All things being equal (same springs) will a SOA with an axle turn up towards the TC in the REAR yield a longer or shorter driveshaft length (distance from flange to flange). It seems the SOA would lengthen the distance and then the turn would shorten it again.
I got this all backwards I think... I'll wait till I can get more info or think some more about this... I think the DS will be shorter, all things being equal..?
I used stock driveshafts on my BJ60 when I sprung it over. My springs were pretty flat. The slip joint were pulled apart more than when I was S.U. I have since added a couple of leaves front and back, and the driveshafts are at their limit, although I haven't had one come apart while wheelin. And just a note: BJ60's have a double cardan front driveshaft. And unless you use a DC rear driveshaft, you shouldn't point your pinion at your t-case. I have found that a IFS 4runner front shaft is about the right length for my truck now, I just have to figure out how to put the larger cruiser flanges on it. Hope this helps.
Just having a geometry homework moment... I don't have the opportunity to actually DO the SOA and do before and after measurements tonight (it's dark and cold out there)
I was just askin' what people's experiences have been.... Do YOU have any experience that you can share?
The most critical measurement is collapsed. You can survive a drive shaft that pulls apart on the trail
but you can bust a T-case with a drive shaft thats too long. Throw away the pictures, measure flange to flange with the axle fully compressed, even if it means pulling the leaf pack apart, then measure
again at full droop. This will tell you if your slip yoke has enough travel. The only measurement I give a
driveshaft shop is a collapsed length. They can't screw that up much.
Would "fully collapsed" be with the axle sitting on the bumpstops on both sides at the same time? While this is not a realistic situation it certainly would be the limit of compression...
Would "fully collapsed" be with the axle sitting on the bumpstops on both sides at the same time? While this is not a realistic situation it certainly would be the limit of compression...
now, assume you never lose a bumpstop while wheelin in the woods....
and assume you never bend a leaf spring.....or shear a center pin....
any good driveshaft shop will not need to build a shaft that works PRECISELY within the limits....add a long-slip and you can cheat a lot of the numbers...I've always run 11" stroke front shafts for this very reason, the travel allows me some fudge factor and piece of mind
When you get the springs and the axle situated, just do a test fit with the axle at full drop. Make sure you have a t least two inches of spline engagement at the slip yoke. Since you are planning on turning the diff up towrds the T-case, I assume you are going to run a CV joint on that rear driveline? If so, you're going to the driveline shop anyway. If you're not planning on doing a CV but you are planning on pointing the diff up, you will get vibes, bad vibes.
Of course I don't want the shaft pulling apart but as was stated earlier that's not as bad as destroying the TC cause it compressed too far.
Prudence dictates that it would be wise to measure BOTH the maximum realistic compression (to the bumpstops w/o springs maybe - hey, if you break a spring/shackle etc you have big problems anyway) AND the full droop (with the springs in place). THEN add a fudge factor in both directions.
I've yet to have any issue with rear shafts....thus far, in every SOA I've done, the stocker works...since the springs mount solidly at the same side as the t-case, the change in length is minimal....and that issue becomes less with the added driveshaft length of the 60/62 series
Been a while since I've worked with an SOA rig, but I can't recall much more than 1" of total movement at the splines...for a rear shaft...
now, a front shaft with a shackle reversal is a different story....MUCH different....
On my 1985 fj60, i bought a 1983 front shaft with a double cardon cv, as they came stock with that cv in the earlier 80 models. I then extended it 4 inches. works great no vibe.
I agree about the long slip joint for a front shaft with a shackle reversal. They are not cheap though-about $200 installed in your driveline.
In the rear, because of the conventional shackle arrangement the length does not change that much with cycling of the spring. As the spring compresses bringing the pinion closer, it also lengthens pushing the pinion further away. The net is just a small movement at the slip joint. Our local driveline shop sets them up with roughly 40% compression reserve and 60% extension. I've never had an issue and they always seem to nail the length perfectly.
One other thing I noticed, and I'm sure this isn't news, but the mini-truck CV shaft has a longer slip joint than the Cruiser (FJ60) CV shaft. Significantly longer, actually. The only problem is that the mini shaft has the wrong bolt pattern at the differential end, so to use it would require drilling out the flange.
