M-818 speed question

[g102]

I AM PULLING A M172A1 TRAILER ON MY M-818 WITH A 250 HP CUMMINS.

THE TRAILER WEIGHT IS ABOUT 16K AND PLAN ON HAULING ANOTHER 20K HALF TRACK ON THE TRAILER.

I HEARD THE 5 TONS ARE DOGS BUT I AM PRETTY DISSAPOINTED IN THE SLOW SPEED IN 2 ND AND 3 RD GEAR. IT SEEMS TO PULL THE BEST IN 4 TH GEAR. IT RUNS 53 MPH FLAT OUT WITH OR WITHOUT THE TRAILER, ADD A SMALL INCLINE WITH THE TRAILER BEHIND THE TRACTOR AND DOWN TO 50 AND A LITTLE LARGER INCLINE 40-45 MPH.

DOES THIS SOUND LIKE A TYPICAL 5 TON?

I SPOKE WITH AN OLD TIMER CUMMINS MECHANIC AND TOLD ME TO CHECK MY FUEL PRESSURE . 176 PSI IS THE 'SWEET SPOT " FOR A FUEL PRESSURE THAT IS SET UP A LITTLE HIGHER AND I AM GETTING 180 PSI SO SOMEBODY TURNED UP THE PSI A LITTLE BEFORE ME. ANY HIGHER AND IT WILL CAUSE ENGINE PROBLEMS, SO HE SAYS.

DOES ANYBODY KNOW WHAT THE ENGINE WILL DO FOR POWER RUNNING ON JET FUEL OVER DIESEL ? i ENDED UP WITH 100 GALS OF JET FUEL FROM GL. I DID TREAT IT WITH SOME LUCAS CERTANE TREATMENT TO GIVE THE FUEL SOME POWER. I HOPE SOME OF YOU GUYS WILL KNOW. I HATE TO NOT BURN IT UP BEFORE BUYING DIESEL. THANKS GARY

 

[rumplecat]

My 818 tops out at 52 mph at 2000 rpm. I have made no adjustments to is since picking it up.
James

 

[dm22630]

Both my 818s run 59mph up or down hills. Pulling something they drop to 50 mph up hills though.

GPS confirmed.....500 miles in each.

 

[Armada]

Mine will run at 60 all day, even on hills. Granted the hills aren't that large around here. The only trailer I've pulled with it is the M146, and it doesn't know it's there.

 

[bulldog_mack13]

This is from my friend John telling me this , You can turn your fuel button up for things like that.

 

[m16ty]

I don't know much about the 5-tons but I do know about Cummins engines. The main thing is don't run it over 2100rpm for very long.

The 250 is a small engine by todays standards. Just having 5 speeds doesn't help in the power department. All that being said, it is a design that's been around forever and will pull just about anything you hook to it. It just may be a little slower than other trucks on the road. There was a point in time where the 250 was about the biggest engine offered in trucks and they hauled as much as the modern trucks of today, people just weren't in as big of a hurry as they are today.

 

[jwaller]

any more than 2100 rpm's for any long period of time will result in major engine damage.

if you speed you bought the wrong truck. you can go faster with bigger tires but you will soon lose speed on the hills as the larger tires take much more torque to pull.

if your going to be pulling the halftrack all the time then don't bother with larger tires as the 250 doesnt have the guts to pull them.

if you want to go faster and have more power then do the 1600 tires and add a turbo. thats what I did with mine. 70mph all day long with 50k behind it.

 

[g102]

I have the standard size tires, radials,

my High RPM is already 2250. and tops out at 53 MPH.

I don't know how you guys are getting 60 mph out of it unless you have the super sized tires on it or the speedo is reading wrong.

I do remember 250's as being a large engine, damn i guess i am getting old LOL

it doesnt smoke bad doesnt use oil seems like a good running motor but it feels like a dog LOL

 

[70deuce]

• Mine 52 MPH at 2100 RPM, 11x20's. Pulling a M971 18,000 lb trailer at 6000' the truck really dies on hills.

 

[m16ty]

Alot depends on what people call "hills". A big steep hill to a guy in KS is only a bump in the road to the guys in the mountains . I've been out west one time. Living in the "hills of TN" I thought I knew what a steep hill was untill I went out west.

 

[dm22630]

Alot depends on what people call "hills". A big steep hill to a guy in KS is only a bump in the road to the guys in the mountains . I've been out west one time. Living in the "hills of TN" I thought I knew what a steep hill was untill I went out west.

"Steep" is a widely misused term. The steepest roads that I have been on here in the East is outside Asheville, NC & in upstate NY.

But....they dont compare to somewhere like Pikes Peak out west I dont think.

 

[Armada]

At 2000 rpm's I'm running at about 55 mph. 2200 and it's doing 60. I always run it at 55 but you have to pay attention or it will easily creep up to 60. I suppose the speedo could be off as I've never checked it against a GPS, radar, etc. The truck is fresh and tight with just over 1000 miles on it, so maybe it actually does run at 60.

 

[DaveP]

here is a shot of my M818WW tach o graph.

I dont run the ole girl above 2100 very often.

I know these old Cummins hate the r's.

sorry for the poor shot.

this thing doesnt hold very still.

 

[70deuce]

For those running 11X20's and doing anything over 55 MPH on a continuous basis with an 800 series 5 ton be careful. You are probably doing more than 2100 RPM and as stated by many and these motors don't like that realm.

 

[DOCUSN1]

Both of my 818's run at 53mph at around 1900-2000 RPM as stated dont run the poor bugger at 2100 very long you will do damage. On hills they do cut back some running between fourth and fith up and down. To be very honest thats whipping right along with a 21000 pound truck. I dont know about you guys but mine both seem to have about as good of brakes as you can get and with the type that they have thats about as fast as I wanna go with them critters. I have lost a front tire on a normal road tractor before, I dont even wanna think about it in one of these beasts, its gonna be one heck of a ride. Hope you got on your S shorts. Doc

 

[BKubu]

JWALLER is correct. Don't turn your motor faster than 2100 RPMs for any extended length of time (i.e., more than a minute or so...and I suggest not even that long). These are low RPM motors and were designed to run at a maximum of 50-52 MPH. Some data plates say a slightly higher speed and I bet there are not many out there because they have come apart in some spectular fashion. The only real way to get more speed out of your M809 series truck is larger tires...but then you lose torque. There is no way around this unless you swap out the tranny or change the gearing.