Rear End Pinion Angle

[RICH MUISE]

Having no experience with engine swaps, and trying to do as much myself as possible, I thought the easiest way for me to get my rear end up to snuff the way I want it (with posi and 3:55's and larger drums), was to send my unit out and having it built rather than buying and adapting a unit from a different car. I figured doing it that way would basically be a bolt-in. HOWEVER...a friend told me when the motor and tranny (current plans are 4.6 with 4R70W) are installed, the pinion angle will probably have to be changed anyways, requiring the rear end to be taken out, old spring brackets cut off and new ones welded on. He stated that would be the correct way to do it, but also agreed that in most cases, guys just don't go thru the trouble of changing the pinion angle every time they change engines. Any " o-pinions " from you racing guys out there? Also, should I have my housing shortened and how much? Are there any instances where you don't want to shorten the housing if your not going to run stock wheels?

[canadian_ranchero]

check with a truck alignment shop for the tapered shims they use to align front axles.they fit between the axle and the leaf spring

[4banger]

Put a protractor on the drive shaft. 3 to 5 degrees angle is what you need at ride height. Do not set at 0. To obtain the right angle, loosen spring u-bolts and shim the spring pad. That's it.

[shopratwoody]

What they said.....Why would it change?? My car has had many engine changes from
6 cyl to fe to 385's. It has been checked and never changed enough to worry about. Just check it.

[JPotter57]

I wouldnt mess with pinion angle unless you're setting it up to drag.  I think I set mine up at neg 5 or maybe 7 degree, so on acceleration, when the pinion tries to rotate upward, the angle is at either 0 or pos 3 degree or so, if my traction bars are working correctly.  More emphasis is placed on stuff like that than needs to be, as it really doesnt matter unless you are trying to hook on slicks and get that last 1/10th out of it....

[RICH MUISE]

Thanks for the input...or "o-pinions". I thought it was a case of over doing it a little, but just wanted to make sure. About shortning the axel housings?

[Lou]

Why would you need to shorten the axle housing, are you planning to "tub" the car?

[RICH MUISE]

No, no tubbing. I've just noticed alot of guys have said their axel housings were shortened and their cars weren't necessarily tubbed. I thought it might add more options as far as wheel choices because some aren't available with optional backspacing...such as the torquthruster model I preferred.

[Hoosier Hurricane]

A friend of mine, a retired Ford engineer, worked on late Mustang "wheel tramp" as they called it.  He told me that at ride height, the transmission mainshaft and the pinion shaft must be parallel to each other for the least amount of driveshaft vibration.  Also, the driveshaft front and rear U joints must be "timed" properly.

John

[JPotter57]

My last `57 had the rear shortened by 2.5 inches overall.  This one is stock so far, but will also be shortened about 2 inches to fit my 15 X 8 wheels inside sufficiently...More later, wife says its time to go, lol...

[shopratwoody]

All the years my car was drag raced the housing wasn't narrowed. Rear wheel openings were
cut for the slicks. Then put some of the sheet metal back in the openings and narrowed the
housing 1 1/2" overall the get the look I wanted

[Lgcustom]

Shopratwoody,

Did you move your spring pads also?

[shopratwoody]

After some careful measuring I took out 3/4" per side without moving spring pads. It has Americans
on it with 275 X 60's. The wheels have the standard backspacing. They're 8 1/2 wide. Seems like
they're stamped 3 1/2 backspacing. I used a tape measure on everything. Hope this helps.
Remember, my wheel openings are not stock