PTO/hydraulic problems.. kinda confused. need help.

[Eafarms]

so I went to use the dump a load of gravel last week.. dump lever was a bit harder than normal to get to fall into the raise gear. once it did, pop bang.. no bed lift. looked under it and saw the shaft from the PTO to the hydraulic pump was laying on the ground. blew a u joint.. took it off to get repaired.
today I wanted to find out why it popped when it had worked fine before. I started the truck and got under to look at the PTO

THINGS OF NOTE

Winch lever was in off position.. winch shaft spinning in time w rear hydraulic shaft. does not stop spinning no matter what ive tried.

dump lever on goes between off and on. no more multi positions for raise, lower, neutral, off.

when dump lever off the winch shaft slows and can be stopped with my hand, but still spins when I let go.
____________________________________________________________________

my initial thought is that something broke inside and somehow locked the winch and hydraulic shafts together.

any ideas, suggestions on tests, anything.. ??

thanks

 

[tobyS]

I thought the M51A2 was the 5 ton dump and an M52A2 a semi tractor. Does the pump turn?

 

[Eafarms]

You are correct. I believe mine was refitted as a dump when it was rebuilt in 90. But data plate says m52

 

[tobyS]

I'm sorry I can't tell you much about the PTO, I've dealt with newer ones. Can you put up a few pictures? Have you confirmed that the pump turns?

 

[Eafarms]

The rear hydraulic pump does not spin because the shaft is out, I should have it back on Monday. Does not spin because the shaft is out, I should have it back on Monday. I'll get some pictures and a video up later today. What concerns me the most is that the front winch shaft never stops spinning. No matter what the Winch lever does.

And the dump lever no longer has multiple positions. Just on and off.. anyone know if fluid has to be moving for it to move between raise lower etc etc.

 

[red]

On my m816 wrecker with the same double sided PTO both shafts always spin together.

With hydraulic spool valves (in general) there is no set position without the fluid flowing.

 

[73m819]

Red your pto is different then the double (2 ptos in one case driven by a common shaft) pto on the older 5ts, sounds like some thing in the pto broke because something in the pump and or the dump control valve body broke, this caused the dropped shaft AND the pto damage, my guess would be a TWISTED common shaft for the pto issue.

 

[73m819]

You are correct. I believe mine was refitted as a dump when it was rebuilt in 90. But data plate says m52

The same frame used on both the m51 and m52, I am posting this so the newer MVers who do not know that much about the older 5ts can understand how a m52 could become a m51, we did this quite a bit in vn, we needed dumps a lot more then tractors, dollies were made from the rears off wrecked m51s so trailers could be still be pulled if needed.

 

[red]

Red your pto is different then the double (2 ptos in one case driven by a common shaft) pto on the older 5ts, sounds like some thing in the pto broke because something in the pump and or the dump control valve body broke, this caused the dropped shaft AND the pto damage, my guess would be a TWISTED common shaft for the pto issue.

Pic of the transmission PTO on my wrecker while sitting next to the transfercase. Looked identical to the double sided PTO I pulled off the m51a2




Why my m816 has a double sided transmission PTO I'm not sure but it does have one.


Removing the PTO doesn't take very long. Keep an eye on the thickness of the gaskets because they serve as shims to get the gear spacing correct.

 

[Eafarms]

Sorry didn't get vid or pics this weekend. It was our daughters bday and we had 17 girls ranging from 11-14 roaming our house all weekend. My mind was going a million different directions at once. Now everyone's gone and I'm going to bed! Ha.

Ill get pics n vid up tomorrow.

