Hawk trucking 2019 Posted December 10, 2019 Share Posted December 10, 2019 Good evening fellas, I’m John. I have a 2019 Mack granite with a 20 ft dump body. This bed raises and lowers slower than cold molasses. Does anyone have any ideas for a fix? Quote Link to comment https://www.bigmacktrucks.com/topic/60127-slow-raising-bed/ Share on other sites More sharing options...
alex g Posted December 10, 2019 Share Posted December 10, 2019 Has it always raised slow? If not pump may not be fully engaging lift valve in pump Quote Link to comment https://www.bigmacktrucks.com/topic/60127-slow-raising-bed/#findComment-437683 Share on other sites More sharing options...
Bullheaded Posted December 10, 2019 Share Posted December 10, 2019 Do you have air or cable hoist control? If cable check adjustment. If air check the air plunger that is mounted on the PTO pump. Sometimes they get dirt in them and won't travel the full stroke. Sometimes a piece of dirt will score the inside of the bore thus allowing air to bypass. Sometimes the o-rings fail. Quote Link to comment https://www.bigmacktrucks.com/topic/60127-slow-raising-bed/#findComment-437700 Share on other sites More sharing options...
Bullheaded Posted December 10, 2019 Share Posted December 10, 2019 Give us more details and I can give a better description of what to do. I can take pics tomorrow of mine to show you where to look. Quote Link to comment https://www.bigmacktrucks.com/topic/60127-slow-raising-bed/#findComment-437701 Share on other sites More sharing options...
Hawk trucking 2019 Posted December 10, 2019 Author Share Posted December 10, 2019 It has air controls. It has done it since new. Was just wondering if there’s a speed adjustment of some kind. Quote Link to comment https://www.bigmacktrucks.com/topic/60127-slow-raising-bed/#findComment-437714 Share on other sites More sharing options...
1965 Posted December 10, 2019 Share Posted December 10, 2019 Wouldn’t this fall under warranty? 1 Quote Link to comment https://www.bigmacktrucks.com/topic/60127-slow-raising-bed/#findComment-437717 Share on other sites More sharing options...
fjh Posted December 10, 2019 Share Posted December 10, 2019 1 hour ago, 1965 said: Wouldn’t this fall under warranty? Yup agree go back to where you bought it and have it checked the valve may not be set correctly! Quote Link to comment https://www.bigmacktrucks.com/topic/60127-slow-raising-bed/#findComment-437723 Share on other sites More sharing options...
david wild Posted December 10, 2019 Share Posted December 10, 2019 wrong pump? Quote Link to comment https://www.bigmacktrucks.com/topic/60127-slow-raising-bed/#findComment-437724 Share on other sites More sharing options...
Bullheaded Posted December 10, 2019 Share Posted December 10, 2019 I'm still going to say check the air plunger for travel first. I've had to replace new ones because they were scorded inside. But yes, if new, will be warranty. I'll get pics later. Going out in a bit to get truck ready for tonight. Minus 25*C here, so gunna go clean the snow off the truck while the sun is out, LOL. Quote Link to comment https://www.bigmacktrucks.com/topic/60127-slow-raising-bed/#findComment-437725 Share on other sites More sharing options...
tjc transport Posted December 10, 2019 Share Posted December 10, 2019 (edited) check the valve for proper adjustment. my 2020 T880 would just barely go up at 1500 RPM, and drop like the box had 25 ton in it when empty blowing the fluid out of the hydraulic tank. after properly centering the control piston it now raises at idle, and comes down without blowing out the hydraulic fluid. Edited December 10, 2019 by tjc transport fix typo Quote when you are up to your armpits in alligators, it is hard to remember you only came in to drain the swamp.. Link to comment https://www.bigmacktrucks.com/topic/60127-slow-raising-bed/#findComment-437728 Share on other sites More sharing options...
Hawk trucking 2019 Posted December 10, 2019 Author Share Posted December 10, 2019 Ok, thank you. I’ll check into the plunger. Quote Link to comment https://www.bigmacktrucks.com/topic/60127-slow-raising-bed/#findComment-437729 Share on other sites More sharing options...
Bullheaded Posted December 10, 2019 Share Posted December 10, 2019 See the cylinder with the 2 air lines with the Drive Products decal on the bottom of the PTO. That is the air shift plunger. The back side is where that little keyway slide is and you can see if it is travelling. Get someone to go in the cab and get someone to shift it up and down and see how that is moving. In the old days it was open on the back so you could hit it with a hammer but now they all have that cover on them. You can also take the air lines off (and check for air supply) and remove those 2 bolts and slide cover off. There is a piston with o-rings inside. Make sure it is clean and lube it with some Krown or Fluid Film orsomething similar. That is assuming you can remove it. Sometimes the pumps are rotated to a different orientation on the transmission. I had one Freightliner Classic that I had to drop the PTO from the trans and drop the oil to get that plunger off. Not a fun job in the bush when you are working. Hopefully this helps. I suck at trying to explain stuff. Quote Link to comment https://www.bigmacktrucks.com/topic/60127-slow-raising-bed/#findComment-437737 Share on other sites More sharing options...
fjh Posted December 11, 2019 Share Posted December 11, 2019 so the second last picture can you manually move that shaft to the front any further that cap with the hole is meant for a cable to attach to pull the valve to the neutral position when the box is raised WHEN operated by cable system on an air set up it becoms redundant Can you push the rod with the pin thru it forward any more! Maybe contact Drive products and ask some questions! Quote Link to comment https://www.bigmacktrucks.com/topic/60127-slow-raising-bed/#findComment-437830 Share on other sites More sharing options...
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