You need a machined surface that you can reference to the centerline of the pinion, like the rear cover surface. It doesn't have to necessarily be parallel to the pinion. A magnetic angle finder works well for this. Your just taking your measurement vertically instead of horizontally.

 

I do have the magnetic angle finder. But the cover is curved. I'll go look again and see if I can get a vertical angle on the edge by the bolts.

Anyone else's input on what horizontal surface is useable would be appreciated.

John

 

Thats why I mentioned "machined" surface, you will have to remove the cover and place your angle finder on the actual surface of the rear end housing. Also, as gear head mentioned, that will work as well.

 

Use the front of the yoke. The front surface is machined flat and is perpendicular to the pinion center line.

 

Okay, I put a piece of flat metal in the gap between the yoke and pumpkin snout and got an angle off of the extended edge of the metal held against the back of the yoke (didn't want to drop the driveshaft or take cover off).

That angle is within 1/2 degree of the angle taken off the horizontal winged flange and the back rim of the cover edge. The bottom flat part of the pumpkin seems to be about 1 degree up angle compared to the other three measurements.

I think I can get the pinion/driveshaft/trans angles close now.

Thanks,

John

 

Are you checking your angles with the suspensiuon loaded?

 

I checked them with the suspension loaded first. Then I jacked the chassis up so the wheels were off the ground and unloaded and noted how much the angles changed just from being unloaded.

Then I made adjustments to the control arms to bring the pinion angle down three degrees and the driveshaft up about 1 degree -- should be almost parallell. First I over shot, then in correcting back it seemed like the control arms were about in the same place I started, but the angles where closer.

Let the car down off the jacks and the angles were almost back where I started. I need a lift, not jack stands if it takes this much trial and error.

John

 

I've used some wooden blocks 6" thick under each wheel so it's easy to slide my phat body underneath.
I measure the angles on the flat part of the yoke where the u-joint cap is.
So what's the angle down on your tranny and the angle up on your rearend?

 

I've done this a couple of times before, but am looking at it again because I started hearing a popping noise under the car when making 90 degree turns onto another street. Also, I just put 1.3 inch taller wheels on the rear. I haven't noticed any vibrations -- just checking things out.

In the past I have run 2 degrees down to the rear on the transmission output, about 1.5 degree down to the rear on the driveshaft, and 2 degrees up toward the front on the pinion.

Car is mild 350 with auto transmission just used for cruises.

When I got under the car I found the angles had changed and noticed the lock nuts on two of the four adjustable heim fittings were loose. The heim fittings on one control arm were not in the same clock position and one end was binding a little causing the pop. I could reproduce the pop by twisting the control arm. So, today I hoped I had straighened everything out just to find out I was in the same position I started, except for getting the pop rectified.

I have tried blue thread lock on the lock nuts but I think it is the control arms rotating loose, getting longer, and pushing the pinion into more up angle. The whole system was fabbed my some good ole boys, its isn't stock.

I'll try again tomorrow.

John

 

What exactly do you have?
Sounds like you're describing a 4 bar with coil overs.
I think you set the rearend pinion different on a 4 bar. Sorry, bad memory. Just remember it being different.

 

I just added a picture of the rear suspension to my photo gallery. You can see it is home grown.

The original suspension was truck arms with coil springs. Shocks were mounted outside the springs. I had no experience with building cars when this went to a shop to be street rodded. The shop said this system would give adjustability, lower stance, and good road handling. The front end is a clip off a 1988 Cutlass.

It does handle good and the car tracks straight, but the ride is stiffer and there are a lot of squeaks and groans. Most groans are from the front springs that were cut to lower the front end. I am thinking about going to the QA1 front coilover conversion kit to get rid of the cut springs and have lowering adjustability.

Feel free to critique.

John

 

Intersesting!
Like a 4 link ladder bar. You must be getting some binding having the pivot of the control arms on the same plain as the mounts for the truck arms.
How are the truck arms attached to the rearend?
Your pinion angle could be changing constantly. The truck arms are usually bolted solid to the rearend and the pinion angle set with shims.
I'm not an expert. Maybe you should start a new thread to ask about your suspension set up.

 

Okay, added another photo showing the "floating axle mounts", brass colored mounts. The U-shaped base of the mount is welded to the top of the truck arms and the axle lays in the U. Then another U-shaped piece comes over the top of the axle and bolts to the bottom U-shaped piece. The axle rests in the circular area through the middle of the two U's with a little bit of free clearance most of the way around so the axle is free to rotate. The red control arms resist the rotation and maintain the desired pinion angle. The panhard bar keeps the axle from shifting sideways. The panhard bar is horizontal when the suspension is loaded.

A couple of builders have looked at it and say it is certainly unusual but doesn't appear to bind as the suspension moves up and down.

John

 

It might not bind but those red bars don't have a hope in controlling your pinion climbing or dropping.and the angle changing constantly. You need a ladder bar and even then they flex a bit. Also your panhard bar is set up wrong. Supposed to be the frame mount on the drivers side, attached to rearend on the pass side.
If it where mine I'd mount those truck arms solid to the rearend, set my pinion angle when I build the mounts, change the panhard bar and cruise.
Here's a link to ladder bars.
http://www.honestcharley.com/manufacturers/pete-jake-s/chassis-parts/rear-ladder-bars.html

 

THey also sell used truck arms on ebay. Off nascar cars.
Trailing Arm 45" NASCAR Truck Arms Chevy Truck | eBay

 

That panhard bar in the last photo is the original configuration on the 1939 Olds.

John

 

Here's a guy in your neck of the woods that sells ladder bars and can custom make them if you want.
Home Page

 

I think I would just go back to the truck arms and take the other bars off. The truck arms work very well by themselves. It would make your suspension much simpler. If those housing floaters work the way I think they do they will eventually cut into the axle tubes.

 

Yes, I have wondered about the mounts wearing a groove in the axle, but can't see any sign of it after 21,000 miles.

How are axles usually mounted on truck bars? The original configuration had U-bolts over the axle with some kind of padding under the U-bolt. But the Olds Cutlass axle that is on it now is a smaller diameter and of course the original U-bolts wouldn't hold the axle from rotating.

John

 

You can buy new perches to weld on the rearend (20 bucks a pair) and a spring shop can make you up some new u bolts (maybe 10 bucks each x 4 = 40 bucks)to clamp it all togethor.

 

So you have the little 7.5 10 bolt in it now? If you are going to be making much power then I would recommend getting rid of that too. The 7.5 has 2 5/8 axle tubes where most other GM rear ends have 3 inch tubes. The truck suspension had perches welded on the bottom of the axle tubes and u bolts that went through the arms and perches.