Novice driveline question

[tx99gtp]

I have been contemplating the installation of my rear suspension and rear end, but hesitant to proceed to fully install because of the drive line angles. I plan to mock everything up, but wasn't going to weld the spring pads on the axle until I had the front suspension in with motor+trans. I'm concerned about the drive line angles, but am I over complicating things? I see plenty of rolling chassis that have a rear end with no power plant. I suppose shims could be used to adjust the rear pinion angle after the fact. Thoughts or suggestions?

Thank you.

- Josh

[dwcsr]

Just tack the perches onto the axle and once its on the ground with motor and sheet metal then worry about the angle.

[_Ogre]

i didn't weld mine until i had the motor and trans in
once welded i went in and touched up the paint

[Jemezcrusher]

Really need to have this angle correct, and can't do that unless the vehicle is at curb weight. Engine and rear need to be on the same parallel plane.

If you can, leave the pads bolted in only and dont weld them up until you have it all together. WHen building my sedan I set the completed car on cinder blocks (under the tires) and tacked at the proper angle. I then dropped the rear springs and pulled it out and welded it up. Is a pain to do it that way, but turned out right

[72Mountaineer]

As per the local crowd, I set my rearend 4 degrees downward.

[Jemezcrusher]

Since my engine was 3 degrees down, I put the rear at 3 degrees up

[OrrieG]

Ideally trans shaft and pinon shaft should be parallel with about 3-4 degrees angle on each end of drive line. Universal joints need some angle to work correctly. But remember that the angle will change as you drive, go over drive way humps, roadway slopes, etc. so exact is not necessary. In my case the engine, trans and transfer case are all installed with 4 degrees down at the transfer output shaft. The rear axle was lifted 4" and installed with a additional 2 degree shim raising the pinion shaft angle. They are not the same. I drove the truck for 15 years as a DD, about 7-10K miles per year, with no vibrations and the universal joints were fine so I did not replace them. Most lifted trucks do not have equal angles or parallel shafts. This also include some extreme off roading that worked the joints pretty good. I like Ogres method.

[Speedbumpauto]

The problem with making the angles parallel in static is the pinion can only rotate up when power is applied. leaf springs can soak up 3 degrees and more during hard acceleration, and that is where one would like the angles to be parallel. I'm using a big tube 4 bar(link) and coil overs so mine is adjustable. Due to the urethane bushings in my set up instead of solid heim's, I gave gave mine a degree and a half down even though the link bars are equal length so suspension travel should not change pinion angle. I figure the difference will be soaked up during hard acceleration, which to me is the most important time. In drag race cars I've done with solid joints, I still left one degree down with the drive train dead level. Stuff WILL move.

[mr48chev]

I'd do as either Dwcsr or Ogre suggested. The tack welding is up to you but I've known some to rotate to the floor even with a tiny bit of moving them around the shop.

If you put it up on blocks under the tires for sake of your life and limbs don't use cinder blocks as those things are well known to crush under the weight of cars and drip the car/truck on the person working under it.

[Jemezcrusher]

Originally Posted by mr48chev

I'd do as either Dwcsr or Ogre suggested. The tack welding is up to you but I've known some to rotate to the floor even with a tiny bit of moving them around the shop.

If you put it up on blocks under the tires for sake of your life and limbs don't use cinder blocks as those things are well known to crush under the weight of cars and drip the car/truck on the person working under it.

Yep, plain cinder blocks would be a bit scary if sitting on their sides, but on their edges they hold up buildings.

I put 2x12 boards on top of them and had no worries. Spread the pressure out over the entire "edge" of the block

[gabe2000]

A quick fix is mock everything from transmission to rear axle. You'll get the proper angle and you see for clearance that nothing is hitting nothing.

[1958Warrior]

For rolling around the garage you should be fine just tightening up the U bolts after getting the rear end centered . being equal from the leaf springs out to the wheel mounting face of the axle,
As far as angel for the pinion , I have been trained to set -3* on diesel and electric motor shaft driven fire pumps for oil rigs high rise buildings ect., These are mounted on 8-12" I-beam frames, They will flex, when they start up there is a lot of torque , upon start up and they run till they get a signal to shut down, many lives depend on them, the -3* is required for the u-joints to function properly .

Now on leaf spring cars/trucks the frames and leaf springs ,basically the whole drive train, on these trucks will flex , how much depends on your engine and how you drive , a stock motor and a light foot actually will not require more than -3* . more torque and a heavier foot will require up to -7*.
A lot of people will dis agree, as well as with politics and religion and dating your second cousin.

There is a lot of flex in the drive line of a leaf spring car/truck , even some that have boxed and beefed the snot out of them for more HP, which is good, but they will flex and twist when the torque is applied .
here is an article you can read through:
2QuickNovas.com - Setting Pinion Angle
http://www.2quicknovas.com/pinionangle.jpg

http://www.2quicknovas.com/pinionangle.jpg