help with driveshaft and pinion angle

[PGSigns]

Post a picture of you engine and trans so we can see how it is setting in the frame. I think your trans is low in the back. I have a rolling chassis here and can post a picture of how they look stock and also give yo a measurement of the stock angle between the frame and the engine. You can not set an engine angle off the rear with everything fully unloaded. The rear will never be in that position when the truck is assembled.
Jimmy

[cebra]

I do see the OP's point in doing all this with the body off being easier and since he didn't do it beforehand, could he not leave it as is..run everything else, and then shim the trans crossmember or mount up once the body is back on and the real rear pinion angle is determined? Just a thought.

[mongocanfly]

Cebra...He really doesn't have much choice now...

[Macdaddy1]

Here are some more photos that I hope will help with assessment. Once again thanks for all of your help and suggestions so far it really helps a noobie move along.

[Macdaddy1]

more photos

[Macdaddy1]

More pics

[geezer#99]

Holy crap Batman!
Bring that tranny back up where it belongs.
Likely about 4 inches.
Put the yoke in the tailshaft and check your angle on one of the yokes ears.
Aim for 3 degrees down.
Measure your pinion the same way.
Aim for 3 degrees up.

Is your tranny centered between the frame rails or offset to the passenger side?

[Macdaddy1]

Here is what it would look like with the engine and trans at 3 degrees

[geezer#99]

Measure with a yoke.
On the plate isn’t accurate.

And how is your tranny between the rails?
Looks like it’s offset to the drivers side.

[chevy_mike]

Definitely looking better but agree with geezer#99. Measurements should be taken on the yoke or on the back edge of the tranny case (the flange area next to the rubber seal). These are parallel with the trans/block mounting surface.

It looks like you are using a stock rear end (I am assuming you did not weld on the mounting perches on the axle). Because trailing arms change the pinion angle as the suspension cycles up and down, this is why it's important to have the truck on all the wheels, full weight at ride height. This will give you a true pinion angle. Anything else is just guessing.

Also, I am not 100% sure on this but I think I have read it many times, to get this trans under the floor, you will need a high hump trans tunnel. I don't think it will clear with the low hump.

Glad you are learning and asking questions. Everyone has to start somewhere. After a few builds under your belt, you'll understand a lot more about best practices and what not to do. Lots of knowledge here.

[Macdaddy1]

Thanks you guys for the responses. I measured the yoke face and it is at the exact angle as the tranny case. i also measured the donor truck hump space and It looks like it will clear fine. For now I will set the tranny angle at 3 degrees for mock up and when I get some time I will transfer the donor cab over so I can check the tunnel clearance. Also i measured the tranny and it should be in the middle between the rails 16 3/4 on each side.

[Macdaddy1]

Is it ok to measure for a new driveshaft at this point or should I wait?

[geezer#99]

You don’t want it centered.
Should be offset to the passenger side.
You want your motor to be parallel with the pinion.
Your pinion is also offset to the passenger side.

Wait on the driveshaft. You need to set your final pinion angle last once your truck is full weight.
Then do the driveshaft.

[Macdaddy1]

Ahhhh did not know that. I will measure the pinion and see how much it is offset to the passenger side.

Thanks for all of your help!

[Macdaddy1]

so if the diif is offset to the passenger side by an inch should I move the trans over to the passenger side by an inch?

[geezer#99]

Originally Posted by Macdaddy1

so if the diif is offset to the passenger side by an inch should I move the trans over to the passenger side by an inch?

Yes, no, maybe! LOL!
You want the centreline of the motor parallel to the pinion.

[The Rocknrod]

When you get the rear end centered on the frame the pinion will be offset to one side a bit. And I wouldn't finish any trans Xmember install until I had a body on there to check for clearance.

[Macdaddy1]

What is the best way of measuring the pinion and trans parallel arrangement?

[geezer#99]

Originally Posted by Macdaddy1

What is the best way of measuring the pinion and trans parallel arrangement?

I’ve used 2 squares and a straight piece of 2x4.
If the tailshaft yoke and pinion yoke are square to each other then they must be parallel.

And I’ve used plumb bobs. Hung from the centre of the harmonic balancer, the tailshaft and the pinion. Marked lines on the floor and checked that way.

[mongocanfly]

Side2side offset from trans to diff is the same deal as up and down offset...
It would be completely acceptable to have the engine trans centered in the frame and the diff offfset...
It would also be acceptable to offset the engine trans to match the diff...either way is fine...some people offset engines to clear the steering components...
But holy cow...that's alot of angle in your 1st pic...the last looks very good....keep in mind that you may have to do some tunnel work....do you have any good pics of the rear axle perches?....
I would temporarily set the engine trans angle at 3deg until you get all the bodywork back on...
DO NOT order a driveshaft untll you finalize the drivetrain angles.....

[Macdaddy1]

I will take some tomorrow morning when i get time but thanks for the replies i always appreciate your valuable input.

[Macdaddy1]

Do you measure the face of the trans output yoke and the face of the diff to determine if they are parallel?

[geezer#99]

Originally Posted by Macdaddy1

Do you measure the face of the trans output yoke and the face of the diff to determine if they are parallel?

Yup!
That’s what I have done.

[Macdaddy1]

OK thanks a bunch now it is making sense which gives me some projects to work on this weekend.

[PGSigns]

DO NOT measure the rear for being in the middle now! The track bar will have it pulled to one side while it is hanging down. Just like the pinion angle you cant take any measurements while the rear is hanging. If you want to see if the rear is close and if you are in the ballpark on pinion angle pull the rear springs and jack the rear up and put it on jack stands. Do you have an idea if you are going stock height or lowered? You can get a measurement from the frame to the housing from one of us to get the rear set close. For centering the engine look to see if the front and rear of the engine are in the same line in relation to the frame. What I use is a chalk line on the floor. Drop a plumb bob from the center at the back and front of the frame and put a mark on the floor. Pop a line from the two marks. Now drop the points from the front and back of the engine and see where you are. The engine does not have to be centered as much a in a straight line parallel with the center of the chassis. The rear can be a bit off of of center also as it will shift from side to side during the travel as the track bar swings through its travel. If you are going lowered one of the things that happens with the trailing arm suspension is the pinion angle needs to be corrected. My 66 has 6" of drop in the rear and I have 2 1/2 degrees of shim in it to fix the pinion angle. You can do the math to see the angle change on the pinion by taking the distance from the center of the trailing arm pivot tot he center of the rear end and multiplying that by .017.
Jimmy
Jimmy