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I used a magnetic protractor to measure the driveshaft angle vs the flat casting on the rear end. As the car sits normally the rear is 2 degrees above horizontal and the drive shaft is 6 degrees above horizontal which gives a difference of 4 degrees. Is there a standard specification for this angle? I ask because the transmission crossmember has no shims now and I have some driveline vibration as I accelerate. I am wondering if the drive shaft angle is too great. Shims would straighten out the driveshaft to pinyon angle. I cannot figure out how to measure the driveshaft angle vs the transmission yoke so I don't know that angle. I know there are many sources of vibration other than driveline but have heard this is a common problem. The driveshaft was balanced by a driveshaft shop and the T-10 and rear end were recently rebuilt. Engine is 340 SHP.
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Re: C-1 crossmember shims
Greg -
Start with 1/4" of spacers to drop the trans crossmember down a little and try that first; both of my 57's needed 3/8" of shims to smooth out completely. -
Re: C-1 crossmember shims
Yes a matter of trial and error adding shims as John said, installing new repro rear springs could need that attention also in this areaComment
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Re: C-1 crossmember shims
Is this the same for powerglide cars? I find I am having a vibration in my driveline at speeds of 50-55 mph
DonComment
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Re: C-1 crossmember shims
I'm chasing the same problem. Assembling my tools and trying to figure out how to attack this. Right now I can't get in the garage because there's 15" of snow in front of it. It's an old style door that opens outward, not a roll type that opens up.
1. What magnetic protractor did you use? Manufacturer and model #. Have you seen the Sears 39840?
2. Where's "the flat casting on the rear end"? Can you describe that better?
3. I believe the 4 degree angle between the rear end and the driveshaft is about where you want to be. Now you want the transmission/yoke to driveshaft angle about the same.
4. With the "X" member in the way, you can't get up to the back of the transmission to measure the yoke vs. the driveshaft. But I'm told that there are other surfaces on the engine that are in the same plane as the yoke. The easiest one to measure is the bottom of the engine, or the oil pan mounting rail. You know the angle of the driveshaft agains the horizon. Now measure the oil pan rail angle against the horizon.Comment
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Re: C-1 crossmember shims
Yes You need to play with shims . then drive the Corvette.Many times it's the trans rear bushing worn on stick or PGComment
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Re: C-1 crossmember shims
Protractor was from one of the big box stores like Home Depot. Dial is about four or five inches in diameter. Pictures on the packaging show it to be used to measure angles when bending conduit. The flat casting I refer to (bad choice of terms) is the flat surface on the bottom of the pumpkin. It appears to be parallel to the pinyon. Your suggestion about using the oil pan rail is a good one. It seems it would be parallel to the ouput shaft on the transmission. I am going to use the crossmember shims that Corvette Central and others are supplying to reduce the angle. The shims appear to be about 3/16 inch thick. I haven't measured them exactly.Comment
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