My First LMTV - M1078 A1 - Fluid Questions

[Sully LMTV]

Hello all! I'm pretty stoked to get my M1078 on the road and have done a ton of reading here on the forum - great bunch of folks!

I have been going through the TMs and also been through the LMTV quick parts reference sheet. In the reference sheet it states:

Steering: 5 quarts hydro fluid or steering fluid
Hydraulic reservoir: 27 gallons hydro

Noob question, but what is hydro fluid? Is it just basic hydraulic fluid, like AW-68, 32 or 46 that can be picked up at O'Reilly Auto Parts? I'm in Northwest Florida and would think the hot months may play a part in fluid selection.

So far my fluids research has me leaning:

Engine Oil: 15W-40 Synthetic
Transmission: Valvoline Dexron III/Mercon Automatic Transmission Fluid - 5 gal (I've read to stay away from Dexron IV)
Hydraulic Fluid: ?

Thanks to all and special thanks to Russ Knight for your help and Sean and Chad for your awesome video series on YouTube - way valuable!

Sully

 

[NDT]

Do you have a winch? That’s what that is for.

 

[Ronmar]

The steering and hydraulic system(did you get a winch truck?) will use AW-32. you could run 46 in it at higher temps if you really planned to work it hard. The winch system would be intermittent use and unless you are really wheeling and working the steering system hard, so would the steering. AW32 would probably be just fine for normal usage... it is also typically easy to find at ranch and feed stores...

Many people use Transynd in the transmission, which is the Allison specced fluid. I have heard of some running dexron 3, and some running a batch of dexron 3 after removing the 15W40 engine oil from the trans as a flush before replacing with transynd and changing the filters...

 

[Sully LMTV]

I'm mobile, so sorry for the abbreviated reply.

No winch. Working on her right now..
Engine oil was low, just topped off with Mobil Delvac 15w-40. Tranny low, don't have the fluid to top off.

Thanks for the fluid info. Want to do full flush of everything (that should require it) and fill with the best. Plan to keep forever, so cutting no corners.

The cab hydraulic box died during a cab lift last week. Ordered the rebuild kit and it just arrived. Also purchased AeroShell 41 to fill it after rebuild.

I'm a group l & ll UAV design engineer, fabricator and test pilot, so hydraulics are out of my wheel house. Looking forward to learning.

Developed a fluid leak after my first 2.5 mile drive to the office earlier this week. Clear fluid. Coming from the front of the motor, low. Front seal? About to fire her up to temp and see if I can spot the source.

Thanks again for replying and sharing your experience, I hope to repay the same. I'm excited about this truck. Already looking for another.
Funny thing is the wife likes the camo and doesn't want her changed one bit. She told me to go find another to build into an exhibition vehicle. Cool to have close support!

Take care brothers.

Sully

 

[Sully LMTV]

 

[Ronmar]

View attachment 827573

Nice looking truck!

You can use AW-32 in the cab hydraulics as well.

If the truck has military oils in it, then it most likely has the same 15W40 in the trans as is in the engine...

 

[Coffey1]

Yes if you got from auction and not private party Ithaca 15 40 motor oil in tranny

 

[Sully LMTV]

Nice looking truck!

Thank you! All I have done to date is:
- Repair the windshield wipers (one was missing)
- A lot of touch up paint (mainly on the front)
- Buffed the windshield with Cerium Oxide (deep gouges from the missing wiper)
- Repaired the left (driver's) door - it wouldn't latch. Fix was a new latch - alignment alone would not do it.
- Switched out the older style light controller on the dash for a touch button controller - drop in replacement
- Stripped down all the canopy poles and repainted them. Cleaned the canopy (pressure washed) and assembled the canopy (very happy with the results).
- LED headlights

Yes if you got from auction and not private party Ithaca 15 40 motor oil in tranny

The individual I purchased the truck from did buy it at auction. He indicated he had done nothing to it since purchasing it in November, so I suspect you are correct in that it does have the 15W-40 in the tranny. I bought the truck two weeks ago.

That leak is getting pretty bad. I need to get into the TMs tonight and understand the different parts of the system. It appears to be coming from the transmission cooling system (maybe). I'm not familiar with the 'can' under the front of the motor. The can has two lines entering from the rear (inlet/outlet?) and a third larger hose going forward, towards the radiator area. The TMs will tell me.

 

[Ronmar]

That leak is getting pretty bad. I need to get into the TMs tonight and understand the different parts of the system. It appears to be coming from the transmission cooling system (maybe). I'm not familiar with the 'can' under the front of the motor. The can has two lines entering from the rear (inlet/outlet?) and a third larger hose going forward, towards the radiator area. The TMs will tell me.

