Bad drive shaft?

[DiverDarrell]

Drive shaft shop says they see failed material in drive shafts often. Easiest way to tell is to take the shaft out and rock it back and fourth and listen. Noise is bad, no noise is good.

 

[Awesomeness]

Drive shaft shop says they see failed material in drive shafts often. Easiest way to tell is to take the shaft out and rock it back and fourth and listen. Noise is bad, no noise is good.

A few days ago I posted this over in Aleigh's thread: https://www.steelsoldiers.com/showt...-catastophic&p=2102931&viewfull=1#post2102931

Another thing I've forgotten to mention about my driveshafts is that the rear one had cardboard in it. The driveshaft guys said it's called a "tube deadener", and is intended to reduce vibrations. They took it out of my shaft, and did not replace it because they said it shouldn't be used on shafts less than 20" longer than the rear LMTV shaft. Over time the cardboard deteriorates and flops around inside the shaft, making it difficult to balance in the shop and then it can unbalance itself in the field.

You can see them on page 16 of this Spicer catalog: https://www.drive-lines.com/catalogs...na/J300P-9.pdf

 

[DiverDarrell]

Your post is where I learned of it. Thanks for all your research!! When talking to the driveline shop they say it’s quite common in the larger stuff.

 

[Awesomeness]

Your post is where I learned of it. Thanks for all your research!! When talking to the driveline shop they say it’s quite common in the larger stuff.

Did they give you any advice about removing it or replacing it? I was a little skeptical of them taking it out, since it was put in there intentionally, but they seemed to have a good technical description of how it should mostly be used in longer shafts with thinner walls.

 

[DiverDarrell]

They said leave it until it’s bad, and replace it. I’m going to update the original post shortly with some tech info I’ve been collecting. Drive shaft RPM for both gear ratios, critical speeds, and such trying to make a one stop info spot for drive shaft issues.

 

[DiverDarrell]

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.

 

[coachgeo]

think I'll go with the driveshaft balancer on my front shaft. The raised rear shaft via axle swap should solve rear shaft issues.

 

[DiverDarrell]

Short shafts have higher RPM limits, and where will you put the balancer? Each end needs to be balanced independent and together at the same time. I’m just going to replace the joints every other year or so. Wear at the joints greatly magnify issues. My plan is

1. Install balanced shaft
2. Install balancing media in each rim
3. Ensure rims are straight and centered will use an indicator
4. Check runout on tires and have shaved if needed
5. Enjoy smooth ride

 

[coachgeo]

Short shafts have higher RPM limits, and where will you put the balancer? Each end needs to be balanced independent and together at the same time. I’m just going to replace the joints every other year or so. Wear at the joints greatly magnify issues. My plan is

1. Install balanced shaft
2. Install balancing media in each rim
3. Ensure rims are straight and centered will use an indicator
4. Check runout on tires and have shaved if needed
5. Enjoy smooth ride

video in link explains where shaft balancer would be installed and why. Look forward to your info on wheel beads install and keeping them out of the CTIS system.

 

[DiverDarrell]

Ran the airsoft pellets in my front tires for a year, no issues and no possible way for the pellets to get into the ctis with the rim locks installed. FYI they worked great to balance the wheels. When I swapped tires I was to lazy to swap rims as well. But now I absolutely feel the difference they make. The only negative is if you get oil into the ctis, then you will mess up the ability for the pellets to move freely

 

[coachgeo]

Ran the airsoft pellets in my front tires for a year, no issues and no possible way for the pellets to get into the ctis with the rim locks installed. FYI they worked great to balance the wheels. When I swapped tires I was to lazy to swap rims as well. But now I absolutely feel the difference they make. The only negative is if you get oil into the ctis, then you will mess up the ability for the pellets to move freely

How many pounds did you put in them?

