I think this is my next project car

extropic said:
@alloy,

I'm concerned that because of the very shallow current drive shaft angle, when you pitch the pinion shaft up, you may find that the pinion shaft is higher than the trans yoke. I'm almost certain that it will be.

What would prevent you from raising the back of the transmission? Could you raise the trans tail shaft to get zero degrees incline on the trans?
That way you will only have to put a 2.2° shim on the rear end and you will get a closer to 3° drive shaft angle
Click to expand...

I also feel that the pinion may wind up a little higher than the tailshaft... but I can't think of a reason why that would be an issue as long as the u-joint angles are within reason...

Just curious... how did you compute the 3 degrees for the driveshaft? I've been trying to figure that out, but I keep thinking that I would have to know the length of the driveshaft to determine that...

-Bear
 
Spitballing here...
If the car on blocks is sitting on flat paved surface, try measuring from pavement to the visual center of both yokes. Just as a reference. Check with the klien gauge to see if that pavement is throwing your measurement wonky.
For measuring with the klien gauge at the rear, could a flat piece of plate be drilled to bolt to the u-joint carrier at the rear? Just to give a more consistent place to stick the klien gauge?
I've only had one cup of coffee, so like I said just spitballing.
 
682bear said:
I also feel that the pinion may wind up a little higher than the tailshaft... but I can't think of a reason why that would be an issue as long as the u-joint angles are within reason...

Just curious... how did you compute the 3 degrees for the driveshaft? I've been trying to figure that out, but I keep thinking that I would have to know the length of the driveshaft to determine that...

-Bear
Click to expand...

I estimated the following:

Front engine mount to trans yoke = 48"
From 3.3° incline, raising the trans rear 2.76" at the yoke will result in a 0° engine/trans incline.

Distance from rear axel C/L to pinion yoke = 12"
From a 2.2° incline, pivoting the pinion axis up .46" at the yoke will result in a 0° pinion axis incline, so engine/trans axis is parallel to pinion axis.

'55 Bel Air has a 115" wheel base. Rough estimate: 115-36=67-12= 55" long drive shaft (yoke to yoke)
At a 1.2° incline and a 55" drive shaft, the trans yoke is currently 1.15" higher than the pinion yoke.

Per my estimates, If he raises the trans yoke 2.76" and the pinion yoke .46" (2.76-.46=2.30"+1.15=3.45"), with a 55 " long drive shaft, it results in a 3.6° drive shaft angle.

@alloy
How long is the drive shaft, yoke C/L to yoke C/L? Tape measure is fine.

What is the dimension from the pinion yoke C/L to the rear axle axis? Tape measure is fine.
 
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I haven't done the math... but just 'guesstimating' from the above numbers, leaving the transmission where it is and raising the pinion 5 degrees will give between 3 and 3.5 degrees operating angle on the u-joints... the driveshaft will be very close to level... and the pinion should still be slightly lower than the tailshaft...

Am I guesstimating that correctly? Or is that some 5am thinking? Lol!

-Bear
 
This is out of my 1940-1960 Chevrolet book. What you want to end up with is for example is 3 degrees down from the trany to drive shaft and 3 degrees up from rear end pinion to driveshaft. If you have a two piece shaft It gets more complicated.
Pierre
FAE90DC0-E770-41A1-A2D2-8583BAA2992F.jpeg
 
These two photos are from the 1960 and newer. Obviously the info for later years is not correct but the theory is still the same.

D928837C-E9C7-49FB-ACD2-96FA795ABE2C.jpegA1976F6B-6181-43FA-A652-ECA853B5830F.jpeg
 
Boy, a lot of info to digest.

And I just realized I set the engine/trans wrong. The tri-5 thread has this. (see pic) In my frustration I just said the heck with it and stuck the angle finder to the trans pan and as it turns out that's not going to cut it. In thinking about it after seeing the trr-5 post the trans pan is probably tilted 3.5 degrees to keep the fluid level the same front to back whith the engine and trans at an angle. If it was not angled then the fluid level would be off and might cause problems with the transmission. I think I'll probably just pop the carb off and check the angle on the manifold flange. Those dang engineers were pretty sharp on this one. They outfoxed me for sure on this. I'm really thankful you posted the link. Kept me from making a big mistake.

I'll do some more adjusting and post what the new numbers are. I never figured this would turn out to be such a big deal. But it's critical to get it right.

I have parts to work on today so it may be awhile before I get to this. For some reason my left arm is really hurting, very hard to use it today. I didn't sleep last night because of it. It's hell getting old it seems, this hurts, that hurts. Did something to it yesterday doing all this, even had a dream about it. Not a good dream. Wife is grumpy this morning because I kept her up most of the night.


Stay tuned............same bat-channel, same bat-time :p


700r4.jpg
 
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