Single Piece Drive Shaft on XLWB 5-tons

[dk8019]

So I spent a bit of time taken apart the remains of my M814 rear drive shaft, and I'm really struggling to figure out why they went to so much trouble to build a two piece drive shaft as opposed to a single piece shaft. I've heard two piece shafts are used for high speed applications because of balance issues, but I'm not sure that applies to a 5-ton.

My measurements show that a single piece driveshaft would be 77" for my truck, I assume this is longer than the standard 5-ton driveshaft for the M813, and much longer than that used for the M818, correct? Does it seem to long to have a single piece driveshaft built if I'm unsuccessful in locating a replacement? I still need to find the output and input flanges for the transfer case and the rear axle, but I have some good leads there already, as well as a source for them off the rear axle if needed, although I would like to keep 6x6 if possible. I have two good flanges on the existing driveshafts which could be removed and put on a new shaft.

What do you all think?

 

[Nonotagain]

With the amount of suspension travel that your truck has I doubt that a one piece drive shaft would allow for the movement required without breaking something.

The multi piece shafts usually have slip joints to allow for compression of the shaft during full suspension travel.

Take your current shafts to a good drive line shop and have them install new tubes, U-joints and balance the shaft. They should also have the proper carrier bearing.

 

[Recovry4x4]

This would be a great time to add a brownie box behind the transfer case for additional roadspeed. They you can shaft it on either side

 

[NDT]

Somewhere the automotice engineers have a little book that says when the driveshaft is over x long, you need a pillow block. Heck, yours had a pillow block and it threw the driveshaft anyway! I would put it back stock.

 

[dk8019]

I think in this case, the pillow box fell off the frame, hence the horrible damage to it. A brownie box sounds interesting, how would it play with the front sprag drive? I was think the single piece drive shaft would have the slip joint to allow for travel still. My biggest issue actually isn't the drive shaft itself, it's the pillow box that's so messed up, and one of the yokes on one end of one shaft. Any one have a recommended brownie box?

 

[gimpyrobb]

PM sent

 

[Recovry4x4]

It woudln't play well with the front sprag. Guess I should keep my nose in the deuces right?

 

[NDT]

Let's see, the front engages when the rears spin faster than the front, with the brownie, the rears would be spinning at what 30% faster with .7 overdrive roughly, the front would engage at the non-overdrive shaft speed, resulting in ??? Most likely busted sprag. You would have to change the front to selectable engagement.

 

[73m819]

install the mwo air switch, this drops the sprag in neutral, then no prob with the brownie, you would have to make sure that the brownie was in direct before engaging the air for the sprag

 

[dk8019]

Good ideas all around, hopefully I'll just find a complete drive line from another XLWB truck and go from there.

 

[steelsoldiers]

GIJoeCzar just went through this with his 814. His carrier bearing bracket was cracked badly. He could not find a new one through the regular sources so he had a machinist relative make a new one. Shoot him a PM if you are interested.

 

[dk8019]

I talked to these guys today:
Dayton Clutch&Joint

They think that a single piece driveshaft, with a fairly large shaft diamter, say 4-5" should do the trick, and they can reuse the welded yoke ends on my existing shafts. So now all I have to come up with are the yoke ends for the flange plates on the tranny and rear axle and I should be good. I scored a pair of U joints off ebay for $30 for the pair, and I've torn the other shafts all the way down to the shafts. I'm taking the parts over to them on Friday after I return from the business trip and see what they can do.

 

[drjconley]

I think I need someone to explain why a brownie box wouldnt work in a forward gear. It is my understanding that the sprag engages when the rear output shaft rpm is higher than the front output shaft rpm. Wouldnt a brownie box reduce the rear output shaft rpm for any given road speed? Why would the sprag engage? If you were to go into reverse though, I think you would have a problem with the brownie box.
Jim

 

[dk8019]

drj,

I actually came to the same conclusion, the output shaft velocity is what matters, and as long as the front wheels are being pushed faster than the fronts, then the sprag wouldn't engage.

 

[drgreg]

With the amount of suspension travel that your truck has I doubt that a one piece drive shaft would allow for the movement required without breaking something.

The multi piece shafts usually have slip joints to allow for compression of the shaft during full suspension travel.

Take your current shafts to a good drive line shop and have them install new tubes, U-joints and balance the shaft. They should also have the proper carrier bearing.

The longer shaft would reduce this problem vs. a shorter shaft.

 

[dk8019]

That's part of the thought after talking to the guys there. They think it should be easy to do, even a 4" shaft should work. Given the issues private guys have with them, and the obvious problem the military had with them on my truck, a single shaft should reduce the issue.

 

[Nonotagain]

The longer shaft would reduce this problem vs. a shorter shaft.

Well Doc, I hate to tell you this, but Spicer Gear recommends a maximum of three degrees angle on drive line components.

http://www.spicerparts.com/measuring.asp

When exceeding this limit, you only have a few choices to correct the angles. Multi piece drive shafts using carrier bearings, CV joints on the forward most shaft or changing the angle of the drive line (lowering the transmission / transfercase mounting brackets) or using shims on the springs or rear axle.

This pdf from Spicer is about 2 mb in size, but gives a lot of good information on designing a driveline and sizing the components needed based on horse power and torque.
http://www2.dana.com/pdf/DSAG-0200.pdf