1978u-model Dump Body

[SWAX]

I"LL START BY SAYING I GENERALLY DO THINKS BACKWARDS AND THIS IS NO EXCEPTION. SEVERAL WEEKS AGO I PURCHASED A 1978 MACK U-685ST17054 WITH A FONTAINE 12 YARD DUMP- BODY TO USE ON MY FARM IN PENNSYLVANIA. IT IS A TANDEM TRUCK WITH A FIVE-SPEED FOWARD ONE- REVERSE TRANS. I DID NOT EVEN GIVE ANY THOUGHT ABOUT WEATHER OR NOT I COULD MOVE THIS TRUCK WITH A FULL LOAD ONBOARD UP UNTIL NOW. THE TRUCK HAS A TURBO ENGINE#ETZ675 230HP YEAR1980. I DONT UNDERSTAND WHY 1980 IF THE TRUCK IS A 1978. MY THOUGHT WAS IF THEY HAD THE DUMP-BODY INSTALLED IT WOULD BE A MATCH TO THE TRUCK. THE BODY WAS INSTALLED WHEN THE TRUCK WAS BRAND NEW . I WAS GIVEN THE ORIGINAL PAPERWORK. I PAID 7000.00 FOR THE TRUCK AND IT HAS 350000-MILES . IT ALSO WAS USED ON A DAILY BASIS WITH A PA INSPECTION GOOD UTILL MARCH 2006. I GUESS WHAT I WOULD LIKE TO KNOW IS IF THIS TRUCK WILL BE SUITABLE TO HAUL A FULL LOAD OF DIRT A SHORT DISTANCE IN NOT THE STEEPEST OF GRADE . THANK YOU

[GearheadGrrrl]

The VIN plate indiactes that this was built as a tractor and the dump body was probably added later. The 5 speed Maxidyne/Maxitorque combo was built to start 80,000 pounds or so on an 8% or so highway grade, so running at 50,000 pounds or so as a straight turck it should be able to handle a bit more. If you need a lower granny gear the 6 speed low hole Maxitorque could be swapped in.

[woberlin]

I have a 68 U tandem axle dump with the 237 & 5 speed. I've had 20 tons on it, and regulary carry 15 tons up some faily steep hills without any problems. You sure won't be the fastest truck on the road, but you'll get there.

[Lmackattack]

thinking out loud here...the straight 5 speeds were better suited for highway use. the 2 stick 6 speeds were good for the on/off road because of the extra "low hole gear" was there if needed... in any way as long as the truck is not completly bogged down in thick mud on a hill you should be fine with the straight 5 speed. Just be easy on the clutch if trhe truck is loaded in the mud.

[GearheadGrrrl]

Converted road tractors make cheap dunp trucks... Problem is they generally don't have the 44k rears and at least 14k fronts a dump truck needs to get a decent payload. The air ride suspension doesn't give the articulation a Mack bogie does, and a 9 or 10 speed gearboxes doesn't have the deep low gears needed for pulling through deep mud and up 30% ramps.

That said, a converted road tractor will work fine for someone like a landscaping contractor that doesn't need to haul maximum payload and drives mostly onpaved streets.

[rsmartyn]

Hi Wax, Single axle tractors to dumps are common and work great, my B's been doin it for 23 years but tandems are different because of the greatly increased weight. Most tractor frames aren't doubled let alone tripled so the twisting torture of being driven loaded off road could take it's toll. You've gotten good advice on trannys and rears. My DM has a 6 speed low hole 21,000 front and 58,000 rears which is standard for tandem dumps around here in NJ and can really take it. In PA I think the max gross is 56,000 on a tandem and a truck with those specs would be to heavy to carry anything but feathers. The price was right on your truck and if you're driving and loading it yourself with it's limitations in mind you'll be alright. Don't know if I'd waste my money on a Mack wannabe truck with the same situation.