1979 cabover tilt ram

[Geoff Weeks]

Problem is, the blue goo can be forced up the stud when the flange is tightened and "glue" the cones in place. I know it happens, but the correct way is a paper gasket. If you ever have to pull one that someone used a whole tube of RTV on, you'll never install with goo again, and always use a gasket.

 I know one that took 3 hrs of digging to get the cones out so the axle would come out. Paper also saves you from having to clean the old blue goo off the parts.

[RS Disposal]

1 hour ago, Geoff Weeks said:

Problem is, the blue goo can be forced up the stud when the flange is tightened and "glue" the cones in place. I know it happens, but the correct way is a paper gasket. If you ever have to pull one that someone used a whole tube of RTV on, you'll never install with goo again, and always use a gasket.

 I know one that took 3 hrs of digging to get the cones out so the axle would come out. Paper also saves you from having to clean the old blue goo off the parts.

This was grey gasket maker and I used very little being it was a metal to metal seal.  Like I mentioned earlier, I will watch to see if it leaks and if necessary pull back off and and make a gasket.

[mechohaulic]

4 hours ago, Geoff Weeks said:

Problem is, the blue goo can be forced up the stud when the flange is tightened and "glue" the cones in place. I know it happens, but the correct way is a paper gasket. If you ever have to pull one that someone used a whole tube of RTV on, you'll never install with goo again, and always use a gasket.

 I know one that took 3 hrs of digging to get the cones out so the axle would come out. Paper also saves you from having to clean the old blue goo off the parts.

have seen a "tube" of goop/blue glue  on only one wheel also!! then find a wheel that the wrong silicone glue was used and the glue was NOT compatible to gear oil. big ring of snot rolling around axle  inside tube. had the fancy pliers made for the cones removal; worked some times most not. don't forget the axle soo stuck on the hub you get carried away with the 20 lb sledge (and pissed) low and be hold there goes a stud or two smashed. not to say I never hit a stud to the point I welded a 5/8th die to a large nut which fit  a  socket !!😱 a good can of brake clean spraying the cones has at times helped the glue shrivel making cone removal easier.be very careful of brake clean messing up  nice polished alum wheel though.

[mechohaulic]

6 hours ago, RS Disposal said:

I was pretty much just going on the previous axle removal and replace where there was just evidence of silicone and no gasket.  I did make sure that the cones were clean.  I do know that the last time the axle was pulled was 30+ years ago due to a pinion gear break.  This truck sees ALOT of salt in the winter being it works up canyon at the local ski resorts.  I had no problem getting axle out.  Two quick hits with a hammer and the axle popped right out. If the axle ends up showing signs of leaking I will just op it back out and make a gasket.

Previous heavy work was all done by my dad who is no longer with us.  I have been keeping up on the lighter pm maintenance work.  But as far as the more intense work I am pretty much a newbie to heavy trucks, as those of you that followed me on my engine breakdown last summer will attest to.  I asked ALOT of questions.  I am a light truck/automotive mechanic so I do understand the basics of mechanic work.

Shop manuals are great for alot of things, but I highly value real world experience. Particularly on older trucks

keep one major thought in mind == you state your a newbie at HD truck repair!! do you think  all  of us just graduated grammar school and became "Master truck mechanics ??? WE ALL ARE /// WERE NEWBIES AT ONE TIME OR  ANOTHER!!! 50 plus years of wrench pushing and following these forums puts me not even a newbie = I'm in "kindergarten and still learning. can't say I want to learn all I read here though. give me old school mechanical over this electronic crap any day.to get back on original topic -- how's the hydraulics working??

[Geoff Weeks]

6 minutes ago, mechohaulic said:

have seen a "tube" of goop/blue glue  on only one wheel also!! then find a wheel that the wrong silicone glue was used and the glue was NOT compatible to gear oil. big ring of snot rolling around axle  inside tube. had the fancy pliers made for the cones removal; worked some times most not. don't forget the axle soo stuck on the hub you get carried away with the 20 lb sledge (and pissed) low and be hold there goes a stud or two smashed. not to say I never hit a stud to the point I welded a 5/8th die to a large nut which fit  a  socket !!😱 a good can of brake clean spraying the cones has at times helped the glue shrivel making cone removal easier.be very careful of brake clean messing up  nice polished alum wheel though.

As you have said, it really doesn't matter what form of RTV is used, some are worse than others, but the fact it can glue the cones in place. I used to buy the gaskets 25 at a time, and still have some on my wall, after retirement.

 IHC and a few others use 3/4" studs through straight holes (no cones) and those you can use RTV, but I still use gaskets.

[RS Disposal]

6 hours ago, mechohaulic said:

keep one major thought in mind == you state your a newbie at HD truck repair!! do you think  all  of us just graduated grammar school and became "Master truck mechanics ??? WE ALL ARE /// WERE NEWBIES AT ONE TIME OR  ANOTHER!!! 50 plus years of wrench pushing and following these forums puts me not even a newbie = I'm in "kindergarten and still learning. can't say I want to learn all I read here though. give me old school mechanical over this electronic crap any day.to get back on original topic -- how's the hydraulics working??

