I have an 86 K5..with 6-8in lift. (Blocks/springs in back..switching to all springs in the winter) and was told my driveline angle was too much. Someone told me about a kit to lower the t-case and restore/lessen the angle. How exactly does that work and are there any major cons to doing it??

 

Doing a slip yoke eliminator kit would be better then trying to lower your t-case. If you would lower your t-case all the linkage and front drive shaft angles might be wrong too.

 

Lowering the transfer case refers to unbolting the transmission cross member from the frame and using anything from a washer to the spacers currently on the top of the frame or a solid chunk of metal to mount the transmission cross member farther away from the frame.

There are a few things that happen when you lower the cross member. Yes, the rear output will be changed by a few degrees depending on how much you lower it. It will also tilt your engine, bringing your distributor closer to the firewall. The lower fan shroud might start to contact the fan blade. Finally the front drive line angle will get worse.

SYE kits are available for NP241's, you can also modify a NP208 by combining the short output shaft from a dodge 208. It is a fairly involved swap gut you'll gain a few inches in rear shaft length that will help by a degree or two.

I think the best solution if you're going all the way up to a 8" lift is to upgrade your drive shaft to a double cardan or CV joint at the t-case output. You will have to rotate the rear axle but it will solve your drive line angles without moving the transfer case.

 

Hey thanks for the info!!! Would a driveline/drive shaft place be able to make the double cardan shaft? As far as rotating the axle...would the degree shims Ive seen take care of that or would I need to have the perch mounts cut and re-welded??

 

Any drive shaft shop worth dealing with will have cv joints around that will work for you.

As far as the rear angle goes that's a toss up. You'll need to measure to see what your specific angles are. I've got 6" springs with a easy inch and a stock 14 bolt out of a suburban and my 8* shims are about 3* too small. Don't use a shim over 8* and never stack shims.

As you rotate the axle remember that the shock tabs will also be moving... Depending on how much you need to rotate the axle you might think about new shock mounting tabs too.

 

Theres a drive line place by me that is pretty good, they are the ones that actually told me about my angle issue when they were re-tubing my rear shaft. So..even if i go with the CV joint set up..do i still have to rotate the axle? why couldnt I just rotate it and use the drive shaft that I already have?

 

The two different types of shafts are single and double cardan shafts. The u-joint has a effect on the rotating speed of the shaft that increases as the operating angle of the joint increases.
I can't remember where the animation is but imagine a joint at a 30* angle, way too much for a joint but just bear with me. the drive side of the joint is going to turn at a constant rate. Now as the joint rotates the first 90* the driven side will be sped up because of the joint profile, now from 90-180* the driven side of the joint will slow down. Again from 180*-270* the joint will speed up again then from 270-360* it will slow down.
As the joint angle increases this speed differentiation during rotation increases. Want to know why you have drive line buzz? Cause your angles aren't right.

this speeding up and slowing down of the shaft is solved in single joint shafts by placing a joint at each end of the shaft and phasing the joints so that they cancel each other out. Pretty smart right But the angles must be within the operating range and still kept at a reasonable angle.

With a CV (constant velocity) joint or double cardan the cancellation is all done within the CV, thus a constant velocity at both ends of the shaft. This means that you need to have close to a 0* operating angle at the other end of the shaft because there is no corresponding joint to cancellation the vibration. A CV joint is better at handling bigger angles, so is the better way to go when using a big lift.

check out "The Ranger Station," they have some good illustrations on drive shafts and operating angles of u-joints.

 

So...whether I stick with my regular u-joint ds or go with a double cardan cv made shaft...I still need to rotate the axle...to get a close to 0* angle...correct? I bought the truck with the lift already on it and plan on ditching the blocks in the rear and putting new springs on. I just dont trust blocks even doing light trail riding. I guess I will wait til I put the springs on and then figure out the angles and either use a shim or if its more than 8* off just get the mounts cut/re welded. I know the blocks that are on there now are angle cut...to what * i have no clue....the pinion does point a lil north already lol.

 

If you are running a single joint shaft, like your stock setup the operating angles of each joint need to be equal and opposite, actually they recommend that the joint at the pinion is 1*-2* smaller than the joint at the t-case.

On a CV shaft you want the joint at the pinion to be 1*-2* down.

This is because as you apply torque to the axle it will rotate, as it rotates it will make the angles work out.