Rear driveshaft length question

[Soylent]

Just installed a rebuilt dana 20 as well as the WH extreme duty output assembly. The current shaft is too long. I measured the running length at 33”. WH website says go with next size up if you are in between. Their smallest is 33.5”. The sales person recommended a custom length of 32.5” want to get opinions if this is the correct length. I’m running the WH 2.5” suspension lift. @DirtDonk

 

[73azbronco]

I'd go with what the sales guy says.

 

[Yeller]

Here’s the easiest explanation I know of. Tom Woods 4xshaft.com can’t go wrong ordering from them either.

 

[fifeb]

You could go to another shop for a second opinion if this one does not satisfy you

 

[Soylent]

Ok thanks. I think I will call Tom Woods directly as they are making it for WH. Just want to be sure as I would guess this is a non-returnable item being a custom length.

 

[DirtDonk]

Don't have an exact answer for you from experience. Plenty of the output shaft installs here though, so maybe others can relate their experiences.
But first, are your doing this with the vehicle on the ground, fully put together (not a frame only in other words)? Sounds like it, but I wanted to make sure.
And before you measure for a new one, make sure your rear pinion angle is correct so it does not skew the length and give you a falsely long measurement.
That does not sound like an issue here either, but any time you lift the rear, the pinion can/will change.

Then follow the usual measuring methods, such as we describe on our site, and see what you end up with.

Paul

 

[Steve83]

The length relates primarily to the slip-joint. If the shaft is too short for the truck, then the slip joint will pull apart at full droop. If it's too long, the splines will bottom in the yoke & punch the cap out against the u-joint, damaging it, the t-case, the rear diff...

So measure the d'shaft length at normal ride height, at full compression (use sandbags or water jugs, or barbell weights...), and at full droop.

 

[Soylent]

Sounds good. The truck is complete and at it’s regular driving weight. I have the 6 degree rear shims in to correct the pinion angle. I spoke with Sean at Tom Woods who said 33” would be correct for me. I understand the idea behind full compression and droop but this truck won’t be rock crawling. I don’t have a way to fully compress. Can’t get to my lift as garage is now full of kitchen cabinets and appliances after the AC gave us a surprise flood while we were in Vegas.

 

[DirtDonk]

Always while you’re away from home. Right?
How the heck do inanimate objects know when we leave the house? I’ve yet to figure that life mystery out.

 

[Soylent]

They do it in the best way. A little stream of water coming down the driveway as we drove up.