The Stovebolt Site Forums The Parking Lot Big Bolts Pinion angle question...

Howdy All --- I swapped the rear axle on my '46 to a Dana 80 to get more reasonable highway gearing. Just started hooking up a custom made 2-piece driveshaft and realized just how far off the pinion angle is. Like 12 degrees!

The steepest angle adjusting shim I have been able to find is 10 degrees. Does anyone here know any other "tricks" for bringing that angle down?

Cut spring pads off axle and reweld.
I made some thick wedges with a pin on one side and a socket on the other for one of my trucks. The concern is the wedge spits out if the angle is great. Forget what angle I made, but 12* might be a lot.

Like Grigg said, just cut the perches off and re-weld in the proper place. Weld a little at a time in different spots so you don't warp the axle tube at all.

Should be parallel to trans and engine in LOADED position.

Ed

Little more to it with a 2 piece shaft. Pinion likely should be parallel to the first driveshaft. First drive shaft is off parallel with the engine/trans by a very small amount. The U-joints need a little angle so the needles roll around and helps it last longer than if they never moved.
Check the Spicer manuals.

What diff was on there?
What was the angle?
Why would it be far off of other diff?
Where is the 12 deg?
What is custom about driveshaft beside rear shaft length and rear yoke?

The 2 piece shaft was built from scratch by a local drive train specialty shop. The front yoke mounts to an Allison w/driveline brake and the rear end is attached to a Dana 80HD. (Note...this is all in a 1946 Chevy school bus).

We set the angle from the engine & thru the tranny to line up with the existing center bearing and mounted the Dana using the existing 1998 Chevy 3500 angle.

According to my shop, the first (Jackshaft) portion's angle is correct but the rear section should be about three degrees below a straight line from the bearing to the rear u-joint to compensate for torque that raises that angle.

The axle already has a 3 degree wedge but is still five and a half degrees above the straight line which means there is a total of 8 1/2 degrees to get to level...then another three to get it the right amount below that line. 11-1/2 degrees total. I might get by with a 10 degree wedge (the biggest I have found) but that would only put it at half the recommended drop. I hope to avoid dropping and re-welding the axle so I may give that a try first, but I am open to any ideas at this stage.

Lets call the rear diff portion of the equation, the pinion. I think I understand the pinion it pointing up. You need to know the angle at trans to front shaft. The angle from front shaft to rear shaft and angle of rear shaft to pinion. The three angles should add to zero. I.E. +3 deg, -3 deg, 0 deg = 0. You need to read the internet re: Two piece driveshaft angles and get a good understanding without the shops numbers. Then see if the shop numbers make sense. If the front shaft is level, then the rear shaft is treated like a one piece driveshaft, equal and opposite angles is desired. 3-4 deg is the number to shoot for. You are right about the torque-up of rear diff. The rear shaft and pinion should be set up so that torque-up moves angle towards zero not towards increasing the angle. If I see your explanation correctly, you are way off. Shims are your choice but reweld is better. Would flipping the leaf springs do anything? I know it's a pain but you would have the axle off it less than two hours.

Instead of trying to explain.... and without pictures or diagrams..
Open the Spicer manual here and read the instructions and look at the pictures, they're worth at least 1,000 words.
http://www.stovebolt.com/techtips/driveline/setup/index.html

I question the 3* offset for expected torque/roll of the axle. I'd set it so the angles are all happy for normal driving, which requires very little torque. Also these springs are very stiff and short, not likely to change pinion angle much even in low gear pulling stumps..
If your shop is accustomed to working on drag cars that may explain their reasoning.

First link is non responsive. Second is 404.

Well that's frustrating, I'll dig up the new links and fix the tech tip. Dana/Spicer/Roadranger has switched the locations on us before.
In the meantime the titles, or even easier, the manual number can be easily searched for: DSIG3311 for example
http://www2.dana.com/pdf/DSIG-3311.pdf
Page 14 is the picture of what's going on in this discussion.

Thanks for the heads up.

pp 14 is interesting. They want front shaft parallel to pinion and they talk about "phasing" the yokes. Good info.

