Many M816 Questions

[fasttruck]

The wires are identified with metal clips with the circuit numbers embossed on them. On any vehicle that has the same circuit it will be identified with the same number. A the lighting is essentially the same except for the length of the wires you can refer to almost any circuit diagram to identify the numbers on the wires.

 

[Guyfang]

Don't forget to read the TM. Its simple, but its simple to make a mistake.

 

[BillTWD]

Reference post 37: from top to bottom: service taillight. 2 bulbs, smaller one is for tail light, larger 2 filament bulb is stoplight/turn signal. Army uses the turn signal circuit in tandem to operate brake lights. Unlike a commercial truck, there is no separate brake light circuit. Next is blackout marker light which on a rearward facing light has 4 red apertures and depending on how far away you are your eyes will resolve 1, 2, or 4 individual lights. Bottom light is blackout brake light which is white when lit. If you are in convoy and you see 8 red marker lights with 2 white lights under them, brace yourself for the collision. The military light switch does not allow blackout and service lights to be displayed at the same time. Front composite light has an amber lens on top which is the parking light/ turn signal and a white blackout marker light beneath it. The operators' manual; has information in it about lights and it is also discussed in the Wheel Vehicle Driver's Handbook. The Wheeled Vehicle Drivers' Handbook is FM 21-305.

I've searched the TM's until my eyes hurt but could not find FM 21-305.

 

[frank8003]

FM 21-305

 

[Guyfang]

Ask, and you shall receive.

 

[BillTWD]

Everything is going well so far. The new light switch arrived and that got me back on track with that. The two major things to square up next are 1.) The transmission won't go into 4th or 5th gear. I think I might take that to someone to get it fixed. 2.) The air system. I am NOT looking forward to tackling that. I don't know anything about the air system or what it does or what it's for (other than the windshield wipers). I don't know if there are major issues with mine or not but something keep banging (like opening and shutting) a lot. Maybe if I ignore it long enough it will just go away....

 

[fasttruck]

Reference post 46: compressed air is a means of storing and moving energy. A M816 has an engine driven air compressor, a governor to control it, a reservoir to store air which must be drained after use to expel moisture, valves to control the windshield wipers, pressure switches for the low air alarm and the brake lights, an air operated mechanism to operate the clutch from the power divider location under the crane, and a hydrovac which acts as a brake booster for the hydraulic brake system. The principle maintenance activity at the operator level is to detect and correct leaks. The banging noise that comes and goes when the engine is running may be the air compressor operating as it does not operate continuously.

Transmission does not go into 4th or fifth gear ? When the truck is standing still or moving ?

 

[BillTWD]

Reference post 46: compressed air is a means of storing and moving energy. A M816 has an engine driven air compressor, a governor to control it, a reservoir to store air which must be drained after use to expel moisture, valves to control the windshield wipers, pressure switches for the low air alarm and the brake lights, an air operated mechanism to operate the clutch from the power divider location under the crane, and a hydrovac which acts as a brake booster for the hydraulic brake system. The principle maintenance activity at the operator level is to detect and correct leaks. The banging noise that comes and goes when the engine is running may be the air compressor operating as it does not operate continuously.

Transmission does not go into 4th or fifth gear ? When the truck is standing still or moving ?

The transmission will not go into 4th or 5th gear regardless of any factors.
The air noise seems to be coming from the firewall.

 

[fasttruck]

If it is the engine side noise could be coming from governor which is mounted on the firewall. If on interior side check low air alarm pressure switch. Air leaks can be detected with windex or soapy water which will blow bubbles in presence of air leak. Just for giggles, is the power take off for the crane (left rear corner of cab by handbrake) engaged ? Engaged is forward or down.

 

[G744]

Get a good, three-lever switch and install it.

Seldom will they give problems like the newer issue pushbuttons do.

DDG

 

[BillTWD]

Get a good, three-lever switch and install it.

Seldom will they give problems like the newer issue pushbuttons do.

DDG

I got a new 3-lever light switch and was able to get all the lights working.

 

[BillTWD]

Slight change of subject here. I'm kind of jumping around to various "issues" and things are going fairly well. Does anyone know how the tach works? I'm familiar with tachs on gas engines but not diesel. Mine "appears" to be working but it bounces way too much and I really don't think it's accurate at any point in the "bouncy" range. It's bouncing between 15-20 max (mostly closer to 15). I'm not a diesel mechanic but I have several diesel trucks and feel as if I have a pretty good ear for RPMS and I'm reasonably sure I'm running at least 2000 if not 2500+. After cleaning out the vent tube on the fuel tank I'm getting decent power. I don't know if I need to buy a new tach gauge or if there's something I can check/try before I buy?

 

[G744]

Disconnect the drive cable and pull the internal wire. It will look like a speedo cable.

Iit has any broken strands or rough spots, replace it. If it looks OK, lube it according to the TM.

If it still bounces, replace the tach head.

DDG

 

[BillTWD]

Disconnect the drive cable and pull the internal wire. It will look like a speedo cable.

Iit has any broken strands or rough spots, replace it. If it looks OK, lube it according to the TM.

If it still bounces, replace the tach head.

DDG

I absolutely love this forum. I get rock solid advice/information for every single question I ask.

 

[G744]

Looks to me your tach is stiff, that is what wore out the drive tang on the cable.

You should replace the inner and the tach as well.

DDG

 

[BillTWD]

Does anybody know what this thing is and/or what it is for? p.s. might not be able to tell in the picture but it's big and it's heavy.

 

[BillTWD]

.

 

[zebedee]

It's called a Whiffletree - spreads the lift of the crane hook out to the two lifting shackles on the front bumper for a suspended tow. Check the operating instructions in the TM. There are a ton of posts on it's use. The unique pins that go through the lifting shackles are like rocking horse poop... The 1/2" bar loop is used by the crane hook to pick it up from the ground when tossed over the side or directly off of the crane bed. Then, as it hangs horizontal - it is presented to the two lifting shackles on the casualties front bumper - where they are positioned at the correct holes, pins are inserted then it is lowered to the bumper and the hook is then repositioned into the big oval hole in the main body of the whiffle tree for the lifting of the casualty. Attach a tow bar to the wreckers pintle hook and the casualties axle and away you go (safety chains, air lines and tow lights also).

 

[BillTWD]

It's called a Whiffletree - spreads the lift of the crane hook out to the two lifting shackles on the front bumper for a suspended tow. Check the operating instructions in the TM. There are a ton of posts on it's use. The unique pins that go through the lifting shackles are like rocking horse poop...

Do you recall what TM specifically?

 

[zebedee]

TM9-2320-260-10