driveline angles

quick question about driveline angles.
adding a transfer case drop kit reduces the driveline angle at the rear output shaft of the transfer case, correct? does that also increase the driveline angle of the output shaft in the front?

Yes, and then some. The powertrain is a three point triangle between the engine mounts and the tranny mount, so if you lower the rear mounting point then the angle will change all the way through the motor mounts up to the front of the engine.

92tahoexj said:

quick question about driveline angles.
adding a transfer case drop kit reduces the driveline angle at the rear output shaft of the transfer case, correct? does that also increase the driveline angle of the output shaft in the front?

Click to expand...

Sure does,thats why a T-case drop is such a bad idea.You lose ground clearance and never really fix the inherant problem!

thanks, that's what i assumed. so, removing my tc drop will help reduce my front vibes and i will be able to get my caster closer to factory specs ?

The angle of the driveshaft where it meets the transfercase isn't typically a factor in the front driveline setup. The effort is spent on trying to get the pinion inline with the driveshaft, but nothing is done to get the driveshaft angle relative to the transfer case. It won't do much of anything for the pinion angle and therefore won't directly help with the caster either. However you might be able to get rid of some vibes by relaxing the joint.

Folks lower the TC to resolve rear driveline vibes. Usually, it won't CAUSE front vibes because the front driveshaft is a double cardon type what can better handle the angle (rear is slip shaft at TC with simple u-joint at differential).

Lowering, or un-lowering your TC won't have any impact to front caster.

Lowering the TC actually will change the angle of the front driveshaft (obviously) but not much, and will affect the angle of the single U-joint at the axle end of the shaft as a result. So yes, in a roundabout way it will limit the range you can set your caster to, but not significantly. The best way to figure out the limitations would be to measure the driveshaft length, angle, TC output angle, pinion angle, etc and play around a bit with some trigonometry. Really doing a TC drop is just a band-aid and to do it right you should remove it and do a slip yoke eliminator install. Remember you'll need to shim the rear axle significantly when you do an SYE, since the pinion angle has to go from being a few degrees below the TC output angle to a few degrees below the driveshaft angle.

maybe my front ds needs balanced. when i remove it the vibes (between 35-55 mph) disappear. the u-joint on the axle end is new.

Have you tried adjusting the pinion angle already

ehall said:

Have you tried adjusting the pinion angle already

Click to expand...

last time i took it in for an alignment the computer printout said my caster was at 5*. that was before i installed the drop brackets. tomorrow i'm installing the adj control arms and them taking it back in for alignment on tuesday.

Caster is determined by axle rotation ONLY, the angle of the arms at the body have no bearing on that. Drop brackets do not affect the rotation of the axle whatsoever, for that matter neither do adjustable arms unless they are actually adjusted to cause rotation.

On mine I eventually ended up to be right in between the optimal pinion and caster angles, a little more towards pinion angle to get rid of vibes.