Pinion Angle With Super Stock Springs

[Bruzilla]

I once again made the mistake of changing two things at once... which one should never do since when a problem arises it makes it just that much harder to figure out... but I replaced the 8.25 rear in my 74 Roadrunner with an 8.75 rear from an E body, and I added Super Stock springs. Everything bolted up fine (after a LOT of issues with the front spring hangers), but the pinion angle on the rear is wayyyy off. I would guess it's a good 10 degrees too high.

So my question is this: is the cause of the pinion angle issue due to the springs, or because I used the same angle for the spring pads as the E body's were at and they are different from a B body? I had to remove the stock pads and weld new ones on .75" outward to fit the B body.

 

[moparnation74]

Call Dr Diff....10 degrees ouch!
http://www.doctordiff.com/


http://www.moparts.org/Tech/Archive/axle/8.html

 

[HEMI-ITIS]

What angle is the rear shackle at now? Are you happy with the ride height??

 

[PurpleBeeper]

Dang it.... I had a similar issue years ago, but I was just installing super stock springs & used the upper holes of the multi-hole longer front shackles to get the back end low enough I could reach into the trunk (barely exaggerating here... the rear bumper was belly button high). Anyway, my pinion angle was way off & I put some 2-degree or 4-degree (?) shims in there and is wasn't even close to getting the pinion angle right. I finally went to the stock/lower holes of the front hangers (corrected my pinion angle) and put 2" lowering blocks in and everything seems kosher now.

Now to your problem..... I've heard that you should put new spring perches in loose or just tack welded slightly, set the pinion angle, then weld them in solid... but sounds like you're past that now. From my spring fiasco I learned that the super stock springs themselves don't change the pinion angle. I wouldn't guess the E-body rears would have a different spring perch to pinion angle than a B-body (they're so similar), but I don't know that for sure. Geez.... if your angle is that far off you might have to do it again. If it's that bad.... drop me a PM and I'll make you a sweartheart deal on an extra set of spring perches I have if I can dig them out of my garage. Calling Dr. Diff is a really good idea.

All this makes me think....do you have the correct front hangers in there? (sorry if that's a stupid question)

 

[69L48Z27]

?...... I had to remove the stock pads and weld new ones on .75" outward to fit the B body.

It sounds like the perches got welded back on at that angle. Here's what I would do:

- remove the rear and leave the spring in the car installed. Level the car, make sure the rocker is level. Measure the angle of the leaf springs where the pad makes contact at the pin. If everything is symmetrical move on. This just insures the springs aren't all messed up and asymmetric.

- install the rear on the springs with the perches cutoff and not welded to the axle. Rotate the rear nose down around 3-5*. Weld it all back together.

Compression should not effect pinion angle that much once they are compressed but you want that 3-5* (down) while the car is on its wheels at loaded ride hieght.

Also confirm you have some angle on the U joints.

Pinion and isn't going to be that dramatically different from car to car. Measure your old axles perches relative to the pinion if you can. That would be a good way to get them reattached out of the car too.

 

[Bruzilla]

All this makes me think....do you have the correct front hangers in there? (sorry if that's a stupid question)

Spring hangers... what a pain in the *** those were! I have a 74 Roadrunner, which is about 3/4" different from a 71-73 spring length. That was problem 1. Problem 2 is the hangers that are supposed to be for a 71-74 B body did not fit. I ended up ordering a set that was listed for the 69-70 B bodies (the longer ones) and drilled new holes that were offset 3/4". I drilled the holes in between the upper and lower holes. I might try taking the hangers off and moving the bolts to the lower holes and see what that does. That should push the springs rearwards, which might lower the angle.

 

[PurpleBeeper]

Spring hangers... what a pain in the *** those were! I have a 74 Roadrunner, which is about 3/4" different from a 71-73 spring length. That was problem 1. Problem 2 is the hangers that are supposed to be for a 71-74 B body did not fit. I ended up ordering a set that was listed for the 69-70 B bodies (the longer ones) and drilled new holes that were offset 3/4". I drilled the holes in between the upper and lower holes. I might try taking the hangers off and moving the bolts to the lower holes and see what that does. That should push the springs rearwards, which might lower the angle.

Wow...maybe that's it....something to do with the front spring hangers. Like my car, moving to a lower hole on the front hanger will lower the nose of the rear end pinion & raise the rear end of the car.

I'm not really sure what the effect would be for a varying spring length. Within reason, the only thing I can think of it doing is making the rear shackles angle more forward or more rearward??? Maybe affect traction in some way? I'm not exactly sure what to think about using '68-'70 shackles on a '74??? Do you have your original '74 front shackles that you can set next to the '68-'70 shackles in the car? I suggest taking a good hard look at that front shackle change just to be sure that's not the source of your problem..... and definitely give Dr. Diff a call

 

[HEMI-ITIS]

Wow...maybe that's it....something to do with the front spring hangers. Like my car, moving to a lower hole on the front hanger will lower the nose of the rear end pinion & raise the rear end of the car.

I'm not really sure what the effect would be for a varying spring length. Within reason, the only thing I can think of it doing is making the rear shackles angle more forward or more rearward??? Maybe affect traction in some way? I'm not exactly sure what to think about using '68-'70 shackles on a '74??? Do you have your original '74 front shackles that you can set next to the '68-'70 shackles in the car? I suggest taking a good hard look at that front shackle change just to be sure that's not the source of your problem..... and definitely give Dr. Diff a call

If you lower the front spring eye to the upper hole it will lower the rear of the car.When replaced the rear shackles with sliders.it lowered it more.