TT driveshaft length quetion

[the frog]

let's suppose that a vehicle's required travel at the rear end is 33" - what would be the minimum length of the driveshaft(u-joint center to u-joint center)?

i'm asking this because i don't want the car to have too much WB and therefore i'll make the driveshaft as long as absolutly necessary and as short as i possibly can.

this involves ofcourse an answer to the question - what is the maximum angle that will still allow a drive shaft to work well at high speed?

thanks for answers from those who really know....:)

[Brandon_Charley]

What u-joints are you using? I wanna take a stab at this and see how much I remember from High School Geometry.

[partybarge_pilot]

Knowing the max angle of the joint is only half of what you need. It will give you the max droop, but the chassis will determine max bump. Also, rotation of the rear for anti-squat will have effects on travel also.

[Samco Fab]

The shorter your upper links are compared to your lowers, the more your pinion will rotate down as it droops.

Like Partybarge mentioned, if you have adjustable anti squat suspension link mounts, check your driveshaft to see if it binds when you adjust your antisquat. I made an antisquat adjustment to a rock buggy once, and found out the hard way that it changes the way the pinion rotates as it droops...oops.

Also, most Trophy Trucks use a 1350 u joint, which is pretty strong, but you could probably get more angle out of a 1450 joint, I dont know exact numbers, but the 1450 is common enough for most rear ends, and has more angle and similar strength as a 1350.

I bet most Trophy Trucks are not designed around the limits of rear driveshaft length and angularity. Chassis packaging and geometry is probably much more important than total driveshaft length.

Look at the Herbst 4wd Trophy Truck, or the McPherson Big Mac. They are relatively normal wheel bases with pretty common Trophy Truck engine positions, but they probably have somewhere around a 12" shorter drive shaft length in the rear with similar rear droop. I never heard of a ton of problems with drive shafts on either trucks, but someone with more experience with these trucks might know better:p