Thanks All --- I have been using those pages as a guide and after re-measuring everything, it looks like a 10 degree shim will put me 1-1/2 degrees below parallel to my jackshaft which I think should be OK. I am checking with local rock crawler places to see what I can find. If not, I can always go online.

Can't you stack them or weld one from 4 pieces of plate?

Just found some 10 degree. In case anyone else is looking (they aren't that easy to come by)...here are the folks who had them and seem pretty knowledgeable/helpful...

Pinion angle shims http://www.knowwhere2jeep.com/

I see 8 deg, I don't see 10 deg?

I had to call them to confirm, but here...

10 degree shims

BTW...they are pre-drilled with a 5/16 center hole for alignment

Will your spring center bolt head be long enough to still engage in the spring pad on the axle?
Or is the shim bolted on to the spring pack with the center bolt?

Make the diff flange perpendicular to the front half of the driveshaft (90 degrees), then tip it downward 2-3 more degrees. Pretty simple with a basic magnetic angle finder.

I plan on welding the 10 degree and the existing 3 degree in place onto the spring mount. Both have holes for the spring bolt.

Getting the getting the rear axle down within a few degrees of the jackshaft is the problem. It is off about 15 degrees. In fact, I will have to add about 1-1/2 to 2 degrees to the jackshaft to make it work even with the two shims. Like I said...way off.

Stacked shims... And welding them...
I'd ditch that plan and do it right by removing and rewelding the spring pads on the axle. You're plan may work OK but it's as much trouble and expenses as doing it the right way.

These pictures may help illustrate the situation.
They're shims I made for my truck after I too welded the spring pads on in the wrong orientation.

PICTURE 1
PICTURE 2
PICTURE 3

They're about 1/4" thin on the little end and close to 3/4" on the thick end, over the length this makes for 6° taper.
They have 3/4" diameter pins that fit well the holes in the spring pads, the pins are welded. Then 1/2" holes are drilled to fit the spring bolt head.

You're talking about a shim that is about 1 to 1-1/2" on the thick end, that's a lot of change.


Before I knew anything about driveline angles I thought it'd be OK to just remove one spring pad at a time and weld it on in the right place (moved over an inch to suit) keeping it parallel to the other pad not yet removed. Then repeat on the other side.
This was not at all a good plan when swapping axles... I later found out.
So that shim at 6° was my solution and not a bad one, but 6° is not a lot of angle.

Were I in your situation now with 12° or so to correct I'd start over with the spring pads on the axle tubes.

Grigg

Howdy Grigg --- The original pads were never removed and are at the same angle as they came mounted on a Chevy C3500. Apparently the one-piece shaft, 3500 axle just sits at a much lower angle than my '46 two-piece driveshaft. I did have to move them outboard just a bit but did that by simply adding a little material outboard on the existing pads.

And while I agree that re-positioning would be far superior, given my limited welding & fabbing skills, I think I'll try the stack first. Removing and precisely matching both sides is probably beyond my skill set.

From your build pictures, it's not beyond your skill set.

Not fair to compare angle of spring pads to pinion on one axle to that of a vastly different and more modern truck axle. They are attached on any axle to suit the entire situation from engine mounting, frame shape, springs and their hangers and locations, driveshaft(s).. Lots of variables.

Not very hard to weld on spring pads. I did mine back when I had very little welding experience, trial and error stick welding.. It turned out just great except for the pinion angle which would have been easy enough to set if I only knew.

You can do this I'm sure. You have already accomplished more difficult task while building the truck and will have even more challenging ones yet to come.

The Dana 80 has 4" diameter axle tubes. Same as AD model 1.5 and 2 tons and many other years. So you can scavenge the perfect spring pads to put on your new axle.

You have at times mentioned a Dana 80 "HD". I'm not aware of that axle, as far as I knew an 80 was always a plain 80? On the other the 70 was offered as a 70HD which is what I have, more or less a normal 70 center but with tubes and axle ends like the 80 has.