Need to relocate the spring perches on my 68 Charger. Looking for a little input.

[Sixpactogo]

A bit of info to start with. I installed a 6.1 and 5R45RFE transmission. Not wanting to raise the hump anymore than I did, I ended up with the engine transmission angled down about 5 degrees. I knew I would have to raise the pinion angle some to correct the driveline angle so I shimmed the pinion up 4 degrees. I still have some vibration at higher speeds and don't want to add more shims so I'm thinking I want to cut the perches and relocate them. I got a used housing and in checking the factory mounted perches, I find the left perch (driver side) is welded on at 5.8 degrees nose down and the right perch is 4.8 degrees nose down.
My question is does anyone know what the factory specs were? It seems to me they should have both been the same. I know quality control was not their number one concern but there must have been some sort of formula

 

[bearman]

Before you start moving perches give this a thought raise the other side to match the 5.8 side. You can use aluminum and shim up the rubber mount to make both side equal. Then see what happens did it increase or decrease. Using shims in between the rubber part of the mount has been going in for awhile have seen it help and then not so much. Good luck

 

[Sixpactogo]

Before you start moving perches give this a thought raise the other side to match the 5.8 side. You can use aluminum and shim up the rubber mount to make both side equal. Then see what happens did it increase or decrease. Using shims in between the rubber part of the mount has been going in for awhile have seen it help and then not so much. Good luck

Not sure what you mean by matching the 5.8 side. Both of the angles are nose down on the pinion. I have installed 4 degree shims to raise the pinion angle nose up but it is still not quite enough. I don't want to add any more shims since the shims actually raise up the whole axle which doesn't do the drive shaft angle any favors causing it to be almost zero. Plus, my U bolts are about out of threads. My plan is to move the perches about 5 degrees which would give me right at zero or level pinion angle while at the same time dropping the axle back down on to the spring which amounts to about a quarter inch. I could also put longer rear shackles in but I don't want to raise the rear any higher. I don't have a problem relocating the perches. I was just wondering if anyone knows what the factory used for a ballpark perch angle. 4.5 degrees or 5.5 degrees. I just expected to find them both the same.

 

[bearman]

Sorry, I was miss leading on my thoughts so please ignore my post.

 

[beanhead]

Just checked a spare factory 8-3/4 outside and with the perches set level the pinion points up a fraction less than 5 degrees, but that doesn't mean it will point there when installed. They are about a half a degree off from each other, yours sound close enough for Chrysler lol..
You're correct that the perches will need moving, but with 5-degrees down at the transmission the factory specs are pretty much useless here. Unless you're running a 4-link or Caltracs or some other aftermarket setup you need to get your pinion 8-9 degrees nose down to get you near parallel with the transmission when driving. It sounds you went up with the pinion which would give you the trouble you're reporting.
Unhook the springs from the axle, roll it into the desired pinion position and measure the perch angle difference, then cut and weld them.

 

[hunt2elk]

Ed, I have both of the original 8 3/4 rearends from my RR and Bee sitting in my garage. If you want to stop over and take any measurements, you are more than welcome.

 

[Sixpactogo]

Just checked a spare factory 8-3/4 outside and with the perches set level the pinion points up a fraction less than 5 degrees, but that doesn't mean it will point there when installed. They are about a half a degree off from each other, yours sound close enough for Chrysler lol..
You're correct that the perches will need moving, but with 5-degrees down at the transmission the factory specs are pretty much useless here. Unless you're running a 4-link or Caltracs or some other aftermarket setup you need to get your pinion 8-9 degrees nose down to get you near parallel with the transmission when driving. It sounds you went up with the pinion which would give you the trouble you're reporting.
Unhook the springs from the axle, roll it into the desired pinion position and measure the perch angle difference, then cut and weld them.

Nope. Wrong direction. In my case the pinion needs to be about zero to 1 degree nose up at rest. Under load it will end up somewhere around 4-5 degrees up putting it parallel with the trans. Right now, I have 4 degree shims raising the pinion up to about 1 degree nose down at rest. Under load, it comes up to somewhere around 3 degrees up. Still a couple degrees too low since the vibration gets a little worse when I lift. That tells me I gotta go nose up.
Thanks much for checking your spare 8 3/4. That tells me that the factory specs are somewhere between 4 & 5 degrees nose down. As I said, mine checked out to be 4.8 on one perch and 5.8 on the other. If mine had both checked out the same, I would not have questioned it. I just thought 1 degree difference was quite a bit. Anyway....... I'm gonna set mine at zero and go from there. Thanks again!

