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'89 K5 The Bulldozer

1989 K5, linked, caged, backhalfed, LS3, Hero case, on 42's
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Plan B is a success. Find new-old-stock steering control unit, put that unit in the truck, and drive. Done.

I know its a super boring outcome. Bottom line is Eaton sold this steering control unit model line to White Drive. There are two part numbers for seal sets which are the same, except for the first two letters, RS and SU, which denote series 10 or series 20 SCU . Most retailers didn't even list the letters. PS series is in stock in most places, SU is not. I bought what was pictured as SU but without letter designators in the description, and it was actually a PS222001. I did order something that should be right so I can fix the old unit and have a spare.

The original problem was noticed last year. Small leak. Then it turned into a serious leak over the past few trail rides.
 
This past weekend I lost my 3rd ARB compressor pressure switch. These garbage switches are ridiculous. It's possible that it was the death nail for my clutch gear which made my axles, locker, and r&p leave the chat a few years back.

Over the winter I might see if I can come up with a solution to eliminate that switch and head to a digital pressure switch. I've got to dig into the programming manuals for the SMC switches I use here in my shop as I have some of those laying around for random applications. I do have a few IP65 rated switches, but they all have barometric openings. So we'll see If I can make it work.
20240930_102539.png

Anyways, onto the structural failure currently progressing. I think the slider is done. Movement has accelerated at a rapid pace and now the lightest taps are further moving the slider. Guess she's going to get some new ones this winter. The original hits that tweaked it were pretty gnarly last year. Can't really complain as they held up since the truck was first built.

20240930_101535.jpg
 
I had always surmised the failure area in these simple pressure switches was seal based or plastic deformation contact failure.

I figured why not find out if my hypothesis was true.

I actually found something very interesting and potentially helpful for a field fix.

The switch is comprised of the following (from left to right):
-Outer case which is rolled over the contactor body.
-Lower plastic shield
-Two spherical deflection discs
-Seal
-Plunger and Plunger housing
-Contactor body.

So its super simple, pressure builds up to a certain amount and then the discs deflect, which in turn pushes the plunger upwards separating the contacts, thusly opening the circuit.
Then when pressure decreases enough the discs will overcome the remaining pressure and deflect to their natural state, which in turn closes the circuit.

for a vacuum based switch the discs would be flipped the opposite way.

The contacts are a simple deflecting body style. The plunger hits the contact and it is simply bent away from its corresponding contact.

20240930_125152.jpg


So, I thought I would either find the seal bad, allowing air to escape or the contact broken or bent.

Right now the bad switch shows open circuit. Pressurizing with air shows no leaks. So I'm thinking contact. Then another resistance reading showed 175 ohms.

After disassembly the contact looks fine. Its not bent or broken.

I connected the multimeter to the contacts again and used my pick tool to start activating it. After about 12 cycles the resistance dropped to .5 ohms. Still not perfect but it was interesting to see the resistance drop with each cycle.




Bottom line is the contact got dirty or whatever and it failed. This voltage drop required for failure would be based on the relay style and what its voltage parameters are.
On the trail we jumper wired the switch. This sucks as you have to manually control the compressor with the switch before it dead heads and burns itself up. That happens pretty quick as such a small volume fills fast. Like seconds. I've never burned one up, but it hits 150psi in less than 10 seconds.

Based on this I could have potentially taken the switch out, used something to activate the switch a bunch of times, and then thrown it back in and hoped for some life out of it to finish the trail. It just needs to be blunt, not sharp, or else you'll screw up the plastic. The opening on this one is 5/32".




20240930_125341.png
 
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Yeah sometimes you can make it better, or just learn how it works
 
Absolutely. I've always taken apart all sorts of stuff. What really blows is the amount of shit around here I could cut apart to figure out why it failed.
 
Tnsejed said:
Absolutely. I've always taken apart all sorts of stuff. What really blows is the amount of shit around here I could cut apart to figure out why it failed.
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Yeah when I was 12 I opened everything to learn and try to fix.
Now at 58 I only open things that are new to me which are getting less and less
 
Started redoing the sliders. Going to cut the old ones off, including all the tie-ins, and then mount these. added some tube inserts to the middle sections where the old ones were giving way. I suppose the old ones don't owe me anything as they took a ton of abuse.

It's ready to get the old ones off but I had surgery last week and now I'm healing.

20241116_073025.jpg
 
Tnsejed said:
Started redoing the sliders. Going to cut the old ones off, including all the tie-ins, and then mount these. added some tube inserts to the middle sections where the old ones were giving way. I suppose the old ones don't owe me anything as they took a ton of abuse.

It's ready to get the old ones off but I had surgery last week and now I'm healing.

View attachment 493045
Click to expand...
What size rec tube is that? Good idea on the added support in the middle. I'm planning 2x6 tube for mine I was thinking the center would be pretty easy to dent in.
 
Bent77 said:
Carpet tunnel surgery?
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Appendectomy. Went to the ER Saturday night and they had me in surgery at 3am.

mrk5 said:
What size rec tube is that? Good idea on the added support in the middle. I'm planning 2x6 tube for mine I was thinking the center would be pretty easy to dent in.
Click to expand...
2x5. I've dented 2x3 all over the place. It takes a hard hit to do it but it happens. There's always a fine line between weight watching and overkill. If it's lighter there is less overkill needed too.
 
Tnsejed said:
Appendectomy. Went to the ER Saturday night and they had me in surgery at 3am.


2x5. I've dented 2x3 all over the place. It takes a hard hit to do it but it happens. There's always a fine line between weight watching and overkill. If it's lighter there is less overkill needed too.
Click to expand...
"Lighter" isn't in my truck's vocabulary.
 
Tnsejed said:
Appendectomy. Went to the ER Saturday night and they had me in surgery at 3am.


2x5. I've dented 2x3 all over the place. It takes a hard hit to do it but it happens. There's always a fine line between weight watching and overkill. If it's lighter there is less overkill needed too.
Click to expand...
Funtastic

Gonna speed hole everything?
 
Tnsejed said:
Appendectomy. Went to the ER Saturday night and they had me in surgery at 3am.


2x5. I've dented 2x3 all over the place. It takes a hard hit to do it but it happens. There's always a fine line between weight watching and overkill. If it's lighter there is less overkill needed too.
Click to expand...
I didn't worry about weight having a turbo diesel powering my k5 so I used a 1/4" wall 2x6.
Nothing affected it
 
Tnsejed said:
Were it really gets you is gravity dropping the vehicle off an 8' waterfall down onto the slider.
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I know that and that is why I don't do waterfalls.
By the way what thickness tubing are you using?
 
Tnsejed said:
Started redoing the sliders. Going to cut the old ones off, including all the tie-ins, and then mount these. added some tube inserts to the middle sections where the old ones were giving way. I suppose the old ones don't owe me anything as they took a ton of abuse.

It's ready to get the old ones off but I had surgery last week and now I'm healing.

View attachment 493045
Click to expand...
Pfft imagine being hobbled by surgery.
 
imiceman44 said:
I know that and that is why I don't do waterfalls.
By the way what thickness tubing are you using?
Click to expand...

I run .1875 wall. Going to .250 wall adds 19lbs a side. I ran the same wall thickness on my old sliders as well, but these are wider, so we will see what happens. My rig is backhalfed with an aluminum motor etc.. I've kept it on as much of a diet as I feel comfortable with.
 
I was just measuring for material and I need 7ft per side. 1/4 vs 3/16 will be a big difference.
 
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