I'm thinking about hard mounting my front diff from both points (no rubber bushing), would this create any problems? I've also got a pile of subaru driveshafts with no slip-yokes, and not enough Lada shaft parts to make drivelines. If I hard mount my diffs are slip-yokes necessary? The t-case mounts have rubber, and the tranny-to-t-case shaft still has the spline output on the tranny for some movement as well.

 

On a side note, I was pulling the rear suspension out from under the car, and noticed that the tube part of the crossmember looked suspicious. So I tapped it with hammer and sure enough the undercoating flaked away to reveal swiss cheese Good thing I found that, I'm not sure how long that would have lasted under a lift and 30s. Its wierd how some parts are completely disintegrated on my car, and others are fine. I suppose it must be from salt damage.

I did a study of the IFS trucks in the parts yard and found that all but one of them had the front diff hard mounted. I chose a hard mount myself. I would not suggest relying on the splines to function as a slip joint, they aren't really designed to slip under load like the slip joint is. Given the chassis flex and driveline movement I would use a slip joint on each shaft for sure. I am picking up my shafts monday and I had them built from scratch other than the slip joints from the nissan shafts so that they would be true (very hard for a shop to do from a collection of parts) and have greasable U-joints stouter than stock. As for the tranny to Tcase shaft, no slip joint is used.

 

Another reason for the slip shafts is: how the heck ya gonna get a solid shaft in there? My rear diff and T-case are in rubber, but there is no way I could get the rear driveline in there if it was a solid unit. The flanges actually have a little recess to them that help hold them. Would be like trying to put in a rear axle without any slip in the DOJ's.