 

[coachgeo]

How many pounds did you put in them?

my bad.. you have a thread on this folk can refer too. As one can tell..... I am very poor at remembering who did what in the past lol.

https://www.steelsoldiers.com/showthread.php?159554-FMTV-LMTV-Tire-balancing/page2&highlight=airsoft

 

[DiverDarrell]

Safety tabs installed. Bad news is I still have quite a viberations sometimes from someplace. Front drive shaft still has the new stickers on it. Time to break out the go pro and see what’s what. Only happens when low drive line stress (coasting or just about to).

 

[wandering neurons]

View attachment 718438Safety tabs installed. Bad news is I still have quite a viberations sometimes from someplace. Front drive shaft still has the new stickers on it. Time to break out the go pro and see what’s what. Only happens when low drive line stress (coasting or just about to).

I like the looks of the safety tabs, but I'm thinking when I get my drive shafts done, I'm going to find some good old safety-wire drilled bolts and do it the old-fashioned way. Once learned, never un-learned.

 

[DiverDarrell]

Mounted the GoPro today to watch under the truck, drove around and of course no viberations. Starting to think it’s a tire issue more and more. Interesting though my camera picked up some gear noise.

 

[Pointman0853]

Have you considered the possibility that the axle hubs need shimming..?

Pointman

 

[Awesomeness]

Mounted the GoPro today to watch under the truck, drove around and of course no viberations. Starting to think it’s a tire issue more and more. Interesting though my camera picked up some gear noise.

What would you expect to "see"? Unless they were huge motions would you really see much?

 

[DiverDarrell]

Have you considered the possibility that the axle hubs need shimming..?

Pointman

Hubs are good, i made a hub lash tool, and set the shims to spec. But I may double check if I can’t figure it all out. I did re-set the ring gear lash when I put a locker in. The gears working into each other was probably the noise heard in the video.

 

[DiverDarrell]

What would you expect to "see"? Unless they were huge motions would you really see much?

. I’ve got a large shake, enough to bounce the whole cab. My guess now is it’s the tires, possibly a bent rim. The shake isn’t all the time, and can be driven through. But the speed it comes at happens at different times. Video is just part of diagnosis. I still need to check the rims and tires. Hey but I did get the ctis figured out.

 

[Pointman0853]

To add my recent experience to this vibration problem question, in the hope that we can all learn..

I pulled my rear prop shaft out and took it to a local drive-line shop here in Sparks, Nevada. They work on mining equipment and heavy 4x4 and 6x6 NV Energy utility trucks, and have decades of experience with heavy trucks.

After reading the previous thread about alternators falling off, I decided it was time to solve the issues I was having before something more catastrophic may have happen. I also read thoroughly read the TACOM axle test report. I inquired with my shop about the possibility of building a CV Jointed prop shaft as well. My shop said it could be done for $2500+, the difficult part being machining new yokes for the pinion input/t-case output shafts. I was also told the the CV joints could not handle as much torque as the Dana-Spicer 1610 and that indeed that was the 'D' upgraded prop shaft and better than the '140' recommended in the TACOM test paper.

It was ready the next day! Verified it was a Spicer 1610. I had one rear u-joint that was bad ( I replaced both) The shaft was bent a tiny bit and straightened and re-balanced. (no mention of cardboard inside)
Here is an interesting video link on the general process: https://youtu.be/yBgaS9FdDhw. According to Tom, the shop owner, their process yields end-resulting specs better than factory, due to the proprietary testing equipment they use.

Today, I got it back in the truck and what a difference! So much smoother and quieter. No vibration at 45 mph and above. Happy, Happy, Happy..

I suspect the front may need the same treatment. Sadly I bought it 'new' from a vendor on this forum less tan 3-months, and the splines have play already..

I also asked about going from the 3.90 to 3.70 pumpkin gears. They have the ability to re-gear my pumpkins for much less than buying new Caiman chunks. I was told that reducing the operating prop-shaft RPM would extend life considerably.

The story continues..

Pointman