Bad drive shaft?

[DiverDarrell]

Well I’m going to blame a random vibration on a bad drive shaft. I did the test and I found some movement with the dial indicator. I will be taking it to a dive line shop tomorrow for further inspection and see what they say. The other day I got .02” movement in the splines, but today I only got .003”. But found that their is noticeable rotational movement in the splines. I’m not looking forward to what the price of a custom HD high speed driveline is.


EDIT:

Through this process I have learned a lot about our drive lines and will share some findings.

1. The FMTV's use spicer 1610 drive line components
2. The drive shaft diameter is 4" , wall thickness is unknown.
3. Drive shaft RPM at 60MPH
Tire Diameter 46.4" travels 12.157' per revolution. 1 mile = 5280.
5280 / 12.157 = Wheel RPM of 434.317
Our stock axles have a 7.80 final ratio (diff & hub combined), and the high speeds are 6.14
RPM for a stock is 7.8 x 434.317 = 3387.6 and for the high speeds 6.14 x 434.317 = 2666.7
4. Using Splicers Safe Driveshaft speed calculator Safe driveline RPM is 3952, but list a 1/2 true critical speed of 3516. at the 1/2 true critical speed there is a harmonic vibration that may occur.
5. There may be a cardboard resonance reducer inside the tube
6. I don't know our drive shaft angles but at 3500 RPM the max listed is 5 degrees, 3000 RPM is 5.8 degrees, 2500 RPM is 7 degrees (RPM is shaft not engine)
Splicer also states any universal joint operating angle greater than 3 degrees will lower universal joint life and may cause vibration.

 

[DiverDarrell]

So today I dropped off the drive shaft to driveshaftsNW in fife WA. After a min of discussion with the guy at the counter, he went and grabbed his lead tech. I explained the particulars of the LMTV and driveshaft issues of the past. He was very receptive and wanted to know more about the drive shaft speed causing the harmonic un balance. So we calculated drive shaft speed at 60mph with the hub reduction and high speed gears. He assured me that the 1610 series of drive shaft components on the upgraded stock shaft are more than capable for the truck, and he would test my drive shaft to see how it was before proceeding. If he did have to rebuild he would spin test the shaft to rpms exceeding expected use after balancing. Now I can see why they came so highly recommended. They do drive shafts for mining trucks to trophy trucks and rally cars.

 

[aleigh]

Well done. If my truck ever moves again hopefully I can get around to this... haha. Let us know how it turns out!

 

[Suprman]

Quick test you can lay under the truck on cardboard with some gloves on and shake the driveshaft hard. If you can feel any play then something is worn.

 

[Johno176]

Agreed, any movement in the spline portion as said else where, should be grounds for replacement. Movement = vibration.

 

[hangarhermit]

DiverDarrell, please be sure and keep us updated on your driveshaft diagnosis and progress.

 

[scottmandu]

Those shafts can be rebuilt so to speak, retubing a shaft or resplining one is quite a bit cheaper than buying an entire shaft new.

 

[DiverDarrell]

Here’s an update, just got a call and they said the axle checked out in spec! I’m going to have them knock the weights off and re balance. For the peace of mind, I’m going to pull my front shaft and have them check that out as well. Going to install all new joints on re-assembly. If this doesn’t fix my viberations then it has to be in the tires.

 

[Suprman]

I have had trucks come in that had dried mud caked on the inner side of the rims like concrete. And it was hard to see unless the rims were off.

 

[aleigh]

What tires are you running now? The Michelin XMLs seem a lot harder to get balanced than the Goodyears I used to run were. Every so often a goodyear would come out wrong, the XMLs seem to come out wrong half the time, even when I get them professionally mounted (although I claim I mount them fine).

 

[DiverDarrell]

I had xzl’s on the front with the airsoft pellets and goodyears in the back. Viberations started after I put goodyears in the front. My lathe is almost back up and running, once I make a ctis adapter I’ll put aluminum rims on all 4 corners and do the airsoft pellets all around.

 

[DiverDarrell]

Just picked up the drive shaft. They spun it on a high speed balancing setup and comes with a 90 day warranty.

 

[Suprman]

Thats one good lookin driveshaft

 

[DiverDarrell]

We will see, next up is to mount it, then mount my go pro up to see how things are spinning. I may take the front to them as well for cheap insurance.

 

[Suprman]

Its the highway driving that does them in. I think with the high speed gearing you would get longer life out of them. At 57mph they are really humming away.

 

[DiverDarrell]

WELL I’ve got the highspeed gears to help. Have brand new joints to install as well. The 2:1 hubs sure don’t help driveline speed but do reduce the torque. I’m going start greasing everything more often that’s for sure. From what I have read and learned at the drive line shop is that often truck shafts have cardboard in them to dampen resonance. If this stuff deteriorated it causes balance issues. Also interestingly my shafts would not balance as nice at slower speeds. After discussing this with the shop they balanced at a higher speed, or more like the normal range for our trucks. I highly recommend anyone looking to have work done on their drive shafts, look for a more heavy duty shop, as they will have more experience and equipment to handle our Drivelines. Also nice that they had u joint in stock for 48 bucks each. I highly recommend Drivelines north west. They do shafts from rock buggies to maritime ships. I got all my questions answered and they showed me how they did it. Also if you need a driveshaft rebuilt heavy duty places will have the parts on hand.

 

[NormB]

I have had trucks come in that had dried mud caked on the inner side of the rims like concrete. And it was hard to see unless the rims were off.

This caught my eye so I’ve been reading through the thread.

NOT LMTV-related, but close.

I’d bought a pair of wheels/tires for my trailer not long ago and finally got around to cleaning and mounting them.

Inside of the wheels didn’t look right. Looked like someone had shot paint that was really rough, lumpy even, so I took a wire brush and pressure washer to them and was amazed at how much stuff came off; paint, caked mud, sand. Took an angle-grinder with wire brushes to clean down to metal and painted with a rattle-can - Rustoleum rust converting primer.

I’m sure they’ll wobble a whole lot less now.

 

[Awesomeness]

Also nice that they had u joint in stock for 48 bucks each.

Another thing that is smart to put on is safety tab washers on the u-joints. They are basically sheetmetal plates that go on top of the u-joint caps and under the bolts. You bend the tabs on the sheetmetal up against the heads of the bolts, to prevent them from loosening accidentally. Once one of the caps works loose, it's game over, as far as vibrations are concerned.

Seen with a u-joint here...

 

[coachgeo]

... From what I have read and learned at the drive line shop is that often truck shafts have cardboard in them to dampen resonance. If this stuff deteriorated it causes balance issues.....

but the question is.... does it deteriorate..... because of imbalance and not it causes imbalance. .. granted water getting in could as well. Quick review of literature... it is common and since it is in there to reduce resonance..... Id say for us that is a good thing

https://www.carid.com/spicer/tube-deadener-mpn-231753-1.html

 

[coachgeo]

well.... the above post got me thinking about stuff in a drive shaft....... hmm... wait...... balance beads???? hmmm.

http://www.balancemasters.com/driveshafts.html ok so not on the inside...... but for install purposes.... that is even better.

https://www.youtube.com/watch?v=L0U5fzPuX4o