Pre Spring-Over planning...


If I do not intend to to use a double Cardan type joint on the TC ends of my driveshafts, then I don't see the point of rotating my diffs.

Uni-joints on the driveshafts give the least vibration when the axis of the TC ouput and the axis of the diff pinion shaft are parallel. Also, rotating the diff so that it points at the TC will compound any axle-wrap and make uni-joint binding more likely.

I have two spare axle tubes ready to go. I just want to be comfortable with the rotation of the diffs before I start cutting and welding. I have seen so many people rotate their diffs when doing a spring over, but I am not convinced that it is the best thing to do.

Can anyone convince me either way?

Thanks

Ben

Ideally the TC and Diff should be parallel with an angle at the universal of between 1-3 deg.

The problem with high lift vehicles is that the angle is too much. So you rotate the diff the minimise the angle but that in turn does not leave the diff parallel.

Basically it is comprimise between the two. Leave the angle as is and it will vibrate, rotate it and it will vibrate.

From personal experience on a landcruiser I found that rotating the diffs was alot better than not rotating them.

If you have a '40 you can get away with this due to the length of the stock driveline. On a Wagon the front driveline is too short not to rotate.

I have seen it both ways and since it is such a straightforward job, i suggest you rotate the knuckles, add some caster (4-5*+)
and reverse the shackles to gain a better approach angle.

Do it once, do it right.:smokin:

With my FJ40, the front driveshaft is so long that the knuckles don't need to be rotated. In the rear, however, the DL is so short that I had to use a CV and rotate the rear upwards.

I don't much care about driveline vibration at under 20 MPH:)
My $0 is a trailer queen...

But, I rotated my diffs F&R in order to keep my U-Joints off the rocks...

Just another view.

Cory

When I didnt rotate mine I had problems in the front with the uni maxing out. Not good. Rotating the diff fixed that problem for me.

Rotate it, it is heaps better.

When running CV joints (double cardan) as you intend to, not rotating the diff up will actually cause a vibration. U-joints need to work in pairs to cancel out their natural vibration caused by working at any kind of an angle. The CV does this in itself so the joint at the diff must have very little or no angle on it in order to not have a vibration. I hope that made sense.:)

Thanks everyone.

I am still unsure. I am trying to keep the lift as low as possible. I have a full set of 55 springs (I realise the rears are longer) to replace the 2.5" OMEs under it now, and I will take the 2" bodylift out. I am aiming to get the leaf pack as flat as possible by removing the lower leafs. I am only going to use 33s or 35s at this stage so clearance isn't really an issue. My main goals are to get better articulation, and soften up the ride.

I have two sets of axles, so i will do the mods (no rotation) on the spare set and swap them in. If I don't like it I can do the rotation on the other set and then swap them back. Sounds like lots of work, but I can do the axle mods at my leisure and keep wheelin'.

i left the front but had difficulties with the shackle reversal plus rotating the front is a head spin
lift the back a few degrees 15 for me i think, and the front was dead level, so i didnt have to worry about a cut and rotate, cause itd be a mission same as steering, plus i had bad visions of cruiseing up the highway