LMTV and Deep Water Fording

[Suprman]

Maybe there are check valves along the lines. Disconnect your axle breather lines and install some temporary ones run up high. Is your ctis disconnected? I will ask one of the mechs I know about it.

 

[Suprman]

Ok went thru the manuals again with one of the mechs. Axle vents appear to go into the ctis quick release system. If you have a clogged release valve maybe ctis air is making its way into the axle. A way to test this is to take out the top plug on the diff and air up the ctis then dump air and see if air is coming out of the plug hole. There are issues with the u-joints if there is more than .025" of end play then damage can occur or you can just throw a driveshaft or two. Wobbling driveshaft can prematurely wear pinion bearing and seal.

 

[tennmogger]

Ok went thru the manuals again with one of the mechs. Axle vents appear to go into the ctis quick release system. If you have a clogged release valve maybe ctis air is making its way into the axle. A way to test this is to take out the top plug on the diff and air up the ctis then dump air and see if air is coming out of the plug hole. There are issues with the u-joints if there is more than .025" of end play then damage can occur or you can just throw a driveshaft or two. Wobbling driveshaft can prematurely wear pinion bearing and seal.

Good ideas. I have done a test that, I think, rules out clogged piping. I installed a pressure gauge in the fill port of the front diff then drove around for several days. I would cycle the tires from HWY to XC to SAND and back and the CTIS worked as it should. No pressure ever showed up in the diff.

The U-joints are tight. There was a low torque spec on pinion preload so I lapped one of the pinion bearing spacers to preload the pinion. Not much was needed but now I know there is no lash on the pinion to wallow out the seal.

Apologies to OP Webrep for this deviation from original question. Hopefully this discussion contributes a little.

Bob

 

[Suprman]

Have the driveshaft balance checked. Or the yoke could be slightly bent. The mech said anything slightly off can cause all kinds of issues.

 

[Suprman]

There is a procedure called "drive shaft hinging inspection" that shows how to measure play. Its in the 20-3 manual and the tolerances appear very tight. The mechs said the driveshaft/driveline being out of tolerance can cause damage up and down the driveline.

 

[Webrep]

Lmtv on national news doing water rescue in MS

 

[Moostang]

The 2 hoses on the front axle are the breather and the front axle air lock. The breather is tied to the rear cab mount cross member. The rear breather is on the front side of the rear frame cross member. The CTIS hoses are behind the backing plate

 

[Reworked LMTV]

We have been using our LMTV to assist in water rescues here in MO but I was curious on what the military manual says on deep water fording in the LMTV. I have been all through the TM's and not much is mentioned except testing fan clutch switch. Anyone got any experience in using the LMTV in deep water? Deep is relative but so far we have kept it above the fan. With the fan clutch on should i see the fan stop moving? Thanks for the info, trying to set some limits on usage.

Do you have any pictures or video of your rescues?

 

[BigMontana]

It will spin a bit but should not be running. It's loud when running you can't mistake it. The assembly spinning with the fan off will cause the fan to spin a bit.

Old thread and all, but for you overland junkies who like to push vehicle capabilities this fan kill switch should also be used when torquing the frame left to right.

Or said another way:

When I used to deliver logging and firefighting equipment in MT/ID/WA/WY sometimes you'd have to intentionally dig one of your trucks steer tires into the outside of a corner/turn where the outside was the high/uphill side of a mountain road, and the inside was a cliff.

This would twist the frame a little, especially with heavy loads, and if you forgot to shut off your fan clutch first your fan would eat the aluminum out of the back of the radiator.

The operator "tell" (sound wise) for when you forgot the fan kill switch was: all of a sudden it sounded like someone was running a table saw/wood groove-er on the front of your truck.

Same with intentionally hopping onto curbs with a heavy haul truck in situations where you either use some sidewalk or take out a traffic light.

 

[ramdough]

Old thread and all, but for you overland junkies who like to push vehicle capabilities this fan kill switch should also be used when torquing the frame left to right.

Or said another way:

When I used to deliver logging and firefighting equipment in MT/ID/WA/WY sometimes you'd have to intentionally dig one of your trucks steer tires into the outside of a corner/turn where the outside was the high/uphill side of a mountain road, and the inside was a cliff.

This would twist the frame a little, especially with heavy loads, and if you forgot to shut off your fan clutch first your fan would eat the aluminum out of the back of the radiator.

The operator "tell" (sound wise) for when you forgot the fan kill switch was: all of a sudden it sounded like someone was running a table saw/wood groove-er on the front of your truck.

Same with intentionally hopping onto curbs with a heavy haul truck in situations where you either use some sidewalk or take out a traffic light.

Wow, the frame twists that much?


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[BigMontana]

Wow, the frame twists that much?

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In extreme conditions like adventure-style offroading in the mountains, where one suspension is against the bump stop and the suspension on the other side is bearing little to no weight, it might, yah...i'm honestly curious to see if it does or not...but i won't be taking the chance since the switch is right there, and it's practically force of habit.

I had that radiotor to fan interference issue on older heavy haul rigs, the new ones not so much...My LMTV is 29 years old.

 

[Ronmar]

There is quite a bit of space between fan and rad on these. I think the first place to contact on a lmtv, if at all would be fan to shroud...

 

[BigMontana]

There is quite a bit of space between fan and rad on these. I think the first place to contact on a lmtv, if at all would be fan to shroud...

Yeah there is a LOT of spare room under the hood, so you're probably right, my head was up my fourth point of contact when talking about the fan's first point of contact.