The Stovebolt Site Forums The Shop Area Engine Shop 12 degree pinion angle??

I have a '55 1/2 ton 4.11 posi rear that I
bought from someone over a year ago.
I was checking this thing out the other day
and the location of the perches put the pinion
angle at 12 degrees. (when perches are level
the pinion shaft points up 12 degrees)
It is definitely not modified. I thought this
seemed unusual. Any guesses as to what the
application was?

It would only mean something if the area of the spring where the axle bolts to was also level. Checking the axle without it sitting in a vehicle with a normal load, means nothing.

Angle schmangle, only thing that matters is that the pinion shaft is as parallel as possible with the output shaft of the trany! That is, with normal everyday weight, sitting on all fours.

Drivline angularity is a science initself. Drivelines have to have an angle or Ujoints dont work right. I cant remember the exact science, but it depends on the length of drivline too, and the angle of the engine transmission. If i remember right, a just straight driveline without and angles will vibrate like heck, because of the speedup, slowdown effect of a ujoint...Dang im gettin old... I used to know the science and set up big trucks that had frames stretched, and drivlines lengthened and shortened... oh well... LOL.. i think i could draw a picture..but cant here...hehehehe

check this link
http://www.pirate4x4.com/tech/billavista/PR-shaft/index2.html

5 to 7 degrees positive is usually the norm.

I realize you set it up in the vehicle
to match the tranny output shaft angle.
I just thought the angle seemed unusually
high compared to all the other rears in my
garage. Which were anywhere from 3 to 7
degrees. I thought it was maybe a special
application, so thats why I asked if anybody
knew what it might have come out of. I
don't even have a truck for this rear...I am
currently putting together a 3/4 ton.

At this point, it has nothing to do with the tranny angle. What if it was a four link rear end?? What is the angle of that?? You don't know 'cause the links could be set at any adjustment. Four link brackets could be welded in at any angle. Same with the spring perches. They could be welded in at a 90 degree angle to horizontal. That would be fine if you had a weird spring set up that way. Where stuff is welded doesn't matter until you have an application.

Now, if you are doing a comparison to what you already have in your truck, well then yeah, the spring perches are odd. What angle is needed for a 1975 3/4 ton Chevy van?? Who knows?? Maybe that 12 degress at level is proper for that 1975 van? It means nothing until you have something to put it in.

As far as what it came out of, could be anything! I mean, it's like, "All the bolts in my garage are 1" long and I found an 1 1/4" long bolt. Anybody know the application?" Could be anything! But as far as comparing it to what you have in your garage, at the very least, we can eliminate that kind of vehicle.

Maybe it came off of a monster truck? Well, that's what grinders are for. To make it fit to what you want it to.

MNSmith,
Thanks for your input, but you don't understand
my question. This is a 1955 1/2 ton 6 lug 4.11
posi rear. Non-modified from stock. It's not a
four link and it didn't come out of a monster
truck or a 1975 van. It came out of a 1955 1/2 ton vehicle. There were 10 models in the 1/2 ton
commercial line and 3 different wheel bases.
I was wondering if someone knew what model it may have been. Also unusual is the fact that is a posi and a 4.11 ratio, not a typical 3.90.
Maybe it was in a model 3442 with 104" wheel base and walk in delivery body or just a pickup
and you could get 4.11 posi as an option? I don't know. I was hoping one of the task force guys might happen to know and would chime in.
It's not really important...I just like to know
what kind of parts I got. Guess I'm kinda funny
like that. Also helps to know if I ever sell it.
Guess I'll put it back on the rack and let it
accumulate dust for another few years.

Doh! Another case of me not reading so well!!

I tend to be the same way, wanting to know where things went and what they came offa.

Sorry I wasn't of much help!

A good fabricator could make anyone think it was original.I'm not saying it has been fabricated,pictures may help. You seem to know that it is out of a 1955 1/2 ton, does the previous owner have any clues ? I'm the same way,i want to know what i have.