Question on fabricating a gearbox X-member

[OzRod]

The vehicle is a 1970 Holden ute. I have the need to design a gearbox crossmember for a Ford Toploader up against a 350sbc. I have seen many fab'd crossmembers made and know the design and materials needed. I consider my welding good enough to attempt this.

I have everything installed on the vehicle (engine, gearbox, tail shaft, etc) except a gearbox crossmember. The car is on stands with the rear leaf suspension compressed, and the front suspension just hanging there.

I am a home mechanic not an engineer, and therefore this is not common sence to me..... so may I ask....

How far UP should I mount the gearbox? Are there any rules of geometry that I must abide by in relation to the tailshaft angle?

I'm probably worrying about nothing as usuall, just want to get it right the first time i gues.

Cheers,
Chris

[Bob Paulin]

The vehicle is a 1970 Holden ute. I have the need to design a gearbox crossmember for a Ford Toploader up against a 350sbc. I have seen many fab'd crossmembers made and know the design and materials needed. I consider my welding good enough to attempt this.

I have everything installed on the vehicle (engine, gearbox, tail shaft, etc) except a gearbox crossmember. The car is on stands with the rear leaf suspension compressed, and the front suspension just hanging there.

I am a home mechanic not an engineer, and therefore this is not common sence to me..... so may I ask....

How far UP should I mount the gearbox? Are there any rules of geometry that I must abide by in relation to the tailshaft angle?

I'm probably worrying about nothing as usuall, just want to get it right the first time i gues.

Cheers,
Chris

A Chevy small block should tilt downward toward the rear approximately five degrees.

You can set a protractor across the lifter valley - OR - you can install the intake manifiold and set the carburetor mounting surface level. The five degrees is built into the intake manifold.

As far as the cross member goes, you probably want to make sure that it, somehow, comes apart once you have welded the ends to the chassis....and that it comes apart wide enough to allow the transmission to drop down through the crossmember.

You can fabricate something up using flanges similar to header hookups, or you can weld a piece of angle iron to the chassis, and bolt the crossmember to that.

Keep in mind that it is a hot rod and that you will be more likely than not to be removing the transmission and/or engine on occasion.


Bob Paulin

[30tudor]

You'll also want the pinion angle of the differential to tilt up a similar number of degrees the engine and transmission are down.

[OzRod]

Ok thanks Bob and 30tudor for the info. I wouldn't of known the 5* rule for the sbc. I will use the carby surface as my guide.

Thanks again. :b-d: