The Stovebolt Site Forums The Shop Area Engine Shop Rear end swap.

Hi Guys,
Well I got the rear axle from my 77 GMC welded onto the existing spring mounts from my 49 GMC. I read to keep the pinion angle slightly down by about 1 degree. That is because when you accelerate the front of the axle will rise. I took it to a qualified shop and had it done. He measured the angle between the existing spring mounts on my 49 axle and axle cover, then welded the 77 axle on at the same angle. Only problem is that it is pointing down by alot more than 1 degree. I would say close to 7. The axle floats and can be lifted up to about the right elevation. I was wondering if that would be okay to hook the d/s up to the lifted axle. Or should I get him to re-weld it. Or can I remove the bolt that the axle floats on and adjust it that way? Thanks in advance.

kskt4

The pinion angle can be adjusted by using a tapered shim between the spring perch and the spring. Most driveline shops or places that do heavy truck repair should have something that can be adapted to work. Be sure the weight of the vehicle is on the springs while you're checking the driveshaft angle, or you're likely to encounter problems with the angle changing once everything is in the running position with the wheels on the ground. If it's really way off, the only option is to cut and reweld, but you need to check everything out with things assembled before you start modifying again. Pinion angle problems will cause oddball vibrations, and short universal joint life unless they're corrected. Next time, clamp everything together before you weld, and mark the housing for the correct fit, then disassemble it and weld the spring perches to your marks.
Jerry

Thanks Jerry.