The hydraulics kinda got put on hold for a bit while doing rear brakes.  I did get a new "cab tilt" pump. Just haven't had a chance to install it though.  Just about everybody I have talked with has said that the two way pump I was using should work.  It does work the ram both directions when just hooked up but not dealing with the weight of the cab when the cab goes over center and and finishes its travel with just the weight of the cab.

I did notice in reading the spec sheet that came with the pump that a certain hydraulic fluid MUST be used or issues with the system could arise.  MIL H-5606  What I used was a hydraulic jack oil.  In researching what this specific oil to be used was and why it might be different it appears that it is a bit thinner than regular jack oil being what is used in aircraft due to the colder temps that those hydraulics encounter.   As we all know, hydraulics don't like the cold as I am reminded every morning I run the packer on my truck up canyon all winter.  in my thinking of trying to remember when my issue became an issue it was early winter here and even though it wasn't the bitter cold I get up canyon, it was colder than back when I can recall the system was working with the old ram before I thought that ram had just worn out.  So I did pickup some aviation MIL H-5606 spec fluid to refill system after I flush it out of the old.  My thinking, if that is the case, the fluids being thicker may of been causing the safety valves in the ram to close. My weekends are tuesday-wednesday so next week I guess I will find out if my new plan of attack is going to work.

[Geoff Weeks]

doubtful the viscosity of the fluid is causing you problem,  The gravity down is the problem, that should not happen on a modern (somewhat) truck cab system. It can trap a man under the cab and crush them if something goes wrong. Somewhere in the system there needs to be a cross-check valve that will not allow gravity to move the cab, it should require pressure from the return side (the side of the piston that is "retracting") to open the check and allow fluid to return.

[RS Disposal]

On 3/16/2024 at 6:17 AM, Geoff Weeks said:

doubtful the viscosity of the fluid is causing you problem,  The gravity down is the problem, that should not happen on a modern (somewhat) truck cab system. It can trap a man under the cab and crush them if something goes wrong. Somewhere in the system there needs to be a cross-check valve that will not allow gravity to move the cab, it should require pressure from the return side (the side of the piston that is "retracting") to open the check and allow fluid to return.

The cylinders would lock up even during the first half of travel raising the cab.  If I remember right my problems started about the time is started getting cold over nite.  I agree that I didn't think viscosity was the problem.  I also didn't think that a generic 2 way pump might be the problem.  The fluid and the generic pump are the only 2 wild cards in the system right now.  The hydraulic cab locks function flawlessly.  The ram is new from the dealer (power packer-  brand). The new "tilt cab" specific pump (also power packer brand) I will be installing hopefully this week.  As far as oil, all I can think of is that the safety check valves are really picky about viscosity.  Starting to get really frustrated as to what I thought was a simple system repair.

[terry]

Can't tell you how many simple repairs turned into a nightmare!    terry

[Geoff Weeks]

On 3/17/2024 at 12:38 PM, RS Disposal said:

The cylinders would lock up even during the first half of travel raising the cab.  If I remember right my problems started about the time is started getting cold over nite.  I agree that I didn't think viscosity was the problem.  I also didn't think that a generic 2 way pump might be the problem.  The fluid and the generic pump are the only 2 wild cards in the system right now.  The hydraulic cab locks function flawlessly.  The ram is new from the dealer (power packer-  brand). The new "tilt cab" specific pump (also power packer brand) I will be installing hopefully this week.  As far as oil, all I can think of is that the safety check valves are really picky about viscosity.  Starting to get really frustrated as to what I thought was a simple system repair.

I had two cabovers (IHC's) that had powerpacker pump and "over center" long cyl. They had the cross checks, and I had one leaky cyl, so had to often add fluid, and I found if it was wet petroleum product, it would work. I would use anything and it worked. ATF, PS fluid or 10W-30. never had any opperational problems because of fluid type.

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[RS Disposal]

7 minutes ago, Geoff Weeks said:

I had two cabovers (IHC's) that had powerpacker pump and "over center" long cyl. They had the cross checks, and I had one leaky cyl, so had to often add fluid, and I found if it was wet petroleum product, it would work. I would use anything and it worked. ATF, PS fluid or 10W-30. never had any opperational problems because of fluid type.

 

In the process of doing rear brakes and this truck the drive hub has to come off so it is a little more time intensive.  Hopefully will get back to my cab tilt problem.  I do have the 5606 spec hydraulic fluid and a new specific cab tilt pump, also power packer.  I normally like to do just one thing at a time until I actually determine what worked, but I think I am just going to put the new pump on and use the fluid.  Just getting frustrated.

