driveshaft length question (1 Viewer)

Joined
Jan 22, 2019
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579
Location
Tennessee
I just got an SM465 installed and now I have to modify my driveshaft lengths. The rear driveshaft needs to be cut down to 25" and the front lengthened to 26". Those distances are tcase yoke centers to differential yoke centers. I've got a shackle reversal on the front and tall shackles on the rear. Basically, it's a 4" lift. Does anyone know how much play to give the driveshafts so that they can expand and compress as may be needed on the road and trail? The driveshaft shop recommended setting the length between yokes to be the mid-point in play in each driveshaft, which sounds completely reasonable. But maybe others know better???

Also, is there any reason why I can't switch the front and rear driveshafts? It turns out that the front is the length that the rear needs to be, so that will save money and effort if I can use the front in the back.

Thanks for your help!
 
Joined
Jan 9, 2004
Messages
1,614
You can switch the front to the rear for sure. You will need a longer slip now in the front because of the SR. Mid point in the slip is where you want the front. The rear can be mostly compressed because it will extend more than shorten as the rear suspension cycles. I have gotten away with early mini truck slip yokes on a SR front shaft but it is close and it will come apart if you ever lift your front tires off the ground while trying to climb ledges (catwalk). If your tires are spinning when the front touches back down it tends to drive the axle away from the truck before the weight comes back onto the front. That is usually when you'll have it come apart.
 
Joined
Jan 4, 2021
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2
Location
Cherry Valley, CA
You can switch the front to the rear for sure. You will need a longer slip now in the front because of the SR. Mid point in the slip is where you want the front. The rear can be mostly compressed because it will extend more than shorten as the rear suspension cycles. I have gotten away with early mini truck slip yokes on a SR front shaft but it is close and it will come apart if you ever lift your front tires off the ground while trying to climb ledges (catwalk). If your tires are spinning when the front touches back down it tends to drive the axle away from the truck before the weight comes back onto the front. That is usually when you'll have it come apart.
Would you be safe to go midpoint on both front and rear?
 
Joined
Apr 2, 2008
Messages
9,792
Location
Victoria, BC
Rear you’ll want 1” shorter than the distance measured. ie. 24”

shortening driveshafts is way cheaper than lengthening them. In my case I shortened two front driveshafts ($55 x2) to end up with the almost equal length shafts that I needed. It’s very easy to do (especially if you have access to a lathe). :D
 
Joined
Jan 9, 2004
Messages
1,614
Personally , I try to minimize the amount of slip for better spline engagement. Less wear over time. You could probably get away with a bit more slip on the rear depending on your setup. Monitor it over time and make sure wear doesn't get excessive.
 

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