Cab tilt question.

[Chickenbone]

How close to level should the truck be before attempting to raise the cab?

I'm specifically asking about sidehill angle, not front to back.

 

[chucky]

If its not flat it just puts everything it in a strain ! Its worth the extra time/movement to go ahead and get flat and ( ALWAYS )!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! jack the cab all the way over to where the cab falls over the final 6 or so inches past 180 degrees to keep the cab from maybe coming down on you if something goes wrong and ALWAYS put a heavy brace under the cab for extra safety ! Cause you might not get a second chance to learn a hard lesson !

 

[Ronmar]

A little side probably isn't a problem, the pivot structure is fairly rigid, and the cab after all is lifted asymmetrically from one side anyway, so it has some tolerance in this regard.

As Chucky mentioned, you don’t want the front uphill. By design, the lift rotates the cab a few degrees past the balance point in relation to the force of gravity, so it will tend to stay there naturally. Leaving the control in the “lift“ position should keep it locked hydraulically.

You can usually see this point when you stop the pump near the end of the cabs upward movement and the cab keeps moving forward by itself. It is real easy to find when using the hand pump. That un-pumped movement is gravity pulling it down the other side of the balance point till the hydraulic cylinder is fully extended.

You can confirm it is past balance by shifting the control from raise to lower. The cab should not move. If it lowers you were not over the balance point... With the control still set to lower, step around to the front of the cab and try to push it back over by hand(might take two people). This is good for you to play with and will give you an idea how much force it takes to get a non hydraulically restrained cab to lower on its own From the other side of the balance point. With the controls set to lower, Once you push it past the balance point, gravity will do the rest.

Also as chucky alluded to, the cab is controlled and restrained by hydraulics. In normal operation, if you raise the cab past balance and leave the control in the raise position, it is pretty safely restrained in that position by gravity and hydraulic control. If you are working on the cab lift hydraulic circuit, you MUST provide an alternate method of restraint to insure the cab stays where you place it until the hydraulics are restored AND pressure tested… this is usually done with a crutch(2X4?) installed between the truck crane lift structure behind the engine and the back edge of a fully raised cab…

 

[GeneralDisorder]

TM operator instructions work package for raising/lower cab:

"Caution must be exercised while cab is raised. Ensure both doors are securely locked in the closed position before cab is raised or lowered. Keeping doors in the open position while cab is raised or lowered can cause stress on the damper which can then fail and crush personnel. Do not allow personnel near front of cab while cab is being raised or lowered. Never raise cab while occupied or when parked uphill on a steep grade. Use extreme care when opening cab door with cab raised. Do not allow personnel near cab and engine compartment when cab is being lowered. Failure to comply may result in serious injury or death to personnel or damage to equipment."

The TM mentions no restrictons other than don't do it if "parked uphill on a steep grade" - I guess it's up to the soldier to determine what the definition of steep grade is.

Also worth mentioning that there is a cam mechanism at the top of the hydraulic ram that is supposed to function when the cab reaches it's fully raised position - this is additional safety that takes the load off the hydraulic ram. On many trucks these are rusted to the point they do not function. It took me 4 hours to get mine unseized and it still requires a few taps with a hammer to engage every time I lift my cab.

 

[Ronmar]

Yep, the cam in the end should stay pointed at the cab floor as the cab rotates. Its purpose is to ride in the long slot in the rod end when the cab is lowered and floating on the air suspension. As you raise the cab it should rotate with the cab into the short slot. This allows the cylinder to maintain tighter control of the cab as it passes over the balance point. Scared the hell out of me the first time I saw one lurch 14-15” as it passed over the balance point while the cam was in the long slot...

I did a video on this once upon a time…

 

[CallMeColt]

Yep, the cam in the end should stay pointed at the cab floor as the cab rotates. Its purpose is to ride in the long slot in the rod end when the cab is lowered and floating on the air suspension. As you raise the cab it should rotate with the cab into the short slot. This allows the cylinder to maintain tighter control of the cab as it passes over the balance point. Scared the hell out of me the first time I saw one lurch ablout 14-15” as it passed over the balance point while the cam was in the long slot...

I did a video on this once upon a time…

You're the best at showing us stuff my friend!

 

[coachgeo]

If its not flat it just puts everything it in a strain ! Its worth the extra time/movement to go ahead and get flat and ( ALWAYS )!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! jack the cab all the way over to where the cab falls over the final 6 or so inches past 180 degrees to keep the cab from maybe coming down on you if something goes wrong and ALWAYS put a heavy brace under the cab for extra safety ! Cause you might not get a second chance to learn a hard lesson !

..."Cause you might not get a second chance to learn a hard lesson !"

Second chance is now officially called... A CHUCKY. So in essence as Chucky knows all to well; his above sentence now reads.....

Cause you might not get A CHUCKY to learn a hard lesson (from)!

 

[Chickenbone]

Thanks for the replies all. Forgot to get back to this one.

 

[MatthewWBailey]

Yep, the cam in the end should stay pointed at the cab floor as the cab rotates. Its purpose is to ride in the long slot in the rod end when the cab is lowered and floating on the air suspension. As you raise the cab it should rotate with the cab into the short slot. This allows the cylinder to maintain tighter control of the cab as it passes over the balance point. Scared the hell out of me the first time I saw one lurch 14-15” as it passed over the balance point while the cam was in the long slot...

