Front drive shaft length?

[chriskent85]

My truck had a 5" lift on it and I replace it with a 3.5" and moved the transfer case back 1" because I installed an AOD trans. Is this drive shaft look to be the right length. Looks like it may be a little too short to me but I have no clue. I also dont have full weight on the front either

 

[Crush]

Thats a very short spline shaft. Is it new? Who made it?

 

[chriskent85]

It was on the truck when I bought it and then started the teardown. I didn't see any markings on it.

 

[DirtDonk]

It's not long enough at this point in the build.
Looks like an original style where the splines are not visible outside of the seal. Some aftermarket types do have splines almost all the way up to the tube, but this style should have the seal riding on the smooth part I do believe.
In fact, you can see where there is a spot near the middle upper part of the smooth section of shaft that appears to have at one time or another had the seal riding on it.

You won't know for sure what you need until you compress the suspension, but it looks like you will be needing a longer shaft due to the transmission pushing things rearward combined with a little bit of lift.
Normally, the 3.5" lift alone is not enough to warrant a longer shaft. But combined with the new location of the transfer case, you will likely need one this time.

There are situations where those that have done what you did simply swap the front for the rear. Or at least one of the old shafts works in the other location and they only need one new shaft. You could at least check that to see if the old rear shaft is a better fit now.

Good luck,

Paul

 

[DirtDonk]

Oh, and if you want to check it for size before you finish the job, you can ratchet strap the suspension down to an approximate distance of 10.5" (give or take 1/2") between the top of the axle tube and the bottom of the frame.
This is not an exact science, and each EB is different. But it gets us very close to what we need for measuring and comparing purposes.

And if gives you something else to do with all that spare time you have while restoring a truck!!!%)

Paul

 

[chriskent85]

dont think i'll be able to switch them up. the rear is 35.5" from yoke nut to yoke nut and the front is 28.5" from nut to nut

 

[sprdv1]

I'd lean toward measuring when ready and replacing..

good luck

 

[DirtDonk]

dont think i'll be able to switch them up. the rear is 35.5" from yoke nut to yoke nut and the front is 28.5" from nut to nut

Then your relocation did not change things consistently. Which seems odd.
The 28.5 puts yours approx. 4-5 inches longer than normal. Which seems consistent with what you did. (although your nut-to-nut measurement is not quite how we normally do it for determining shaft length). But your rear at 35.5" is just at the long side of normal. We keep that size in stock.

Presumably these measurements were taken with the chassis still well above expected ride height? That would explain some expected discrepancies, but that sure seems like a lot of shaft to shorten just by compressing the suspension. Since we're expecting things to be at least 1" shorter than stock, that long measurement of yours is strange.
But at current height, nothing is going to be as needed when you end up at ride height. So it's just all guessing at this point.

If you want more accurate readings ahead of time, you will still have to compress the suspension to the previously mentioned level, AND verify the rear pinion angle is correct (or correct if needed) because that has a huge effect on your shaft's length.

Paul

 

[chriskent85]

I did move the rear axle back 1" as well. I will probably just weight till I get the truck together. thank you for all the info.

 

[jmangi62]

I just went through this, for an accurate measurement make sure to measure from center of bearing cap to center of bearing cap, then I called WH and I ended up with a Woods shaft, sweetness!

 

[chriskent85]

Is it also normal to have the double u-joint on both front and back drive shaft. If so I guess I should install those on the transfer case then measure from there?

 

[chriskent85]

Nevermind, I will answer my own question. I looked on all the vendors sites and they all have the double joint

 

[jmangi62]

Yep, both fr & rr, transfer case side.