The Stovebolt Site Forums The Parking Lot Big Bolts lets talk differentials

so in my research to get my Chevy 1.5 ton war truck up and rolling for the WA drive ive come to discover that relying on tall tires for speed is probably not going to work, mainly because tires that are skinny enough to fit in my dually set up don't come that tall and tires that tall don't come skinny enough for my dually set up. so that's pretty much out.

however someone mentioned to me that my axles were the same as all the civilian Chevy trucks and that they came came in taller ratios.

if i could get a hold of some taller ratio gears that would make things a lot easier, i could settle for 36" tires which i can get fairly cheap and i wouldn't have to worry about lifting the truck up and clearing tall tires.

i have 6.67's right now and i would need something in the mid 5's.

so what year and model trucks should i be looking for these in? and what ratios did they come in?

also if anyone has any up for sale, lets talk!

thanks

-Luke

54 still listed 6.17 as the fastest ratio on 1.5 ton. what size tires are you running? 7.50? or are milatary tires designated differently.

even a 6.17 will help a lot. im running 35" tires now but im planning on running 38"-40" if the differential thing dosent work out.

Fastest ratio was actually 5.43 for the single speed axle, but the chances of finding one are pretty slim. That gear was an option for most Chevrolet 1.5 ton trucks, but came in some school busses and some other odd models. GMCs also used them in the 300-350 series range, but again an option mostly or in some of the odd models. Pretty much any single speed axle from the 40s-50s will probably have 6.17s.

There were a bunch (Timken and Eaton made some) of different axles used in the military trucks, could you get us some pictures of the axle so we can see whether or not its the same type?

Jeff

didn't see the 5.43 going to have to look a little closer to the manuel.looked at the manuel again, didn't have the 5.43 listed but i was looking in service manuel not build sheets, didn't offer optional listings so more than one source is good for information.

this is the best picture i can get, its not mine but it shows a little bit of the axle.

http://s114.photobucket.com/albums/...amp;current=ChevyTracteur_BartDecock.jpg

nice project

Im not exactly sure of the years the 5.43 was listed, but I know it could be swapped in a multitude of different rears. I went through three axles (1941, 1947.1, 1953) and a stack of NOS parts before I had enough to rebuild the rear end in my COE. All of those axles had 6.17 ratios.

Ive seen the same rear end in the local junk yard under a 1960-66 Chevrolet 1.5 ton, but Id guess the internals were probably different.

Jeff

im pretty sure the axles are the same because some of the guys over at the CCKW forums (the tandem version of my truck) said that the later CCKW trucks came with a the 6.16 axles. and i can use those in my truck. i can ask my dad to get a better picture of my axles if that will help.

Even with 6.17 gears (down from 6.67), youll only be looking at about 3-5 MPH more with 36" tires.

http://www.onlineconversion.com/bigger_tires.htm

that 3-5mph is a 3-5mph i need. combined with a newer 230-292 engine the 6.16 paired with taller tires is all part of a combination that's going to get me moving on the freeway.

I'm exploring the possible{?} option of using a more recent rear axle in my Grumman {P30 chassis}, there are many ratios available, question is will they fit or can be made to fit, and driveshaft compatibility.

Well, Ive got a used 6.17 if your interested.

Jeff

well i would send you a private message about it but i cant seem to find it here.

any way . . .

how much and can you send me pictures.

[email protected]

Ill see if I can run out in the next few days and get some pics. You can have it for the price of shipping, I have a few other 6.17s and am only saving them in case someone needed them.

Jeff

Rustednuts your my hero

my dad is supposed to get a few pictures of my truck for me in a few days i will make sure he gets a few of the axles to make sure they will work.

Do you ever make it north into the Seattle area? Im on the Kitsap Penninsula, just across the ferry from Edmonds, but Ill be in the Edmonds/Lynnwood area for my spring quarter and maybe we could meet up in person.

Talk to ya later, Jeff

hmmmm im normally not but for Free Differentials i would make the trip

im waiting on a dirt trans from my Trasmission guy for my baja, once its done i should be able to scoot up there one weekend.

Rustednuts is right 6.17's wont help that much. My truck has 6.17 with 38 inch tires, and a factory governed max speed of 49mph, however I never even run it that fast. I keep her between 40-45 mph and drive other drivers nuts. I don't like runnign the engine that fast.
However I'm going to try something... just last week I pulled a 4 speed tranny out of a really bad shape 1950's international 2 ton (picked it up for 10 bucks). Gear ratio's are really similar to my trucks tranny. (4th is 1 to 1 and 3rd is about 1.7 to 1.
Anyway I'm going to install it backwards between the original tyranny and the diff and run a linkage system up to the cab through the starter button hole (my engine is a 1959 and has an electric actuator that eliminated the starter button). The linkage will only shift from neutral to 3rd and 4th. This will give me normal speed in 4th gear and in 3rd it will give about a .59 step up. Making my truck cruse at 55 at a bit more than 1900rpm. It's a bit more of a step up than I was looking for, but it's better than buying a $3000 overdrive spliter.

im not going to rely on any one aspect to get the better top speed, its going to be a solid combination of taller tires, and engine that can hold higher RPM's higher and longer without any problems, and a differential thats taller than what i have. over all i just needed the truck to be able to cruise at 55 with the engine at around 2500 RPM - 3000 RPM's

Just curious Luke ,isn't your truck a 4 wheel drive, what are you going to do to get front axle gears to match the rear?

so what would the ratios be on a two speed rear axle?

6.13 and 8.10 are the two speed ratio on the light trucks.