Tail Shaft, Pinion, Drive Shaft Angles

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Couper

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Aug 26, 2020
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Thought I'd put this here instead of my build thread. I've been messing with this Trimec Drive Line Angle program on the wife's smart phone and can not dial the numbers in. Seems that this phone app does not work right...no matter where I place the numbers I can't get a green light.

I lowered my motor mounts by 1.750 to get my rear pinion / tail shaft heights closer....it was a 4.5 difference now it's 3". It may not have been needed, but I'll do better in the way of body roll and it does have a better look. The bottom of oil pan is 2" above the axle.

I just used the Spicer Calculator online.. my kid told me to plug in parallel numbers. Tail shaft 3 degrees down and pinion 3 degrees up. My drive shaft angle (piece of tubing right now) is 4 degrees. These numbers seem to work and give me operating angles of 1.5 which is a green light

So the question is....does 3 degrees down on the tail shaft / 3 degrees up on the pinion make sense? I wasted a good part of the day trying to work around what I read about the pinion should be facing down.... ARRG

Maybe I eat too much turkey :eek:(
 
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Your kid was right, the transmission output shaft has to be parallel to the pinion shaft, and that's what you have now. Good show.
A side note is, make sure the shafts are parallel side to side also.
There are some good U-tube videos showing why you get vibrations with bad angles in your driveline. When you transit power through a bent U-joint the driveshaft changes rotational speed twice per revolution. If your driveshaft is in phase and has an equal and opposite angle at the other end, the speed changing is negated and the pinion shaft is driven at a constant speed.
 
Your kid was right, the transmission output shaft has to be parallel to the pinion shaft, and that's what you have now. Good show.
A side note is, make sure the shafts are parallel side to side also.
There are some good U-tube videos showing why you get vibrations with bad angles in your driveline. When you transit power through a bent U-joint the driveshaft changes rotational speed twice per revolution. If your driveshaft is in phase and has an equal and opposite angle at the other end, the speed changing is negated and the pinion shaft is driven at a constant speed.

Best way of explaining it I've heard.[cl[cl Mac, you're a word smith.:D
 
Thanks Merc...

Been researching all morn and I think the reason why it wasn't coming out in the calculator was my "ups and downs" where confused.

The definition from the spicer site is:

Up: Rises from front to rear of vehicle
Down: Descends from front to rear

Trans shaft.... simple = angled down towards rear

Drive shaft..... simple = angled down towards rear

Rear pinion (you'd think proper term is angled up cause the end facing the motor is up to the sky) It's not, it's down because per the description - Down: Descends from front to rear

1) Very simple video by Spicer. Around 4.30 they show you how to do the math.....simple.

Video here: https://spicerparts.com/videos/measuring-driveline-operating-angles

If interested in seeing the calculator its here:

https://spicerparts.com/calculators/driveline-operating-angle-calculator#more

Maybe this info will help someone who coms along who doesn't understand it.

The only thing that doesn't make sense to me is why the trimec smart phone app keeps coming up red.
 

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I use "equal and opposite" angles. However the included angle in a given u-joint should not exceed a certain number, which I can't remember. (maybe 5 degrees from straight through???)
 
I've always used 3 degrees down on the engine/tranny & 3 degrees up on the rear end... never a problem!

BoB
 
I've always used 3 degrees down on the engine/tranny & 3 degrees up on the rear end... never a problem!

BoB

And I generally use level engine and level pinion. Depends on the build. If the elevation difference between the engine and rear end is too great (That included angle again) then I start tilting stuff.
 
This stuff is confusing as hell..... Somewhere I read 3 degrees on the motor. But also level carbs. How in the hell do you get both??????

It seems that all will be driven off driveshaft angle which I can't change.....or only change slightly with tail shaft / pinion angles.

Once I have the drive shaft I'll adjust to get that 1.5 operating angle.

My biggest dilemia was not understanding pinion pointing up is really front to back DOWN.
 
Somebody will correct me if I'm wrong. I believe some Chevy engines were installed from the factory angled to the rear. The intake manifolds were designed with the carb mount level with the engine slanted to the rear. Using these manifolds on a level engine would result in the carb tilted forward 3 degrees.

It's common in the hot rod world to install the engine slanted 3 degrees to the rear and the pinion pointed up 3 degrees.

To add to the confusion, in drag racing the pinion is frequently pointed as much as 6 degrees down regardless of the engine angle. This allows for rear end "wrap up" under hard acceleration.
 
Hey Bob

I'll have the drive shaft on Monday and will be able to get an accurate number on my drive shaft angle. Right now I'm playing with a piece of tubing but I do think my numbers are close.

I'm thinking I'll be 2.0 on the tail shaft / 3.5 on the drive shaft angle and 2.0 on the pinion for a 1.5 angle on both joints.

