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#626832 - Mon Mar 08 2010 12:55 AM Dump bed PTO Hydraulics  
dliptak  Offline
New Guy
Joined: Feb 2010
Posts: 26
Fort Collins, Colorado
This may not be very specific to my Chevy 1.5 ton but I thought I'd ask, as I'm sure there are quite a few folks familiar with lifts.

I've got a short wheelbase '59 Viking 40 that has a dump bed on it. For what I know, everything looks to be there: PTO enclosure, cable to tranny, cable to PTO and the hydraulic lift itself.

Problem is, I don't know many details on maintenance or how it works...and I'd rather learn than guess smile I've got the basics: pull the cable that goes to the transmission to disengage the input shaft from the truck's driveline and engage the PTO shaft. Engine powers PTO for the pump. I'm guessing the other cable is pulled to control how much/fast fluid is supplied to the lift, causing it to extend. Pushing it 'closed' would prevent forward fluid flow and allow the lift to contract.
Can anyone point me to a good primer on a setup that would be similar to what I have? I'm curious on how to change fluid, etc.

A little about what I've observed: There is one massive line (maybe 1-1.5" in diameter) from the PTO to the 'fixed' end of the piston; not a long run, maybe half a foot? Then there's a longer, more flexible line, about 1/2" in diameter that runs from the PTO up toward the far end of the piston. This line is cut...or possibly cracked, as it is currently in two pieces. It looks more like someone cut the line to me. It'd be good to replace the line as a whole anyway, as it doesn't seem to be as flexible as it should be. There is also a very long cable that is attached to the same lever on the PTO as the cab-cable. I'm guessing that as the bed lifts, the cable tightens and prevents the lift (or bed) from overextending. Sort of a self-shutoff.

No rush on this, I'm mainly curious at this point! There's a few other things I've got to work on getting the truck to stop and start on its own (in that order...however tempting it is to work on the engine! :-D)


Last edited by dliptak; Mon Mar 08 2010 12:58 AM.

1958 Chevrolet Viking 60
All shared photos. Mostly Viking albums

#626895 - Mon Mar 08 2010 03:15 AM Re: Dump bed PTO Hydraulics [Re: dliptak]  
crenwelge  Offline
Shop Shark
Joined: Jan 2008
Posts: 4,659
Fredericksburg, Texas
There is all kinds of rigging, but you should have either a lever or a cable which operates the PTO. It should be attached to the pto which is bolted to the transmission. If it's working, you should be able to step in the clutch, pull the cable and the PTO should engage. If you let the clutch out a little bit, you should hear and feel the PTO turning. The pump should have 3 positions on it. Raise, hold and lower. You will want to replace the bad line. Most automotive or farm machinery dealers can make up hydraulic hoses. I'm not sure what other cable you are talking about unless it operates the tailgate. Usually there was a lever on the side of the dump bed where a driver could reach it through the window. Someone may have rigged up something to automatically open the tail gate to make sure the tail gate got opened. Dumps will turn over if they raise without the tail gate open. Many dumps now automatically open the tail gate with air when the dump goes up. I prefer to have my drivers to get out and look where they are dumping and manually dump the suspension and open the end gate.

#627013 - Mon Mar 08 2010 02:55 PM Re: Dump bed PTO Hydraulics [Re: crenwelge]  
Rich'sToys  Offline
Shop Shark
Joined: Jul 2004
Posts: 3,057
Janesville, Mn
If you could post some pictures, it would be helpful. 53Moneypit has forgotten more about hoists than the rest of us will ever know. When he checks in, he will be able to answer all your questions.


'47 Loadmaster

Politicians and Lawyers have twisted everything in this country into knots that we can never unravel.

I would rather live my life as if there is a God and die to find out there isn't, than live my life as if there isn't and die to find out there is.

