Jeep rear end spring perch placement

[Dan Babb]

For the Jeep rear end (96 model), how far from end of the axle do you weld in the new spring perches.

With the pumkin in the middle, it's hard to get a good measurement and I want to make sure I get the perches centered and in the right spot.

I got my brackets cut off last night...just need to do some grinding and then I can weld in the new perches (after making sure I check the angle of the transmission end).

[Plymouthy Adams]

with the axle out of the car, one can use a plumb bob and mark the existing centers on the floor beneath and once you have this established you can measure and mark in/out as needed to obtain the spring perch width to match the existing rear axle..it is often difficult to get an absolute due to the curve of the carrier housing and any possible offset..

[Dan Babb]

So simple, it's genius. Thanks for the idea.

[NiftyFifty]

remember that the yoke isn't centre of the diff, it's offset if I remember so you need to make sure your getting that in the centre not just welding the perches exactly the same distance from the brake backing plate.

I had all that stuff written down, but again I have a 1ton so might be different with the bigger springs?

[Dave72dt]

I would think you'd want them the same distance from the backing plates to center it. Measuring from an offest center section would hang it quite a bit out one side. Be sure to set pinion angle before welding the perches on also.

[Dan Babb]

After grinding off the rear end today, I started to line things up. I'm not sure I'm doing this right.

I put some tape down and marked where the original brackets were.

I also marked where the pinion shaft is.

Then I put the Jeep rear end on the spot where the pinion mark is. My thinking is that I'd want the pinion in the same location...then mark the tubes where the perches need to go.

Some pictures:

My confusion is this. The axle tubes on the original rear are about the same length. The tubes on the Jeep axle are not...one end is shorter. So if I go with my logic of keeping the pinion shaft in the original location, the wheels won't be centered.

I'm thinking the best way to do this is put the rear end in under the truck and get the springs to be the same distance from the backing place on both sides. Then the wheels would be centered.

Is there an easier way?

[Dave72dt]

Measure your tape marks for the orig spring perches, subtract from the distance of the Jeep rear axle backing plate to backing plate, divide by 2. That should be the distance of the Jeep backing plate to the new perch location and should be equal on both sides. You can double check your work by measuring in between the new perch locations. Should be the same as your original tape marks.

Don't worry about the pinion location side to side. It's irrelevant. What is important is the up/down angle of the pinion relevant to the perch horizontal setting. Set your side to side , then the up/down. If you're using the old perchs, you'll need to know the degrees setting before removing them.

[Plymouthy Adams]

your logic is off..the position of the pinion is inherient to the axle for sure but your position of the axle to the frame equally is your concern for proper fitment to the body and wheel well opening...the slight offset of the pinion you show is of no consequence..it is so slight in comparison to many production vehicles...the phasing of your driveshaft allow for offset both up and down (pinion angle) and left to right (offset) and includes a margin of error to be several inches in difference in plane (the seperationg distance of the equal parallel lines)

just keep in mind that during your phasing the angle of the pinion and the output of the transmission should be equal imaginary lines

if you just concern yourself with postion of your perches equally to the backing plates and matching your original width...and match the angle of the pinion to your newly installed hemi/tranny..the rest will fall in place...the builder of the driveshaft will ensure the proper phasing position of the front and rear U-joint on the shaft and I assure you the offset of your pinion input will not be a problem..

[Dan Babb]

OK...It's sinking in.

Position of the pumpkin (being centered) isn't a big deal. Just making sure that the angle of the pumpkin is correct is the big thing. So if the tailshaft of the tranny is 3 degrees down, the pinion end of the pumpkin is 3 degrees up. Right?

Making sure the axle perches are the same distance from each backing plate will make sure the wheels are centered in the wheel wells.

[Plymouthy Adams]

Dan..go to this site..may make things a bit clearer in your mind..will show proper phasing of the rear offset and how you should not be worried in the least...

http://www.jeepfan.com/tech/tech_driveangles.htm

The Dodge Route Van is an example of extreme offset with zero complications using a single tube drive shaft...Dodge Dakota rear I am using is centered pinion..I also have used the Dakota front clip..the engines in this case are factory positioned some 3 inches offset to the right..in a truck without a full floor..no prob...but with the application of my station wagon body I have a full tunnel + a firewall already positioned for center placement..so I moved the engine on the Dakota frame to the rear about 5 inches and also to the left about 1 1/2 inches..this gave me an excellent drives haft placement in regard to the tunnel..I still have an offset..but it is still less than factory donor and still on the correct plane..moving the engine is due to the use of the V6 and the position of the imaginary center line of the front axle (wheel placement under the fender and maintaining the correct 111 wheelbase) stock mount location kept the engine to far forward of the firewall..so moving it back made engine placement more eye appealing plus gave me all the room I need for placing my radiator with minimum changes to the radiator support. All this was done using stock mounts and supports..just relocated as needed..there are many other small details using the clip but will not get into this here

[Dave72dt]

OK...It's sinking in.

Position of the pumpkin (being centered) isn't a big deal. Just making sure that the angle of the pumpkin is correct is the big thing. So if the tailshaft of the tranny is 3 degrees down, the pinion end of the pumpkin is 3 degrees up. Right?

Making sure the axle perches are the same distance from each backing plate will make sure the wheels are centered in the wheel wells.

Yes, you got it!