Hot Rods Pinion Angle...Issue or not?

@Budget36 ’s one post starts off with “ extreme example”
- which is a very good way to show a problem.
Then the example noted is “equal but opposite slopes”
Ok, to me that means he following the BS mantra of 3 down 3 up. ( doesn’t fit every build. especially lowered vehicle or short wheel base higher vehicle)
The equal but opposite means the angels are opposing, intersecting, not parallel.

The next thing mentioned is the drive shaft crashing into crosmembers.
That’s telling me his vehicle is probably lowered where the transmission is closer to the ground than the differential or it’s really jacked up high, high clearance vehicle

How am I doing so far?

To help I we need a value to put on the 18” drive shaft. I’m guessing since he said it’s like the picture but single drive shaft the slope is negative.

@Budget36 said his Google math says the ujoint working angles are 9 or 10 degrees. Too much really. The trans and pinion are “just like your pic” so everything is negative.
Drive shaft slope minus 3 is 9 or 10. so the drive shaft slope is 12-13° negative.


He needs double cardan joints to get close.
Or or or ,,,,
Is up and down was found in rule 4

 

I will let Budget36 answer that........ I can't know if you have made it clearer for him or not.

 

So I’m at work now, but next break I’ll draw a stick picture of what I’m describing and what my plan is.

 

I’m guessing off of clues

 

Holy shit storm Batman. TIG welded axle brackets tearing our worm hole! WTF!

 

Since the OP has probably checked out, let me tell you why I have what I have.
The truck came with wood spoked wheels, some odd ball sized tires I didn’t want to purchase just to roll it around. I bought an early 30’s (‘31 or ‘32) Plymouth front end and rearend so I could bolt on some steel wheels.
With the cab, bed, and around 500 lbs of tractor weights on the front over the axle, frame “rake” looked fine to me.
I checked the pinion angle of the original rearend and it was just about 3 degrees up. , so when I put the Plymouth axles under it and moved the spring perches on the rear, I tacked them in with the pinion at 3 degrees up, just about the same as what dodge had done.
This where I made a mistake #1 I never put the L6 and transmission (original) in the truck to see where things sat/etc.
So I fashioned up some motor mounts and centered up the engine (318) without the 727 behind it. That was mistake #2.
So with the pinion point up 3, I had the 318 between the rails, centered, 1.5 inches or so from the firewall , sat the 318 three degrees down.
So then I went and rolled the transmission under and bolted it to the engine to make a transmission mount. After the transmission was bolted up, I then realized how long the 727 was, dug out the original BH and 3 speed, did some measuring and went crap.
So my guess is the original engine/transmission sat lower between the rails besides being about 1/2 as long as the 727 (I exaggerate).
Grabbed a 2 foot level and wanted to used my angle gauge so see what I was up against, but something happened to it (was a few years back) and I don’t recall what it was. So I measured from the ground up on both the piñon and transmission, measured the distance between, and let Google tell me the angle of the triangle. Being that the transmission and pinion are not in a straight line, the calculated value can’t be correct. So I probably am in the 12/13 degree operating angles.
I’ll draw it out, but I think @twenty8 and @31Vicky with a hemi understand the transmission is higher than the pinion, transmission is pointed 3 down as view from the side, viewed from the same side the pinion is pointing up 3.
So what I need to do, is disregard 3 up and 3 down. Set them in line with each other, then take point then trans down and the pinion up to achieve a good operating angle. In fact I think it’s going to be easier once they are in line, to raise the transmission to point up over the center line between the two, and the pinion ponying below the center line. I’ll find out in a few weeks.
It’s not a lot of work, but I’ve been on 50-60 hour night shifts for the past 3 years, finally we hired a guy for back half nights, and I’ll be back to 4 nights and (usually) 40 hour shifts once he’s up the speed. So the truck will now become the winter/cold weather completion project as it’s in the the back shop area that won’t to too long to clear out around it.

 

Hey @Budget36 , it would be good to see that stick pic you were going to do showing the slopes.
No, not that sort of pic. I said stick pic.....

 

I’ll find time tonight.

 

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