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Discussion Starter #1
I got a new driveshaft and before installed it I wanted to double check what I have for drive line geometry. In checking, I found that my crank/trans center line is pointed a bit low due to my rack and pinion/steering linkage not letting me get the engine down another inch or so and the trans tail housing is already too close to the trans tunnel for comfort so I can't move it up. It is pointing low about 1.1° which is about 2 " below the rear pinion yoke at the intersecting point. I had been running the steel driveshaft like that and didn't notice any issues but that doesn't mean there aren't any issues.

What kind of tolerance for alignment is there when changing or setting up the engine/trans angle? What is it going to affect if it's off too far?

Thanks
 

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What is the pinion centerline angle? I would expect same as crank/trans minus 1.5 to 2*. What is the driveshaft working angle with pinion angle set?
 

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Discussion Starter #4
2" lower than pinion?

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The engine points down front to back about 3°, but it is pointing about 1.1° below the diff yoke. I don't have a way of getting under the car with it level on it's wheels to get actual angles. I need to get some cinder blocks this week and see what the pinion angle is. I just know it's off 1.1° based on the 2 inches.
 

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Discussion Starter #5
So got the car up on cinder blocks so I could get some measurements.

The engine is pointing down 2° and the rearend yoke is pointing down 1°. So 3° out of parallel.

Car is 3100lbs, ladder bar, 29.5" tire, and about 900hp. .....right now.
 

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Adjust ladder bars to bring pinion up to same no. of deg but UP instead of down. Opposite of the trans....i usually put it about 1/2 down from there to compensate for rise on initial tire hit

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Discussion Starter #8
Adjust ladder bars to bring pinion up to same no. of deg but UP instead of down. Opposite of the trans....i usually put it about 1/2 down from there to compensate for rise on initial tire hit

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So that would raise the pinion up another 1/2" making the angles better but making my trajectory off about 2.5".
I cannot move the motor without building new headers or redoing my steering linkage and getting a different rack and pinion.
What are the negatives (if any) of the parallel lines of the engine/trans and rearend pinion being 2.5" apart?
 

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Your -2* engine is the same as mine. What rear suspension? I run a 4 link. So your -2 on the motor, would have the rear end +2* up, to get yourself to theoretical zero. At that point, on my 4 link, I then back the pinion angle down 2* from theoretical zero, for a total of -2* pinion angle. Your driveshaft play's no role in this set up at all.
 

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^^^^ Great info and spot on for what worked for me.

Just went through this with my 55' Chevy

I never checked the car when I bought it , but once I lowered the rear , the driveline began to vibrate and make noise.

Corrected the trans / engine angle first , then attacked the rear and ended up 2deg neg.
Art Morrison chassis.

No noise and car seems to hook a bit better
 

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Discussion Starter #11
Your -2* engine is the same as mine. What rear suspension? I run a 4 link. So your -2 on the motor, would have the rear end +2* up, to get yourself to theoretical zero. At that point, on my 4 link, I then back the pinion angle down 2* from theoretical zero, for a total of -2* pinion angle. Your driveshaft play's no role in this set up at all.
I have ladder bars. Are you saying you have your pinion set at 0°? What about my transmission shaft/crankshaft center line being pointed ~2" low?
 

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I have ladder bars. Are you saying you have your pinion set at 0°? What about my transmission shaft/crankshaft center line being pointed ~2" low?
Reread my post. I thought I had made it pretty simple.
Your -2* DOWN engine/trans is the same as mine. What rear suspension? I run a 4 link.
So your pointing DOWN or -2 on the motor/trans, meaning your down at the tail stock of the trans. This means you would need to have the rear end pointing +2* UP, to get yourself to theoretical ZERO.
At that point, on my 4 link, I then ROTATE THE PINION ANGLE DOWN 2* from theoretical zero, for a total of -2* pinion angle. Your driveshaft play's no role in this set up at all. Don't take offence to the capitol letters. I'm just trying to make my first post a little easier to visualize in your head.
 

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Discussion Starter #13
Reread my post. I thought I had made it pretty simple.
Your -2* DOWN engine/trans is the same as mine. What rear suspension? I run a 4 link.
So your pointing DOWN or -2 on the motor/trans, meaning your down at the tail stock of the trans. This means you would need to have the rear end pointing +2* UP, to get yourself to theoretical ZERO.
At that point, on my 4 link, I then ROTATE THE PINION ANGLE DOWN 2* from theoretical zero, for a total of -2* pinion angle. Your driveshaft play's no role in this set up at all. Don't take offence to the capitol letters. I'm just trying to make my first post a little easier to visualize in your head.
No offense taken to the caps. I have a bad habit of not making myself clear. I am pretty sure I understood you but when I said "Are you saying you have your pinion set at 0°?" I meant with the earth, not your theoretical zero.
If theoretical zero = 2° pinion up + -2° down on the motor/trans and you roll the pinion down 2° making it 0° to earth means 0° pinion angle + -2°E/T= -2° ?
I appreciate the help.
 

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Yes. Zero to the earth. OR, put your angle finder on the harmonic balancer, then on your pinion yoke. That number, should be the same number, to be at theoretical zero. Once you are at theoretical zero, lower your pinion towards the ground 2*, for -2* pinion angle.
 

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Exactlywhat i said about 5 posts ago....make pinion the same but positive, ie. trans down 2 then pinion up 2....2 deg down after that is too much for a ladder bar,1/2 to 1 deg back down to compensate for slack in suspension....

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Maybe I missed it but OP asked about the crank CL pointing 2' below the rear pinion CL. This affects pinion angle but is separate issue. I just went through this on my car, ride height, rear tire size and engine angle all affect how the engine CL will point at the rear pinion CL. I set car up at right height with the tires I plan run and adjusted the engine angle to point just slightly below the rear CL. My engine CL points about 3/4" below the rear pinion CL....the pinion angle was set just as described above.
 

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Discussion Starter #17
So I got the pinion angle up 1° as that is all it would go. I think my heims are butting up end to end inside the adjuster and I need to screw the upper heims in more to get any more positive angle. That is a bigger job than I feel like tackling right now. Also had to do a bit of engine re-alignment and now it's down 2.5°. So my total is -1.5 (-2.5° + 1°= -1.5°) and the drive shaft is angled down at the trans 1.5°.

I don't like it but I am stuck with it until I do new headers or re-do the whole steering system. I am also going to center up the engine when I eventually do new headers as it is still too close to the pass side of the trans tunnel for my liking.
I have 2-3/8" Lemons headers and the are keeping the engine offset where it's at for now.

Thoughts?
 

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Discussion Starter #18
Maybe I missed it but OP asked about the crank CL pointing 2' below the rear pinion CL. This affects pinion angle but is separate issue.
I also meant to say thank you deputydog. Still have not got that one answered. the negative driveshaft angle does have me concerned.
 

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Set your rear pinion angle at +.5 of a degree. That's a half degree up from earth zero. That's as good as it will get with your limitations mentioned above.
 
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