Centering new rearend ?

-
mbaird

mbaird

mbaird
Joined
Dec 10, 2005
Messages
9,341
Reaction score
6,555
Location
Boise, Id
I have a newly resized 8 3/4 that still needs to have perches welded on.

Besides pinion angle is there a proper way to center the housing relative to the driveshaft vs springs vs frame ? Were they offset or centered from the factory ?

I've done a search and find nothing related to this.

I am having a driveline shop do the final install but I need to drive it over there (gently) ... But am mostly curious .
 
Not sur this helped with proper centering of housing on springs... If it did I assume the reference to 43" on center is the part..... Does that mean I should have the pinion 21.5" from each perch center ?
 
Chrysler centers the housing in the car. Don't worry about the pinion offset. Each spring pad will be equidistant from the corresponding axle flange.
 
I just measured my rear end and I found that the pinion is not centered between the spring pads. The center line of the pinion measures about 2&1/2" closer to the pad on the passenger side. I thought that was odd so I measured it THREE times to make sure I didn't tell you wrong info. This rear is for my '67. The distance from the spring pads to the brake is the same on both sides though.

Here is a link to another thread with some more dimensions that might be useful.

http://www.forabodiesonly.com/mopar/showthread.php?t=120497
 
Hey all,

I'm currently building a Ford 9" for my '72 Scamp and am really struggling with how to set the housing up. My wife is using the Scamp as a daily driver, so I can't pull the current 7.25 to check measurements.

I'm aware that factory is 43" between spring perches, so that's easy. I also know the overall width I want between the drum brakes (57 1/8 factory, so I'm chasing 55 1/8). I'm really struggling with where the pinion centreline should be in relation to the spring perches etc. The Ford diff has it dead centre between the perches currently.

1967 'cuda says above that the Mopar pinion is offset to the passenger side by 2.5 inches. Can someone confirm that measurement for later A-bodies?

Would really appreciate some advice on this.
 
ValiantHardtop said:
Hey all,

I'm currently building a Ford 9" for my '72 Scamp and am really struggling with how to set the housing up. My wife is using the Scamp as a daily driver, so I can't pull the current 7.25 to check measurements.

I'm aware that factory is 43" between spring perches, so that's easy. I also know the overall width I want between the drum brakes (57 1/8 factory, so I'm chasing 55 1/8). I'm really struggling with where the pinion centreline should be in relation to the spring perches etc. The Ford diff has it dead centre between the perches currently.

1967 'cuda says above that the Mopar pinion is offset to the passenger side by 2.5 inches. Can someone confirm that measurement for later A-bodies?

Would really appreciate some advice on this.
Click to expand...

ValiantHardtop,
As I stated, I thought it was odd. So, I'd really appreciate if others could see if they get the same measurements that I did too.
 
............yes the pinion is offset to the pass side as the motor was offset to clear the steering box....ofcourse that means the tranny is over also.....kim...
 
Thanks Kim. I wonder if it's offset the opposite direction if it was a right hand steer vehicle...
 
Mine is still left-hand drive, so my measurements will match yours!

Would be great if someone could confirm the 2.5" offset to passenger side measurement though - I have been searching this forum and the rest of the web for days and have also seen references to a 1 3/8 offset.

Thanks for your help!

NH
 
ValiantHardtop said:
Mine is still left-hand drive, so my measurements will match yours!

Would be great if someone could confirm the 2.5" offset to passenger side measurement though - I have been searching this forum and the rest of the web for days and have also seen references to a 1 3/8 offset.

Thanks for your help!

NH
Click to expand...

I think the spec might be the same. My pinion is about 2&1/2" closer to the passenger side which would mean it's offset about 1&1/4".
 
Now I'm confused... Would you be able to give your measurements between spring perch centres (probably 43") and then distance from each perch centre to the pinion centre?

By my calculations (if I'm understanding you properly), these should be 24" (43/2 + 2.5) and 19" (43/2 - 2.5)...
 
Give me a couple of minutes, the rear end is on saw horses in the garage.
 
On an 8.75 rear measure 21.5" from the center of the housing, weld works well, for your perch location. Pinion offset is taken up by the 3rd member. That's why both axles on 8.75 rears are the same length on our cars unless someone goofed.

I often will move a rear slightly one side or other to get equi-stickout of the the flange end in my wheelhouse. If there is any variation, it's usually not much.

You driving it over with the perches loose? I wouldn't do that.

RHD no idea, never dealt with one.
 
Wow, that is pretty close! Although I was in Omaha a few months ago, so it's not out of the question.

Thanks for confirming those measurements.
 
1967 'cuda said:
View attachment 1714712558
Click to expand...

I believe that measurement of @2 1/2" pinion offset is incorrect. Pinion offset is 1 3/8" but if you do the math, the one side at 21 1/2" minus 1 3/8" and the other side at 21 1/2" plus 1 3/8" makes these measurements @2 3/4" different. The pinion centerline is @1 3/8" toward the passenger side measured from the centerline between the perches, period!
 
howToOrderTop.gif

B=52 1/2 (A-body)
PO= 1 3/8"
 
Great info ! So there should be equal lentpgths of housing protruding beyond each spring on the ends ? The pinion position in the pig offsets for driveline alignment ?

Just to clarify.....
On a Ford 9" it is a more obvious offset ...
 
mbaird said:
Great info ! So there should be equal lentpgths of housing protruding beyond each spring on the ends ? The pinion position in the pig offsets for driveline alignment ?

Just to clarify.....
On a Ford 9" it is a more obvious offset ...
Click to expand...


Yes, equal lengths protruding beyond each perch. Yes, a ford 9" is more offset in relation to the center third member, but the pinion centerline should be adjusted to match the 1 3/8" Mopar offset which means different length axles from side to side.
 
mbaird said:
Great info ! So there should be equal lentpgths of housing protruding beyond each spring on the ends ? The pinion position in the pig offsets for driveline alignment ?

Just to clarify.....
On a Ford 9" it is a more obvious offset ...
Click to expand...

If using a Ford rear with a different pinion relationship to center of vehicle, then that rear end should be modified to compensate to match the offset that Chrysler designed. But for the 8&3/4 you say you're using now, you should be in good shape. Just hold to that 43" center to center measurement for the spring pads and keep them equal distance from the ends of the axle tubes (unless you'd like to fudge it slightly to compensate for tire centering in your wheel wells). Of course this is assuming that you have not used a spring relocation kit. Get your pinion angle set and you're good to go.
 
1967 'cuda said:
If using a Ford rear with a different pinion relationship to center of vehicle, then that rear end should be modified to compensate to match the offset that Chrysler designed. But for the 8&3/4 you say you're using now, you should be in good shape. Just hold to that 43" center to center measurement for the spring pads and keep them equal distance from the ends of the axle tubes (unless you'd like to fudge it slightly to compensate for tire centering in your wheel wells). Of course this is assuming that you have not used a spring relocation kit. Get your pinion angle set and you're good to go.
Click to expand...

Correct, if you want to use a 9" factory length (no modifications), not having the 1 3/8 offset is OK, but if building a 9" from scratch you should figure in the Mopar offset.
 
You must log in or register to reply here.
-

Back
Top