RIO68

Threads have said that the angle should be 3 to 5 degrees but should they both be the same plus or minus? If the trans tail shaft is 3 positive should the pinion be 3 positive or could one be positive and one negative or both negative??

Thanks for any direction here--

Garys 68

Google "driveline alignment" or setting pinion angle", lots of info.
BTW, corvettes with IRS are pretty close to 0 degrees.

7T1vette

It is not critical that they be the same...just that they are both less than 5 degrees (less is better, of course). The universal joint is designed to work up to that limit.

RIO68

OK but can one be positive and the other negative? Should both ends be positive or negative? Not mixed or does that matter--

7T1vette

As long as the jointed ends of the [main] driveshaft are not of significant length, it shouldn't make any difference. The two joints may need to be 'phased' properly to minimize vibration.

pauldana

if your drive shaft and tail shaft both point to ether one side of the car or the other, you will have vibration. ie.. rear end pointing left front, transmission pointing right rear, or visa-versa is good.

jerome1979

nose of you rear axle point up so your trans nose need to point down !!!

RIO68

Nose of pinion is down and so is the trans tail shaft on mine. I do not have one up and one down--both appear to be down.?????????

Garys 68

To raise the front of the diff, you can remove the rubber mount and cut it thinner. To raise the trans tail, add some shims under the trand mount.

pauldana

this angle is also very important...... again, not just the up down angle, but the left right angle....

wcsinx

Unless your car was wrecked, I don't see how that would change and/or how you'd go about adjusting it.

pauldana

I fought this vibration problem for years... and this is what it came down to, fixed this angle, vibration went away...
if you loosen all the mounts (rear, trans, engine) you can make this adjustment.

http://forums.corvetteforum.com/c3-t...lso-still.html

wcsinx

Yeah but there's no lateral adjustment in any of those mountings. Up & down sure but left to right? The diff. sure as hell won't pivot left to right with the way it connects with that huge transverse support. The motor mounts only hook up one way. I suppose the tranny mount could pivot ever so slightly. Did you replace the motor mounts? I suppose if one were busted, it should shift the engine laterally a teensy bit.

pauldana

I understand where you are coming from... it drove me nuts for years....but if you loosen these mounts up, you can get some adjustment, remember, 1/4" up front (engine) amounts to a LOT at the transmission tail shaft. As I said, I fought this for years..... did EVERYTHING first... balanced everything, replaced all that I could.... Vib still there.... did the alignment.... 90-95% of my vibration disappeared. p:-)

RIO68

Which is which?? Trans tail shaft points driver side or passenger side? Mine is an undamaged car but the trans is 700R4 with Bowtie Overdrive xmember so it might be off some?? No slot in xmember holes for the mount but the mount has slotted holes to move the trans over either way.

pauldana

as long as they are pointing different directions, at equal angles ~1-3* you are fine..... The problem is when they both point towards the SAME side, ie: both passenger side, or both drivers side

sly vette

As I understand it the trans should be parallel with the frame rails with a 1" offset to the pass. side. The trans should have an approx 3 degree downward angle and the diff should have the same degree angle but up wards. Equal but opposite in the vertical plane.

René K.

Hey guys, this is René from Germany. I currently got my driveshaft balanced to reduce vibrations. That worked quite well. However, looking at the trans and diff angles I think I have a problem... and I do not know how to fix it. I have a pretty original 72 Small Block with Muncie 4 spd. The trans is pointing 2° downward... but the diff is pointing 2° downward too. Now, all mounts (motor, trans and diff are brand new. How ca it be, that the diff is still pointing downward? The car never had an accident. I used high quality mounts... the rubber at the diff is roughly 1" thick. I would assume, the dimensions are correct so do I really have to cut it thinner to get the angles fixed?

Desperately looking for help - thanks!

Cheers...
René

ignatz

If you don't have a vibration you don't have a problem. There are two possible configurations for the angle at either end, as long as the angles are equal, either will work.

René K.

Hi Ignatz, thanks for your reply. Wel, actually that is what I am hoping. I had a true "apocalyptic" vibration in 4th gear... the car was smooth as silk until 3500 rpm... but over 3800 rpm brutal vibrations started almost instantly as if the car would fall apart. I never was brave enough to do more than 4200 rpm for just a second or two. Now, with the driveshaft balanced all these vibrations are gone and the car accelerates in 4th gear almost vibration free. Just above 4500 rpm (that is roughly 125 mph) minor high frequency vibrations are present (shift stick is slightly rattling). I do not know if this is still an issue (i am mostly driving on open roads and rarely on the autobahn... and if I do... mostly around 80 mph max) but I would like to understand if there is anything else I can do to further improve. So I thought about the driveline angles... however, they are difficult to measure. But I still have the impression the trans and diff are both pointing 2 degrees downward to the center of the car (instead the diff pointing upward).

What do you think?

Thanks!

René