A body 8.75 dimensions needed

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I suppose i could shim it up to correct it, even thought about it ,but why shim it to correct it if they are welded at an unworkable angle, when i can just cut and reposition them and reweld them now before i repaint the axle.
 
Pinion angle would depend on what springs you run. If you set it up one way now and then change springs it would probably need different shims in the future anyway. If you can get a good measurement for you transmission output you could set it up spot on for now though.....
 
i looked at my 7.25 axle again tonite now that i got home. yes indeed the flats on the end flanges are at the same angle perpendicular to the spring perches, and the pinion angle is 5 degrees up.

my used 8.75 i got could have even been out of a C body, and narrowed. the guy i bought it from had it under a 67 cuda coupe drag car. where it came from is anybodys guess. but the flange to flange width is 52&7/8" or 1/4" wider than a stock A body, and the welds tho they are very good looking, arent as smooth as a factory weld. the width is no biggie as it amounts to only 1/8" wider each side. but the end flange flats on this axle are exactly 90 degrees out from the mounting surface the chunk fits to. i will have to cut the perches back off and reposition them.

so the old greybeard was right. the axle flange flats are perpendicular to the perches, and if the rear wasnt narrowed with the ends reclocked 90 degrees out you should be able to line these points up and have a stock 5 degree up pinion angle.

now i have built a few mopars in the past, and never messed with pinion angle from stock. mostly big block B body stuff. i wouldent think this should be such a big deal as A body cars are just slightly smaller versions of B body stuff. if the stock angle is 5 degrees up for a stock engined car, wouldent 3 or 4 degrees up be a little better of an angle for a modified car because of spring wind up. plus im going to use a set of PST stock height performance springs, not superstock springs. Or i may go with the hotchkis TVS spring setup.

I think when these companies design the springs they sell they take into concideration the 5 degree up stock pinion angle. If there was a problem with it the new springs would come with shims to re adjust the angle, or instructions to cut the perches and reweld them at a different angle. Since i never had problems with stock pinion angles in the past, but never had to weld any perches on anything i have ever built, i am going to set mine at probably 4 degrees up to take into concideration spring wind up under hard accelleration and call it a day on this one

Thank you everybody for your input. Hope some of you got some info out of this thread, i know i did.

Matt
 
Hi Y'all

i feel like im beating a dead horse here but i still have more questions. i have heard there are no stupid questions. i cleaned up all my mating flanges and stuff on my old 7.25 rear axle from my 74 dart parts car.

i levelled the perches at exactly flat 0 degrees. i also cleaned up the rear cover mating padof all of its gasket material and positioned my angle finder on the rear end cover mating flange and got an angle of 9 degrees up. i also cleaned the flats on the yoke and also got 9 degrees up.

what is the absolute "stock" up angle on the 8.75 axle housing for an A body as measured from the mating flange where the center chunk mates to the housing?

is this angle supposed to be different than the angle i am getting off the 7.25 housing. i want to set the 8.75 rear up as either stock 8.75 A body angle or a few degrees down from it for spring wind up. i am sure there is a little fudge factor since these rears move a lot under accelleration, decelleration, and with suspension movement a degree or 2 down from stock will probably be fine

everybody is saying 5 degrees up is stock. is that on an 8.75 rear? my 7.25 rear is 9 degrees up stock. im sure grandma didnt set a custon pinion angle on the 74 dart parts car. why is this one different

This car is not going to be an all out race car. Its going to be a street car with a fairly stout v8 , 4 speed, and handling type suspension

please LMK facts not speculations please

thanks
matt
 
The 5-degrees 'up' is only build in the axle-housing.

The correct angle of degrees is always measured in relationship with the driveshaft and the transmission angle.
It's way more important to get your total number of degrees correct.

COMPARED to the driveshaft, a regular rearaxle has a nose-down angle of around 5-7 degrees (depending on your spring stiffness and setup).
 
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