So as the judge sometimes says....******** next case! And I'm on to my next challenge. Seeing ZZ's steering component pics made me want to take a look at my steering box and stuff. Pretty easy assembling it but of course my input shaft on the vega steering box falls right on my motor mount. Not on the rubber but on the metal fabrication. I'm thinking I will bore a hole thru it and weld in a piece of heavy wall DOM to make a tunnel if you will. Actually looking at it again, a 2" aluminum mounting block would push it away from the frame and motor mount. Maybe that's a better option. You guys see anything wrong with the front end works?

Some pictures attached.....

Going to watch some TV with the boss lady....she asked me what my name was when I came in to eat tonight....lol
 

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Bob, I can't correct you when you're right all of the time. Some motors have their carb bosses at three degrees so when the motor is tipped back the carb sits level. Of course, flathead fords with three deuce manifolds don't have those slanty bosses so the carbs lean back if the motor leans back. Those Holley type carbs from that era don't work well leaning back so you have to make wedge risers under each carb to stand them up.

Coup, I think you've got the driveline figured out.
I like the tunnel idea, too.
 
I level the carb pad front to back and side to side, then build mounts to suit. Whatever angle the trans tailshaft ends up being, I rotate the pinion the same amount in the opposite direction with full rear weight on the springs.

As to your steering, I'd just take a "C" notch out of the mount. You could box the C, but it wouldn't be necessary unless the motor mount gets real thin on the end.
 
Bob, I can't correct you when you're right all of the time. Some motors have their carb bosses at three degrees so when the motor is tipped back the carb sits level. Of course, flathead fords with three deuce manifolds don't have those slanty bosses so the carbs lean back if the motor leans back. Those Holley type carbs from that era don't work well leaning back so you have to make wedge risers under each carb to stand them up.

Coup, I think you've got the driveline figured out.
I like the tunnel idea, too.

I'd like to know 10% of what Bob knows....

My carb mounts, distributor boss, damper, and tail shaft angle are all on the same angle.....

That drive line jazz burnt up a lot of brain ram on me but yes I think I'm on track.

Cool Beans on the tunnel.....I'll be on that and the trans cross member tomorrow.

Now if I could only fall asleep
 
I level the carb pad front to back and side to side, then build mounts to suit. Whatever angle the trans tailshaft ends up being, I rotate the pinion the same amount in the opposite direction with full rear weight on the springs.

As to your steering, I'd just take a "C" notch out of the mount. You could box the C, but it wouldn't be necessary unless the motor mount gets real thin on the end.

Thanks Bama...I'm gona work on that mount tomorrow. Do you know if that input shaft to the box is suposed to be level or angled up? I believe the shaft is parallel to the pitman arm.
 
I don't think it matters too much if it's level or pointing up a few degrees, I don't think you would want the shaft to point downward though. The grease in the box should recirculate, but if the shaft was down it looks like it might want to walk out the seal with gravity pulling against it, but that's just my thoughts.

I would definitely keep the box bolted as close to the frame rail as possible. Any spacer puts more stress on the mounting bolts, and they are under enough stress already. I had to put a 1/4" spacer under one of the pads on my Saginaw power box because it sat higher than the body of the box. That kept my box about 1/8" or less off the frame. Without the spacer, the box body sat against the frame and would wiggle just a bit when turning, the spacer under the pad stabilized it, no more wiggle. Yours looks like it sits flat on the mounting pads, so you should be good.
 
Thanks Bama

Point up a bit....got it.

Due to where the shaft falls I decided to make a 1" mounting block. It will bring the shaft out and give me plenty of clearance. It'll actually be 1 1/16 towards the rear and 1" in the front so the input shaft will be straight left to right. (I have a full machine shop at my work place) It'll be the exact size of the mounting plate for the box. The 1" block will get welded to the frame rail. It'll be solid and even maybe strengthen the rail at the attachment site.

Was gona make an aluminum block but then it has to be bolted and here comes that wiggle...

Thanks again for being on the other side of the keyboard...
 
Still Stuck :eek:(

Well I'm still at this. I got my drive shaft today....fit's nice. With the angle I have on my drive shaft 3.7, the 3 degrees down on the tail shaft (high at the motor / low at the tail shaft) and 3 degrees at the pinion (low at the pumpkin high at the drive shaft connection) gives me bad u-joint angles.

I thought I was ok tonight with Tail Shaft 1.9 degrees down (front higher the the rear), Drive shaft angle 3.8 (front higher than the rear) and pinion 2.0 (low at the pumpkin high at the drive shaft connection) and that is giving me operating angles of 1.9 and 1.8. And was ready to go to bed....


I have a friend that said I need 5 degrees at my pinion. I believe if I move my pinion that much it's going to change my drive shaft angle and throw all the numbers off. This guy is pretty spot on but I want to make sure I have his right.

You guys have any additional input for me on the 1.9 & 2.0 numbers?

Sorry & Thanks!
 
It sounds like both your u-joint angles are in the right range. I have no idea why your friend is telling you that you need 5 degrees. On the surface, it sounds like really bad advice. He may be trying to say that you need to account for pinion movement under load, but if your angles are already that good I say leave it there and double check it again once the truck is fully assembled with all weight on it and a full tank of gas.
 

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