Quote:
Originally Posted by TheWhiteElephant
Okay, I have to clear up some things here.
First off, lowering the T-case is not meant to help with the length of the driveshafts. On '73 and up trucks, installing the lift will increase the angle of BOTH driveshafts. What this does is create a vibration in most situations, especially in shorter wheelbase vehicles like K5 Blazers or short wheel base trucks. Lowering the T-case will decrease the angle again, therefore eliminating vibration in most cases.
Think about it this way--when you lift a truck, you "push" the frame and t-case up while the differentials stay at the same height. The higher the truck goes, the more severe the angle of the driveshafts. Since the driveshafts connect to the t-case, if you lower the t-case, you will decrease the angle of the driveshafts.
I lowered the t-case on a '79 K5 I had with only 4 inches of lift and felt a noticeable (huge) difference in driveline vibrations. Depending on your truck, you may already have some factory spacers on the t-case mounting bolts on top of the frame/crossmember at the t-case bolts. You just need to relocate these spacers to the bottom of the frame between the frame and crossmember. Very easy one-man job.
Bottom line here is that lowering the t-case decreases the driveshaft angles. By the way, I'm not familiar with the '67-'72 suspensions. Hope this helps.
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67-72s are the same design. I absolutely understand everything involved with lifting a truck. That's why I say,if you think about it,only the rear shaft angle is decreased by spacing the transfer case lower in the frame. The engine,transmission,and transfer case are all mounted together as a rigid unit. This "unit" mounts to the frame in the front using the motor mounts and in the rear using the mount under the transmission/transfer case adapter on top of the crossmember. So,when you lower the rear mount you tilt the unit down to the rear. I can see how this will decrease the angle to the rear shaft. But,I see it cancelling out what it's meant to gain by increasing the angle to the front shaft. It is the shortest shaft with the steepest angle. I have never lifted a K/5 more than 4" and that much angle has not been enough to cause concerns in anything I've driven...no vibration problems,broken u-joints,or even prematurely worn ones. It just seems that raising 4" and dropping 1" isn't really going to help the angle much at all anyway and you lose 1" of high center clearance. If people want to drop transfer cases,I don't care. I'm just saying I have never done it and don't feel I've missed a thing by not.