#627019 - Mon Mar 08 2010 03:22 PM Re: Dump bed PTO Hydraulics [Re: dliptak]  
51 ashton  Offline
Shop Shark
Joined: Apr 2005
Posts: 1,193
Originally Posted By dliptak
This may not be very specific to my Chevy 1.5 ton but I thought I'd ask, as I'm sure there are quite a few folks familiar with lifts.
Problem is, I don't know many details on maintenance or how it works...and I'd rather learn than guess smile

when you put box up measure just in front of the rear wheels from the ground to the bottom of the box. this is for the props your going to make to support the box in the upright position for servicing the hoist or anything else in that area. there are other ways to support the box but i got a pair 6"x8"x 8' and they worked out perfect. they lock in at the top on the closest channel and at the wheels. some people laugh at the mass of them and they are heavy but not as heavy as the box is. i know it isnt coming down when im under it.

Last edited by 51 ashton; Mon Mar 08 2010 03:26 PM. Reason: we should get spell check

#627074 - Mon Mar 08 2010 08:18 PM Re: Dump bed PTO Hydraulics [Re: 51 ashton]  
53moneypit  Offline
Joined: Dec 2003
Posts: 2,901
Smallville IN
Hi dliptak. That's a different screen name for sure. How did you come up with it?
What part of CO are you in?

Ok, I'm a little thrown by your observation of a cable going to the transmission to "disengage the input shaft form the driveline". That is not what it does. As crenwelge pointed out that is done by depressing the clutch to stop the transmission. Then you pull the PTO cable out to engage the PTO. Then you have properly observed that the other cable operates the pump valve and yes it does control the hoist speed. The large hose is the suction line and it uses the cylinder as the reservoir by drawing fluid from one end and pumping it to the other end (work side of the cylinder. So far so good. The other or third cable of which you speak would be attached to the body near the rear and would pull the valve back to neutral as the body raises. It is not attached to the PTO but to the hydraulic pump valve spool. People often make that mistake if unfamiliar with the nomenclature or just how these things work. So your understanding is essentially correct. I think you will find that the suction hose is attached to a pipe along side the cylinder that goes to the rod end of the cylinder which is where the oil comes from and is stored (reservoir) on top of the piston. So it is a simple recirculation of oil and about as straightforward as it gets. The oil only needs to be changed if 1: it is dirty, 2 if it is contaminated (generally by water) or 3: if it is aerated. If foamy or milky then by all means change it. There will be a plug on the cylinder at the top to refill the system and the oil is drained by removing the pressure hose from the pump after and ONLY AFTER SECURELY BLOCKING THE RAISED BODY. This is dangerous and can cost you your life!!! if not done correctly. READ IT AGAIN! Then remove the hose which will have some residual pressure in it and drain it out. Refill and cycle it several times to bleed off the air it will have in it. Some systems are different and use a separate oil reservoir and that makes life a lot easier so I hope that is what you have. If you have doubts or feel insecure about any of this then by all means take it to a qualified professional body builder like Kois Bros. Equipment Co. in Denver or Layton Truck Equipment in Colorado Springs or Maxey Truck Equipment in Ft Collins.

NEVER run the truck with the PTO engaged unless spreading gravel. ALWAYS make CERTAIN that it is not engaged after lowering the body. Just pull the cable to raise and if it doesn't then your good to go. Place the pump cable back in neutral so the next time you use engage the PTO the hoist doesn't start before your want it to.

The PTO driveline U-joints require greasing and zirks are provided for this. Make sure they are in good operating condition and that they are in phase with each other or it will shake you out of the cab. Use a little graphite lube on the cables or whatever your choice is and that there are no kinks or bends in them. Check the output shaft seal on the PTO for transmission grease.

The equipment houses can also supply you with safety decals for the cab and that may be a good idea. Even experienced operators forget or get dumb at the wrong time occasionally.

That should cover the basics and if you would e-mail me personally I will send you an operators manual for a current hoist. It will be different from yours but not so much that you won't get the drift. OK? If you have specific questions or are unclear do not hesitate to e-mil me and I will do my best to answer. Good Luck and send us a photo of your truck.