 

[Eafarms]

Best video I could manage alone today.

https://youtu.be/9673D1NDNlI

 

[M543A2]

Unless I am not seeing what I am supposed to, it looks as if your hydraulic system is driven off the two way PTO on the transmission. The M51 trucks I have drive the hydraulic system for the dump bed off a transfer case PTO, not the transmission PTO. The lever at the left side of the seat at the back of the cab both engages the transfer case PTO and selects the positions for the hydraulic valve such as lift, lower, hold as you move it forward. The drive shaft between the back of the transfer case and the hydraulic system on the bed can be turned easily. In fact if there is residual pressure in the system just after lowering the bed and the lever is moved to the PTO disengaged position (fully to the rear) the pressure can be heard spinning the shaft backwards for a short while. The selector lever in the cab can be freely moved between all positions with the truck shut off.
Am I right yours has been set up different from my trucks that have been M51's all their life? If you are driving off the transmission, if the PTO drive for some reason is not shifting to neutral, overspeed of the pump PTO shaft can happen during road travel, destroying it.
Is your pump and valve an integral unit, located at the front of the dump bed frame along with the oil reservoir? One can actually lift the dump bed and its frame off the truck as a unit, all of the hydraulic system mounted to the bed sub frame and coming off with it.

 

[red]

M543a2 the m51a2 dump truck that I parted out is setup identical to Eafarms using the transmission PTO.

Have you tried one of the other neutral positions for the front winch?

 

[M543A2]

Red, thanks! You got me to go out and look under a truck! So, everyone, ban me to a pit of itchy leaves with no food and water for a week! I was wrong about the pump drive coming off the transfer. I got my memory confused with the drive for the fuel pump on my 2 1/2 ton fuel tanker truck. That one comes off the transfer with the same kind of shift lever beside the seat. The dump hydraulic drive shaft comes off the back shaft on the transmission PTO unit. When in neutral I can easily turn the shaft by hand, feeling the pump working. All else I related above about how the bed and sub frame for it are built is correct. I have a complete sub frame with pump, valve, and tank that some idiot cut the bed off of at the rear frame rails and instead of removing the ram pins just cut off the ram cylinder rods with a torch! GRRRRR! Oh well like we say, if someone had not done that we would not have what parts we do.
By the way, if anyone wants a 2 1/2 ton tanker body I have one I would like to move down the road. Seems to be in good condition with lined tanks and special filter. Rough on outside.

 

[tobyS]

Red, thanks! You got me to go out and look under a truck! So, everyone, ban me to a pit of itchy leaves with no food and water for a week! I was wrong about the pump drive coming off the transfer. I got my memory confused with the drive for the fuel pump on my 2 1/2 ton fuel tanker truck. That one comes off the transfer with the same kind of shift lever beside the seat. The dump hydraulic drive shaft comes off the back shaft on the transmission PTO unit. When in neutral I can easily turn the shaft by hand, feeling the pump working. All else I related above about how the bed and sub frame for it are built is correct. I have a complete sub frame with pump, valve, and tank that some idiot cut the bed off of at the rear frame rails and instead of removing the ram pins just cut off the ram cylinder rods with a torch! GRRRRR! Oh well like we say, if someone had not done that we would not have what parts we do.
By the way, if anyone wants a 2 1/2 ton tanker body I have one I would like to move down the road. Seems to be in good condition with lined tanks and special filter. Rough on outside.

I live down the road

 

[Eafarms]

success!! got the shaft back today, threw it on and got it spinning. as others and myself had suspected/hoped. once there was fluid movement I could then engage raise lower neutral off portions of the lever throw..

I believe before it was always in neutral not off could never get the lever all the way back to the wall, contributing to the short life of the fairly new looking u joints in the shaft.

 

[Eafarms]

https://www.youtube.com/watch?v=kT-Ovalm2Nk

 

[M543A2]

It might be a good idea to check the linkages for the shift lever. A sticking, rusted pin and clevis or pivot point can make shifting unreliable and difficult. Keep them oiled.

 

[Eafarms]

Collecting all the fluids for a big maintenance overhaul once the weather breaks which is feeling like it's gonna be soon.

 

[gimpyrobb]

Now get your tailgate latch fixed!!!!!!!!!!!!!!!!!!!