pinion angle

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3404spdfish

3404spdfish

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ok so I am almost done with the spring relocation in the 65 barracuda gift to my brother. at the beginning with the 7.25 still in the car I measure its pinion angle with no weight, it had a 5.5 negative angle, it has SS spring in it. would be correct to set the 8.75 narrow rear end in car and set it up with the 5.5 negative angle again? i am not sure how to set the angle with a new rear end with un welded purches with no weight on springs. the 5.5 angle i started with was with u bolts in and torqued on the 7.25
 
i assume it ran fine. its been sitting since 1985 ish. i picked it up in pieces, it was a 273 car, automatic, soon it will be a 360 car with 727, and as you know a 8.75 rear end
 
All that matters is the relative angle of the powertrain and driveshaft. If it was me I would get the rest installed and check your angles, adjust and then weld the perches on.
 
If your a heavy guy throw weights in the car to match.
Measure 4 points around the car, bumpers will do.
get the car up at a working height, jack stands under axle.
Do the math, bring up front of car to mock height sitting on the ground.
Check the degree at the tailshaft down angle, pull rear pinion up the same degrees, with maybe 1 deg. down for axle wrap up at cruise.
JMO
 
Here what is important. Set and make your adjustment while the car is on the ground for the pinion angle otherwise you will have twist in the perches. I tack weld a small square piece of metal next to the perch on bot sides of the car so the rear stays center while rotating in place.

SS springs have different arches from left to right side if hanging in the car. Make the angle 5-7 degrees down from being parallel with the shaft in the trans.

Example: If the shaft in the trans faces up compared to the level ground then the starting point on the rear should be facing down the same degree. If the trans shaft is level then then the starting point of the rear is level. The starting point for the pinion angle is the trans and rear should be running parallel. Then 5-7 down from there.

If you are running the older 002 003 springs. Jack the car in the center of the rear and level the front with the stabilizer bar in the front disconnected. When you let the rear down it should have lean to the left. This is race position. To level for the street look turn the left torsion bar up one turn in the front on the left side and install the end links on the stabilizer bar.

to race it remove one end link and take the turn out of the left bar.
 
ok on to drive shaft length. i have to get one cut and balanced. so as i under stand it push the slip yoke in on the transmission side all the way and pull it out about an inch, measure center to center of u joint and all is good right.
 
ok so i had time to finish spring relocation, i am going to center the rear end, whats the best way? so far i measures from backing plate flange to new perch No backing plates in place yet.; i get a number, a little tap tap i get the same number on each side, my main concern is the pinion sits offset of center of car with this be a problem?
 
Simple. Just match the angle of the new perches with the old ones on the 7.25.
 
i can do that, but side to side centering, the pinion sits more to pass side. will this be a problem? because i think i will have to start over on narrowing another 8.75 dif. and since there equal length axles this offset is normal right.
 
3404spdfish said:
i can do that, but side to side centering, the pinion sits more to pass side. will this be a problem? because i think i will have to start over on narrowing another 8.75 dif. and since there equal length axles this offset is normal right.
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The pinion shaft itself should be centered. Check to see if it is and simply center the pinion up on the new rear end.
 
well if i center the pinion in the car, the axle is pushed to driver side and i will run into tire clearance on one side and maybe tire clearance on the springs on the other side. hhhhmmm i will see about getting a picture and post it tomorrow.
 
3404spdfish said:
well if i center the pinion in the car, the axle is pushed to driver side and i will run into tire clearance on one side and maybe tire clearance on the springs on the other side. hhhhmmm i will see about getting a picture and post it tomorrow.
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Double check that you are correct on that. I don't think you are. The pinion on the 7.25 is offset, so in order to center the pinion in the car, the axle housing must be offset to one side. I can get you some pictures if you need them. My 64 Valiant with a unmodified 7.25 is less than 50 feet away.
 
ok i will take a picture. in early a bodies i did notice the engine does not sit center in car due to K member design. right
 
if that's the case, maybe i am fine, i shouldn't focus on transmission hump but more on tail shaft 7.25 is still has equal length axels correct. I have removed many of them but never in them.
 
3404spdfish said:
if that's the case, maybe i am fine, i shouldn't focus on transmission hump but more on tail shaft 7.25 is still has equal length axels correct. I have removed many of them but never in them.
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I honestly don't remember if mine are equal length and I've had them out more than once. lol. I would assume they are all the same length.....but you know what they say about assuming. lol I know to get the Ford 9" I am getting ready to install pinion centered, I had to have the tubes and axles different lengths.
 
I am taking apart a C body, it has 8.75 i will check axle lenght and maybe even put housing back in car and look at it's alignment
 
i looked at a 72 Camero yesterday and it had a 10 bolt in it and it to sits just off center to the right but is inline with the transmission. this must be accurate with equl lenght axle cars
 
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