The Stovebolt Site Forums The Shop Area Engine Shop 1940 Chevrolet pinion angle

Good evening all...Im replacing the stock rearend on my '40 1/2 ton chassis with one from a '70 nova. My question is what should the pinion angle be? Do i go 2 degrees negative on the rearend and 2 degrees positive on the tranny as a norm because i will now have an open driveline? or do i set it up like the original enclosed driveline angle-wise?. if its relevant the engine is a '54 235 with an M22 Muncie. also without the original bellhousing to the chassis in hand, i will have to "find" the correct crankshaft centerline to chassis angle. thanks for any and all help.

Put an angle finder on the bottom of the starter since the starter is that part of the engine that would run parallel to the crank. Read that angle and that is the angle to match the rear end to.

Run a modified 48-54 truck bellhousing. It will bolt to your enfine and the crossmember just like the original, and will also bolt up to the m22. Buffalo Steve and Jim Carter sell them with the brake and clutch pedal mounts just like original.

Just out of curiosity what gears and tires will you be running?

I have a 40 jimmy that will be running a nv4500 behind a 302 jimmy 6. 4.11 gears and 30 inch tall tires.

If the trans is X degrees down, the rear axle will be X degrees up.
Get one of those cheap angle finders, Speedway Motors sells them, along with Home Depo and others.

You want the pinion parallel to the crank, with 1 1/2 to 2 degrees offset under normal driving conditions. The u-joints need some angle for them to work properly or they wear to fast due to setting in one spot. Most joints can stand up to 4 or 5 degree of angle, thats why most guys install them around 2 degrees, its right in the middle of its range.
If the truck is really lowered, then the pinion could face down instead of up, as long as the two angles are still the same, this would make the drive shaft level in respect to the two end angles.

Race cars, angle the pinion down a few extra degrees so when it hooks up under a hard load, the pinion is at the right angle, with our low horsepower trucks, that shouldn't be a problem!
Joe

bigbadswingdaddy, im running 3.36 gears and will probably run 670-15 (28.4 diameter) tires which should let me run about 2385 rpm @ 60 mph.
thanks for everyones helpful input!