serious discussion of 5-ton speed increase via gearing (transmission, differential)

[OPCOM]

A different truck would be interesting but there are steeper cost issues associated with that route when comparing apples to apples. The cost for the same thing is quite a bit more than for a military truck. Each time I have seen a heavy duty (at least 2 tons highway rated) all wheel drive diesel civvy truck with a lift gate, rugged body not the plastic motorhome crap, generator, etc. it is alwas starting around $60K and that is for a beater with 350K miles on it, the price goes up from there. $120K is about right and that is a bit much. Whomever suggests the use of a civvy truck, please suggest a suitable one that does not cost as much as a yuppie dwelling.

I have owned two former bread trucks and I liked them for the most part. With a V8 and a 3.73 hypoid, the better one was a 1-ton and had no problem doing 65MPH all day. It was low deck and the ATV fit right in with the dirt bikes, etc. However, there was no external place to mount a generator so it ended up inside and was noisy and nasty, vehicle was not diesel, had 75000 miles, and the roll-up door in the back just sucked dirt in constantly. It had no a/c, but niether does this one yet. The other one had doors too narrow to get an ATV in. They were low to the ground and could get stuck. It was not all wheel drive either.

If anyone has a civvy truck to trade me that has an enclosed body 7x12 ft of walk-around space, mounted generator, lift gate if the deck is high, and other rugged amenities, or anything close, let's see it! It's got to fit my driveway so <25FT is best.

Sure I could get a trailer and pull it with a pickup truck but where's the fun in that? Then I got to store the low-clearance thing as it can't be backed into the yard.

For truck-suitability-for-purpose reasons I'm willing to consider working on the M818 in order to cruise 12% faster (60). It's already been explained why cruising reliably at 60 means a 65-70MPH redline.
In the order of preference as of today (not considering cost) -indeed the order of preference could change.

1.) ~4.88 differential gears all around
2.) better trans. and move the transfer back a little to accommodate
- which trans? Most seem to have an 0.78 OD, no difference. *
3.) aux. trans behind the transfer, depends on length. 8031C** Brownie (28"?) speed's right, the unit is 'large'. might work.
- What is the length of the 818 rear main drive shaft, will that even fit?
- disengage front when in OD
4.) change rear axles to tractor trailer type with better gears and have gear made for front
5.) just do 50MPH and the heck with it. but what does that gain?

* Spicer CM60 series 6253B = OD of 0.69, 2100RPM @ 60MPH & 1927 RPM @ 55MPH. Unknown length.
* Spicer Easy-Shift ESO66-7B = OD of 0.74, not too useful. 32.87" L
** Spicer 8031C OD= 0.75 according to No.2diesel
** Spicer 8431 also has an OD, unknown what ratio R8341-C, D, E, F, G ratios. unit AKA AM0610-4L.
** Spicer 7041 OD=0.83, L=25 3/16"
** Spicer 5000/58xx series, too light on torque, 580 FT Lbs.

Regarding the Spicer 6400 series, of which the 6453 is used in the M818, the 1.79:1 "hole" everyone hates is really no better in the 6453B which is slightly smaller at 1.89:1

What is the length of the Spicer 6453 transmission?
Attached is a nice cutaway of it fromthe parts manual as well as a Spicer model ID document from the www.

I'll be researching more transmissions as time goes on but it doesn't look that great. If anyone has data for a suitable transmission with a decent OD better than 0.69, that would be interesting. I can sure use the help for any unanswered questions and more technical information will make the topic better.
In parallel, I an going to research some of this other stuff (axles, gears). Nothing happens in a day.

 

[OPCOM]

IMO the 900 series 5 tons with the full airbrake have too much brake. How is that possible? What would make me say that? It is the fact that they have been installing anti-lock brakes in the trucks because they have had too many accidents because the brakes lock up and spin the truck out of control.

When we took driver training on the 900 series 5T we were warned that if the brakes are mashed with no load, the back end of the truck is going to come around and it might flip. We were shown what to look for to see if the air brakes on the truck had ABS and drive accordingly/safely.

 

[Kevin C]

It just amazes me how everybody wants to go FAST in a 30 to 40 year truck that was designed for mainly off road with 25% on road use, these trucks are SAFE for the intended use and intended speed , the truck design is basically a late 40s/early50s to start with, most have a single wet brake system, thay were designed for the road speeds at that time, who would have thought a #80000 semi could go down the road doing 90 all day.
Remember the saying SPEED KILLS especially in a 30 to 40 year truck.

