Rene

First off I went through the driveshaft investigation five years back and got a lot of good input including measuring the angles and that there were two configurations. Here is that

https://www.corvetteforum.com/forums...aft-angle.html

Since you're stock you don't have to know about what I think was called the W-arrangement but it was a pleasant surprise since I was able to fix an otherwise difficult alignment problem. Here's a reference as the other info from 427Swede is now a 404 not found.

https://www.machineservice.com/wp-co...ine-Clinic.pdf

The two angles need to be relatively close but not necessarily dead on. The digital gauge worked well for me and if you difference one measurement to the other you can see how close they are. There are some pictures in the thread.

However with all the rotating components back there your vibration problem could be any of a number of things: tire imbalance, too much camber, tailshaft wear, driveshaft bent.

Note also that there is an angle difference in plan because the motor is offset. That is built into the car. There is a little play in the transmission mount so I suppose if you were tracking down second order effects, wiggling the tailshaft around might fix that.

You haven't described what changes you made, if any, when the vibration first appeared. The gear shift rattling is not that unusual.

If you can get your vette as quiet as my wife's BMW you are a better man than most of us!

 

Correcting Pinion Angle


http://forum.grumpysperformance.com/...hp?f=71&t=1889

 

Ignatz, thanks for your detailed response. I read carefully through the other thread you added as a link and the document on the second link. What I did on the car before was/is... tires perfectly balanced, new engine mounts, new transmission mount, new differential mount, transmission and differential have been updated with complete new bearing sets... chassis setup is completely according to specifications, flywheel and clutch are also checked and without any imbalance and the half shafts are in an almost horizontal position. Having all this in mind my last idea was to check the drive shaft. As I mentioned... the balancing added 15g to the diff side, 5g to the trans side and an 0.6mm bend was corrected. In addition, the joints at each end of the drive shaft were replaced in addition (the "old" ones hat a little play (0.2mm axial).

Now, with all I have read so far in your comments and the linked other threads I assume that obviously a Corvette C3 has a W-arrangement of angles (factory original). If this is the case it is exactly what I have on my car (trans 2° down and diff 2° down... and, btw, driveshaft angle 1° (higher end at the trans). So, this would mean my car is OK!?! Even if tried, i would not see how I could raise the front of the diff to get to 2° "up" to achieve a Z-arrangement. This would require a 4° change and even with cutting the front carrier bushing down to a minimum I could never get to these 4°.

Conclusion... Corvette C3... W-arrangement of angles... factory original... OK... no vibrations... no reason to change anything... Basically what you wrote: "If you do not have vibrations you do not have a problem!"

Hope my conclusion is right.

Thanks again for all the comments, explanations, recommendations... time and patience with the "German Guy".

Cheers...
René

 

This is she... my white beauty!

 

Great picture, and no castles like that around here!

 

If it ain't broke don't fix it my friend. So I have never measured the driveline angles in my corvette. To me pinion angle should parallel tailshaft angle. That's a rule of thumb for hot rod engine swaps. Plenty of information on the internet about driveline angles and you need to sort it for yourself.

 

Hi Cardo, obviously there is no "issue" I could detect (apart from the drive shaft which was corrected), however, the damaged trans and diff bearings I fixed some time ago must have had some root cause. Currently there are no vibrations anymore after the drive shaft balancing. I just thought about the angles because I wanted to exclude them as potential additional root cause (and to avoid future damage again). What I learned during my investigation is two things... many people corrected diff angle upward by cutting the front bracket rubber. However, this would mean, that there was/is a design issue with this part. Obviously two opinions and documentations are available for angles... the Z-arrangement (trans pointing down and diff pointing up)... and the W-arrangement (trans and diff pointing down). To me it seems that the majority of people believe in the Z-arrangement and even consider changes to the original design of parts to achieve that (means, the original set up was a W-arrangement). Others do not modify the set-up and also have no issues. This leads me to the conclusion that the Corvette C3 (should also be true for C2) has a W-arrangement as design intent right from the factory. For that reason and other comments I think I will leave the set up as is is right now (hoping, no damage will occur over the next thousands of miles). Finally... again the current angle values of my obvious W-arrangement... Trans 2° down... Diff 2° down... Driveshaft 1° up towards the Trans. This also should work in terms of working angles for the u-joints.

Cheers...
René

If anybody still has comments... please continue to post them... I believe this is still going to be a very interesting conversation!