A2 cruising speeds

[Jesse6325]

FWIW I try to run mine no faster that 2200 Rpm, Sometimes bump right around 2500 shifting, 45-50 is plenty fast for a 40+ year old truck weighing 6 1/2 tons.
Really happiest at about 1700-1800 RPM wich gets me about 40 MPH or so.

 

[rrrr]

Stock my deuce like about 47mph. I put 395's on and now it likes around 56mph. I also added a brake resevoir so I can monitor any leak issues. I have not turned up my fuel but did add a pyrometer and boost gauge to make sure I don't beat up the truck. I can lock up all my wheels without problems. When I flipped the rear hubs I checked over the brakes. When I replaced the front boots I also looked at the brakes. All my pads, springs, etc in the brake system are in great shape. Even with this I will limit my speed to 60mph even though it will go faster.

 

[PsycoBob]

To agree with most of the posters above, the easiest speed upgrade is tires. You even get better mileage & treadlife out of the deal. Other than tires, speed parts don't excite me enough to blow that much money on them.

I'd not upgrade any other speed parts until you've invested in some kind of split brake system (Stock drums are fine, single-circuit brakes AREN'T). Sudden failure of a single line or seal can mean a crushed minivan.

In my case, RPM's depend on how loaded the truck is & hills. The more hills & the heavier the truck, the closer to 2400--2600 I'll run. Flat, downhill w/o another uphill, I prefer to be at 2000-2100. My speed is, well, whatever. If I'm going to be late getting somewhere, it means I didn't leave early enough.

 

[Amram]

On the way home my duece chugged down the highway happily at 55mph around 2400 rpms. It still has the NDT tires on it. I tried to slow her down to 50 and just relax but the rear end would start bouncing so I would speed back up to 55 where the truck would start singing to me. Seems mine is happiest running like a bat out of Hades.

 

[mcmullag]

modern folk, do not buy a duece.

There are a couple parades a year I do out of town where I run 55 mph to get there. The truck though sounds really happy at 40 mph on a flat road with a tailwind. I look at it like these trucks were built to live on dirt roads and max out at 40 mph doing their work, convoys and such carrying supplies, really probably slower than that most of the time. Think about all that stuff spinning in the axles, the double reduction gearing... do you really want to spin all them there nicely machined metal parts faster than they would be going at 55 mph?

 

[Welder Sam]

mine usually stays around 50-57'ish. i did hit 68 saturday on a nice smooth flat road. just had to see what itd do and still backed out of it.

 

[nmdata]

I am running the equations on a different transmission configuration, 60mph with the engine rpm at 1950, the 5th gear od ratio would be 3.577:1. taking the standard 37" tire footprint. from what i have read, the engines optimal efficiency range is between 1900 and 2000 rpm, so at 60mph the 5th gear ratio would have to be 3.577:1, for a 42" tire at 60mph running 1950rpm, the ratio would have to be 4.061:1 .

does anyone else have the math to figure this out and verify for me? also has anyone found shop that can make the change? this would be something that should bring the fuel economy up to approximately 18mpg, therefore increasing your range on a 50gal tank to 900 miles. according to my calculations, ideally it would be 23mpg but i also am figuring an increased load on the engine and therefore slightly more fuel use. so the 18mpg is a compromise. this is also figured for running singles on the rear.

give me some input on this guys.
thanks in advance

 

[PsycoBob]

Radial tires for reduced rolling resistance, front hub lockouts, one rear lockout, synthetic lube for everything. Bigger air-filter might not be a bad idea.

Your calculated mpg might be possible, but max efficiency rpm doesn't make nearly as much power as 2500rpm. 2200rpm is a real nice crusing speed, if you're willing to rev up a bit before & during hill climbs. Otherwise you wind up in 4th-low.

60mph @ 2000rpm on flat ground is possible, but I'd expect you to be at or near 100% fueling just to maintain it. Lower ratio axle gears are available, if you've got really deep pockets.

It kills me to see people who refuse to let the engine get over 2200-2300, for fear of throwing a rod. Above 2400 efficiency drops pretty hard, but shifting from 3rd to 4th drops rpms from 2200 to 1200 & 50% less HP, according to the engine's chart. Just pound it off 2600 for the time it takes to shift, then cruise at whatever you feel comfortable with.

http://www.steelsoldiers.com/attach...t-rpm-do-you-guys-get-best-mpgs-fuel-rate.jpg

Right, here's the only current transmission gear swap option for our Spicer 3053 transmission. .69 ratio. Stock is .79.

http://www.waterloospecialties.com/overdrive/index.html

****it, another edit. RPM/speed calculator, anyone got one with better fields? 6.72 axle ratio, .79 od stock, 19.25" radius on 900r20's.
http://www.advanced-ev.com/Calculators/TireSize/index.html
http://wahiduddin.net/calc/calc_speed_rpm.htm

 

[hof3414]

Don't waste your money making your truck fast. Leave it alone and drive it slow and you will have more fun then you could ever imagine. Take the money you were gonna spend on making it faster and buy a sports car. My opinion I know, but thats what I did and I love it. Plus you can drive different vehicles different days. just my

 

[PsycoBob]

With the .69 od upgrade & 1100r20's, you can manage 60.7mph @ 2200rpm, nicely within the lowest part of the fuel-consumption curve.