"Speed doesn't kill! Suddenly becoming stationary - thats the killer." -Jeremy Clarkson

With that said, I'm into drag racing and autocross. I like going a bit faster than 50 sometimes. However, your point is very valid. Unless the trans is upgraded, the brakes are upgraded, IF the axles can handle the RPM, and if the tires are rated for more speed, I see no problem with doing around 65 to keep up with traffic. Just have to keep safety in mind at all times, make sure you're constantly aware that you're in a quite large truck that could just completely flatten most cars on the road today, and seriously injure/kill people if you aren't paying attention.

I instantly thought of larger tires when I saw this thread, then read that the OP doesn't want to go back to 53's. I don't even own a Deuce yet, and I know I'm sold on 53's already. because of what I saw in person earlier tonight. I walked up the street to a store to grab a drink a little after 11 P.M. and they had a very large crane truck in to finish up some work I suppose. (It's a new store)

Anyhow, this giant had 525/85R/25 Bridgestones on it. I believe that's a 60 inch tire. Not too much bigger than 53's, and, wow they are amazing in person. It's just the neatest thing to stand next to a tire that's nearly my height, and I'm 6 foot 1.

I need to stay up tonight, walk back up there when the sun comes up, and grab some pictures.

 

[98hd]

Calulators from www.4Lo.com

Here is a good site, use the MPH calculator.

Here is the post I mentioned on the 939 t-case.

http://www.steelsoldiers.com/5-ton-up/51175-m939-speed-mystery-solved.html

If that ratio is actual, it seems you would be way under geared.

 

[XanRa]

"Speed doesn't kill! Suddenly becoming stationary - thats the killer." -Jeremy Clarkson

With that said, I'm into drag racing and autocross. I like going a bit faster than 50 sometimes. However, your point is very valid. Unless the trans is upgraded, the brakes are upgraded, IF the axles can handle the RPM, and if the tires are rated for more speed, I see no problem with doing around 65 to keep up with traffic. Just have to keep safety in mind at all times, make sure you're constantly aware that you're in a quite large truck that could just completely flatten most cars on the road today, and seriously injure/kill people if you aren't paying attention.

I instantly thought of larger tires when I saw this thread, then read that the OP doesn't want to go back to 53's. I don't even own a Deuce yet, and I know I'm sold on 53's already. because of what I saw in person earlier tonight. I walked up the street to a store to grab a drink a little after 11 P.M. and they had a very large crane truck in to finish up some work I suppose. (It's a new store)

Anyhow, this giant had 525/85R/25 Bridgestones on it. I believe that's a 60 inch tire. Not too much bigger than 53's, and, wow they are amazing in person. It's just the neatest thing to stand next to a tire that's nearly my height, and I'm 6 foot 1.

I need to stay up tonight, walk back up there when the sun comes up, and grab some pictures.

you need to do that

 

[mudguppy]

... Changing the engine to gain RPM is not a good option because the present engine is like new with 8000 miles on it and it runs like new.

i think you should re-visit this option. an engine swap to a 6CTA or DT466 would give you great rpm range potential, and more power to boot (if you'd like). the 6CTA can be run up to about 3200 safely, and the '466 higher than that. either way, the stock 'high-idle' governor springs will likely be set much higher than the 2100 rpm that you're suffering under now. each of these engines should be quite plentiful and relatively inexpensive. heck, you could even throw a 3126 Cat into the option pool.

and with your engine being in such good condition, then maybe it is worth something. so either a sell / buy outright or possibly even a trade with a truck yard (unlikely). parts would be common to bolt to the 5T transmission.

honestly, i think the engine swap would be the least amount of work and cost compared to re-gearing axles, aux-trans wedging, or trans swaps.

 

[kastein]

that's the problem 65-70, whats the speed limit, bet its not 65-70, if your doing the speed limit, your NOT going to get a ticket, now if your doing 35 in a 60 zone , yes you will if your holding up traffic if there is no where to pass.
Anybody that's wants to do 65-70 in these truck needs to have to really RETHINK, they were NOT designed for that use or speed, nor safe for that speed (if someone thinks it is, there kidding them self). these 1600s look good, but at 65-70,or for that matter any speed, besides the weight of the truck, there is a massive increase in rolling innursia (the 1600s act as a flywheel) for the brakes to overcome. remember speed kills, just hope no one here is the cause
this is one of my pet peves, IM DONE

as far as the 819 doing 60 and 65 redlined, I got that from my wife who was following me in her car, my speedo was saying the same thing, though I didnt beleive it till she told me her readings

You are missing something in your line of reasoning.

