I recently got a Dannmar/MaxJax M6 lift. I raised and lowered it several times with no load and it worked well. So I put my Mazda B2300 on the lift as a test. I know trucks are heavier in the front so I estimated the center of gravity to be closer to the front of the truck. The truck was 20" from each post and the posts were lined about where the steering wheel is. Going up went smoothly but when I started to come down it wouldn't budge.
When I release the hydraulic pressure, the hoses would "relax" and the hydraulic cylinders could be wiggled (they do not have load on them), but the carrier wouldn't come down and the locks were not engaged. I tried raising the truck more then lowering with some wiggling but no luck. I put jack stands under the frame on drivers side and screwed them up until they took the pressure off of the M6 lift arms and at this point the M6 arms and carrier dropped maybe 1/4 - 1/2" and loaded the hydraulic piston. At that point (with no load) the carrier moved up and down freely. I lowered it all the way and applied much more grease to the entire track it rides in, then raised it to the top and applied more grease to the bottom of the track. Then when I put it back under the truck and put just a little load on it it would stop moving down again.
I was able to do the same thing on the passenger side. There seemed to be more weight on the rear arms of the lift (based on looking at the attached pictures and other things). The blocks that slide up and down in the post guides are tilted toward the back when you look down from the top (see pics). I then tried putting the jack stands under the rear of the vehicle and raised them to take some of the weight off. At this point the blocks the carrier ride on in the rail seemed to be more centered in the rail (not wedged toward the back like they are in the picture). At this point the drivers side would drop, but the passenger side wouldn't. The passenger side blocks still seemed slightly angled toward the back and I suppose this is why it wouldn't come down. It seems the slightest imbalance of a few tens of pounds will prevent the carrier from dropping.
I called Dannmar and they talked me in to lifting the truck then wiggling more aggressively as I got a 2nd person to press the lever on the power unit. This time (with more grease and wiggling the back of the truck instead of the front), I got it to come down some and after a while had the truck back on the ground.
I just assumed I was way off on the center of gravity and this caused the binding. However I used 2 jacks and placed them on the frame at the same position on each side of the truck. I started at the back and moved them up a few inches at a time until I got to a point where the truck would easily "see saw" back and forth. I assumed this was the true center of gravity. This was only about 5 inches from where I had centered the lift.
So is this typical? I would assume that being within a few inches of the center of gravity would be good enough. I really didn't expected this lift to be that sensitive to getting the center of gravity perfect. BTW, the posts are both perfectly square (124-1/16" from back of the base plates on both sides, and also checked with a couple of really long levels I have). Also the posts are nearly perfectly plumb. The level says 89.7 degrees on one and 89.9 on the other. Putting any of the shims under the lift makes it closer to 90.8 degrees (so more off in the opposite direction). So it is as plumb as it can get with the shims.
When I release the hydraulic pressure, the hoses would "relax" and the hydraulic cylinders could be wiggled (they do not have load on them), but the carrier wouldn't come down and the locks were not engaged. I tried raising the truck more then lowering with some wiggling but no luck. I put jack stands under the frame on drivers side and screwed them up until they took the pressure off of the M6 lift arms and at this point the M6 arms and carrier dropped maybe 1/4 - 1/2" and loaded the hydraulic piston. At that point (with no load) the carrier moved up and down freely. I lowered it all the way and applied much more grease to the entire track it rides in, then raised it to the top and applied more grease to the bottom of the track. Then when I put it back under the truck and put just a little load on it it would stop moving down again.
I was able to do the same thing on the passenger side. There seemed to be more weight on the rear arms of the lift (based on looking at the attached pictures and other things). The blocks that slide up and down in the post guides are tilted toward the back when you look down from the top (see pics). I then tried putting the jack stands under the rear of the vehicle and raised them to take some of the weight off. At this point the blocks the carrier ride on in the rail seemed to be more centered in the rail (not wedged toward the back like they are in the picture). At this point the drivers side would drop, but the passenger side wouldn't. The passenger side blocks still seemed slightly angled toward the back and I suppose this is why it wouldn't come down. It seems the slightest imbalance of a few tens of pounds will prevent the carrier from dropping.
I called Dannmar and they talked me in to lifting the truck then wiggling more aggressively as I got a 2nd person to press the lever on the power unit. This time (with more grease and wiggling the back of the truck instead of the front), I got it to come down some and after a while had the truck back on the ground.
I just assumed I was way off on the center of gravity and this caused the binding. However I used 2 jacks and placed them on the frame at the same position on each side of the truck. I started at the back and moved them up a few inches at a time until I got to a point where the truck would easily "see saw" back and forth. I assumed this was the true center of gravity. This was only about 5 inches from where I had centered the lift.
So is this typical? I would assume that being within a few inches of the center of gravity would be good enough. I really didn't expected this lift to be that sensitive to getting the center of gravity perfect. BTW, the posts are both perfectly square (124-1/16" from back of the base plates on both sides, and also checked with a couple of really long levels I have). Also the posts are nearly perfectly plumb. The level says 89.7 degrees on one and 89.9 on the other. Putting any of the shims under the lift makes it closer to 90.8 degrees (so more off in the opposite direction). So it is as plumb as it can get with the shims.
