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I was wondering if there is any way to eliminate the howl coming from the drive train. I presently have the top off so it’s a little more enjoyable driving but as everyone knows it’s way worse with the top on. My truck only has 25000 miles on it and my plan is to leave it all original but without the noise. Anybody have a cure?

You can add sound-deadening to your floor from underneath; however, the gearing is straight-cut which causes the whine. Hearing protection is a must, especially for longer trips.
Gary

Assuming fluid level in the units are where they should be, the only way to eliminate drivetrain noise is to freshen up the units to ensure all bearings, shaft needle bearing surfaces are good and within specs. Buying a used truck and not knowing how the truck was used or abused makes it difficult to determine which unit may have problems resulting in noise. Most of the time the transmission is the unit that results in noise from worn shafts and bearings, that would be the one I would start with to freshen up and go from there. If you have splined hubs on the front axles you might consider installing manual locking hubs to eliminate any noise that may be generated by the front axles turning. Go to page 129 of the PIF, see link and you'll find part numbers for parts, the company you can get the parts from and what parts interchange between the M37 early model NP210 transmission and the later NP420. If you have one of the repair manuals for the M37 covering the transmission, it will give you the max wear limit for needle bearing surfaces and it's important that you mic the surfaces to determine the wear, just replacing bearings and seals will not eliminate the noise generated from those worn surfaces. If all the units are within specs., the only thing you should be hearing is engine and tire noise. [https://www.dodgepowerwagon.com/pw/pw_pif.pdf]

I noticed that things are a bit quieter when I have some random stuff piled in the passenger footwell. I suspect it is dampening the vibrations in that sheet metal. I keep meaning to try cutting up some heavy rubber mats to make floor mats to see how much of a difference that makes.

So it more or less sounds like it’s the nature of the beast. I could do a lot of tinkering but it still won’t do miracles. It looks like the a drive train swap is the cure. My truck is in real nice shape luckily with no rust so the thing I should do is long term change out the drive train and motor but in the short term I’m enjoying driving around with the top off doing a crazy 20 mph. I went and saw “Retired guys” truck that he had done a chassis swap and put a 89 W250 with a 5.9 Cummins in it. That was one sweet build. I’ve done a couple of them so may go down that rabbit hole. Might look for a gas job with a small V6 to do it to, any suggestions on a specific vehicle that people have used. I know an older Dodge the frames are roughly the same so swapping is a little easier.Thanks for the help.

I noticed that things are a bit quieter when I have some random stuff piled in the passenger footwell. I suspect it is dampening the vibrations in that sheet metal. I keep meaning to try cutting up some heavy rubber mats to make floor mats to see how much of a difference that makes.

You might try some rubber washers with the correct bolt dia. between the floor pans and cab, that might help.

As far as conversion, whether you rebuild the 3rd member, TC and switch out the trans and engine, or full drive train, your in for some work. If noise is an issue, do you want a rattly diesel? Dodge engines 318/360 are a tight fit unless you find a Canadian M37 radiator to give you more room for the water pump/fan and you'll have to switch the lower water outlet to the left side for a short water pump, otherwise you'll probably be using electric fans to cool the coolant. VPW sells engine mount kits that bolt the 318 up to the original 230 mounting locations, but they are not fully insulated around the bolt on the mount so you'll pickup drivetrain noise. You'll need to find a civilian NP420 the Military version will not bolt up to a civilian bellhousing. The Chevy small blocks are a good choice, they are shorter and fit nice in the engine bay and with the ZIPP or Vintage Air water pump high riser allows you to use your radiator shroud/fan for good cooling. Your choice of transmissions that are good for off roading are the SM420 (lowest first gear of the 4 speed truck trannies) or SM465. The SM465 is longer and heavier than the SM420 and when the SM465 racks up the miles, it has a tendency to pop out of third gear, look for one with the cast iron cover, later ones use the aluminum cover, avoid it. We all like more power, and some also want reasonable gas mileage, so your smaller engines are generally better mileage, with less power. I installed a 65 Corvette engine in my Power Wagon and the SM420. Although the 327 is shorter stroke than the 350, the lower SM420 first gear makes up the difference and I also get better fuel efficiency than a 350 or 383, it's a good balanced combination. The SM420 has a whine to it like a big truck, but it's not annoying, just a neat sound. No one make engine mounts for conversion so you'll have to make your own. VPW also sells a hanging pedal kit so you can install power brakes and hydraulic clutch. Go to page 352 of the PIF file on the Dodge Power Wagon - open link and you can see the conversion picks. [https://www.dodgepowerwagon.com/pw/pw_pif.pdf]

I just got an M37 and know next to nothing about maintenance/repair... yet. My driving skills are improving, but one thing that does bug me is the whine I hear while tooling around. I thought it was just my truck, so it's somewhat comforting to know that I'm not alone.

Not alone at all; just reading this thread puts the whining in my ears!
Gary