The lower you go with your rear suspension with that 12-bolt, the larger your U-joint operating angles will be. You can run a 1" drop and easily end up with excellent U-joint angles. A 2" drop would be at the limit for not having to cut the tunnel open to adjust angles and anything more than that I wouldn't recommend unless you were running a Ford 9" rear.

 

Whats the transmission output angle with the forward mounts, 4L80E, with the holley crossmember?
Thanks

 

2.5 degrees is the number achieved during my development efforts, but that doesn't mean a hill of beans to your car unless you measured the same reference point on your frame that I did on my development car with your car at the same ride height and there was no damage to your frame. That reference measurement is only important as to how it relates to the U-joint working angles associated with it, which in the case or your car using the Hooker engine brackets and crossmember would be less than 3 degrees.

 

Todd sorry for all the armature questions. I am really new to this driveline stuff. Engine and transmission work are my cup of tea. Does the transmission point up 2.5 degrees or down? How much tunnel clearance do you have with the hooker crossmember? Do you have enough to push the transmission up more if needed with shims?
Thanks

 

The transmission pointing down. I had a minimum of 3/8 clearance between the trans case and tunnel everywhere. You can shim the tail of the transmission if needed somewhat, but there's only so far you can go before you'll have to cut the floor open. I can tell you from working on the eight various 68-72 A-bodies that I used to develop the components that you will be cutting the floor to acheive desireable U-joint angles using a 12-bolt rearend and any rear suspension drop beyond 2".

 

Thank you so much.

 

If cutting the floor is not desirable and you still want to lower the car more, you can get a CV driveshaft, which is what I have in both the 70 GTO and my Cougar.

http://www.driveshaftshop.com/domest...-or-muscle-car

In the Cougar I also run a CV at the pinion gear, while on the GTO the rear uses a u-joint. If I was to do the GTO over again, I'd do double CV joints. Frank at The Driveshaft Shop will probably tell you that it's not necessary, but the Cougar is super smooth even when the driveshaft is spinning at 5000 rpm...

Andrew

 

Thanks for the advice. I don't like the idea of cutting up my car. Whats the power this driveshaft could hold? I can be tough on stuff.

 

The CVs are very strong. They are designed to be used at the axle after the torque multiplication of the ring and pinion gears. They did testing on a carbon tube and a 1350 yoke failed before the tube.

Andrew

 

Thats impressive.

 

A suitable 1970 El Camino was found to replace the first one we brought in for development of an El Camino/convertible transmission crossmember and found its frame to be severely bent out of shape. I've finished the preliminary in-car mock-up work and so will be moving this project into the CAD phase next week...here's a couple of images for those interested in what a complete Hooker/Holley/Quicktime set-up looks like installed under an El Camino; a convertible installation would look the same

 

Todd,

Presumably the new El Camino had transmission tunnel work to accommodate the T56?

Andrew

 

No Andrew, we're using the forward bias engine brackets and the trans is a T56 Magnum, which has a more forward shifter housing location than the 4th-gen F-body T56...the only tunnel cutting/rebuilding that is required with this configuration is immediately adjacent to the shifter housing. By comparison, the entire tunnel would have to be cut-out and rebuilt If this same selection of components was attempted to be installed using the Hooker rear bias engine brackets...it's a night and day difference.

 

Interesting....Do you happen to have a picture of the interior and shows where the shifter comes up?

Andrew

 

I don't have one in my possession at the moment, but I can surely take one for you on Monday morning.

 

I'd appreciate that!

Thanks.

Andrew

 

Any ETA on crossmember availability?

 

Hey chuckd71, going off the development timeline of previous crossmembers at this stage, I'd guess around 60-75 days.

 

Hey Todd,

Did you happen to take this picture?

Andrew

 

No, I haven't had the opportunity to do it yet as the car is still up on the lift. As soon as I can lower it I'll take a shot for you.