Adding PTO to 923A2

[Csm Davis]

Can the exhaust be moved? Looked at a few frames and doesn't look to be any difference on the cut out.

 

[74M35A2]

Not easily. The Chelsea distributor said this PTO (the 221 model anyway, which mine has a different number) can be flipped over so the engagement cover is pointing down. When doing this, it will raise the pump driveshaft about 1" he says. This driveshaft seems to sit very level right now, but may be able to handle a 1" raise on one end since it uses U-joints on each end and a slip yolk joint.

So, now it just becomes how badly do I really want to do it, possibly having to raise the pump 1" if it does not like the new angle.

I'm sorry for the thread-jack. I wanted to take advantage of PTO experts while they were in the room.

 

[spicergear]

Am I reading this correctly that no air shift PTO's were installed on the M939 series? Please tell me I'm mistaken.

Also, were any of the PTO & pumps married so the pump was bolted directly to the PTO or were they all divorced with a driveshaft from PTO to pump?

 

[Csm Davis]

Am I reading this correctly that no air shift PTO's were installed on the M939 series? Please tell me I'm mistaken.

Also, were any of the PTO & pumps married so the pump was bolted directly to the PTO or were they all divorced with a driveshaft from PTO to pump?

Learned a long time ago to never say it wasn't ever done to a military vehicle but have seen lots of the 939 series trucks and haven't ever run across an air shift pto or a married pump and pto.

 

[spicergear]

SON OF A -.-.-!!!!!!! THE PTO/PUMP COMBO OLD MECHANIC SOLD ME THAT WAS A PUMP FULL OF RUSTED GEARS AND BUGS AND A PTO WITH RUSTED GEARS AND WATER IN IT WAS AN AIRSHIFT PTO/PUMP COMBO. Nearly $500 I'm out to be told, "all sales are final," and then told, "...at that price you can afford some clean-up."

It's NOT clean up when both gears/shafts in the pump are rusted to the point of pitting and center housing is scored and it' snot clean up when you have to buy one of the three remaining gears in the US left for that model PTO because the main double gear set is rusted and pitted. Man, ticked... sent me two cores that weren't even off of an M939 truck. It's a Muncie PTO too not Chelsea. Nice to be able to trust people-- thanks for stealing money from me a-hole! They know there's NOTHING you can do. That is what sponsored my last year or so hiatus from this site. When I posted about it, there were people that backed him on the sale, yet admitted they wouldn't have sold items like that. *rant off*

Had a line on a BRAND NEW PTO for that price but because of being lied to, lost that as an option.

 

[patracy]

Sorry spicegear. I have sent you a PM about this.

 

[Daytodog]

So after hours of reading, asking questions and help from other members I got the hotshift PTO installed on the truck. A big thanks to those that have helped. What I have learned I will pass on maybe it will help someone in the future. Let me throw out a disclaimer since I didn't install the 221 series I am justing passing along what I have read and what others have said from their experiences.
Chelsea PTO 221 series is the mechanical PTO that fits the 900 series truck. There are two models 221X and 221R. The 221X has the cable linkage at the 2 o'clock postion once bolted on transmission. The cable linkage lever will have to be rotated 180 degrees to avoid hitting the frame. Also some have said they had to grind more of the prenotched frame out to get it to fit, not sure about that. The 221R (last picture)has the cable linkage on the top and have been told doesn't need any grinding of the frame, but is close to the exhaust.
I ordered the 271 series (first 2 pics)which is a hotshift with remote electric solenoid. I screwed up and ordered the 271 blah blah -5 series with housing on top. Had I known the 271blah blah -3 would have put the housing hanging down allowing it to sit inside the frame rail and fit, I would have ordered that one. Since I had the -5 I removed the end plates and flipped the clutch pack around so it was like the -3. It is still a tight fit but placed the PTO inside the frame rail and slid it along the rail from the back forward. I did have to remove some of the bolts that hold some brackets on the frame but wasn't bad.When I get some more time I'll finish hooking up everything.
Would someone that has a PTO already installed be willing to tell me which way the PTO rotates? Tried to find it a TM but no luck. Just want to make sure my PTO rotation is correct for the standard military pump or if I need to change it before installing the pump. Sorry couldn't get the pics rotated properly.

