G Force Crossmember 700R4 Transmission Angle

[Texas82GP]

I had to modify that same crossmember for use with my T5. The transmission was sitting way too high. Check out posts 387-388 and then 403 in my build thread.....

Space City 1982 GP Build

The trunk looks good. I may have to do that.

gbodyforum.com

 

[Michael Bennett]

It just dawned on me that maybe Im measuring the trans angle wrong?? Im measuring with the angle finder on the pan bolts because I cant get to a machined surface without pulling the pan. Where should I be measuring the trans angle.

 

[fleming442]

Both yokes

 

[Michael Bennett]

I measured another 700r4 we had rollong around the shop and the eng mounting surface and pan surface seem to 2-3 degrees different so the back of the pan angles up. Seeing that, I Measured off the front of the cylinder head and got 2.5 deg down angle. My driveshaft angles down 5 deg so that would give me 2.5 deg difference. My pinion angle is 1.5 so that would make it good?

 

[Michael Bennett]

Both yokes

The front yoke is right above the exhaust crossover and it doesnt have a machined surface.

 

[fleming442]

Pinion Angle Measurement

www.quickperformance.com

 

[Michael Bennett]

Measured at the front yoke with the socket method and right off the u joint cap. Got 2.5 deg down just like I did off the head.

 

[fleming442]

From what I understand, that's perfectly acceptable.

 

[mstravens]

My transmission agle seems wrong. With the car on the hoist and the frame level, the transmission is tilted up 2.5 degrees at the rear. When I drained the fluid it actually came out of the front of the pan first. That's what made me notice it. The angle between my trans and driveshaft is 7 degrees which seems like way too much as well. I'm measuing the trans angle off the pan rail surface. The trans is mounted using a G Force crossmember for my 700R4 and energy suspension mount pn 3.1108G. The small block chevy is mounted using stock car clamshells on the engine and factory style V8 mounts on the frame. Also, I am getting vibration at the big end of the drag strip and I believe it's coming from the driveshaft to trans angle. Trying to figure out where I went wrong? What's wrong with this combo?

I do not know for sure, but check your your U- Joints for bad or going flat needle bearings

 

[dedub]

I agree that angle is wrong. Most G-body's have a -2 ish degree angle from parallel ground (some variances obviously) That is referring to the crank which is the same as the rest of the drive line. From there, most drive shafts will increase in negative angle to the rear end. You didn't mention if you have adjustable upper control arms, but that's where you can make your pinion angle less obtuse. If there is a difference of more than 3 degrees in any of those two points you will have vibration issues. If you have solid uppers, you're going to have to experiment with different transmission mounts and shims. If you have a +2.5 from ground like you said, that means you already have close to a 5 degree difference! No bueno.
There are books written on this and 1000 opinions. IMHO, you NEVER want a 0 degree difference between the transmission yolk and drive shaft, or the driveshaft and rear end. at a minimum a .5 deg, you HAVE to make the universal joints do there job. Next.... Try and match angles. ie, if the DIFFERENCE between the driveline and driveshaft is 2.5 degrees, adjust your uppers to get the same angle at the other end of the drive shaft. Keep in mind when you adjust one, if affects both so it's a balancing act.