 

[Cycletek]

I bought my M813 to slow down, I had a 06 Mustang GT with a Supercharger and all the go fast stuff you could imagine. A $350.00 speeding ticket in Northern California for 85 in a 65 got me thinking. An opportunity to get the truck I always wanted came up and I grabbed it and got rid of the Mustang. The 5 ton is my daily driver, I really enjoy driving it and I live in Southern California. We have the worst traffic on the planet, but when I am driving my truck i smile constantly. I have 20 x 14's and I will tell you, with these brakes, it is as fast as I care to go with this behemoth! I am retiring this year and I "READY" to look at the scenery I used to fly by!............

 

[PsycoBob]

Split the brakes, then start other upgrades. If you can't afford to use split masters & airpacks, you can't afford gearsets anyway. Going to 1100's can be justified, especially if your current tires are whupped.

All the power upgrades to make you accelerate faster can be done whenever you want, but going faster with 47" tires or other upgrades should happen AFTER the brakes.

Of course, a m939 series truck with air-brakes & abs plus gearing already set up for 65mph cruising is an option for those who need speed. Of course, you might want to get some instruction & practice on driving a truck with airbrakes. No pedal feel like hydraulic brakes.

 

[Cycletek]

In keeping with Bob's brake upgrades, of which I have been looking into for my own truck, remember these trucks have no rollover protection to speak of either, I know no one wants to think about that, but it is a concern. Plus you want to stack gear on top of these already maxed out engines. These early diesels were at the end of their development and power adders tend to decrease the life of these powerplants greatly. Happy to cruise at 2000 RPM and know I will not run over someone that has foolishly cut me off.........

 

[nmdata]

if i want to go fast i can just jump on my street bike and go, however the issue out here is the oilfield traffic that cruise at 75+. a state cop got ram by a truck 2 weeks ago and is still in the hospital because he was only going 55mph on the hwy and a group of oilfield tankers tried to "push" him faster. they haven't found the trucks yet that were involved. anyway, the truck will have radials on 22.5" rims so resistance will be lower. the truck will be averaging at least 350 miles a week to move some equipment. some of the sites are on some rough, remote roads that are 15 miles + off a paved road. more remote than anything.

 

[Stretch44875]

I run it at 2500 rpms, all day, everywhere I go. It's been all over the state, hauling lots of weight. First truck I got is still going strong, 7 years later.

With the 11-20's I get 59 mph. I also installed the overdrive gear set in my other truck, and love it. It's the way to go, shifts nice when splitting gears.

I should also note, brakes on both trucks are top-notch, and I check, fix, and adjust them regularly.

 

[PsycoBob]

nmdata, I'm rather surprised every truck on that road going over the limit hasn't been stopped & given a few hours worth of sobriety & safety tests for a few weeks straight. Deliberately injuring an officer without any of the other truckers noticing & reporting? State/county cops near me would be out for blood.

Given that most new police cruisers have cameras everywhere & monitoring systems everywhere, cops are doing the speed limit just to avoid getting nailed by their own gear. Most dept's have a policy of not speeding unless they're responding to something & new monitors are catching drivers that used to ignore it. I'd bet the injured officer's new car will have a camera pointing out the back.

 

[Wildchild467]

I never have mine above 2300 ever. i like to cruse at 2200 rpm, it seems like a good speed and i dont want to push the engine until it blows. all respect to what everybody else does, i just think i like driving it everyday to work and dont want to feel the depression in my chest if i see a hole in the block. I figure if people take theirs to 2600 all day long, mine should last a long, long time at 2200 crusing. I love my truck and take pride in how reliable it is. It never once let me down when I asked something of it. 2200 is about 47 mph I think.

 

[F18hornetM]

If you need to do 75mph on the highway and haul a big load and put 350 miles a week on it, buy a commercial truck. Just my 2 cents worth of course. Will get better fuel economy, less maintenance etc.
As for my duece, have never had over 50. Like Wildchild 467 says, ours likes 47 mph. Just less than 50 mph and it purrs right along. We usually avoid the major highways if possible. Of course where I live no roads are over 55mph. I dont need the truck to make money with, if I did I'd buy something else. So I want it to last. Again just my thoughts, everybody has their own ideas.

 

[91W350]

This thread and all of the high speed thoughts got me to wondering, so I grabbed the handy gps and hit the Interstate. My 68 hits the governor at 2700 according to my tach. 1100 Michelins with 70 pounds of air, 63.2 mph. That's it, flat out, screaming for relief, back to 2,000 rpm for me and my baby. I really did not know if this engine would pull over 2200, never had it that high before. Glen

 

[Rambling Wreck]

I am running the equations on a different transmission configuration, 60mph with the engine rpm at 1950, the 5th gear od ratio would be 3.577:1. taking the standard 37" tire footprint. from what i have read, the engines optimal efficiency range is between 1900 and 2000 rpm, so at 60mph the 5th gear ratio would have to be 3.577:1, for a 42" tire at 60mph running 1950rpm, the ratio would have to be 4.061:1 .

does anyone else have the math to figure this out and verify for me? also has anyone found shop that can make the change? this would be something that should bring the fuel economy up to approximately 18mpg, therefore increasing your range on a 50gal tank to 900 miles. according to my calculations, ideally it would be 23mpg but i also am figuring an increased load on the engine and therefore slightly more fuel use. so the 18mpg is a compromise. this is also figured for running singles on the rear.

give me some input on this guys.
thanks in advance

nmdata,

This is the THIRD thread today that I have seen you have post this exact same question. Another member already warned you that this was against site rules. Please refrain from this practice.