[mechohaulic]

On 3/17/2024 at 1:38 PM, RS Disposal said:

The cylinders would lock up even during the first half of travel raising the cab.  If I remember right my problems started about the time is started getting cold over nite.  I agree that I didn't think viscosity was the problem.  I also didn't think that a generic 2 way pump might be the problem.  The fluid and the generic pump are the only 2 wild cards in the system right now.  The hydraulic cab locks function flawlessly.  The ram is new from the dealer (power packer-  brand). The new "tilt cab" specific pump (also power packer brand) I will be installing hopefully this week.  As far as oil, all I can think of is that the safety check valves are really picky about viscosity.  Starting to get really frustrated as to what I thought was a simple system repair.

glad you wrote cyl locks in up mode;; I almost went to far space with a suggestion of putting cyl on up side down which I never heard of== but. basically you covered any practical solution. it's not a complicated system or it shouldn't be.,, 

[RS Disposal]

Im the type of personality that I prefer to do one repair at a time when trouble shooting a problem.. I like to know what works and what didn't.  This problem was starting to get me really frustrated so I actually did two things at once.  Not sure what the end problem was, but I got the tilt cab system working.  I put on a new "tilt cab " specific pump (rather than the generic 2 way pump I had on it) and I flushed and filled the system with the Mil H-5606 aviation fluid.  This fluid is definitely much thinner viscosity that regular jack fluid. Pretty expensive also. $55 a gallon of Amazon.  nobody here in my town had a clue what I was talking about.  LOL. Maybe the newer check valves in the ram are really picky.

[Geoff Weeks]

Off topic but... Years ago I was working on a large NG boiler. It hadn't been in use for a while and once it was repaired wouldn't fire up properly. It would light off and the main gas valve started to open, got about 1/2 way and then stopped. Guy I was working with determined that the valve was hyd operated, and was low on fluid. He pulled a sample and said "this smells like nothing I know". I took a sniff, and knew I smelled it before, It took a while and then it came to me Skydrol! it was over 15 years since I had been around it. Made sense, fire resistant hyd oil! Sent him off to Midway airport for a pint, problem solved!

[JoeH]

Is truck parked outside in the cold or inside in the heat? Are you trying to tilt cab in sub freezing temps? You could have water/ice acting as a check valve flowing back and forth.

You could also have the lines hooked up backwards/in the wrong ports.

[JoeH]

I'll snap a picture of my cylinder fittings if I remember today.

[RS Disposal]

6 hours ago, JoeH said:

Is truck parked outside in the cold or inside in the heat? Are you trying to tilt cab in sub freezing temps? You could have water/ice acting as a check valve flowing back and forth.

You could also have the lines hooked up backwards/in the wrong ports.

the truck is parked outside.  The problem first appeared before it got cold enough for water to freeze.  The plumbing was reinstalled the same way the original cylinder was plumbed.

[JoeH]

[RS Disposal]

18 hours ago, JoeH said:

My lines actually go up the side of the ram and over the frame rail and along side the inner frame rail where they come out behind the front quarter fender to the pump

[JoeH]

We got our truck with 415k miles, so no idea how it was from factory, but this is how it was routed when we bought it. "Push" function first T's into the passenger cab mount latch, then splits to go to tilt ram and the driver cab mount latch. "Pull" function just goes to retract the tilt ram.  When the cab comes over center and starts coming down on its own weight it creates enough pressure on the "push" circuit to force the latches back open. Once the cab is seated, the springs on the latches hook the cab to keep it locked down. I assume your truck is the same way, but yours is 24 years older than mine.

Not sure how the "push" circuit creates the resistance during "pull" function to open the latches, there may be a small orifice the oil has to pass through in order to return to the pump. Not sure why you're having the problem you're having! Something must be acting as a check valve somewhere, or the cylinder is binding!

[JoeH]

Glad you got it working. I think you mentioned your system has fine mesh screens in the fittings. I could see this being the blockage point with cold hydraulic oil.  

[RS Disposal]

On 3/28/2024 at 5:24 AM, JoeH said:

We got our truck with 415k miles, so no idea how it was from factory, but this is how it was routed when we bought it. "Push" function first T's into the passenger cab mount latch, then splits to go to tilt ram and the driver cab mount latch. "Pull" function just goes to retract the tilt ram.  When the cab comes over center and starts coming down on its own weight it creates enough pressure on the "push" circuit to force the latches back open. Once the cab is seated, the springs on the latches hook the cab to keep it locked down. I assume your truck is the same way, but yours is 24 years older than mine.

Not sure how the "push" circuit creates the resistance during "pull" function to open the latches, there may be a small orifice the oil has to pass through in order to return to the pump. Not sure why you're having the problem you're having! Something must be acting as a check valve somewhere, or the cylinder is binding!

Yea, thats the way mine works.  Not sure which of the two things (tilt cab specific pump & Mil H-5606 hydraulic fluid) I did at the same time was the actual problem. Ordinarily I would of only done one at a time, but I was getting frustrated, so I did both.  The way my brain works I like to know for sure what works and what doesn't when doing repairs that required trouble shooting.  But, it's working now. So onto my next item on my list

Just want to thank everybody, again, for all the help and insight.  This site and everybody has been invaluable.