Driveshaft angles

[jacksprat1599]

Hey guys,
I swapped in a 14 sf in my 89 suburban and I have pretty bad vibration at 25 & 50mph.I bought a magnetic angle finder at home depot and measured 11 degrees at the pinion joint and 7 degrees at the X-case joint.Is that enough out of phase to cause vibration.Also I'm not sure I am measuring correctly so someone correct me if I am wrong.I measured the angle of the driveshaft and then held it as level as possible with the pinion and then added those 2 together to get 11 degrees,Is this right? If it is I am thinking I need about a 4 degree shim to stop the vibes.Oh ,the axle had new perchs put on it so they are not the factory angle.

 

[Rolled]

Try lowering/raising the t-case. It takes about 15 minutes.

You can drop the tcase quite a bit and you should be able to raise it up some too.

I'm not sure which way it needs to go (mine had to be dropped) but go get a hand full of washers and play around with it /forums/images/graemlins/smile.gif

 

[jacksprat1599]

I have a suburban not a blazer so I have plenty of drive shaft length.I just need to know how to measure the u-joint angles so I can shim the rear pinion angle.Oh yeah, my truck is stock height no lift.I think that t-case drop aproach is to allieviate drive shaft angles on blazers lifted 4 in or more because of the short rear shaft.

 

[big83chevy4x4]

if you drop your tcase, it will help lower the angle between the two.

also to figure out what shim you need, measure the driveshaft from center of ujoint to center of ujoint. then measure from center of axle tube to pinion ujoint. divide the two. then multiply the angle differnce between the ujoints to the number you get and you get the shim you need.

 

[bigblock44k5]

Do you have a CV on the rear shaft? If not, both angles should be equal to phase properly. If you have a CV the shaft to pinion angle should be 0.

 

[jacksprat1599]

No cv shaft.I realize the u-joints need to have equal but opposite opperating angles.That is the point of my original post.I would like someone to tell me if the way I got my angle measurements is correct.I don't want to drop the transfercase as I don't beleive this would help in my case.My truck is totally stock except for the 14sf in place of the 10-bolt.The 14sf has the perches welded on in such a way as to point the pinion down more than the 10-bolts was so I need to know how to measure the angles at the transfercase and the axle so I know how out of Phase they are and what shim to order.If I had a welder I would just cut the perches and rotate the pinion up to make the angles equal but I don't so I need shims.

 

[fatbob]

I checked my angles from the yokes before I had a driveshaft in it. I turned the yoke vertical and put a framing square against it, Anything with a true 90 degree angle will work, then I set my homemade angle finder on top of the square and measured it. Jack up the rear and turn a wheel untill that yoke is vertical and measure. There might be an easier way with everything hooked up, but this is the way I set the angles when I welded the perches on.
Good luck
Bob

 

[bigblock44k5]

sounds like you did it correctly