JoeH

Do you have much mechanical knowledge/support? You're missing a fair bit of peripheral parts on that engine. If it's a free truck that you have to invest a bit to get running I say go for it, but double check first that you can get a title for it and get it registered and legal for the road. Would be a pain to get the truck running then not be able register it because of paperwork issues.

How many miles are on the truck? This truck should have an AI-350 motor I expect. Don't pick up an AC motor for it, it's a different bag of garbage emissions stuff. The AI motor you can delete the emissions stuff and create a much better breathing engine. Just look up "loggin dog dead dog remediation" on this forum.

Look for cracks around the top of the truck frame at the very front of the dump body. I've seen otherwise perfect used trucks that had cracked frames there. As the frame flexes going down the road the front of the dump box creates a pressure point on the frame.

Allison Autos are usually paired with 350-375 hp motors, much more than that and you'll burn out the clutch packs during shifts. Your rear axle ratio is going to be important for quarry work, in PA quarry roads are STEEP! Not sure where you are. Truck has camelback suspension which is ideal for quarry work in my opinion, assuming it's rated for the loads you'll put on it.

The way I see it, Castle Law applies. Someone breaks into your house, make sure you don't shoot them in the back...

Bridge approaches are sketchy in our truck, never noticed how badly interstate roads drop before you enter/exit bridges, but our truck would throw you pretty hard. Fortunately most of our driving is local non highway.

We have an mr688 we put together 2 years ago. Best truck to work on, tilt the cab forward and EVERYTHING is right there. But it rides rough, with a 20k steer axle. Wish I could put air bags on the rear cab mounts...

If it continues, I'd pull valve covers and double check valve lash. You could have a dropped valve seat.

Changed fuel filters, put 425/65-r22.5 tires on the steer axle, worked through a laundry list of small punch list items, then took it for a test drive today. Only complaint I have is it has a stumble in the idle, most noticable when it's in gear at a stop. (It's an automatic so it puts the engine under load)

Man such a difference in cultures. IDK what to think, lol. On the one hand "Atta Boy" to that 9 year old. But I've got a few nephews in that age range, and the thought of sending them on the road with the bickering they do with their siblings... IDK lol...

2003 MR688S, AI350 w/ Allison HD4560. Can anyone point me in the right direction on these ABS codes? Before the rollover I had no ABS codes, now post rollover I have 4. I'm guessing these primarily just mean I suddenly have 2 bad sensors... Posting this on my rollover thread under Modern Trucks, but I'm putting it here as well that's catch more eyes...

Can anyone point me in the right direction on these ABS codes? Before the rollover I had no ABS codes, now post rollover I have 4. I'm guessing these primarily just mean I suddenly have 2 bad sensors...

Cracks were both inside and outside the flywheel housing on mine IIRC. Leaks were internal I believe.

I've always thought a pallet jack would be the way to go.

Brief googling, the flashing 6 is probably because it has a shift inhibitor, it won't let you put it into drive while moving. So it locks you in neutral until the controller deems it safe to change shifter range. It probably had a drop in power that rebooted the transmission computer. Could be faulty wiring, weak circuit breaker/fuse contacts, drop in communication between different computers, etc. The shift display going blank makes me think the power supply dropped out briefly, shutting off the transmission controller. If your truck is anything like my MR688 with AI350 and an Allison HD4560, then the transmission should have a "clean power" (independent power supply directly off one of the batteries) supply via positive and negative wires that has a fuse in the battery box on the positive wire. Maybe you'll find fault with this wire. CleanPower means a power source independent of any other circuits, it's directly off the battery so the transmission has full battery voltage without possibility of voltage fluctuations from sharing power supply.

Being a two man company, I prefer Budds because brakes are much easier to replace by yourself. But on the roadside, a flat tire is much easier to replace with spoke hubs instead of Budds, if you have someone able to bring you a wheel and a lug wrench.

9" 22.5 budd rims are rated for 10,000 lbs. My MR688S has 315 duallies on the drives. Most 315's are rated for 10,000 lbs, so on a tandem axle with duallies you have 80,000 lbs of tire and rim capacity. That's plenty for 58k rears....

https://www.webbwheel.com/online_catalog_hubs.php Might be able to find hubs here

https://www.truckpaper.com/listing/for-sale/31897769/1987-mack-rd688sx-flatbed-trucks Nearest I could find, has budd front wheels, can't tell about the rear axles though....

https://truckpartsinventory.com/part-details/82219704/used-stud-pilot-budd-rear-wheel-end-spoke-hub-for-sale Pulled this off the googleweb. Haven't been able to find a P/N. Gonna hop on Truck Paper and look up RD/DM SX models and see if anyone has budds. Then you can pull a VIN off the truck,go to Mack and get drive hub part numbers.

How many miles and which auto trans is in it?

Dumb question, is the seal the problem? I have an etech ai350 that the old seal had popped out, we replaced it, still leaked! Pulled it apart, looked closer, and it turned out the aluminum flywheel housing was cracked from starter motor (10 o'clock) to the passenger side around 3 o'clock!

There is room for the GMC here in there other truck brand section. All our trucks are Mack's, except for a 1995 Ford L8000 single axle cab chassis we picked up for $2500 from a local oil delivery company I drove for briefly. We slapped a dump on it and a salt spreader a year or two later. The right truck is the right truck to come along at the right time.

Hydraulic pump hooked up, electrical plugged in, water tank installed... Hydraulics and electronics all functional, but we need to disassemble and clean out the cement metering augers as some humidity got in and hardened enough cement to cause problems. We had the driver empty out the main hopper of the cement bin back in November, but without being able to run the hydraulics back in the Fall we couldn't empty out the metering augers.

If humidity is an issue in your shop air you can run it the air through 20 to 30 ft of metal pipe before the air hits the hose, this should allow any humidity in the compressed air to condensate before it gets to the hose. You'll want a purge valve (just a regular ball valve) on a vertical drop of pipe near the air hose coupling to be able to blow any excess moisture out as it collects. Blowing moisture with you paint is horrible, I have to use the air hose on the far side of the garage from the compressor to paint. The air goes 40ft across the ceiling through a metal pipe then drops 12 ft down from the ceiling to the air hose connections. By the time the air gets to the hose there's negligible humidity in it.