JoeH

My absolute favorite is 23-021 https://macktrucks.vg-emedia.com/ProductListing.aspx?keyword=23-021 It's a data program that has just about every Mack wiring diagram from 2000 forward. Engine wiring, chassis wiring, transmission, vendor engines, emissions wiring... Well worth the $180, though your 1995 won't be in there.

Macks emedia website is chock full of free downloadable manuals as well as buyable paper copies either through website or your dealer.

https://macktrucks.vg-emedia.com/ProductDetail.aspx?ProductId=6401&GroupId=411

I started an account on PAI website which is great for the parts catalogs, but I assumed I'd be able to order parts online too, but I don't see any function for it. Where/how do you guys buy PAI Mack parts?

https://www.ebay.com/itm/384440040267 buy this and you'll be ahead

Probably the sensors on the diff lock mechanisms.

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....