63 rear pinion angle

[Henry A.]

We are playing with the rear pinion on my restored 63 coupe. We have put a Tremec 5 speed in and have a vibration in the drive train. So, we are looking at the angles of the trans and the rear pinion to see if it is a driveshaft issue. What we need is the factory specs on the rear end pinion angle...does anyone know the pinion angle spec?

Thanks.

[John H.]

Re: 63 rear pinion angle

Henry -

I've never seen it published anywhere - it's not in the Chevrolet Engineering Information Package or in the detailed Chevrolet A.M.A. submission either. All those two sources address is the engine installation angle (3* down).

Typical driveline design practice is to have the pinion angle parallel to the output shaft angle, which would put the pinion angle at 3* up. Automotive U-joints never run at a zero angle, as that will brinell the trunnions.

[Stuart F.]

Re: 63 rear pinion angle

There have been several articles published recently in different Corvette publications that addressed the various concerns with installing the Tremec 5-speed and kits. Can't put my finger on them tonight, but if no one else has brought them forward by tomorrow, I'll see what I can find. I specfically recall discussion about vibration issues/concerns. One conclusion I do recall, is that the Tremec people provide excellent Technical Support. I trust you have availed yourself of their service as well.

Stu Fox

[Henry A.]

Re: 63 rear pinion angle

Thanks, we appreciate the input and help...we seem to have chatted with everyone on this subject. Our vibration is from about 1700 RPM up, with a load...at 75 MPH on the highway in 5th it is smooth as silk...but getting there with a hard pull is uncomfortable. We also have a strong harmonic with the vibration.

In measuring the angles we are finding that the rear pinion is pointed down as is the transmission. This is obviously causing the two to cross over...or create an "X" instead of being parallel. We believe this to be our primary issue. We are currently trying to change these angles enough to get them to parallel or as close as possible.

So, John, if the 3* is correct, would the General have a plus and minus to allow for the change in the angle under tourqe?

Stuart, if you have any info....I would appreciate it. I have heard that the battle we are fighting is common...If someone has some insight to a solution we are at a point to look at any and all possible solutions. Our vibration is constant under load...some I have heard of are at a specific speed or RPM. Our is constant.

Thanks for all help and input. Henry

[Tim S.]

Re: 63 rear pinion angle

Henry,
Did your car have the vibration before the Tremec install? If my thinking is correct, there should be no change under power due to the fact the Corvette rear center section is fixed. My experience with the Tremec trans itself has been good. Currently, I have a 67 Nova with a Tremec supplied by one of these firms that offers a complete "kit". Not happy with the kit including the pinion angle supplied by the "engineered" crossmember. I do know the Tremec is a tall transmission compared to a T-10 or a Muncie.With that in mind, does your kit have the trans pointing down to fit? It seems to me you will need to shim the trans up in order to restore pinion angle. I suppose that could be a struggle due to the space restrictions in the stock tunnel. I won't bring up any brand name kits on this thread.......but........I know one that is overpriced and under engineered.

Tim

[Henry A.]

Re: 63 rear pinion angle

Tim, you are correct. Since the rearend and the transmission crossmember are fixed all we can do is shim to max tolerance without hitting the trans tunnel or having the u-joint at the pinion hitting the tunnel. We have been able to gain some but we are not to parallel. Thanks.

[Stuart F.]

Re: 63 rear pinion angle

Henry;

I have looked for the magazine articles I eluded to in my previous post and, so far, have only found one in the July 08 Corvette Fever Mag. I know there were several more and will continue looking (maybe not Corvette mags). The CF story did not have much of value toward your problem, leastwise not anything that you probably don't already know as far as you've gone. They mentioned removing the tunnel insulation. Also, they were dealing with a newer engine transplant which shouldn't affect things.

I strongly suspect you will have to emphatically pursue tech support from the kit provider. They should have all the answers from their vast experience - seen it all, etc.

Stu Fox

[Dick W.]

Re: 63 rear pinion angle

As long as your angles cancel each other out, you can eliminate that as a source of vibration. Normally driveline angle vibrations will come in at a certain speed, be felt for 3-4 mph and go away. They will come back in at twice the highway speed i.e. 35 mph, then 70 mph.

A little information on driveline vibrations http://www2.dana.com/expert/wc.dll?cvsp~Decrits~

And another source to do some calculations
http://www2.dana.com/expert/wc.dll?cvsp~Dedsang~

These are from the Dana "Expert" site for trucks, but the theory and calculations remain the same for cars.

Remember you are dealing with some offset also on the driveline. Complicates it just a little more