Yea, thats the trans cooler. Could be it, could also be oil from the oil pan or timing case cover above it... you said it was clear though, which would probably indicate trans oil as the engine oil goes dark/black very quickly in service.

 

[coachgeo]

....

Yea, thats the trans cooler. Could be it, could also be oil from the oil pan or timing case cover above it... you said it was clear though, which would probably indicate trans oil as the engine oil goes dark/black very quickly in service.

but clear? could it be power steering hydraulic oil from back of the air compressor)

 

[Sully LMTV]

but clear? could it be power steering hydraulic oil from back of the air compressor)

Good question! The back of the air compressor is dry. I saw a video on the compressor being replaced, so I was familiar with it when I saw it while laying under the frontend. The leak favors the passenger side; there is more 'spray' or residual on the front of the gas tank and less behind the front-left or driver wheel.
I can confirm the fluid is clear.

Late start today - I'll investigate further before dark.

 

[Coffey1]

I know of no clear fluids in a fmtv.
10 weight for cab lift would have to be brand new for it to be clear looking

 

[Third From Texas]

Hydraulic leak?

It's the clearest I can think of, and it will mist all over the place if it's leaking at the latch/hose/control panel.

 

[ckouba]

Hydraulic leak?

That's what I started thinking if it's all over the fuel tank. Check cab lift cyl connections maybe?

 

[Sully LMTV]

What is the default (resting, driving) configuration of the knobs and lower Cab 'push and turn? I had the lower right Cab push and turn knob, pushed in and locked to the right.
Could this cause the system to pressurize and leak?
I haven't rebuild the cab hydraulic pump yet. It does leak when attempting to lift the cab (so i am not using it).

 

[Third From Texas]

You are showing the default (driving) configuration there.

The "Cab - Push and Turn" inflates the airbags for the cab suspension. If you have leaks in the airbags or the associated lines there will be leaks of course. Leaving that knob "out" will cutoff any leaks in that part of the system beyond the valve.

 

[Ronmar]

What is the default (resting, driving) configuration of the knobs and lower Cab 'push and turn? I had the lower right Cab push and turn knob, pushed in and locked to the right.
Could this cause the system to pressurize and leak?
I haven't rebuild the cab hydraulic pump yet. It does leak when attempting to lift the cab (so i am not using it).View attachment 828201

it won’t cause the hydraulic system to pressurize. There is a safety valve built into the brake system that disconnects the air used for the air operated hydraulic pump when you apply park air/release the park brakes.

as mentioned you want the lower right button in and locked for cab suspension. The air for cab suspension comes from the wet tank protection valve(same air that feeds ctis and fan control). The air for the AOP comes from the pri/sec brake service tanks...

 

[Sully LMTV]

You are showing the default (driving) configuration there.

I appreciate the conformation this is correct.

The air for cab suspension comes from the wet tank protection valve(same air that feeds ctis and fan control). The air for the AOP comes from the pri/sec brake service tanks...

I wasn't positive of the breakout of the tanks responsibilities - this helps me understand the air sys better.

I can't find the source of the leak. I am considering cleaning everything up, drying the surfaces out and mounting cameras under the truck, record to an onboard NVR, drive and then review the footage. Look for what gets wet (turns a different shade of color).

As stated earlier, the fluid id relatively clear:



I can start the truck and let it warm up in the driveway. It does not leak until it is driven. After a short drive, this is what is seen: Fluid is predominantly on the passenger side. The passenger side hose going to the trans cooler can is wet; the (like) hose on the driver's side is dry (right side of pic):



I need to get familiar with the components. Later yesterday I took the final pic after a short drive around the block (as it got dark out):



I am starting to suspect the green flexible adapter on the left, connecting the can with the down tube. I did tighten the clamps last week in passing, but not too much as I hadn't read the torque specs in the TM yet.

You can see the fluid on the passenger side, oil pan bolt heads. I don't think he fluid is coming from above that point - I believe the fluid is being blown up there when driving and fan operation. Maybe I'm wrong.

 

[Ronmar]

The big connections on each end are coolant... could be the trans connections in the middle, loose or with a bad seal. Once the trans fluid warms up it is able to squirt a little out. I notice a little all the way up on the housing under the crankshaft. Unless you have a lot of airflow, gravity usually takes it down. In this case the fan blows back and down under the engine... How clean is your engine oil?

 

[Sully LMTV]

For completeness and follow up... the leak is the front main seal.

...now to fix it and replace other items while I have it apart. Harmonic balancer or I think Cat calls it an engine dampener, is on the list.

Sully