JoeH

I have 2 wheel loaders that use air over hydraulic brakes. The rotochamber applies the rod movement to operate the hydraulic master cylinder. If that one only operates the front brakes and the front brakes are already disconnected then you can unplug the air line from the rotochamber and cap it. Before doing this, verify that this rotochamber/master cylinder doesn't operate the rear brakes as well. If you plan on using this rig on the road then I'd say you need to fix the front brake system.  If you're just using it on your own property then the safety of your own property is your call.

You should be able to convert that rotochamber over to a Type 24 or Type 30 air chamber instead.  

4 hours ago, r8f1k said:

Would one be able to add air ride to a cab of these ages?

Air ride cab no, don't think so. Air ride rear axle, yes.  Air ride cabs, the front cab mounts would need to be hinge type pivots while the rear cab mount is air bags with a leveling valve.  The issue will be on hood impingement. The cab will need to rotate on the front cab mounts, which will crush into the butterfly hood.

8 hours ago, r8f1k said:

Can someone remove an axle to make a single axle unit?

Depends on suspension. Mack Camelback suspension, no, not without swapping entirely different suspension and axle in, which is entirely doable.

Also not sure what your state's driver license laws are. In PA, a CDL is required for anything over a 26,000 lb weight rating. Also need an air brake endorsement to drive trucks with air operated brakes. And now if you take your CDL skills test in an automatic, you're restricted from driving manual transmission trucks.

If you're looking to have a payload of 15,000-20,000 lbs on the truck then you're looking at needing a 33,000 lb GVWR, which in PA is max on a single axle truck. If you're trailering the load then that may buy you some wiggle room on the truck chassis you swap a cab onto.  I believe you still need a CDL in PA if the gross combined (trailer and tow vehicle) weight rating exceeds 26,001 lbs, but I've always been fuzzy on the details on GCWR.

As someone who owns one, I don't think you can beat a 5.9 12v Cummins, but I understand they may be pricey.  They use a hydraulic brake booster off the power steering pump, so you remove the need for a vacuum pump.

Personally I'd stick to a mechanical engine. Fuel and coolant and oil and you're running. 

Not sure what region of the US (I assume) you're in, but in PA there used to be a lot of Ford L8000 single axle oil delivery trucks. I have one I converted to a dump truck that has an 8.3L Cummins with a 6 speed transmission. Rear axle is geared for local driving, it'll do 55, barely.

For easiest conversion I imagine you'd need the radiator/CAC from a later R model. E6, mid-late 1980's I would think could work. There will be some minor differences on hood hinge brackets, unsure if this would affect the radiator/hood alignment at all.  These spring-type hood hinges combine with rollers on the cab/hood mating brackets to allow the cabs to have air ride rear cab mounts. The radiators then use a diagonal brace from mid radiator level back to the frame around the upper shock absorber bracket. The cab air ride wouldn't work with the old style rod braces that stabilize the radiator off the cab's firewall.

These coolant lines on your engine mounted CAC are weird. Looked at my 1979 the other day, it doesn't have those.

Around 10-15 psi is when the 283hp version kicks into the power band and really starts pulling. My gauge I added on my '79 endt676 only went to 25 psi and it pegs that pretty well. Not sure what the endt675 237hp motor does. Probably similar.

Dont know if these are what you're looking for. I was planning on cutting the fuel neck out of one to fabricate a filler neck for my flatbed pickup.  

On 12/13/2023 at 7:39 PM, cheech147 said:

See title

I've got a couple from a U model.

The AI motors are also vmac III so I don't really see any reason you can't. Sounds like you more or less know the major differences between them. Years make a mild difference, early etechs had the EECU under the turbo. 2001 they moved it to the other side.  

2000 & 2003 mr688 cab/chassis bulkhead wire connectors. Look like theres a big nut to unscrew before unplugging. Are there lock pins that need to be pressed in before undoing the nuts?  There's 3 of these round plugs, one with probably 15 or so wires for the ABS on the pass side of radiator, and 2 with similar or more wire counts on the driver side if radiator. Doing a cab swap so I need to unplug these things.

On 12/14/2023 at 11:26 AM, Santos said:

Hi i currently have no turn signals or hazards. I purchased a relay from Napa and also installed another Mack’s turn signal switch and no luck. Anywhere else I should look at? Thanks. 

You probably have all LED lights and the one incandescent bulb you have on the turn signals failed.  Probably the dash indicator bulbs.  There's a special turn signal flasher for LEDs that has a grounding wire coming out that you're supposed to attach to a good ground. LEDs don't draw enough power to trip the old style turn signal flashers, so they've made that special electronic one with the grounding wire to overcome this issue.

We had to add Prince pressure compensating valves to the auger and conveyor to balance the flow properly.

Volumetric concrete mixer. Has to run hydraulic water pump, conveyor, mixing auger all at certain speeds to maintain the right material ratios.  We had a hydraulic company design the system for us, it's garbage.  Section pumps are the way these trucks need to be set up.

We have a pump like that on one of our trucks, it's a piece of sh*t in our application, but the swash plate adjusts very fast on ours.

Our system requires multiple hydraulic valves to need to be synchronized, and the type of control valves don't allow for it well.

Getting ready to do a cab swap myself.  Dealer says they gut the donor cab, and transfer all harnesses over from old cab into donor cab. Too many truck specific options to just plug and play.

On 12/7/2023 at 12:46 PM, Mackpro said:

The local Kenan gas tanker trucks had those transmissions in them many many years ago. I went on many late night service calls due to the drivers leaning over on the gear shifter and the shifter would pop out of the slot for the shifter fork. We finally found out if we left the gasket out and just used RVT/silicone the shifter would stick down in the top cover just far enough to keep this from reoccurring. 

Sounds like the o-ring in the shifter tower was missing. Our Eaton 8LL would do that. Bought it used, and after the second time fixing it on the road we drove it back to the yard, pulled the tower out, disassembled, and found bits of what was left of an o-ring on the top side of the shifter ball/socket. New o-ring, hasn't happened in the past 10 years now.

That's plenty of power for me! I've only heard one in person once, and I loooove R models, so I'd be happy as a pig in ____ to have one of those to drive every day.

Not sure how big your pump is but I'll take a wager that 1,000-2,000 psi pressure relief will probably get the job done on shifting. If you go this route I'd start on the low side pressure relief setting and build up to the sweet spot.

Hydraulic oil doesn't compress, so the response time could be better than you're thinking. Don't think you'd build all that much heat if you just used it as a shift assist, you're talking about 1-2 seconds of braking time per shift. It will mean more wear and perhaps shock load on your hydraulic system, mostly I'm thinking about the pump drive shaft.

You don't need 150hp of braking power to slow the engine down.  You may be stalling that thing out doing that.  Typical Jake's have an electric switch on the clutch pedal, another on the throttle lever on the pump. Then there's a manual system hi/lo/off switch on the dash.  Hi/lo is two heads/one head. If you were going to run your pump as a brake I'd build it into your pedals so it's instantly on or off.

If you put a butterfly valve on, you'd need to use it constantly for shifting and probably clean it every so often. Lack of use the soot will jam up the butterfly valve and it can jam when it engages and not release. As far as using it as a brake for the truck, I'm not sure the exhaust valves can handle the back pressure. Fine when shifting, but on actual braking it may generate too much pressure any closed valve springs.