M936A2 Value/Diagnosis Help

[tylerryals]

I am currently attempting to purchase a '91 model M936A2, it was still in the military as late as '06-'10; took the first trip to look it over (4.5hrs away) and check it out. It is personally owned, already titled, and ready to use. I would like some advice on the value of it and some help with diagnosis of some of the problems I found, from other MilSurp wrecker owners (or anyone knowledgeable, a lot of these problems are generic M939 family problems). It has 250 miles, 850 hrs, impeccable tires, and clean looking engine. When I first got there to check it over, I checked all the fluids, looked it over really well, fired it up, let it run for 5-10 minutes, built up pressure just fine (100+psi primary and secondary), but I couldn't get the brake release to blow off, I didn't monkey with it too much at this point, done a quick function check on everything (inside the cab), and shut it down and encountered first problem, the electric kill solenoid would not shut it down, I gave it a minute or two, still nothing, honestly I got a little worried, but I forgot about the manual kill cable, killed it done another walk-around (leak/problem check), had to blow up two tires (took several minutes they were flat), was going to get it out and drive it and do a real function check, but here is where the real problem in my opinion came about, fired it up, it had leaked down to ~50psi, gave it 10 minutes at high idle, no build in pressure, gave it 15, still no build, finally hit the emergency brake override, just so I could roll it out and function check everything for real, wanted to take it on the road, but obviously that went out the window, put it in low range and ran it through as many gears as I could space permitting (up to 4th), parked it, engaged the PTO (encountered another problem, but honestly could have been my fault details ahead), had problems engaging the wrecker pump (honestly just stove up from none use), got it in worked the recovery winch and all the crane functions. Overall all the systems worked without much issue, with the exception of the air, the kill solenoid, and the PTO. I honestly believe I may have engaged the PTO in the wrong sequence, I went: parking brake up, trans to neutral, transfer case to neutral, and engage the PTO, wouldn't go in without grinding (Disclaimer: I didn't allow it to grind; shut the engine down and engaged the PTO and restarted), and shifted to 1-5. In all honesty I'm not 100% familiar with the PTO sequence on these trucks; after further thought on it, it may should have went trans to N, transfer case to N, trans to 1-5, engage PTO. They are asking $15K for the truck as is. It is at a used car dealership. While very helpful and more than accommodating, the guy trying to sell it (by his own admission) has zero idea about these trucks. I will list the problems I found below:

1) Air would not build up (on second try)
2) Believe CTIS is leaking severely (same two tires went flat after ~45min)
3) Electric kill solenoid not functioning
4) Missing two-four batteries MilBatts replaced with 2 small commercials)
5) Did not auto idle up with PTO
6) Blower motor does not have low speed
7) Could not get front winch to move (selector lever is froze up/stuck; cant confirm whether its in or out and didn't have help to work winch and cab controls sima.)
8 ) Tow bars are missing (or hid in the bottom of the tool box)
9) Evidence of rats invading the cab (this scares me)



One of the things I noticed, is the crane and rear winch move slow, granted I don't have much experience with the M936 in particular, I own a M35A3 and have driven several M923 Cargo Trucks, new to med. wrecker, but I expected more. Is this normal or indicative of something else? Another note, I can tell where the timing cover had been removed and replaced, and with low hours/miles, seems suspicious. In everyone's opinion, what is a fair price as is? What could be causing the air system problem and the kill solenoid problem? They are my two main concerns, but any other advice/questions are welcomed. My end use would be as intended, recovery, not much towing, and material handling (we own a farm and mechanics shop). Some of the highpoints of it: the tires are impeccable, all of the MilSurp rigging appears to be on it still (except for the towbars), including the axle chains for the towed vehicle, and everything mechanical seems to be impeccable (trans, steering, engine, transfer case, drives, etc.)