The brakes for these trucks were designed to stop well enough (not great, but well enough) with five to ten tons of cargo. Going ~30% faster is not going to be as difficult to stop as that - 30% faster = 70% more kinetic energy, ten tons of cargo = 87% more kinetic energy. This is assuming you use stock or close to stock tires and transmission/axle gearing or an aux trans is used for the RPM increase.

As long as you do not try to go that much faster while loaded to spec, you'll be fine IMO. Almost no one on here actually loads their trucks like the military did, and I like to think that everyone here is smart enough to not mat the pedal if they do so.

If you want to double check my math, I based this off going 65mph instead of 50mph and fully loaded being 43k pounds (23k stock + ten tons cargo) with empty being 23k pounds. The rest is just E = 1/2mv².

Also, don't lock the brakes up to stop quickly. Locking the brakes is a good test of how strong the brakes are, but the truck will stop faster if you brake just to the point that the tires start to talk a tiny bit. The static friction coefficient is higher than the dynamic, if you can find a material that has a higher dynamic friction coefficient than its static coefficient when used on asphalt and cement, talk to the tire companies and you will be a rich rich man.

 

[Ferroequinologist]

Waller is right about that hole between 3rd and 4th. No matter the tire size or engine power, the only thing that will help that is a transmission swap. Swapping the transmission will not gain you top speed, however. It might increase your average speed, by keeping the engine in the power band longer during shifting and not lugging/screaming it when pulling a load. You can get pretty creative with the transfer case and compensate for some of the gearing issues, but not by much. I have been contemplating a transmission swap, but only to make it a smoother hauler, not a road speed demon. If I start hauling this WVO I will just buy a m915 however, as it was built to haul loads at highway speeds, on improved roads.

Then I won't need to do anything to the m818, and I kind of like it that way.

 

[Hammer]

This is why I opted to go the 916/920 route, rather then change my 818.
It would actually be CHEAPER to get a 920 and modify it how I want, then try and change the 818 to even be close to where the 920 even started at!

Btw, for duals, you can get 44' to 46" tall tires.
As for lighter, the commercial super singles, which can be had in a LOT of sizes, but 48" is common. And they are lighter then your duals, and a lot lighter then the big 16's.

 

[gavan]

There are several RTOO series transmissions like the RTOO12513 that have 2 overs, with .63 being the upper overdrive ratio. Should be able to handle the Cummins with no problems, and help your at speed RPM and clear up that nasty 3-4 shift.

PLUS, you get that good old fashioned non syncro'd airshifted box-o-rocks goodness!

 

[kastein]

hmmm... that interests me greatly!

Any idea where one would procure such a transmission?

Guess if I do something like that, I'll have to figure out how to air-shift the T138, since I don't think it will do very well at all with an overdrive on only the rear wheels with the sprag shift setup still functional.

 

[gavan]

They are in heavy truck junkyards, it might take a lot of calling to find one for a decent price. They are not small and you might need to move the transfercase or modify the jackshaft, but they are SAE transmissions and finding all the parts to bolt them up should be OK.

There are a bunch of different RTOO transmissions, that is Eaton's designation for double over. Usually they have .62ish double over, but some do not. I think you can get a LL version of the OO, thats their double low. Something tells me 16-19:1 (depending on the transmission) plus 2:1 of the transfer plus 6.17 gears sounds like a recipe to break something. Thats around 200:1 reduction!

Googling fuller rtoo should get you started on specs and whatnot of the transmissions.

 

[73m819]

the big problem in changing trans, is the front drive line clearance on the left and the pto for the winch on the right, a old style skinny 8 or 10 speed will work, the new 8 and 10s are wide but not tall and on some the ptos comes of the bottom and are set up for rear facing work

 

[M813A1]

OPCOM !! An idea I have that might suit your cause is try and put on some 1200 x 20 tires they will fit on the factory rims and should give you a little more road speed and not loose pull power I have 1400-20 tires on my M813 and it rolls nice but it looses to much pull power with that tall of a tire !!! Also the 1200 x 20 tires come with the combat tread

 

[73m819]

I have done a quick research on OLD skinny trans that might fit. looks like fuller 10-B-1120 10 speed, R95, R950, R96, R960 10 speed, spicer 8125 12 speed, 8512, 8516 12/16 speed its long but might fit

 

[Kevin C]

you need to do that

I was disappointed. Apparently they moved it, or started work early. I might head up there again and see if I can get a picture of it.

 

[OPCOM]

About the mass and the speed, others might consider hauling heavy stuff fast, but in my case the goal is a 12% increase from 53 to 60.
The headroom is there for the engine, but I'm informed that engine does better at 2000 than wnat I was thinking 1800.

