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What is the preferred pinion angle for 8.8 swap into 65 mustang?


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If you're going with a standard leaf spring set-up I'd probably shoot for 5* down. If you're going with something more "rigid", like adding traction bars, maybe 2-3* down.
 

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sorry to revive an old thread but here goes.

If you're going with a standard leaf spring set-up I'd probably shoot for 5* down. If you're going with something more "rigid", like adding traction bars, maybe 2-3* down.
"5* down" as in the pinion is angled down towards the ground- below horizontal? I've seen lots of articles where down or negative is relative to the front of the car. so higher in the front than the rear is down or neg (like the transmission or DS are naturally).However, lower in front but higher in the rear (ie the pinion angled below horizontal) is positive. This is how both the spicer/Tremec calculators do it.

to make matters worse I've seen it intermixed even in the same articles so it's hard sometimes to tell what is meant. this drawing shows what i think of when i say the angle is down. but that's different from the calculators and even spicer warns about the differences in their instructions.


the next question is how does this balance with the need to keep the u-joints between 1-3* of movement?
5* of downward deflection plus 1-2 * of DriveShaft down exceeds the u-joint specs. right? or am i doing that math wrong?

I know I've seen some discussion about ~5* of down for pinion with leaf springs. so is that 2* of DS and 3* of rear end combined for 5*- or some combination to reach 5*? . the image above ignores u-joints and only focuses on pinion relative to transmission but the tremec/spicer apps seem to only focus on u-joint angles unless i'm not understanding something
 

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Yup. Old thread. All the calculations and opinions are actually worthless without the driveshaft angle as well.
U-joint operating angles of 2 or 3 are the gold standard. You can crank your own situation into the Spicer calculator.
Unless you have something ultra slick for a rear leaf spring or a "link" style rear suspension you're going to want
zero or maybe 1 down at the pinion..... because in general, the pinion will climb under hard acceleration.


ex-Global West GM
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Yup you're going to want
zero or maybe 1 down at the pinion..... because in general, the pinion will climb under hard acceleration.


ex-Global West GM
1991-1995
that was the rationale I read for having ~5* at pinion. you're saying not so?
 

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While the pinion will climb under hard acceleration, most of us street car drivers don't spend the lions share of the time accelerating... So would the recommendations be the same?
 

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While the pinion will climb under hard acceleration, most of us street car drivers don't spend the lions share of the time accelerating... So would the recommendations be the same?
To me it sounds logical to try to optimize the angles for when most torque are pushed through the driveshaft and the joints are seeing the most stress. I've seen some under car go-pro videos of cars driven and I guess the axle in a leaf spring setup twist more than most preople may think, even under light throttle.
 

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that was the rationale I read for having ~5* at pinion. you're saying not so?
You can't really look at it without factoring in the driveshaft angle but
5-degrees down at the pinion? (Maybe on a 3 leaf spring segment and the spring has a zillion miles on it)
The pinion would never climb that much. And how much time will it spend at max engine torque, with the tires "locked up with no slip against the pavement?"

Run the numbers on the Spicer calculator for various scenarios. Assume the most pinion will climb is 3 degrees.
See what the numbers do.

ex-Global West GM
1991-1995
 

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You can't really look at it without factoring in the driveshaft angle but
5-degrees down at the pinion? (Maybe on a 3 leaf spring segment and the spring has a zillion miles on it)
The pinion would never climb that much. And how much time will it spend at max engine torque, with the tires "locked up with no slip against the pavement?"

Run the numbers on the Spicer calculator for various scenarios. Assume the most pinion will climb is 3 degrees.
See what the numbers do.

ex-Global West GM
1991-1995
will do. I need to take measurements anyway. was just reading and learning. trying to track down a vibration but before I started I wanted to have an idea of what I was looking at/for. also I've seen the 5* number mentioned a good bit most recently in post #5 above.

I'll get some numbers tomorrow. I may be fine where I am but was trying to be prepared going in.
 
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