I did a video on this once upon a time…

Since we were talking about cylinders on the other thread, I started snooping around on this rod end connection. Yours and other pictures show a straight edge on the cab joist, mine looks bent. Does this seem bent to you?... or am I needing an eye exam.

 

[Ronmar]

Your cab is bent!

 

[MatthewWBailey]

Your cab is bent!

Glad I don't need to goto the eye doctor.

Also seems like that little cam plate is on the wrong side of the connection compared to your video.

 

[Ronmar]

Glad I don't need to goto the eye doctor.

Also seems like that little cam plate is on the wrong side of the connection compared to your video.

yes it does...

 

[MatthewWBailey]

yes it does...

So I assume this has a very short half life before it fails on a lift attempt. That buckling looks like cracking, then tear out will be next, given the forces.

I wonder if the truck was operated with the lift cylinder valve in the raise position without being all the way down. Seems like bouncing induced bending of the frame.

im not buying a new cab so ill need another lift point

 

[Ronmar]

Almost looks like the bend angle is the worst/aligned with the fore axis when the cab is raised. what does the angle look like when the cab is lowered. there is a good view with the grill removed when lowered.

yea the long slot is to allow cab suspension travel, but the control should be in the lower position to alow the cylinder to find the lowest point of suspension travel for the slot to function properly...

 

[MatthewWBailey]

Almost looks like the bend angle is the worst/aligned with the fore axis when the cab is raised. what does the angle look like when the cab is lowered. there is a good view with the grill removed when lowered.

yea the long slot is to allow cab suspension travel, but the control should be in the lower position to alow the cylinder to find the lowest point of suspension travel for the slot to function properly...

This pic shows it better. The angle is bent upwards towards the floor of the cab when looking thru the bumper, parallel with the floor. For ref, that horn is parallel with the ground when the cab is lowered. The outer support is really flaring outwards. I'm not lowering until I have some solution on lifting at this point.

I get that SS had limited space for this lift cylinder but both this and the spare tire lift have really horrible leverage. I can't find a spec on cab weight but swag is 2000lbs?

could I put a telescoping cylinder off the air lift beam somehow? I'd have to add an open center valve thou

 

[GeneralDisorder]

That's wild! I haven't seen that before. I imagine soldiers did something stupid to cause that. Ran into the cab with another truck while it was lifted perhaps?

I'm not seeing how that could happen with the cab in the down position. I can only guess that the cab was lifted while the truck was on a side angle or steep grade.

The other possibility...... some soft-cab trucks were field upgraded with armored panels and glass and the early stages of this process did not have any provision for upgrading the cab lift system and they would fail due to the cab being too heavy and only being lifted from one side. The LTAS (Long Term Armor Solution [as opposed to the field upgrade short term solutions]) has dual lift rams - one on each side - to support the 4500 lb armored cab. This could be a result of a field armor upgrade that was then removed. Or the truck had a gun mount and it was lifted on a side angle.... My guess is the lift ram and support were heavily overloaded or abused.

 

[MatthewWBailey]

That's wild! I haven't seen that before. I imagine soldiers did something stupid to cause that. Ran into the cab with another truck while it was lifted perhaps?

I'm not seeing how that could happen with the cab in the down position. I can only guess that the cab was lifted while the truck was on a side angle or steep grade.

The other possibility...... some soft-cab trucks were field upgraded with armored panels and glass and the early stages of this process did not have any provision for upgrading the cab lift system and they would fail due to the cab being too heavy and only being lifted from one side. The LTAS (Long Term Armor Solution [as opposed to the field upgrade short term solutions) has dual lift rams - one on each side - to support the 4500 lb armored cab. This could be a result of a field armor upgrade that was then removed. Or the truck had a gun mount and it was lifted on a side angle.... My guess is the lift ram and support were heavily overloaded or abused.

Never thought of that. Plus I realized that even with the valve in the raise position, it leaks enough to allow the cab to fully lower slowly (2-3hrs), and won't hold pressure. So it must've been raised against weight? The passenger side mud flare is pushed in on that side but straight on the driver side. Maybe it was half rolled at some point. The Armour stuff sounds realistic too. In a war zone, who cares about the cab lift rating lol.

 

[FarmingSmallKubota]

I wonder if the truck rolled on its side at some point and the truck was rolled back with cab unlatched

 

[MatthewWBailey]

I wonder if the truck rolled on its side at some point and the truck was rolled back with the back unlatched

Rick pointed out the truck must've seen service bc I found a 2016 date code MRE cinnamon bun on the trans, & MRE heater. There were busted optics and a slew of 223 casings in the bed and around the spare tire when I got it. The turret cover has a bad caulk job so must've been off at some point. If there was a camera system recording the life of the truck over 9200 miles I'll bet it would have some wild images. Pretty good truck to raise hell with

 

[MatthewWBailey]

Almost looks like the bend angle is the worst/aligned with the fore axis when the cab is raised. what does the angle look like when the cab is lowered. there is a good view with the grill removed when lowered.

yea the long slot is to allow cab suspension travel, but the control should be in the lower position to alow the cylinder to find the lowest point of suspension travel for the slot to function properly...

Took another photo of this for posterity.