Thanks again for the help

 

[spicergear]

Thanks for the post and especially the pics. Did you happen to see, in your research, if they have an air operated hot shift PTO. Do you think it is possible for a married pump to fit if it had both ports on the rear cover?

 

[spicergear]

Daytodog: What ratio did you go with for the PTO? My supplier tells me there's four ratios--

 

[tobyS]

I have to add to this thread.

I went through Parker and a (very knowledgeable) Chelsea rep got back with me to clarify the difference in the old style PTO that all 939 series use and the new style PTO that does fit the Allison tranny, but may have an frame interference problem, especially on the A2 . The PTO used on our 939 series is considered "obsolete", but there is a critical difference in the new style that replaced it. The new one is 1/2" wider.

So for people seeking a PTO install on the Allison, and specifically the 939 series A2, which is said to be even closer to the frame than the A0 or A1, I believe you should be looking for the old style. I also found that the shafts and direct mount kits for the new style 6 bolts (and the air shift), will fit the "obsolete" style (installed on all 939series).

So I purchased the direct mount pump kit (for the new style PTO) and have it mounted on the old style (NOS that I have a few of). Below is a picture of the "kit" installed on the old style. It fit perfect, but I'll warn you to buy new bearings, the old is hard to get off the shaft while in the housing and heating it will destroy the temper (and they only cost about $14 each, new).

Note I'm intending on putting this on an M35A3, which does not have the frame problem but does have a transfer case interference problem (so remote mount pump does not fit due to length problem). Also, the M35A3 only has 55 teeth in the tranny, vs 77 for the tranny in a 939 series, so will turn closer to 1.1/1 vs about 1.5/1 for 939 series.

So now I'm researching air shift. Like the shaft and pump mount, I'm finding the parts are interchangeable between our obsolete PTO and the new style (so now ordering air shift kit).

I'll update again when I take some measurements off my M929A2 in regards the air shift.

Edit....re rotation. The engine turns counterclockwise and the output of the PTO turns the same direction. But the PTO rotation is viewed from the shaft end, SO THE PUMP ROTATES CLOCKWISE.
Do not buy a left handed (counterclockwise) pump (like I did... learn the hard way).

 

[74M35A2]

I'm particularily interested in the air or electric shift. I confirmed it is availble for the M939 PTO, but it appears to hit the exhaust pipe closely overhead. The cable lever cover is the lowest profile.

 

[tobyS]

I'm particularily interested in the air or electric shift. I confirmed it is availble for the M939 PTO, but it appears to hit the exhaust pipe closely overhead. The cable lever cover is the lowest profile.

Your absolutely right! I saw that it is extremely close in the photo above by the OP. Exhaust right next to an aluminum part that has seals does not seem to be a good idea, even if you could get it in. I wonder if a section of SS flex could put in and some heat blanket. I guess this is the reason one does not hear of air shifts on the 939. Does the exhaust on an 923A0 (250) have that same issue? My recollection is that it's different, but it been a while since I sold the one I had.

On the M35A3, my setup requires floor modification (not frame), but there is no exhaust.

I have some 1.5" air cylinders.

 

[74M35A2]

Exhaust heat no problem, can insulate. Issue is height clearance. It crashes hard into it by 2". Air cylinder may work?

 

[tobyS]

Cylinder yes, if it has the stroke matched to the arm travel (or mechanical stops). But, is it really that useful or is it a "bells and whistles" kind of addition, even if it did fit? Okay, now I'm reconsidering doing it on this unit, going into the M35A3.

I admit to having more miles on my 817 with a Spicer 5 speed than the M929A2 Allison, so don't have operation down on the newer truck. I first tried to put the PTO into gear in Neutral, running. A slight grind told me not to do that. If I had thrown an air shift, what would happen with air pushing it in? That would be a mistake. Unless someone gives me a good reason to go air-shift, that is not a modification I'm going to make.

 

[WILDBOY6X6]

Hi what happened did someone remove the stock pto? or do you just want to change it

 

[74M35A2]

For me, I'm wanting to go all electric solenoids for hydraulic control, can then do wireless remote easily on them. From there, remove cab control tower for more room in cab, I often have 3 or even 4 adults in there.

Good point on the engagement concern. It can be easily aleviated by running the circuit through the neutral start switch in the shifter. Trans in neutral, PTO will not engage. This would work for an air solenoid that only needs momentary power to change positions, as you don't want it to pull out once back in neutral to operate.

