Narrowed 8 3/4 Rear standard dimensions

[440Swinger]

I am narrowing an 8 3/4, which is pretty striaght forward but I have a few questions that probably have pretty standard answers I wanted to see if anyone was familiar with.
First this is going into a 1971 Swinger with the springs moved inboard and wheel well brought into the frame rails.

1. I have searched for the pinion offset from center and can't find any info in writing.  When I measure the center section it looks like it is 1-1/4"  offset. When I measure the spring perches from the center of pinion I get a 2" difference which I though meant it would only be a 1" offset.
2. With many people running inboard springs are there already dimensions for the spring perches off of the pinion center that people are using. I have figured them to be 3.5" in on each side, but I'm not using an A-body rear so I'm starting fresh from the pinion center and wanted to get a double check, if its out there, and make sure the driveline is located correctly.
3. I thought I read once that the Car Dana 60 axles and the 8-3/4 axels are the same, So if I narrow the 8 3/4 then blow it up, can I narrow a Dana to the same dimensions and use those axles and brakes on the Dana? 

Any help would be apprieciated, I feel fairly comfortable with my measurements but can't find anything in print to confirm.
If anyone has any suggestions on measuring tips I would like to here them also. I have a Pinion center locating template from Dutchmans coming that I think helps eliminate the problem of measuring with the offset from the front of yoke to the axle housing.
Thanks a lot.

[smallbigblock]

 

I have same questions

[dodgeboy]

Go here and read. http://www.moparts.org/Tech/Archive/axle.html.  I believe the pinion offset on a mopar is 2.25". If you have not cut the axle housing yet I don't think you need to be concerned with the pinion offset. Just find the center of the uncut housing and make all of your measurements from there. Since both axles in the 8.75 are the same length you just have cut an equal amount off both sides of the housing and the pinion offset will automatically be correct.

Roger

[BigSlim]

I purchased this rear used, it is out of a Dart that is running low 9's. It was done professionally by a local guy who owns a frame shop.
Let me know if you need ant measurements, I'll be glad to help out.

[440Swinger]

Thanks a lot.
Can you let me know what the distance is from the center of pinion to the cener of each spring perch.
Are the axles the same length?
I'm also curious about what the overall length from Axle flange to axle flange is.

[robx4406]

1. I have searched for the pinion offset from center and can't find any info in writing.  When I measure the center section it looks like it is 1-1/4"  offset. When I measure the spring perches from the center of pinion I get a 2" difference which I though meant it would only be a 1" offset.

Find the center line of the housing and make your cuts/shortening from there. If you do that, no need to worry about recalculating offset.

2. With many people running inboard springs are there already dimensions for the spring perches off of the pinion center that people are using. I have figured them to be 3.5" in on each side, but I'm not using an A-body rear so I'm starting fresh from the pinion center and wanted to get a double check, if its out there, and make sure the driveline is located correctly.

My car has the perches at 35.5" center to center. Housing is 53.5 with each perch 9" in from the flange.

3. I thought I read once that the Car Dana 60 axles and the 8-3/4 axels are the same, So if I narrow the 8 3/4 then blow it up, can I narrow a Dana to the same dimensions and use those axles and brakes on the Dana? 

IIRC, car Danas had 30 and 35 spline axles. A 30 spline may work as 8.75's are also 30 spline.

[BIG DOG]

If this was me ....I would make the rearend to fit your car I wouldn't go by what someone else has .If you have your springs moved in to your frame Your spring pearch centers are going to be some where between 34" to approx 37" depending on how much wider you make the back of the springs compared to the front.So to make it easy lets say they are 36" .You would work off the center like dodgeboy said and mount the pearch at 18" to hole center and at the proper angle for your pinion.Going by Bigslims rear your measurements may be off as it is out of a different car and you don't know how or where the springs were moved to .Maybe the spring centers on his car is 34" maybe 37" with the rears wider or narrower you could be out up to 1 1/2" or more .Measure your car and figure it out!

[dodgeboy]

I don't know what width you need but let's make a practice run and narrow a rearend to a drum to drum of 50". Since the housing flange to drum distance on most 8.75 axles is 2.5" (A bodies are an exception) you will need a housing flange to flange distance of 45". I have just completed one of these and mocked it up today to make sure I have the correct fit.

The picture below shows how to find the center of the housing. The mid distance between the two studs with the nuts on them will be the center of the housing. I have a piece of wood notched with a hack saw where the center of the housing is located and I use this point to make all my measurements. You can see it in the picture with a tape measure hooked in it. So the distance from this point to the housing flange should be 22.5". Cut your housing to give this length with the bearing support welded in. It's as simple as this.



The axle shaft length would need to be 50" minus the 1.5" thrust block divided by 2 for an axle length of 24.25".

This is the simplest method I have been able to come up with. Hope this helps.

Roger

[BigSlim]

440 SWINGER,
Sorry it took so long to get back to you. Work has been crazy and its been so wet that i have to mow grass at every opportunity. At any rate, I measured the rear: Its 36" on center of pin holes on the perch pads. Center line of pinion is 18 3/4" one way and 17 1/4" the other. Let me know if you need anything else. I can do pics if needed.

[440Swinger]

Thanks guys,
I didn't realize the housing is centered between the frame rails and that locates the pinion amd makes the axles the same lenght.
I have the dimensions figured for my car and just need to make the cuts and weld it up.
I just got my aluminum pucks on Friday and will be putting an axle order in next week.

I apprieciate the info.