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Discussion Starter · #1 ·
Hello! First post here and am hoping for answers to my dilemma. I’m trying to set the pinion angle on a Ford 9” differential which swapped into my car. From most of my reading, I assumed that he pinion angle should be close to opposite that of my engine. If the engine tilts rearward 1 1/2 degrees then the pinion angle should be up 1 1/2 degrees.
Then I noticed that the multiple sources I was using were for coil while C1 Corvettes had leaf springs. So according to an educational I found on a Ford forum, the rear pinion should point down to compensate for axle housing upward twist under heavy acceleration.
To complicate matters I have very heavy traction masters to attempt to eliminate pinion rise. So now, I’m really confused.
Any assistance would be appreciated.
This is the Ford reference: https://www.diyford.com/ford-restomo...pension-guide/
617266
 

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Ok so...Here's the rub.
Both answers are correct to varying degrees. Its honestly application dependent (or at least it should be). If you're just driving the 'vette around then the bread-n-butter "Equal and Opposite" will get you out of the weeds and most likely be problem free; regardless of coils, leaves.
If you are under heavy acceleration often, then having a different angle at the pinion to compensate for axle housing rotation is pretty commonplace.

Best idea: Tell us a little more about what you've got and (most importantly) what you want it to do. Is the car supposed to look like a D/Gas car, but be street friendly; or, are you wanting to drive a brawler down the street? And pics of a hotrod 59 vette are ALWAYS appreciated.
 

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Discussion Starter · #3 ·
617272
Ok so...Here's the rub.
Both answers are correct to varying degrees. Its honestly application dependent (or at least it should be). If you're just driving the 'vette around then the bread-n-butter "Equal and Opposite" will get you out of the weeds and most likely be problem free; regardless of coils, leaves.
If you are under heavy acceleration often, then having a different angle at the pinion to compensate for axle housing rotation is pretty commonplace.

Best idea: Tell us a little more about what you've got and (most importantly) what you want it to do. Is the car supposed to look like a D/Gas car, but be street friendly; or, are you wanting to drive a brawler down the street? And pics of a hotrod 59 vette are ALWAYS appreciated.
Ok so...Here's the rub.
Both answers are correct to varying degrees. Its honestly application dependent (or at least it should be). If you're just driving the 'vette around then the bread-n-butter "Equal and Opposite" will get you out of the weeds and most likely be problem free; regardless of coils, leaves.
If you are under heavy acceleration often, then having a different angle at the pinion to compensate for axle housing rotation is pretty commonplace.

Best idea: Tell us a little more about what you've got and (most importantly) what you want it to do. Is the car supposed to look like a D/Gas car, but be street friendly; or, are you wanting to drive a brawler down the street? And pics of a hotrod 59 vette are ALWAYS appreciated.
Ok so...Here's the rub.
Both answers are correct to varying degrees. Its honestly application dependent (or at least it should be). If you're just driving the 'vette around then the bread-n-butter "Equal and Opposite" will get you out of the weeds and most likely be problem free; regardless of coils, leaves.
If you are under heavy acceleration often, then having a different angle at the pinion to compensate for axle housing rotation is pretty commonplace.

Best idea: Tell us a little more about what you've got and (most importantly) what you want it to do. Is the car supposed to look like a D/Gas car, but be street friendly; or, are you wanting to drive a brawler down the street? And pics of a hotrod 59 vette are ALWAYS appreciated.
Good point. I thought my post was too long to begin with, so I left out details.
Engine is 355 cid SBC with Eagle forged crank, Manley H-beam rods, Wiseco 2618 alloy pistons, Strip Dominator with Holley 750 CFM double pumper. Set up to run direct port wet fogger NOS nitrous, but at a later date. cam redlines at 7000.
Super T-10 leading to Ford 9” with Detroit locker.
Stock HB Corvette leaf springs.
I really think the true Traction Masters will handle some of the pinion lift. The car will be a street cruiser with an occasional stop light drag race. We used to have a great drag strip here, but it was recently demolished in the name of progress.
I’ll try to upload photos. But the street photo is old. I haven’t done body work yet.
 

