12 Bolt rear end saddle angle

[Chevys10dr]

Hey guys,

Hoping someone can help me out, I'm switching over from leafs to trailing arms, the rear end I have is setup for leafs, I need to weld on trailing arm saddles, what is the angle that they are welded on or are they parallel to the yoke?

[Zeroman]

I've got a differential sitting in my garage that I am rebuilding.

It is not parallel to the pinion shaft. The saddles tilt downward towards the front of the truck.

Not sure how I would measure the angle.

If someone could tell me how to measure the angle, I'd be happy to tell you what it is.

[mechanicalman]

Originally Posted by Chevys10dr

Hey guys,

Hoping someone can help me out, I'm switching over from leafs to trailing arms, the rear end I have is setup for leafs, I need to weld on trailing arm saddles, what is the angle that they are welded on or are they parallel to the yoke?

I believe parallel. I would assemble it without welding, with the truck fully assembled with bed on and at operating weight, and at the suspension height you intent to leave it. Then rotate the pinion parallel to the trans output shaft or carrier bearing then weld it in that position. Of course make sure the panhard bar is in place and that the rear-end is centered in the truck to your satisfaction. (you might have to use a bottle jack and a mallet or get creative with a come-along).

I have never done this before, just thought about it. I would for sure defer to more experienced fabricators on this forum and use my advice, in this case, as a last resort if nobody else replies.

[Zeroman]

mechanicalman, I think his question was concerning the saddles on the axle tubes, not the pinion angle.

Here is a pic of my differential I am rebuilding. You can see the pic is taken directly over the pinion shaft which is pointing straight down, and the saddles are tilted down towards the front.

[IMG][/IMG]

[mechanicalman]

Originally Posted by Zeroman

mechanicalman, I think his question was concerning the saddles on the axle tubes, not the pinion angle.

Here is a pic of my differential I am rebuilding. You can see the pic is taken directly over the pinion shaft which is pointing straight down, and the saddles are tilted down towards the front.

[IMG][/IMG]

My bad, I thought he meant pinion angle parallel to the yoke of the trans, as the goal of getting the brackets at the right angle is to achieve proper pinion angle as parallel to the output shaft location (see picture). Maybe I should have started on a more basic level so here goes.

Getting back to the brackets, they need to be installed at an angle to get the drive-shaft correct, and that means the pinion needs to be parallel to the trans output shaft or primary drives-shaft if a 2 piece shaft. When I said assemble it without welding, I meant put the brackets on the axle shafts without welding, then rotate the pinion to the proper angle (see picture). The panhard bar is going to center the rearend, but best check placement before welding in case something needs to be done to the panhard bar and that depends on ride height (unknown factor).

The angle of the brackets vs the angle of the pinion, by itself without respect to the drive-shaft angle, is a crude method at best. The best he could hope to do is to try to get close to what you have, and that might not be right for him depending on his drive-shaft configuration and ride height.

If he welds them on wrong resulting in an improper driveshaft angle, he can get a custom adjustable cross-member or shims between the brackets and the trailing arms to correct it.

[Chevys10dr]

Thanks guys, I was hoping there was a factory placement angle, so that I could weld up and install, the setup I am using uses the stock setup and no pinion angle change needed.

[mechanicalman]

Originally Posted by Chevys10dr

Thanks guys, I was hoping there was a factory placement angle, so that I could weld up and install, the setup I am using uses the stock setup and no pinion angle change needed.

Good luck, have fun, and stay safe.

[Zeroman]

mechanicalman, your explanation is spot on in regards to setting the pinion angle.

Chevys10dr, I am going to set up my diff with some magnetic mounted levels later today, and should have a stock angle for the saddles.

[Chevys10dr]

Thanks Zeroman, that would be awesome, greatly appreciated

[Lees68GMC]

Here's my 12 bolt 1975 rear installed in my 68 GMC SWB. These are the stock spring saddle locations and angles resulted and as you can see I'm going to have to install 4 degree angle pinion shims (Speedway) to get the nose of the pinion down. Hope this helps. I did nothing to lower the rear except remove some leafs. Main thing to worry about is oil starving the pinion bearing at such an angle. Something that works good to See straight lines and visualize angles under your dark truck is one of those cheap Stanley laser levels the Wife uses to hang pictures on the wall. That and degree levels should do it.

[Zeroman]

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.

As mechanicalman stated though to set the saddles perfectly you would have to have everything in alignment.

Hope this helps.

[calvin78612]

Originally Posted by Zeroman

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.

As mechanicalman stated though to set the saddles perfectly you would have to have everything in alignment.

Hope this helps.

Can you show a pic of this ? Not sure I understand what flange your talking about,plus 13.5 sounds like a lot.

[Chevys10dr]

Perfect, gives me somewhere to start, thanks again.

[geezer#99]

Read this.
http://www2.dana.com/pdf/J3311-1-DSSP.pdf

Or this
http://www.drivetrain.com/parts_cata..._problems.html