 

[Sixpactogo]

Ed, I have both of the original 8 3/4 rearends from my RR and Bee sitting in my garage. If you want to stop over and take any measurements, you are more than welcome.

Thanks Joel, I have what I need but I do have to stop over and check out that Bee. Probably the only way I will get to see it. LOL

 

[dvw]

Measure on the u joint caps on the transs an axle yokes. Not the yokes connected to the drive shaft. The axle yoke should be April 3 degrees down from the trans. Don't worry about anything else. If the teans is truly 5 down in the rear the axle needs to be be 2 up.
Doug

 

[RemCharger]

With the engine swap, how much higher is the crank center line from stock?

 

[Sixpactogo]

Measure on the u joint caps on the transs an axle yokes. Not the yokes connected to the drive shaft. The axle yoke should be April 3 degrees down from the trans. Don't worry about anything else. If the teans is truly 5 down in the rear the axle needs to be be 2 up.
Doug

Yeah maybe, but I don't want to move the perches 7 degrees. I'm pretty close now with the 4 degree shims but still get some shudder when I lift. I'll be good with zero or one degree up. The other thing is by eliminating the shims, I will be dropping my axle about 3/8". I want to keep the drive shaft heading down. I did shim the tail up a little with a 1/4" washer on rear mount so I am just under 5 degrees down now. Thanks for your input.

 

[Sixpactogo]

With the engine swap, how much higher is the crank center line from stock?

No idea. Never checked it but I doubt if it is much if any. The transmission size is what caused the problem with drive line angle.

 

[33 IMP]

Pretty sure factory spec for perch angle was 5° down. Why not swap out your 4° Shims for a single piece 6° shim? Easier and cheaper than cutting the perch off and rewelding.

 

[dvw]

Theres been much discussion over pinion angle over the years. The angle of the driveshaft itself means nothing, unless we are talking about some wildly raised 4x4. The idea is to get the crank C/L and Pinion C/L parallel under load. It doesn't matter if the crank or the pinion is higher or lower than the other. Rear suspension type will alter how much wind-up there is is the housing. Ladder bar and 4 link don't need much angle, 1.0-1.5 degrees. Cal Trac's maybe 2.0. Leaf springs 2.0-3.0 street, sometimes 5+ in a drag car.
Doug

 

[Sixpactogo]

Thanks for all the input guys. I have a plan. I do understand pinion angle. My reason for starting this thread was when I found the perch angles different from side to side. I was reasoning the factory may have done it because of the extra spring leaf on the driver side causing them be one degree different from side to side. It sounds like that is not the case.

 

[33 IMP]

Thanks for all the input guys. I have a plan. I do understand pinion angle. My reason for starting this thread was when I found the perch angles different from side to side. I was reasoning the factory may have done it because of the extra spring leaf on the driver side causing them be one degree different from side to side. It sounds like that is not the case.

Thanks for all the input guys. I have a plan. I do understand pinion angle. My reason for starting this thread was when I found the perch angles different from side to side. I was reasoning the factory may have done it because of the extra spring leaf on the driver side causing them be one degree different from side to side. It sounds like that is not the case.

Assuming the factory was dead- nuts precise on the angle (?!) the difference in your housing might be as simple as a 1° worth of housing twist. It wouldn't surprise me, either way.

 

[beanhead]

Nope. Wrong direction. In my case the pinion needs to be about zero to 1 degree nose up at rest. Under load it will end up somewhere around 4-5 degrees up putting it parallel with the trans. Right now, I have 4 degree shims raising the pinion up to about 1 degree nose down at rest. Under load, it comes up to somewhere around 3 degrees up. Still a couple degrees too low since the vibration gets a little worse when I lift. That tells me I gotta go nose up.
Thanks much for checking your spare 8 3/4. That tells me that the factory specs are somewhere between 4 & 5 degrees nose down. As I said, mine checked out to be 4.8 on one perch and 5.8 on the other. If mine had both checked out the same, I would not have questioned it. I just thought 1 degree difference was quite a bit. Anyway....... I'm gonna set mine at zero and go from there. Thanks again!

Yeah...you'd need to have the pinion 5 up under load to be parallel. What'd I say? I f--ked that all up! And I know better, I try to re-read the questions and proofread my posts, missed that one by a mile....sorry for that.

 

[dvw]

Thanks for all the input guys. I have a plan. I do understand pinion angle. My reason for starting this thread was when I found the perch angles different from side to side. I was reasoning the factory may have done it because of the extra spring leaf on the driver side causing them be one degree different from side to side. It sounds like that is not the case.

The reason they are different is the housing is bent.
Doug