EDIT: I would have to say the biggest disappointment of it all, is that, although it appears to be desert tan in the pictures, it was actually painted white (or attempted to), over the tan and it turned into some kind of battleship grey/desert tan/cream/off white conglomeration. It really bothers me, be-it my OCD tendencies, purist mentality, or whatever, I have to factor in some type of paint job to the purchase, even if its Milspec; cover the windows and lights, close your eyes, and paint everything. (joking)

 

[98G]

I see a $7000 fixer. Certainly not a $15k truck.

The tires are *NOT* impeccable. Sitting flat means they need replaced.

The hour/miles shouldn't even be looked at on a military truck. The odds of them being accurate on that one are exactly zero....

 

[fsearls92]

Yep, I would walk away from it. For that price you can find one that functions properly.

 

[tylerryals]

Thanks,

The tires are *NOT* impeccable. Sitting flat means they need replaced.

I see the large you hole poked in my logic (no pun intended; maybe a little), I was mostly referring to tread wear and dry rot, but I do see your point.

.

I see a $7000 fixer. Certainly not a $15k truck ​

The hour/miles shouldn't even be looked at on a military truck. The odds of them being accurate on that one are exactly zero... .

​

I can see this (as mentioned above), the fact that the timing cover has been removed before, leads me to be suspicious.​

 

[tylerryals]

Yep, I would walk away from it. For that price you can find one that functions properly.

Thanks

 

[98G]

Decent M936A0 and M816 wreckers can be had for $10k. $15k should get you a pretty good M936A2.

$7k really is about right for that one. It may make for a pretty decent truck, but it's going to need gone through and the air system completely rehabbed at least. Paint. Tires.

The trucks with CTIS are notorious for allowing the tires to sit flat. This weakens the sidewalls to a pronounced degree and you get catastrophic failure without warning. It's happened to me...

Timntrucks has an M816 wrecker for sale for $10k that is quite a bit better than that one. (Just as a point of comparison).

 

[tylerryals]

Decent M936A0 and M816 wreckers can be had for $10k. $15k should get you a pretty good M936A2.

$7k really is about right for that one. It may make for a pretty decent truck, but it's going to need gone through and the air system completely rehabbed at least. Paint. Tires.

The trucks with CTIS are notorious for allowing the tires to sit flat. This weakens the sidewalls to a pronounced degree and you get catastrophic failure without warning. It's happened to me...

Timntrucks has an M816 wrecker for sale for $10k that is quite a bit better than that one. (Just as a point of comparison).

I definitely see point about it sitting flat, thanks for the help

 

[1 Patriot-of-many]

I paid $6200 for my M936A2 in the dead of winter taking a chance on GL with 3 foot of snow on everything. Lucked out. Had to cut off about 3 foot of hoist cable that was kinked up, The part where the speedometer cable hooks up below I needed. Everything worked except the rear winch auto winder or leveler or whatever it's called didn't move from side to side the way it's supposed to, needs grease probably. Mine doesn't auto idle up either, I use the hand throttle to set it 1350RPM. Mine also grinds slightly when I engage the PTO, I throttle up directly after. 15K is too much IMO also. Probably the orings in the wheels causing them to go flat but never count out airline from the wheel valve being loose. I'd pass.

 

[tylerryals]

I paid $6200 for my M936A2 in the dead of winter taking a chance on GL with 3 foot of snow on everything. Lucked out. Had to cut off about 3 foot of hoist cable that was kinked up, The part where the speedometer cable hooks up below I needed. Everything worked except the rear winch auto winder or leveler or whatever it's called didn't move from side to side the way it's supposed to, needs grease probably. Mine doesn't auto idle up either, I use the hand throttle to set it 1350RPM. Mine also grinds slightly when I engage the PTO, I throttle up directly after. 15K is too much IMO also. Probably the orings in the wheels causing them to go flat but never count out airline from the wheel valve being loose. I'd pass.

Thanks for the response.

