M37 Gear change

What is needed to change the gearing in the M37. I have never been inside the rear ends. I know that my rear pinion will screw in and out so it will need to be fixed. I don't have the truck here to look at. I saw a gear set that says it will change the ratio from 583 to 489. The PIC of the gears did not have a ring gear. Does the Dodge use a ring gear or will the internal gears change the ratio.

Time and Money... The 489 gear sets are available, plan on spending 1000 bux plus labor before you are done...and you might as well convert to disc brakes so you can stop from the higher speeds..in the long run you will probably live a 100 years before your amortise the cost of the conversion unless you drive a 100 mile commute to work daily....ACE

By the time you change a bearing here and there (seems like one always gets torn up), and you replace front end parts, seals and gaskets you're going to spend more than $1,000.00.

IMHO I'm not concerned about using the drum brakes as long as you keep the mud out of them and keep them in good shape.

The real problem with 489 gearing is the 230 Chryslers ability to turn them. Another compllication is the wide spread between 4th and 3rd gear. When you hit a grade 4th gear doesn't have a lot of scoot and you have to slow "way" down before shifting into third.

Not sure at this point what condition the 230 is in. It was locked up when I got it. Head has been pulled and motor freed up. Lost of gunk in the oil system. If it is salvageable I will run it for a while if not a motor swap to either a 283 or 350. I was looking for some way to increase fuel mileage.

Honestly, if you are going to go to all the time and money to swap gears, engine, etc. it would probably be easier and cheaper to find a later model 4x4 and swap the body off. That way you have late model brakes, etc.

put it back together stock and drive it 45 mph for the next 50 years just like it did the first 50...You will have no major problems and save a lot of $. If you want to go fast and drive more than a couple of thousand miles a year, get a F150... ACE

NO FORD..........I would like to make it a daily driver, 6,000+ miles a year. At 6mpg I can put $1,000 in it and recover that in one year in gas alone. My M725 get 7mpg and the big ugly deuce gets about the same. CJ5 comes in at 15mpg, gee I don't have anything that gets good milage.

I question whether it's possible to get over 10 MPG on a 230 flathead.

I've got a completely rebuilt (but broke in) 230 in a modified M37 that refuses better than 10 MPH. The truck doesn't have a top or troop seats or canvas, has highway friendly Denman tires, electric fan and 489 gearing and still refuses to get over 10 MPH.

I there is anyone out theere with a 318 in an M37 I would be interested in knowing what they are getting MPG wise.

Re: RE: M37 Gear change

SasquatchSanta said:

I question whether it's possible to get over 10 MPH on a 230 flathead.

I've got a completely rebuilt (but broke in) 230 in a modified M37 that refuses better than 10 MPH. The truck doesn't have a top or troop seats or canvas, has highway friendly Denman tires, electric fan and 489 gearing and still refuses to get over 10 MPH.

I there is anyone out theere with a 318 in an M37 I would be interested in knowing what they are getting MPG wise.

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Wow - it won't do better than 10 MPH... is the parking brake on?

Yep, I know you meant 10 MPG - you're not encouraging me to run my 230 at all -

"Tanner"

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Round trip to Aberdeen with the ECC in my M37 with the Cummins 4BT, ZFs5-42 (0.76:1 fifth gear), 4.89 gears. Hardtop, bows mounted over cargo area, but canvas not mounted. 900r16 Michelin XZL tires (35" diameter). Max speed for trip about 55mph, had to keep it down due to trailing M35A2C for entire trip (mine, driven by my buddy Chuck) and due to the rest of the guys in the Convoy having similar pace vehicles so average was around 50mph (what I tried to hold it at)... Only had a M37 cab, a winch, and fourteen one gallon cans of string beans and potatoes in the bed for the ride up, ride back I had a M37 hardtop and a generator.

It was a 758 mile roundtrip. I burned 30 gallons of fuel... works out to 25mpg...
My "normal' leadfooted driving habits around town and on the highway yield an average of 17mpg, but I routinely am running at 75mph down the Interstate to work and/or doing the stoplight dragraces downtown...

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Cabell...I had "heard" that it was scary to run an M37 up that speed...your thoughts as you're obviously doing it??

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alphadeltaromeo said:

Cabell...I had "heard" that it was scary to run an M37 up that speed...your thoughts as you're obviously doing it??