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As a gearbox specialist; Im inclined to tell you that an ST10 may not live a long life; depending on your 1st gear ratio and clutch engagement. For a car like yours, Id want at least a 3.73 with a 2.64 1st ST10, or maybe a 3.50 with a 2.88 1st. With those tires, I'd want your Starting Line Ratio (rear gear x 1st gr) to be at least 10:1...and prefer 12:1) Let off the giggle gas before you shift.

I would set it up either with the same pinion/engine angle, or slightly adjusted pinion angle. Set it up for 80% of its use and deal with the accelerated wear as par for the course. I have some t-bucket friends who go through Ujoints like no ones business. Swap em out every 2yrs as preventative maint.

LOVE the car!!
 

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Discussion Starter · #5 ·
As a gearbox specialist; Im inclined to tell you that an ST10 may not live a long life; depending on your 1st gear ratio and clutch engagement. For a car like yours, Id want at least a 3.73 with a 2.64 1st ST10, or maybe a 3.50 with a 2.88 1st. With those tires, I'd want your Starting Line Ratio (rear gear x 1st gr) to be at least 10:1...and prefer 12:1) Let off the giggle gas before you shift.

I would set it up either with the same pinion/engine angle, or slightly adjusted pinion angle. Set it up for 80% of its use and deal with the accelerated wear as par for the course. I have some t-bucket friends who go through Ujoints like no ones business. Swap em out every 2yrs as preventative maint.

LOVE the car!!
Thank you! My first gear is 2.88 and the diff. Is 3.5. Looks like a ratio is 10. 😖
Do you think solid anchored Traction Masters will help with pinion lift at launch?
 

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Discussion Starter · #7 ·
617274
Thank you! My first gear is 2.88 and the diff. Is 3.5. Looks like a ratio is 10. 😖
Do you think solid anchored Traction Masters will help with pinion lift at launch?
Here is what I’m running.
Driveshaft Angle is needed as well.
Yes, thanks. It is indeed required as a variable to use the TREMEC calculator, but the driveshaft angle is a trigonometric function of engine angle angle, pinion angle and driveshaft length. Correct me if I’m wrong. However we measured driveshaft angle at 8 degrees.
Since I’m concerned with the effect of Traction Masters, reducing pinion angle elevation, I put in a call to Traction Masters. The gentleman told me that Traction Masters would eliminate axle housing twist about 75%, this really confuses the matter.
 

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87 Dodge Dakota 6.1 hemi, 39 Chevy Master 85- work in progress
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If you have 1.5 transmission down with 8 degree down driveshaft it's 6.5 u joint angle. Its not going to work well. You want 1-3 degrees of u joint angle. The farther you get over 3 the less rpm the driveshaft can take.

You need some negative pinion in relation to transmission. With the driveshaft angle at 8 it will not be happy.

Maybe the driveline angle needs to be increased, more transmission down and driveshaft will be less. You need the first angle to be good before doing pinion.

Are you sure the angles are correct?

As you change the driveline angle, pinion angle, raise or lower rear axle it changes the driveshaft angle.
 

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I run 1 to 2 degrees pinion down depending on power, tack my spring brackets, then take the thing for a drive.
Bring it up to 100 then back down on a straight flat stretch of road. No vibrations and I finish welding the brackets. If I have vibrations then I look at whats causing them and experment until they are eliminated.

Yes under hard throttle your pinion angle will change. But a majority of the time if you set it for your "cruising angle" then the thing will generally be fine when you give it hard throttle.

U joints have 20 to 30 degrees of angle before they bind. If your mashing the thing and running at the strip then you should pay more attention. If your just street driving it with a few burnouts every now and then. Running 1 or 2 degrees will probably be fine.
 
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