 4 degrees each.

Anyone else get crazy analytical on their angles? What did you see?

Not on a Chevelle but years ago on a 49 Merc my Brother had we messed with that a lot. Initially the rear U joint was tilted down (car was lowered) and front was up. car vibrated and he had the drive line balanced (waste of money) then we got a booklet published by Spicer on U joint angles and velocity flutuations. We got an angle shim for setting caster on a leef spring front end like an old jeep and tilted the rear axel so the angle was equal and oposite and all was much better. After that learning experiance we raised the rear back to stock height and modified the front MM (it had a chev v8 conversion) to lower the front so the angles where 2-3 degrees up from pinion and down at the trans so we where equal and oposite.
My recolection is the the Spicer book recomended 2 to 4 degrees angle and definatly equal and opposite, more would cause excess wear, less would pound the needles flat.
Somewhere more recently I read that they recomend very slightly more angle on the rear (fraction of a degree) so they would be equal when under acceleration, not certain that I buy that as the velocity fluctuation thing needs to be monitored at all throttle positions.

Dave, you recall that having to little u-joint angle beats the needles? Interesting. While studying for a mechanical engineering degree, I remember the weird kinematics associated with U-joints, and the requirement for each end of a shaft to have the same angles for constant velocity.

In general, what is everyone seeing with their angles? My transmission will aim downward more than the drive shaft, so it looks a little funny. That has to be the norm with a typical engine/trans combo, and normal ride height in the rear, doesn't it?

No one can confirm that my engine/trans 5.1 degrees down is in the normal range?

When doing the TH400 to TKO transition, I measured the vertical distance difference between the mounting tabs to the shaft centerlines on each, and massaged to cross member to get the exact same dimension with the TKO as I had with the TH400. In theory then, the driveline systems should be and behave the same before and after.

I got a digital angle meter, which shows the transmission was/is down 5.1 degrees. My pinion angle was up 1.1 degrees. I never noticed any vibration as it was with that large difference... but then again I never expected this car car to be very refined and smooth.

Anyway, I got some Edelbrock adjustable upper A arms and dialed the pinion up to 5.1, so the two shaft centerlines are exactly, exactly parallel. Man, that was EASY. The driveshaft is down 1.1 degrees, for effective u-joint angles of 4 degrees each.

Anyone else get crazy analytical on their angles? What did you see?


I do have to say, you've taken every pre-caution on this swap and from all the things you've tested im confident that you're going to have one smooth ride. I hope you reading all my problems helped, thats the reason i shared them all. good luck on your first voyage my friend :thumbsup:

With 4.2 degrees of u-joint working angle on my car the vibrations at 75+ mph with 3.42 gears were so bad my rear view mirror would point itself at the floor after 15 seconds or so. To say the vibes were bad is an understatement.

I tried everything I could... I adjusted my rear end from +5 to -5 in 1/2 degree increments and drove it at every step and the vibes would not go away... the working angle was just too great.

Now with a 1 degree working angle the drivetrain is almost as smooth as my 2005 daily driver... smooth as glass-- no more vibes. Took a lot of work to get the angles down that low though...

http://www.chevelles.com/forums/showthread.php?t=213271

For the least amount of vibration and highest speed operation you want the minimum working angle allowable, and 1 degree of working angle is the manufacturer's specified minimum... any less and the needles will not fully rotate which doesn't provide proper lubrication and they will fail prematurely. Spicer has all the info on their website.

Thanks Brian. I have been so careful because:

1. I always get too wrapped up in stuff I do. I tiled a shower once, it took 6 weeks but is the best tile work I have ever seen :D

2. I don't EVER want to have to take this system apart. :noway:

3. I don't want to do something stupid, that is my fault, and unknowingly bug the guys at Classic Chevy 5 Speed (again). Those guys have been absolutely incredible to work with, but everyone has to have a breaking point, don't they?

sorry, i think i ruined this thread...