1953 Chevy 5-window 3100
In the Stovebolt Gallery
More pix on Picturetrail

Engine & Driveline Moderator

If you can't make seventy by an easy road, don't go. ~~ Mark Twain

#627243 - Tue Mar 09 2010 04:11 AM Re: Dump bed PTO Hydraulics [Re: 53moneypit]  
dliptak  Offline
New Guy
Joined: Feb 2010
Posts: 26
Fort Collins, Colorado
dliptak is admittedly non-creative: d-for-denney and liptak is my last name. I'm in Fort Collins which will be quite convenient for visiting Maxey as was mentioned above.
I appreciate the detailed post and also the safety notes. I'll graciously take any safety recommendations!!
I've taken some photos and tried to heavily 'caption' each image. I believe this will be pretty helpful in discussion and to help my own comprehension. I won't say the pictures are fantastic...but not bad for just crawling around under the truck.
I believe most of the sludge is blowby from leaking engine oil but I won't rule out transmission and hydraulic leakage. The sludge does mask detail from the pictures but hopefully the main things are visible. There are a couple other albums on my main page with more photos of the truck.
The truck isn't currently operational so I'm working on that now. Work on the lift will come later this Spring/Summer.
That makes sense about not disengaging the transmission from the trucks driveline! It didn't occur to me that you'd want to drive while the bed was raised...but the gravel pouring idea makes perfect sense. Seems that'd take some skill and practice!

I looked at the u-joints and the zerts appear to be ~90 degrees out of phase from each other...does that sound good?
I appreciate the clarification on PTO vs. pump. Thinking more about it, the terminology is apparent. For some reason I was calling both units power-take-off. The PTO is the drive unit on the transmission side. What's on the other end could be anything; music box for an ice cream truck, 1980's 'heavy duty' cell phone charger, or in my case - a hydraulic pump!

Here's a couple questions. Is the cylinder drain plug visible in photo #5? I suppose it would make sense that if you had the piston extended, this end of the piston would be at the lowest end of the system and would drain fairly well. I'm hoping that the 'cap' looking thing I see in photos 12 and 17 would be where I could add fluid, rather than by some other trickier means; does this setup look like it has a separate reservoir? It does seem that the bed would need to be raised to get easy access to this plug, if that is indeed what it is. This is where the 6x8's mentioned above would come in handy.

53moneypit, I'll send ya an email for the hoist manual you have...thanks!

Thanks again and if anyone wants me to clairfy or add detail to a photo, let me know! Hopefully this thread can be useful to other dump-bed newbies as well.

1958 Chevrolet Viking 60
All shared photos. Mostly Viking albums

#627384 - Tue Mar 09 2010 04:24 PM Re: Dump bed PTO Hydraulics [Re: dliptak]  
53moneypit  Offline
Joined: Dec 2003
Posts: 2,901
Smallville IN
Here are some quick observations.
1. Yes, it does have a reservoir tank so that makes things a little easier.
2. The cylinder has been changed and it now has an "ag" type truss rod cylinder and it appears to be a little small on the diameter. The original cylinder would likely have been about 7" dia.
3. The hose coming from the top of the cylinder is a return line and a way for air to escape.
4. Your PTO is leaking badly but it is very easy to replace the 6 bolt gasket to the transmission. Just be sure to replace with the same thickness to maintain gear clearances. Gaskets are available in many thicknesses.
5. The grease zirks won't tell you about the phase of the u-joints but if the yokes are the same "clocking" then your OK.
Your transmission oil level is sure to be low and dirty. I'd change it while I had things apart.
Hope this is of some help and encouragement.

1953 Chevy 5-window 3100
In the Stovebolt Gallery
More pix on Picturetrail

Engine & Driveline Moderator

If you can't make seventy by an easy road, don't go. ~~ Mark Twain

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