rear axle sadle location help

[bbcmudtruck]

I need help figuring out exactly where to weld new saddles to my axle. Originally the axel was under a coil spring truck. Someone cut the coil saddles off and welded leaf spring mounts to it. Well, I've since switched back to a coil spring frame and need to locate my saddles. I'm pretty sure the axle isn't centered in the frame. The frame is bare at the moment with only the front suspension in place, so there isn't any weight on it. Does anyone have measurements handy?

[bbcmudtruck]

I found what I was looking for. It took quite a while of digging through old threads though, so here it is for future help. http://www.67-72chevytrucks.com/vboa...d.php?t=217421

However one other thing I need help with is pinion angle. I believe I will need the full weight of the vehicle on the chassis with the motor and trans in place before I can set the pinion angle. Does anyone have any guidance?

[Sklptrljay]

Do a search here- http://67-72chevytrucks.com/vboard/s...d.php?t=624445

I just did this yesterday and it worked great. A few 2x4's and and angle finder is all you need.

[Sklptrljay]

I just read what you said more carefully, you don't have an original to use as a template. Like I said, I have mine sitting out still from yesterday so if you need me to measure anything let me know.

[bbcmudtruck]

That's s great idea! I think I actually have an old 12 oem coil spring axle I can go grab. I'm installing ECE's trailing arm cross member as well as their trailing arms and 6" drop springs. Should I set the pinion angle back to oem or wait until I get weight on the frame? Or will the new aftermarket parts correct the angle for me? Thanks a bunch!

[Sklptrljay]

Originally Posted by bbcmudtruck

That's s great idea! I think I actually have an old 12 oem coil spring axle I can go grab. I'm installing ECE's trailing arm cross member as well as their trailing arms and 6" drop springs. Should I set the pinion angle back to oem or wait until I get weight on the frame? Or will the new aftermarket parts correct the angle for me? Thanks a bunch!

I'll tell you what I was told.....Don't over think it.

As the truck height drops and the trailing arms rise the angle self corrects for the most part. Unless your looking to have it be for serious performance don't worry about it, and set it to stock.

I'm not sure if the ECE arms will change anything. You might want to give them a call.

[bbcmudtruck]

Ok thanks for your help!

[bbcmudtruck]

Ok so after working through a few problems, I've managed to mock up my rear axle saddles and bolt it to the trailing arms. Here is the problem that I'm running into now. I took some string and marked out the center of the frame on the front, middle and rear. If I run a string down the centerline of the frame, the string passes through the trailing arm cross member perfectly. However the string does not line up with the pinion on the rear axle. The axle sits over to towards the passenger side of the truck around 3/4 of and inch or so. Should I locate the axle saddles so that the pinion is centered and aligned with the center of the truck? I feel very comfortable that I have the axle saddles mocked up in the factory location. There are two problems I see. The driveshaft will not pass through the trailing arm cross member or it will be very, very close. The second thing that concerns me is that using the pan hard bar to pull the axle over will bind the trailing arm bushings as well as put stress on the coil springs, bending them towards the driver side of the truck. My common sense tells me to locate the axle with the pinion in the center of the truck, rather than offset to the passenger side. Input and advice is greatly appreciated!

[Sklptrljay]

Is the yoke centered on the rear end or is it offset. If it's center then your frame could be off. There are guys with tons of knowledge about these issues, and I'm not one of them. You might want to post this question in the drive train part of the forum.

[bbcmudtruck]

The yoke is off center. From all the reading I've done on here, that is normal. I guess what I'm trying to determine is whether or not to move the saddles over an inch or there about to put the pinion in the center of the frame. I suppose I don't understand why I would want to position it off to the passenger side, then turn around and pull it over with the panhard bar? That is going to put stress on the coil springs as well as the trailing arm bushings. I'll post this question down in drive train forum and see if anyone else has any knowledge on this. Thanks for all of your help!

[Sklptrljay]

If the yoke is designed to be off center I'm sure there is a reason the engineers did it.
I would definitly check with someone who really knows what they're talking about before changing the geometry.
Good luck, let me know what you find out.

[Zeroman]

What year model truck do you have? I have a 12 bolt out of a 1972 in the garage, I could measure it up for you.

Let me know.

[haysonj]

I would measure from centerline to backing plate front and back to make sure it tracks straight. Mine ended up off 1 inch and you could see the truck was off when you followed it. I ended up moving the rear axle over.

[Chevys10dr]

For the pinion angle here is what I found

Re: 12 Bolt rear end saddle angle
I set up my diff with the flange on the back of the case vertical "0".

The resulting angle of the bottom of the saddles was 13.5 degrees with the leading edge of the saddles down. This would be for a stock ride height suspension.

[Sklptrljay]

So I checked my 12 bolt and 10 bolt. Both pinions are offset the same amount to one side. I think you shouldn't worry about that and just get the ends of the rear end equal distance from the edge of the fenders.

[bbcmudtruck]

I can't thank you guys enough for your help! I think i'm going to mock the saddles up in the stock location and then bolt the bed onto the frame. That will let me know how the wheels sit inside the rear tubs.
I just don't understand why you would want to mount the axle off to the passenger side, then use the pan hard bar to pull it back over! Doing that is going to put stress on the trailing arm bushings as well as the coils. I just don't get it, what am I missing here? Does something funky happen to the location of the rear axle once all the weight of the vehicle is on it?

[Sklptrljay]

As long as your saddles are equal distance from each end, and you have the correct distance between the saddles you are good to go. Forget about the pinion being off center because obviously GM designed it that way.
You have a 2 piece driveshaft I am assuming.
The driveshaft from the carrier bearing to the diff on a short bed is roughly 4', so your only talking a quarter inch per foot angle. That shouldn't be rubbing on anything.