When doing a lift on the rear end, Is it better to rotate the rearend upward or leave it at the stock angle?

I'm Preparing my mind to do a spring over axle conversion on my project truck and I wonder if this is a good or bad idea when welding the new spring mounts??? The conversion should net about 5" of lift.

I would love to hear the thoughts of all you seasoned wrench slingers...

 

If you are using a Double Cardan joint the pinion should point directly at the t-case output.

If you are not, then the pinion should be on the same plane as the t-case otput shaft.

 

Ideally, the operating angles on each end of the driveshaft should be equal to or within 1 degree of each other, have a 3 degree maximum operating angle and have at least 1/2 of a degree continuous operating angle.

The reason for this is because a cardan joint is not a homokinetic mechanism, this means that they produce uneven shaft speeds when operated at joint angles of more than a few degrees, and to correct this rotating speed variation the yokes on the main shaft are disposed with an offset angle of 90°, so that the accelerating and decelerating phases are canceled.

A double cardan joint, despite not being a constant velocity joint, is a good approximation of it, and can manage joint angles up to 5-6 degree in continuous operation.

 

Umm... Is your project truck an XJ? It's already S.O.A. Not trying to be rude...Just curious!

 

Sorry I wasn't clearer. It's actually the chassis of a '92 Explorer that I am rebuilding/lifting by 5" and Putting the body off my 1950 Ford F-1 pickup onto. https://www.cherokeeforum.com/member...loder-chassis/

I thought this was a basic geometry question that the great minds here would have the answers for...

What's a double Cardan Joint?

Does "continuous operating angle" mean when at full travel?

What I am getting from this so far is; it would be best to have the Double Cardan joints and rotate the pinion. I am great at computers, electronics, construction and auto body but "don't know squat" about auto mechanics!

This project is costing me more than I have but I want to do the setup the right way the first time. This should be a one of a kind rig around here and I don't want it to be noted for always being seen on a car hauler! I figure it's worth having the patience to do it the best I can and avoid re-work because I didn't do my homework and tore something up...

Is my take on your replies correct? Is the use of Double Cardan joints the best way to go even if my angle is < or = 3 degrees?

This phase is still in the planning stage, once the body is roughed into position I will be able to measure my ride height, the angles and drive shaft lengths. If the Cardan joints are the best route, I'll weld my spring perches with the pinion rotated and get my drive shaft sized to fit...

Thank you all so much for the infusion of knowledge you share with the posters like me! I know that they say, "there are no stupid questions" …but, "I can come pretty darn close"!

 

Here are two diagrams on how to set it up.

 

Between me, FrankZ and 4.3xj the question has been fully answered.

This:


No, it means normally driving conditions on plane pavement. (highway)

Yes, since you have a 5 inch lift you will probably experience plenty of suspension travel and the double cardan is necessary.

 

Thanks guys! I am so thankful I asked! I'll plan the Double Cardan into the parts list for the rear end. Seems like I should include one up front too. Because of it being IFS and I can't adjust the pinion angle at all, should there be two?

Do you guys have a recommended source or should I get them through the shop that I have make my drive lines? I truly believe in word of mouth. I tried a vender, that I have never used before, for some of my frontend parts and It has turned out to be a nightmare!

Other than waiting for parts, I made good progress over the last two weekends. My chassis is ready for pressure washing/sandblasting and the scrap body has found a new home at the scrap yard. It’s kind of weird having space in the garage again...