69 Vette Driveline
Thread Starter
Staging Lane
Joined: Dec 2009
Posts: 78
Likes: 0
69 Vette Driveline Hey guys I am doing a swap on a 69 Corvette using a GMPP 425HP E-rod and a 4L60. I have the Engine and trans in the hole and now need to fab up a trans cross-member. The car was originally a 4 speed so it has the weld in trans member and somewhere along the way someone swapped in a auto trans so the cross-member has been hacked up pretty good. so there is no original reference points left.
Is there any one out there that knows where the engine and rear diff angles would be or should have been from the factory?
I poked around for a while but was unable to find any reliable information on the Vette specific Drive line angles. Do the same principles apply to the independent rear as say in a Chevelle? should I just match the front pinion angle in the opposite direction to the rear?
Thanks In advance
Is there any one out there that knows where the engine and rear diff angles would be or should have been from the factory?
I poked around for a while but was unable to find any reliable information on the Vette specific Drive line angles. Do the same principles apply to the independent rear as say in a Chevelle? should I just match the front pinion angle in the opposite direction to the rear?
Thanks In advance
They were pretty flat from the factory, both at about 0 degrees.
Most end up with a down angle on the motor with LS swaps, but you can push the trans as high as possible.
Changing the diff angle is complicated on the C3 IRS in matching a down angle trans to up angle diff. I was able to raise the pinion up by cutting the diff rubber front mount isolator to about 1/8" thick. No vibrations.
In theory you could match a down angle motor to down angle diff since the diff is fixed to the chassis. But I've never tried it.
Most end up with a down angle on the motor with LS swaps, but you can push the trans as high as possible.
Changing the diff angle is complicated on the C3 IRS in matching a down angle trans to up angle diff. I was able to raise the pinion up by cutting the diff rubber front mount isolator to about 1/8" thick. No vibrations.
In theory you could match a down angle motor to down angle diff since the diff is fixed to the chassis. But I've never tried it.
Thread Starter
Staging Lane
Joined: Dec 2009
Posts: 78
Likes: 0
They were pretty flat from the factory, both at about 0 degrees.
Most end up with a down angle on the motor with LS swaps, but you can push the trans as high as possible.
Changing the diff angle is complicated on the C3 IRS in matching a down angle trans to up angle diff. I was able to raise the pinion up by cutting the diff rubber front mount isolator to about 1/8" thick. No vibrations.
In theory you could match a down angle motor to down angle diff since the diff is fixed to the chassis. But I've never tried it.
Most end up with a down angle on the motor with LS swaps, but you can push the trans as high as possible.
Changing the diff angle is complicated on the C3 IRS in matching a down angle trans to up angle diff. I was able to raise the pinion up by cutting the diff rubber front mount isolator to about 1/8" thick. No vibrations.
In theory you could match a down angle motor to down angle diff since the diff is fixed to the chassis. But I've never tried it.
Keep in mind, the C3 IRS with solid mounted dif is a different animal from a live rear axle that moves up and down. I was able to push my trans up as high as possible, minimizing that angle, and then raise the pinion to try to match. It's not perfect, but within 1 degree and no vibrations. There's a C3 over at vettemod that raised the pinion by modifying the front diff mount by moving the mounting holes.
And be sure to check angles on all 4 wheels. My 68 conv. flexed A LOT on jack stands.
And be sure to check angles on all 4 wheels. My 68 conv. flexed A LOT on jack stands.