 

[162tcat]

Most commercial rigs (90's vintage or older) have no safety on air pto engagement. If you flip it at the wrong time, the grinding noise will remind you its not time. They last a long time in commercial applications so I'd be shocked if anyone ever wore one out on an mv. Your more likely to have issues from the cable shift being out of adjustment than anything else.

Sent from my SAMSUNG-SGH-I537 using Tapatalk

 

[tobyS]

Hi what happened did someone remove the stock pto? or do you just want to change it

I've had several 939 series trucks that I wanted to add hydraulics for a dump or plow or other aux functions, but never did. I'm not the original poster, so I don't know about their motives. This thread was recent and came up in a search.

I bought a 'lot' of NOS PTO's from GL, so have a few now to experiment with. One will be going on my M931A2 and one on my M35A3.

I bought the M35 with an Allison tranny problem. It came with the original tranny in a box in the bed and a "used" one in it that has the same reverse and fourth gear out. The gears and bearings looked like new in the one in the box so I rebuilt that tranny and torque converter and have it ready to go in. While apart, I took measurements and realized that the same PTO (6 bolt) can attach to either Allison transmission, the deuce has 55 teeth turning it and the 5 ton has 77, but gear and other mount dimensions are the same.

The M35A3 has plenty of frame clearance but the transfer case is in a position that blocks a driveshaft driven pump like on the 939 series, so I began to consider mounting it direct to the PTO. There were a few threads that mention this type mount, but I didn't find a definitive one.

The Parker rep explained how the new style PTO is 1/2" wider and can have frame interference, but that the shafts and flange kits will fit the old style or the new ones. I thought that was good info to add to this thread. It seems this thread arrived at the same conclusion, but never said the reasons (that the new is 1/2" wider). This thread seemed to be the best to get answers for the 939 series, which is next on the list after the deuce.

74M35A2 kindly pointed out the reason that air shift would not fit. It didn't seem to be frame, but is indeed exhaust that is apparent in the picture above (turn your head 90*). Now it is obvious that the air shift will stick up and interfere with the exhaust pipe on the M939 series... but it wasn't when I started. I haven't made a conclusion on the 5 ton direct mount pump and frame issue yet...it still appears it will fit with end ports on the pump.

 

[Wagoneer]

Did anybody ever get anything to work with the electric solenoid setup to control the PTO? I have had no luck finding the A2 cab control box.
I was thinking of using a 24vdc linear actuator to engage the PTO but was running into a mental block on the electric control of the winch. Does the winch have to be engaged fully or can you control the flow by barely pushing on the lever in the cab?
I wanted a potentiometer style control so I could adjust speed and soft start the winch, My other issue would be a return to center actuator so when I let off the switch it would stop the winch.

 

[tobyS]

Did anybody ever get anything to work with the electric solenoid setup to control the PTO? I have had no luck finding the A2 cab control box.
I was thinking of using a 24vdc linear actuator to engage the PTO but was running into a mental block on the electric control of the winch. Does the winch have to be engaged fully or can you control the flow by barely pushing on the lever in the cab?
I wanted a potentiometer style control so I could adjust speed and soft start the winch, My other issue would be a return to center actuator so when I let off the switch it would stop the winch.

Wagoneer, you can use a cable that mounts on the dash or a bracket attached to the dash. Pull it out to engage and push it in to disengage. I haven't seen an electric or air setup that works on the 939 series without something hitting something.

As far as operation, that will depend on the pump and valve you use. Standard pump is a positive displacement and the valve is open center. Like any mechanical valve, as you pull the lever the spool begins to close off the thru flow and opens to one of the ports (the other is simultaneously going to tank/return). It will give you some low speed, but not full pressure at low speed.

Your questions about pots, speed and soft start get into a whole different beast than the farm, open center style we are using. Can it be done...yes if you have enough money. I haven't thought it through but will probably require a variable displacement pump and both pressure and flow compensation. Then there is the valving. If you want real proportional control, get ready to pucker up.

I control positioning of machinery by a poor mans method, one valve for high speed and one for low. Movement starts on low, brings in the high speed and at X- 1" stops the high speed and continues to position at low speed, preventing over-run of the position. A simple hand button for low and one for high would work (but not on the positive displacement pump system). If you are going that far, might as well add remote control (wired or wireless) for electrically operated valves.