 

[Csm Davis]

Okay tyler which pto did you engage the one in the middle of the cab or next to the door?
As for the tires did you look at them before airing them up?
The kill solenoid is not a reason to knock but maybe 150 off an A2 , I take them off if they fail and never replace them.
The air problem was probably just the drier vent stuck open, because you didn't say you could hear the leak.
Did you set the idle at 1300 rpm or so when trying the boom?
The detent ball on the front winch is probably just stuck a little PB blaster and some wiggle would probably get it free.
I wouldn't walk away untill i knew the answer to these easy questions but would use all of them to bring price down.

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[tylerryals]

Thank you for the response and questions, replies below:



Okay tyler which pto did you engage the one in the middle of the cab or next to the door? For the front winch - Middle ..... For the wrecker - Cab Corner

As for the tires did you look at them before airing them up? Yes, no signs of dry rot, cuts, knots, etc., honestly they looked brand new. Either two tires are leaking at virtually the same rate, or there is a CTIS leak.

The kill solenoid is not a reason to knock but maybe 150 off an A2 , I take them off if they fail and never replace them. I gathered that it must have been a pretty frequent occurrence, for the factory to add a redundant kill mechanism.

The air problem was probably just the drier vent stuck open, because you didn't say you could hear the leak. After I had a few days to ponder on it (the air problem), I'm fairly certain that it was/is the dryer causing the issue. The only other question would be to what extent the dryer is dysfunctional; if it just needs a good cleaning out and a rebuild, the rebuild kits are pretty cheap, but if it has to be replaced, I believe those Haldex dryers are fairly pricey.

Did you set the idle at 1300 rpm or so when trying the boom? Yes, and the speed (movement speed) could be a none issue, as I said I have no experience with these wreckers, I may have been simply expecting too much, I'm used to working with cranes and such that operate fairly speedily.


The detent ball on the front winch is probably just stuck a little PB blaster and some wiggle would probably get it free. I do not doubt that it (the winch in general) is just a stiffness issue. I believe the field expedient remedy for this is for one person to gently work the wind/unwind back and forth while the other person attempts to move the throw lever? I just didn't have an extra knowledgeable hand at the time to attempt this.

I wouldn't walk away untill i knew the answer to these easy questions but would use all of them to bring price down. I am planning another trip to look at it (and taking some help), try and troubleshoot it, and do some further inspecting.

Sent from my SM-G930V using Tapatalk[/QUOTE]

 

[tylerryals]

As an update:


I made a return trip to check it out once more, I took some qualified help this time. Most of the problems, I diagnosed/dismissed. The air leak is definitely the dryer, seems to be full of trash and water, got the purge valve unstuck (for a little while), enough to drive it, but I didn't get but about ~10miles out of it before it stuck open again (as a disclaimer it idled for 1+ hour while I checked everything over). The truck drives great down the road, tracks good, shifts good, brakes were good after I got the rust burnt off of them. Got the front winch engaged, took someone jogging the wind/unwind while the other threw it in gear, it works good, but I still cant get the PTO (front) in gear without it grinding, still may not be doing it in the correct sequence, but I tried it both ways I thought to be correct. The wrecker PTO went in gear a lot easier, actually just fell right in, as did most of the problems I attributed to being froze up/stiff, but I think they drove the truck into a vat of WD-40 and PB blaster; you could smell it everywhere (which isn't a bad thing really, I went through 3-4 cans on my M35 when I bought it). I didn't diagnose the tire leak, but the CTIS does seem to be functioning, while the air was pressurized they stayed inflated and I was there a good 1-2 hours (they went slack in ~45 min the first time). Auto Idle still does not function, but I didn't bother with it, its a non-issue in my opinion, I'm perfectly ok with using the hand throttle. Kill switch doesn't function, that I will hold against them, and I intend to fix it if I get it. I forgot about checking the blower motor, but that's not a huge issue, neither monetarily or in my mind. The tow bars and adapters are definitely missing, I hunted them all over, they are MIA, and will have to be replaced, but everything else seems to be there (within reason, technically there are a lot of BII's missing) . There have definitely been rats in the cab, but I didn't see any electronic or wiring damage, hopefully they just camped out for a while. As far as the speed of the winch/crane it still seems slow to me, but I got my wife to watch a YouTube video of an M936A2 operating while I done similar motions with this one and they seem to be tit for tat, I'm pretty sure my expectations were just too high; as I said I'm used to working around full fledged cranes that can scope in/out and hold the load at near full speed and it just aint going to happen with this. I crawled all over the engine, underneath, all the mechanicals seem to be impeccable, but I did find two new problems I missed the first time; the packing in one of the main boom cylinders has a small leak (took several strokes to develop) and the right fuel tank hasn't been used, is contaminated with water, and the fuel gauge doesn't appear to read correctly. Neither one are huge issues, but another reason to knock the price down. I have been trying to get a hold of the owner of the dealership to talk with him about it, but cant seem to nail him down; none of the salesman are authorized to negotiate (or so they say). Hopefully I can get a hold of him soon and talk with him, I really want to get this truck, I think it would be a great asset and hopefully he will deal with me. I don't see being anywhere near $15K with all the problems Iv found.....

