Why No Tach ???

[w30bob]

Hi Guys,

I guess I'm not familiar with cars older than the late 60's, but why was there no tachometer in the M37? I'm guessing most passenger cars from back then that had manual transmission didn't have one either, but on a military vehicle wouldn't you be more concerned with not exceeding the max RPM than how fast you were going? I don't think the M38s or MBs or GPWs had tachs either, which is kind of odd since you'd think the military wouldn't want young GI's revving the snot out of those Jeeps. But I think the M35 had a tach.....so why not the M37??

thanks,
bob

[Carter]

Because they have a governor to limit engine rpm.

[w30bob]

Hmmmmm......well ok. But I've got a tach on my John Deere tractor and my industrial log chipper and they both have governors on them (but to be fair my 2 Farmall tractors don't, and you don't drive a log chipper). So what you're saying is having a governor kept soldiers from getting over zealous with the throttle. Ok, makes sense.

thanks,
bob

[Cav Trooper]

Another possibility, back then it would have been a mechanical tach driven off the distributor most likely. More pieces of equipment to maintain ie; drive cable and tach. It all added up in costs for mfg and maintenance. Just a thought.

[Carter]

Sal sent this PM to me, he believes my answer is incorrect :

"Carter. I don't think the answer you gave about why the M37 doesn't have one was correct. I use to drive a M52 Gasser Tractor when I was in the NG and it had a governor and a tach... "

If I am wrong I apologies to all for making a mistake.

[w30bob]

Carter,

It's pretty tough to be "wrong" on this forum due to the lack of real data or information out there that's been lost to time. Your answer is just as good as any other, so the best we can do is gather the most answers and then see what we think makes the most sense. Usually the right answer ends up being a combination of things. The last thing we want on a forum like this one is people not saying what they think because they might be wrong. Then we'll learn nothing.

regards,
bob

[Sal]

Im sorry I sent the PM Carter. I wasnt looking to hurt anyones feelings.

sAL

[Carter]

You did not hurt my feelings, just wanted all to know your thoughts on the subject.

[Cal_Gary]

I haven't seen any material pertaining to the lack of an M37 Tach; hey, I use my ears to know when to shift!
Gary

[k8icu]

I do not have any hard evidence but most MVs didn't have tacs. In fact the M35 didn't get a Tac until the A1 version when a diesel motor was put in. I can't think of any WWII vehicles that had a tac. Certainly not the Dodge WC. The MB didn't, the CCKW didn't. The M38 and M38A1s didn't. The M151 didn't. The M37s replacement the M715 didn't. The M211 didn't but then again it had an auto trans. The M35 didn't as stated until it went to diesel.

I think the military just didn't think they needed them. And the reason for it in the diesels was to not over rev the motor which you can do when listening for the shift point in a diesel.

That's my $.02 for what it's worth.

Joe

[w30bob]

Joe,

That makes a lot of sense. I guess I'm so used to having a tach in vehicles with a manual trans it seemed odd to me that the M37 didn't have one. Plus like Carter said....these engines were governed, so you couldn't over rev them even if you wanted to.

The reason I asked this question is really because I keep seeing military tachs for sale on eBay and I'm thinking a tach would be more useful to me than a speedometer, especially in a vehicle that can't break the speed limit if it tried. But as Cav pointed out (and I totally forgot) these tachs are all mechanical and without the drive output on the distributor there's really no way to install one in my M, unless I used an aftermarket electric tach.....which wouldn't look right.

I think we put this puppy to bed. Thanks everyone!

regards,
bob

[RMS]

no need for a tack when you have a "maximum permissible speed" data plate on the dash.

[w30bob]

Ah.....so you're saying soldiers never drag raced their machinery when they got bored.
later,
bob

[ZGjethro]

no need for a tack when you have a "maximum permissible speed" data plate on the dash.

These specs seem a little optimistic. I don't use first since as soon as the truck rolls it is time to shift. Second goes to 10mph. third to about 25mph. Fourth maxes out around 40. 45 going downhill. 55mph seems a unrealistic, but maybe these engines like to rev higher than I like to push them. I am happy with 45 mph as a top speed.