M-37 / R-2 Rescue

[Halfdunn]

Can anyone update me on your highway speed for a 1956 M-37/R-2 Rescue truck? I can only seem to get about 40 mph out of mine without the engine screaming. I realize it has 5.83 gears in it. Any discussion?

Thanks, Halfdunn

[Elwood]

Lots of discussion here and elsewhere about the speeds for these old trucks. The search function is helpful.

Short of it is that the rated top speed was 55mph, but that's really pushing it hard. The flathead six doesn't much like being held at the top end, the transfer case will get very hot at that speed, and the brakes just weren't intended for high speed use. Add the brick-like aerodynamics of your R2, and you'll be putting even more strain on the drivetrain at higher speeds.

I don't like getting much above 45mph with a stock truck.

If you need to run with modern traffic, a driveline swap (including brakes) is a better option.

Welcome to the forum.

[sturmtyger380]

The timing of your question is a good one. I have pulled my rear differential and was thinking about changing to a 4.89 as I read it would help with the top end.

Well it does but then it causes a chain reaction with all your other components. Since you are going faster your brakes need to be top notch and folks suggest going to disk brakes - $$$. Then the old 6 cyl engine when you hit a hill in 4th gear starts to run out of breath and you have to drop down to 3rd right away. So there goes your speed unless you are really revving the engine which is why you went to 4.89 in the first place. I live where there are mucho hills. So the next step is to do an engine and tranny swap – more $$$$.

Then the question – what kind of driving do you plan on doing? Daily driver – 3K miles and up a year or weekend trips to the Dairy Queen for treats.

I thought about it and since I will maybe put 1K miles on it in a year and no hwy speeds with lots of hills; I will just keep it stock and put the $$$$ into fixing what I have and enjoy life at 45 mph.

Alan

[jim lee]

I have stock gearing in my M37 and I cruise at 47mph according to the speedo. But, my motor is pretty new and has been balanced. Its entire driveline runs really smooth. On my carryall, theoretically the same setup, 45 is about it. The motor just doesn't seem to run as smooth and the driveline still has some vibration issues. Granted this is up from the max of 10mph when I started on it.

Meaning? They'll go faster than 45. But, in order to do this, you really have to get everything dialed in and working well.

-jim lee

[RMS]

too much advance will hold her back @ 40mph, 4.89s = 20% increase in speed, 38in tall tires will give you about 8% more top end speed ?

[Cal_Gary]

Mine runs comfortably at around 43MPH; however, I noticed a bunch of slop in my timing chain and plan to replace it soon so that might help my power curve a bit.
Gary

[Kaegi]

that one is much heavier than a M37 so might be slower.. with everything in good shape I have run 100s of 1000s of miles over 50 mph with stock 5.83 gears. if it wont run fine between 50 and 55 then you have other problems. RPMs with stock 36 inch tires and 5.83 gears is under 3200 rpms and these engines will do it all day long. the brakes should work fine at those speeds as well. there is shoe material that was on the market years ago from places like napa that was way too hard and caused impossible stopping. Also the adjustment is critical. if not done properly they wont stop well. if done right should stop on a dime at any speed.

[Halfdunn]

Thanks all for the possible solutions/answers to my speed question. You people are the BEST!

[808morgan]

The timing of your question is a good one. I have pulled my rear differential and was thinking about changing to a 4.89 as I read it would help with the top end.

Well it does but then it causes a chain reaction with all your other components. Since you are going faster your brakes need to be top notch and folks suggest going to disk brakes - $$$. Then the old 6 cyl engine when you hit a hill in 4th gear starts to run out of breath and you have to drop down to 3rd right away. So there goes your speed unless you are really revving the engine which is why you went to 4.89 in the first place. I live where there are mucho hills. So the next step is to do an engine and tranny swap – more $$$$.

Then the question – what kind of driving do you plan on doing? Daily driver – 3K miles and up a year or weekend trips to the Dairy Queen for treats.

I thought about it and since I will maybe put 1K miles on it in a year and no hwy speeds with lots of hills; I will just keep it stock and put the $$$$ into fixing what I have and enjoy life at 45 mph.

Alan

Yeah something to think about, I ordered some 4.89s from VPW and they are not shipping yet. I'm painting my truck now, doing elec ignition/fuel pump etc.. I don't plan of going really far with the truck but there are some roads where people go 55 or over, flat road, so I thought I should keep up. I drive Andy's M37 when I visited him and he has them, he likes it. I will have to practice a double clutch for 4th to 3rd! I guess I pan to drive it without the gear swap first and see how it fits my needs.

[sturmtyger380]

Are you planning on putting the 4.89s in both the rear and front of the truck?

Has anyone tried the Lock Right Lockers? https://www.justdifferentials.com/PT1210-p/pt1210.htm

[rickf]

You pretty much have to run them in both ends unless you never plan to put it in four wheel drive. And even then an accidental engagement would mean you would be so bound up you would spend hours creeping back and forth trying the find the sweet spot to get it out of gear. And if on pavement you could be looking at a broken axle. And I have used Lock-Rites in many vehicles with no issues, They work great. I never tried them in an M37 but I see no reason why they would be any different.