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Not scarry at all, in MY truck... I wouldn't do it in anyone else's truck, although there are some whom I would ride with if they did (There is a M37 with a 3-53N in AZ that I'd like to ride in for instance... )

Keep in mind that I have turned a wrench on every single bolt and fitting on my truck, I have gone through things like steering and brakes, etc. I have seatbelts, and electric wipers, and H2 E-code headlights, and four wheel disc brakes with a dual circuit master cylinder, and new brake lines, and new wiring harness, and LED full red lense (M561) tailights, and turn signals, etc... I go under and over it on a weekly basis. In short, I know my rig, it's well maintained, etc. I also pay attention to what's around me as I drive, and adjust for road conditions (including MY condition, and that of folks and the environment around me...).

Honestly, I'm more nervous riding with a coworker in his 2005 Buick with the half bald, half inflated tires that only gets worked on once a year when it gets inspected... Especially when he drives by one of the colleges in town and spots a blond, brunette, or redhead...

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When you did your re-power...did you go through the 4BT thoroughly or what exactly did you do to it?

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3-53 in an M37 eh? Sounds like something Dennis would do.

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Recovry4x4 said:

3-53 in an M37 eh? Sounds like something Dennis would do.

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Yeah... That's the one...

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alphadeltaromeo said:

When you did your re-power...did you go through the 4BT thoroughly or what exactly did you do to it?

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Dropped the pan (wanted to take a slice off the front corner to increase clearance on the differential) and noticed that it was the cleanest engine that I have ever looked at (excepting ones that had just been rebuilt but not yet fired...). Ran it for five years, then pulled the injection pump and had the throttle shaft resealed (should have installed the 3200 rpm govenor spring while I was at it, 2500 spring was loose enough that I was turning 2600, now I am back to 2500 and, although I don't want to run down the road turning that many rpm's, it would be nice to wind it up in third on a couple of hills that I know before sliding it into fourth...).

Bassically, I change the oil and filter every 5k miles, change the fuel/water seperator every 10k miles and drive it....

The engine came out of an Entenman's bakery truck (P30 Chevy that had a repower. Engine is a 1990 ReCon Cummins 4BT-a, (105hp, turbo, non-aftercooled, 286lb-ft).


I have had very good success with takeout Cummins engines. They just purrrr... or hummmm.... Of course, I get mine out of fleet vehicles that have been well maintained, Frito Lay, Entenmans', etc.

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An easier option is to put taller tires on the m37. The 1100r16s 38" tires fit on the stock rim and give you a the same effect as changing the gear ratio while retaining the look of the old rims. Also mine has a 318 which like any v8 gives you a higher rpm range so you get a little more speed.
Right now I am running 41 inch tires and that gives plenty of speed (70)

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What kind of fuel mileage are you getting with your 318?

Are you running the standard New Process M37 Transmission?

If you want to do a cheap gear swap to 489's like I did, I found my 489's out of a late 40's to late 50's dodge civilian 1 ton, as they use 489 gears and the carrier is the same as the m series dodge and the power wagons. All you have to do is change the pinion yoke and front seal ( best to do it while you have the yoke off) and you are done. The casting numbers on the carrier are the same for the civilian,m series and the flat fender power wagons.

After installing 489s and a locker in the rear last year I finallty got around to doing the same in the front last week.

The front axle assembly was the only thing I hadn't crawled all through so I decided to completly rebuild a spare assembly and swap it out as a complete assembly.

In retrospect, if I had it to do over again I wouldn't re-gear an M37. It's simply too expensive and too much work. To go 489s and lockers front and rear figure at least $2,000.00 and a lot of work.

Once you get the new gears installed you end up with a truck that has a serious horsepower problem. I've had my M37 (The Woogie) for going on 15 years and I have personal reasons for wanting to repower it with a 265 Spitfire BUT I wouldn't recommend choosing an M37 to attempt to make a 60 mile per hour vehicle out of.

A bobbed deuce is a much better, easier piece of raw material to work with. With a bobbed deuce with 5-ton rubber you've got sufficient gearing, power and brakes to run in traffic plus more truck and better fuel economy.

Having said all of this --- I'll get off my soap box --- here are some pictures of the front axle rebuild project. We rebuilt the pumpkin last winter so no pictures of the gearing and locker installation are included. I bought my gears and lockers off of Bob Stahl at Veterans Vehicles. If I were to do it again I would send the differential cage (approx 30 lbs) to Bob and let him install the locker. Installing the locker is a royal pain in the butt and Bob is equipped to do it without hassle.