The load weight is not 10 or even 5 tons. The truck has an M109 box on it so that is about 3550 lbs IIRC. I'll trade the weight of the missing 5th wheel and huge steel blocks that went with it etc. for the diesel genset and lift gate so that is a wash. The truck w/o w is 19500 per TM 9-2320-260-10 plus the 3550 box, so in reality it weighs 24000 until I can get it to a scale. Thre is no pintle, no 5th wheel, no towing. (pics attached - this is the beast the Diesel Fitters built in January, except the tires are the 11.00x20's now)


On the 939 transfer, if it is really .732:1 and not 1:1, that is a beastly OD. Too much but not out of the question to consider. The M939 TM says the top speeds are 55 and 22 for HI and LO respectively. The HI ratio is 2.5 x the LO. (speculation because the T-case has not been looked up) The LO range then seems to be 1.83:1 which is similar to the usual T-case. The TM says it is a Rockwell T-1138.

5-speed shifting TM redline speeds for the M818:
7
12
23
40
52

same redlines with that scary 939 transfer:
9.6
16.4
31
54
71

(71 would be at 2100 RPM, and 1774 RPM at 60, which is slow for the engine based on what I was told - it likes to run 2000, but at 65 it would be 1922 RPM, better but a little fast)

It's great to discuss all of these possibilities. None are going to be perfect but some are OK.


How much is a typical M920 or M939? No one has commented on the cost of other trucks yet.

 

[OPCOM]

that's the problem 65-70, whats the speed limit, bet its not 65-70

It is truthfully 70 during the day and 65 at night in many places.

On the posibility of an engine swap, those are some interesting engines. A moving truck I rented had a DT466 in it and that one turned 2500RPM IIRC.

BTW - of all the major refurb-dealers, who is closest to Dallas? Is it Memphis Equ.?

 

[OPCOM]

OPCOM !! An idea I have that might suit your cause is try and put on some 1200 x 20 tires they will fit on the factory rims and should give you a little more road speed and not loose pull power I have 1400-20 tires on my M813 and it rolls nice but it looses to much pull power with that tall of a tire !!! Also the 1200 x 20 tires come with the combat tread

M813A1, Tires are always worth considering, but seeing as the huge ones I didn't like only gave me 63MPH at redline, I'm going to try something else if possible. Want to stay off that redline.

Could I be wrong, in considering redlines of the NHC-250 in the same category as redlines in the Multifuel? Lots of beautiful Multi's have blown up from over speed, even by those that swore up and down the M35 would run 65 all day, and I don't want to join that club by detonating my stately NHC-250 with only 8Kmi on the clock.

 

[OPCOM]

This is why I opted to go the 916/920 route, rather then change my 818.
It would actually be CHEAPER to get a 920 and modify it how I want, then try and change the 818 to even be close to where the 920 even started at!

Btw, for duals, you can get 44' to 46" tall tires.
As for lighter, the commercial super singles, which can be had in a LOT of sizes, but 48" is common. And they are lighter then your duals, and a lot lighter then the big 16's.

I admit right off that the 16.00's were too heavy for me to handle alone.

The plan with the 16.00's was to install an I-beam across the back of the inside of the M109 box up near the ceiling and put a 4-sheave roller block (or a 1 ton ATV winch) on it, so I could get the 1600 up off the ground if one ever fell over while I was changing a wheel. I did not feel safe on the 16.00's, it's OK for me. That is the main reason I got rid of them, I did not feel stable and safe driving on them.

16.00's are 53", and enabled 63MPH. anything shorter, like 44 or 48, won't help in this case.

That said, I liked the OTR steer tires I put on the deuce, I know I'll like 'em on the 5T, when the time comes to replace what is there. They have higher weight ratings and have stiffer sidewalls when pressed up. Beside 20" rims, there are 22.5" and 24" rims that ought to fit the Budd hubs on the truck. Those good steer tires gave me some peace of mind and even after 17K miles of highway use, I could hardly see any wear on the fronts. In contrast to the NDTs that were on it before, the deuce ate those up in about 4000 miles. The OTR steer tires also improved the behavior of the truck. (handling is for sports cars..)

I did not realize until recently that there is another kind of rim that looks just like a Budd, but does not have countersunk holes, and it is not to be used in place of a Budd. I was over to the local (18-wheeler) trailer repair shop looking for used rims and the service manager showed me this and explained it.

Bottom line is that I'll be looking into commercial type tires and tubeless wheels later. In the same vein (vain vane?), the Wingfoot dealer nearby has the gear to check everything on the M818 front end and do an alignment incl. shims for caster, etc. All they do is align OTR tractors.