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

[OPCOM]

Drove it today again, been a while. It is absolutely amazing keeping up with traffic. I was running 60 most of the time, with a burst to 65 to pass a garbage scow.

I am exploring the big hole between 3rd and 4th. We all know it is there on an 5 speed OD transmission. I am looking for data that will tell me the horsepower requirement for maintaining a given speed. The wind resistance model could be an M109 since that is close to the profile I am pushing.

Is HP per MPH a linear function? Not sure, maybe not.

 

[Flat Black]

HP versus speed when calculating for things like coefficient of drag and friction, etc., is exponential, not linear..

Bugatti added 200hp to the new Veyron to gain something like 10 mph in top speed (260 mph +) Air is like syrup at those speeds.. Now at 60-70 mph that should not be as much of an issue, but you are driving a barn down the road.

If you have not turned your pump up yet, I would start with that.. (sorry, did not read the whole thread) You can also look at things like intake and exhaust, fuel and air filters, injectors, etc.. Those are all easy/free/cheap mods for diesel HP..

Gearing and bigger tires are great for lowering RPM but it takes a given amount of HP and TQ to go a certain speed down the highway, thats just physics and you arent going to change that..

 

[patracy]

I'd like to know more about the possibility of custom gearsets. Specifically, I have a MK17 I'm thinking about merging with the front of a M55A2. But the ratio up front would need to be 5.57.

 

[cranetruck]

Patrick, this info may be old now, but anyway, the weight ratings I have for the 1100-20 NDC tires are 5,190 and 5,920 dual or singe config respectively.

I got print-outs at the scales, typically as show below with the deuce hauling the 8x8.

 

[mudguppy]

... I am looking for data that will tell me the horsepower requirement for maintaining a given speed. ...

the easiest way to estimate the power it takes to cruise at a certain speed is a simplified coast-down test.

it's a very simple test and can have some pretty accurate results. we experimented with this test in our dynamics class in college and it seemed to make sense. it doesn't differentiate the effect of different forces (Cd vs Crr, for ex.) but gives the total resultant power required.

i couldn't find the equation or test procedures that we used, but stumbled across this old article; this looks to be the same test we performed before. it includes an acceleration test to help determine total engine power available (which would also be interesting).

in the article link, the test i'm referring to is the first test - pretty straight forward and would be fun to test for different speed ranges. in the test we performed in college, we would test, say 60 mph, by broadening the range to 10mph above and below 60 (test ranged 50 - 70). then do the same test for 50, 40, etc. w/ the advent of GPS, seems like getting good speed data should be pretty easy.

 

[cranetruck]

You can also get a rough measure of power by using the amount of fuel used (mpg) and the efficiency of the engine.

There is a relationship between BTUs burned and horsepower.

I once came up with a rough estimate for the deuce, which was about 100 HP to maintain a speed of 50 mph on the level highway.

 

[OPCOM]

Custom gears are a possibility. There's a 4.55 set IIRC but it is rare (earlier in this thread). I can give you the phone # to the guy that knows who has them. It was a parts cost of $3000 shop cost per axle for the ring and spur IIRC, unknown how much for the other (top) two required gears in the axle as there are four in each one. It was cheaper to swap the transfer case, but a lot of hard work. I think $5000 in the job give or take, and that is with a $1600 case, which is half what they usually go for. It could be cheaper if one is resourceful.

The suggestion for turning up the NHC-250 is welcome, but we have been advised several times not to turn that engine up. I have a brand new PT pump calibrated to the military specs and do not want to mess with it. It has new filters, etc. and the exhaust is huge already. i could pull the muffler, but the racket is already deafening.

That old article is a very interesting method. Driving both ways is likely best as the time for acceleration is large. I will need Soldier B to do the stopwatch.

The fuel economy way seems good, but the windage can play a major role, so a reversal is also needed, and the wind can change. On a relatively still day on a long flat road like 59, it could be done well.

The 3-4 hole is not bad on a flat road with a 23K# truck. It starts at 1200RPM, so one has to operate the truck properly accelerating in 4th. It would be heck with a load. But mine is a "utility camper of doom", so it works for me.

Some have suggested a NC-400 with tall tires or gears. I would agree, but how much is that engine co$t? And who's going to change it out? I have no shop space or hoists to do these things so I usually beg local establishments to help with the heaviest projects.

Or, I just drive to 54Reo's place!

 

[cerial0411]

Bringing this back up to the top to ask about your pinion bearing. I am looking at running a set of 5 tons in a expectation rig that will see stretches of highway at mostly 70. Now before everyone goes off no that this thing will weigh right around 6200 with 3440 of that being axles, brackets, breaks, 1/2 linkage, 22.5 rims, tub less tires, steering linkage, air ride, and so on. Yes the cab is very light considering. The ratio is currently 5.81 which will be changed to the more common 6.44 when I rebuild the chucks. I have 3 overdrives .92, .75, and .54. The .75 will be used mostly with the .92 being used on steep grades and the .54 being used on flat areas. The biggest issue I see is that at 70 MPH in the .75 ratio the drive shafts will be spinning at 3500 rpm. Actually the engine am using using makes Max torque at 3000 rpm so I could see small spirits going 75 with the drive shaft spinning at 3750 rpm. The tires are rated for 70 though and I do not see any need to exceed that.

