82Vette'ster

I知 finally almost finished putting my rebuild diff with 3.73 gears back in. This is on a 82 which has the stock 700R4 trans and Dana-44 differential. In the process I removed the trans cross member and trans tail cone to replace the speedo drive gear, which means the trans mount was removed and put back in. (it looked almost new). The car is up on 4 jack stands with a fair amount of room to move around underneath. I知 having difficulty determining if the transmission and drive shaft are aligned correctly. Just eyeballing it it looks like the tail of the trans is over to the passengers side too much.

What痴 a method of checking trans/drive shaft/diff alignment, in the car, body on, cross members, exhaust and all connected? I don稚 see any reference points on the trans to measure from. Are 2 of the trans pan bolts in a direct shaft alignment (700r4)? If I just center the drive shaft in the tunnel it might not be quite right. Anybody know the tolerance on this alignment?

Presently, the drive shaft in the tunnel definitely sits over to the one side near the trans and angles slightly as it goes back to the diff.. I have about a fingers width between the tunnel and the drive shaft on the one side and abut three times that on the other. So it looks like it needs to be moved over. At the back the diff input shaft/u-joint appears more centered in the tunnel.

I知 also having some difficulty moving the tail of the trans. I have the mount bolts loose, but I think I知 going to have to disconnect the exhaust again I think it might be keeping the motor from pivoting.

Thanks

norvalwilhelm

To check alignment of the drivetrain I made a bunch of plumb lines. I took about 2 feet of string and tied a big nut on either end. I hung one over the front of the engine, one over the output shaft of the transmission, one at the pinion yoke and another one at the back of the rearend but centered on the cover.
I then ran a string pulled tight down the center of the car tied at one end to the sway bar and centered in the front pair of strings hanging off the front of the motor and centered between the strings at the back of the rearend cover.
Then I checked the tailstock of the transmission and the pinion and found they were off alot from this center line.
I then made a tool for the pinion that went on the pinion with the driveshaft out and a long pointer that was fixed in this plate on the pinion and found it didn't point anywhere near the transmission output shaft.
I did align everything so it formed a staight line but that involved moving the rearend to change where it is pointing.
I was pointing alot towards the passengers front wheel.
I solved all my vibration problems.

norvalwilhelm

Here is a poor shot. It is of an old tire combination but if you look closely you can see the strings.

jeaux

How did you move the rears position?

82Vette'ster

Thanks Norval,

I'm going to give the string lines a try. I'll just need to find where the shaft center would be on the 80-82 batwing cover.

I like the pointer idea also. I think I could make a pair of pointers out of a couple old U-joints. Just replace the grease with epoxy and weld a rod as a pointer to the center. To get it square, I'll just need to mount it and rotate it, then adjust it till no run out (wobble).

Thanks again.

JoeRags

I need to align mine as well. There is definatley a visible offset that needs to be straightened out. Since my rear is mounted, and not really going anywhere, how can I adjust the tail end of the tranny?

Thanks

Joe

Brown78

My tranny tail shaft drifts to the drivers side of thr tunnel.

jeaux

Are we moving tranny or rear end for alignment?

69vettester

Someone correct me if Im wrong, The impression I get from the pro's, is , The trans and diff arent supposed to be in line, neither up and down or side to side. There is a specific angle built into the layout so the ujoints will work right. If everthing is in straight line, the shafts ujoints will bind or otherwise fail, Its an engineering thing.
If Im wrong or missing the point I stand corrected.
Tom

Twin_Turbo

You are quite correct, the tranny isn't supposed to be straight back both in a horizonal way but w/ opposing angles at the trans & pinion but also sideways when looking from the top, the yoke is offset to the passenger side so there's always an angle @ the driveshaft.

JoeRags

yea, that does sound about right, but mine is way out of whack horozizontaly. I would take a picture to show you guys, but my car is about 1300 miles from me. Its been 2 weeks (5 months, 2 weeks to go) and I miss my baby already.

82Vette'ster

I hung a set of string lines to see where everything was pointed, at least as viewed from above. I couldn't put one on diff input because the D44 housing has the front support cast in, I ended up placing it on the drive shaft just in front of the cross member, which will create some complication. The rear spot (in line with the shaft) of the D44 was a bit difficult to determine (it痴 not in the middle), but I had a spare to measure.

TT, From what I understand of general prop shaft setups (drive shafts etc.), the two angles made with the shaft should be equal and opposite such that the incoming and outgoing shafts are parallel but not necessarily in line. So should I be able to get close by running 2 string lines, one from the engine front to the trans tail and another from the front and rear of the diff. Then check to see if they are parallel?

I assumed that the trans (700r4) and the engine crank are axially in line without an offset, But I知 not sure that痴 true.

Twin_Turbo

yes the 2 angles should be opposing, looking from the top it's a no brainer, just make sure the transmission sticks out dead straight and you have it set up correctly since the pinion comes out dead straight also (if not you have a frame problem) So yes, they are parallel.

from the side looking at the horizontal position you can adjust these by shimming the pinion mount and the trans itself.

How are you going to run strings from the engine to the rear and from the diff to the front? Just use a carpenters square on the driveshaft and the yokes.

Yes the trans and engine centerlines (crank and in & output shaft) are axially inline.

82Vette'ster

Sorry, I wasn't real clear. I was using the plumb bob method and attached short strings with weights on the ends from the 4 points along the drive train (bottom of balencer, trans yoke, rear of drive shaft, and back of the diff. Then using a taught string line, I lined up the end of where the strings hung down. But I don't know how accurate it's going to be. The back of the trans going side to side is the only real adjustment I was trying to make. I was hoping to do this without pulling the drive shaft again.

I can see getting a square on the back of the trans but It would be tuff doing something on the rear, there's not much room in there. Maybe it's enough to just point the trans straight down the tunnel?

I considered making a pointer out of a old U-joint with a rod welded to it. Maybe I'll try that this weekend.