 

[tobyS]

Mine also grinds slightly when I engage the PTO, I throttle up directly after.

How does the gearing work with the TC driven PTO? On the Alison tranny mount PTO, like the M929 or 925, the truck should be stopped (or nearly stopped) and in gear. That stops the part that the ring gear is attached to and lets the PTO slide over, normally no grinding at all. However if you do it in neutral, it's going to grind. Going from an 817 to the M929A2....it made sense after having my A3 tranny apart and fitting a PTO to it.

What is the secret to engaging the TC driven PTO?

Edit....Yes, reading above, you are trying to put the front PTO in gear in neutral. GRINDS....put the auto tranny in gear and stay stopped. Reverse or forward does not matter.

 

[simp5782]

How does the gearing work with the TC driven PTO? On the Alison tranny mount PTO, like the M929 or 925, the truck should be stopped (or nearly stopped) and in gear. That stops the part that the ring gear is attached to and lets the PTO slide over, normally no grinding at all. However if you do it in neutral, it's going to grind. Going from an 817 to the M929A2....it made sense after having my A3 tranny apart and fitting a PTO to it.

What is the secret to engaging the TC driven PTO?

Edit....Yes, reading above, you are trying to put the front PTO in gear in neutral. GRINDS....put the auto tranny in gear and stay stopped. Reverse or forward does not matter.

Transfer case to neutral, engage power divider, transmission to 1-5 or 1-4. Spring brakes auto engage when the pto comes on.

Similar
https://youtu.be/jovlIA0Vs5U


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[1 Patriot-of-many]

How does the gearing work with the TC driven PTO? On the Alison tranny mount PTO, like the M929 or 925, the truck should be stopped (or nearly stopped) and in gear. That stops the part that the ring gear is attached to and lets the PTO slide over, normally no grinding at all. However if you do it in neutral, it's going to grind. Going from an 817 to the M929A2....it made sense after having my A3 tranny apart and fitting a PTO to it.

What is the secret to engaging the TC driven PTO?

Edit....Yes, reading above, you are trying to put the front PTO in gear in neutral. GRINDS....put the auto tranny in gear and stay stopped. Reverse or forward does not matter.

Are you saying the TM is incorrect? I follow the TM directions and mine grinds as I pull back on the lever to engage. TM 9-2320-272-10 page 249 of the PDF.

 

[1 Patriot-of-many]

How does the gearing work with the TC driven PTO? On the Alison tranny mount PTO, like the M929 or 925, the truck should be stopped (or nearly stopped) and in gear. That stops the part that the ring gear is attached to and lets the PTO slide over, normally no grinding at all. However if you do it in neutral, it's going to grind. Going from an 817 to the M929A2....it made sense after having my A3 tranny apart and fitting a PTO to it.

What is the secret to engaging the TC driven PTO?