I have designed the drive train to be stout yet cheap to maintain and replace. The 472 caddy engine, 465 transmission, 3 speed brownlipe, .75/1 custom built scs awd transfer case, and dcdl locking 5 ton axles have all been designed to allow this thing to cruise down the highway then go off road without concern. After 4 years building this thing I am at the halfway point where I am looking at rebuilding the chuck.

My question is after driving for a hour or so at 60 do you have pinion bearing issues with the stock bearing and seal?

 

[m-35tom]

on my deuce i commonly run the driveshafts at 3695 rpm for long periods. no issues at all. what is a 465 transmission??

 

[mudguppy]

NP465 4-speed transmission; 1:1 top gear.

 

[cerial0411]

That is great to hear about the rpm's. I was really concerned about the oil foaming or the pinion bearings becoming hot. I was looking at using composite bearings costing 3-4 times as much as the only alternative to keeping the top of the chuck alive. By using normal bearings I can save a great deal of cash as well as making replacement parts easier to find.

The np465 is rated for 465 lbs of torque. It is the lightest, toughest, and cheapest transmission to rebuild and replace that will mate to the 472 big block that makes 500lbs of torque at 3,000. That 500lbs of torque rating is without accessories and after the added propane injection loss I expect more around 430lbs. The power then runs through a brownie. I still need to confirm the brownies low ratio but the middle is 1/1 and the top is .72 to 1. Then I have a .75/1 single speed transfer case which is nothing more then 2 spur gears, 2 shafts, bearings, seals, and a thick aluminum case. The engine is rear mount and this case reverses/corrects the direction. By using the .75/1 ratio in the transfer case I change the np465 ratios from 6.55, 3.58, 1.57, and 1.0 to the now 4.91, 2.68, 1.18, and .75. By shifting the brownie from direct to high I obtain a .54/1 ratio for use on the highway.
This lets me either have 5 or 4 useable street speeds by either leaving the brownie in direct then shifting up into high at highway speed providing better acceleration. I can also simply place the brownie in high changing the gears to 3.53, 2.01, .84, .54 making 1st gear useable.

Seems my math was off and the .91 stated earlier is actually .84. I can also shift the transmission in the 5 speed pattern going 1-4 in direct then going high. If I come up to a hill I can shift into 3rd leaving the brownie in high for the .84 ratio then go into direct 3rd 1.18 having less of a speed loss then going to 2.01.

Using the sm465 was the best alternative to the more costly options out there to obtain the overdrive ratios I wanted. It really gives tons of options for different situations while letting me keep one hand on the wheel at all times. In the event the brownie was to fail it is divorced and can be removed and the front drive shaft used in it's place. The .75 ratio and 6.44 gearing means I can drive back to the house from out of state at 70mph pushing 2900rpm and not hurt the engine or drive train. Being a expedition it is designed to drive out to the middle of nowhere in weather from 20 below to 120 above and get back with out issue.

Thank you for all the help and reassurance in the 5tons resilience to abuse.

 

[mudguppy]

have you considered using the nv4500?

 

[84rzv500r]

Just wanted to say this is a great thread... Learned a lot and I still know just enough to be dangerous... Anyway I am building a 1972 GMC K55 (Napco axle) "pickup truck"... I ditched the 350 Chevy, 5 speed, Rockwell T-223 for an 8V71NA Detroit, RTO-9513 and a T-1138... Jimmy with a jimmy 8 LOL my project is called jimmy**2

with the obvious issue that the gasser RPM range (750-4500) and the Diesel maxing out at 2350.. was gonna be a problem with 7.20 gears front and rear... I balanced the drive shafts cause I know the RPM's are gonna be at the upper end..

https://plus.google.com/photos/113725834400702154269/albums/5799608682879507761?banner=pwa

anyway I had and issue with the driveshaft from trans (spicer 1710) to the transfer case yoke (the original NLA from spicer) so I noticed that the front axle yoke/flange is the same spline as the input flange...

Problem solved... I moved the output yoke to the input shaft and used a 1610 u joint... and ordered a replacement part from Memphis...

anyway with 11R22.5 rubber, OD in the trans and OD in the high range of the transfer case I can get 65 MPH out of the old girl....

Oh and the street rate for the T-1138 seems to be $1200-1500 and make sure they give you enough of the drive shafts to make it easy to reuse the yokes otherwise its a bunch of manual labor to cut the old tubes off,...

I am also upgrading the brakes to a front/rear system with a Dual master cylinder off a early 90's truck with Hydraboost... the old vacuum reserve ank is re-purposed as a Puke tank for the Detroit breathers...

I am in the assembly phase now...
thanks again for all the great info...