Edit....Yes, reading above, you are trying to put the front PTO in gear in neutral. GRINDS....put the auto tranny in gear and stay stopped. Reverse or forward does not matter.

Are you saying the TM is incorrect? I follow the TM directions and mine grinds as I pull back on the lever to engage. TM 9-2320-272-10 page 249 of the PDF. I can't figure out how to get the PDF pages to the right size on this forum.

 

[tobyS]

Are you saying the TM is incorrect? I follow the TM directions and mine grinds as I pull back on the lever to engage. TM 9-2320-272-10 page 249 of the PDF.

Sorry, can't read that TM.

At first I thought you were referring to the transmission mounted PTO then also thought you meant the TC main crane hydraulics. I posted that before your longer explanation where you say ; "but I still can't get the PTO (front) in gear without grinding".

Since it's an A2, it has the same front PTO as my M929A2 dump. At first, when I got my dump, I ground gears, trying to engage the PTO while the transmission was in neutral. I didn't have the TM's available but found that when the truck was in gear and stopped, it slipped perfectly into gear with no grinding.

Picture below is the Alison auto for my M35A3. It has a 55 tooth ring and the 5 tons have 77, I think. They both take the same Chelsea PTO but the 5 tons don't have enough frame room to have the flange mount pump, while the A3 does. Anyway...that ring rotates at engine speed, it has to be stopped and having it in gear stops it.

 

[1 Patriot-of-many]

Sorry, can't read that TM.

At first I thought you were referring to the transmission mounted PTO then also thought you meant the TC main crane hydraulics. I posted that before your longer explanation where you say ; "but I still can't get the PTO (front) in gear without grinding".

Since it's an A2, it has the same front PTO as my M929A2 dump. At first, when I got my dump, I ground gears, trying to engage the PTO while the transmission was in neutral. I didn't have the TM's available but fount that when the truck was in gear and stopped, it slipped perfectly into gear with no grinding.

Picture below is the Alison auto for my M35A3. It has a 55 tooth ring and the 5 tons have 77, I think. They both take the same Chelsea PTO but the 5 tons don't have enough frame room to have the flange mount pump, while the A3 does. Anyway...that ring rotates at engine speed, it has to be stopped and having it in gear stops it.

Yeah I can't figure out how to get the proper size from the PDF without printing it out, scanning then uploading what a clusterF. The TM says the opposite in any case, so I'll have to try your method. TM says 6. transfer case shift lever to neutral. 7.Pull TC power take off lever back. 8. Put transmission in 1-5. 9. Use hand idle to 1300(previous step said with a certain MWO it would auto idle up probably because transmissions were being wrecked when soldiers forgot to idle up) No I never said anything about the front winch, I'm talking about the Hoist/rear winch PTO. Think you're confusing me with the OP.

 

[1 Patriot-of-many]

Okay that was a pain in the arse, print, scan, upload

 

[tobyS]

Tylerrayals said:

"I went: parking brake up, trans to neutral, transfer case to neutral, and engage the PTO, wouldn't go in without grinding (Disclaimer: I didn't allow it to grind; shut the engine down and engaged the PTO and restarted), and shifted to 1-5. In all honesty I'm not 100% familiar with the PTO sequence on these trucks; after further thought on it, it may should have went trans to N, transfer case to N, trans to 1-5, engage PTO."

With the front tranny mounted PTO the reason it would grind is because the tranny ring gear is turning. Shutting down the engine stops it, but putting it in gear (not neutral) and not moving also stops it.

I wan't clear about engaging the TC driven which Wes provided the video of. But I'm not sure the manual tranny is the same as the A2 Allison.

Tylerrayals again repeated about the grinding in his update. From what I can tell, the TM is for engaging the TC PTO, not the "front".

When you (1 Patriot) said: "I follow the TM directions and mine grinds as I pull back on the lever to engage."....It sounds like the same issue, so I thought you were referring to the tranny (front) PTO.