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I've had my M37 for over 15 years. During that time it has leaked oil from the engine, transmission, transfer case and front and rear differentials. It’s never gotten worse over the years.
My question is does yours leak?
I was told by a vendor and a couple other owners that even if I replace gaskets and seals I will still have leaks and that these truck are notorious for leaking.
When I park the truck in my garage I have plenty of cardboard around to catch the drips. I don’t use engine oil, just drip it. I top off all of the 80-90 weight gear oil and things are fine for the year. I’ve tightened all of the suspect bolts with no change.
What’s your experience?

That is how you tell if the engine, trans, transfer, or axle is out of oil is when it stops dripping All you can do is tighten up the bolts and regasket when you rebuild that partiuclar item. Tom

Yep! Old M37s are a lot like old Harleys. They drip oil, and there's nothing you can do to stop it. That doesn't keep them from being highly prized toys, though. On the positive side, you know you have fresh oil every time you top it up.

Why do M-37's leak oil?? Their just marking their territory.
Or if it doesn't leak it's empty.

Yep, mine drips from the oil pan, diffs, trans, transfer case, and a little from one of the axles. None are more than a few drips here and there, and the axle drip is only once in a while. My rear diff used to leak like a seive until I replaced the seal, now it drips maybe three drops of fluid a month, if that much.

I read somewhere that there were allowances for leaks that were considered normal for these trucks. I do not know how true that was/is, but I figure a few little drips here and there from a 45+ year old truck is par for the course. I keep a poly tarp under my truck while its in the garage just for the unexpected.

Well folks, drips & leaks are par for the course on trucks that haven't been rebuilt correctly. We have built many that were leak free & this experience has given us opportunity to learn how to stop it. Really it amounts to this, if you want to put up with it, fine. If you don't like drips & leaks you don't have to put up with it, they can be stopped by doing repairs correctly & completely while replacing junk NOS seals with modern sealing technology, it's up to the individual.

More Bad Info, just like the "Splined Driveshaft Bolts" that are on every truck.

Bryan Sage

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Mine DOESN'T leak. Now I'm not sure if that's a good thing or if I need to check my levels!

MSeriesRebuild wrote:Well folks, drips & leaks are par for the course on trucks that haven't been rebuilt correctly. We have built many that were leak free & this experience has given us opportunity to learn how to stop it. Really it amounts to this, if you want to put up with it, fine. If you don't like drips & leaks you don't have to put up with it, they can be stopped by doing repairs correctly & replacing junk NOS seals with modern sealing technology, it's up to the individual.

Well, considering my truck hasn't been rebuilt at all, other than the few things I've done to it, I guess the above is a moot point....

I used one of those "NOS Junk Seals" as you call it. I went from a good sized leak to a few drips a month. I consider that pretty good considering the age of the seal.

Nickathome wrote:

MSeriesRebuild wrote:Well folks, drips & leaks are par for the course on trucks that haven't been rebuilt correctly. We have built many that were leak free & this experience has given us opportunity to learn how to stop it. Really it amounts to this, if you want to put up with it, fine. If you don't like drips & leaks you don't have to put up with it, they can be stopped by doing repairs correctly & replacing junk NOS seals with modern sealing technology, it's up to the individual.

Well, considering my truck hasn't been rebuilt at all, other than the few things I've done to it, I guess the above is a moot point....

I used one of those "NOS Junk Seals" as you call it. I went from a good sized leak to a few drips a month. I consider that pretty good considering the age of the seal.

Just sharing experiences, if you are happy, GREAT. I was sharing a totally different point, you are speaking of slowing the leak to a minimum, I'm speaking of leak free. Most of our customers don't want to see leaks after they pay us to rebuild a truck, thus we have endeavored to learn how to build them without drips. When you get her on the road & are able to log a few hundred miles, give us a drip report at that time, I imagine you will better understand why I made the comment then.

M376X6 wrote:More Bad Info, just like the "Splined Driveshaft Bolts" that are on every truck.

Bryan Sage

[/quote]

Yes Bryan the M GOD as spoken

If after a quality rebuild, your truck leaks.
That just says something about the quality of the rebuild.
My engine does not leak (now), after the new transmission,
it doesn't leak either. Both diffs leak and the Xfer case do but
those are next on the list.
J.B.

Okay...okay! Let us not get into a "contest" here, gentlemen. I said that old M37s and old Harleys leak oil. This is primarily due to warpage of parts and weakening of gasket material over time. It is possible to rebuild both so that leaks do not occur. In some cases, it may be necessary to mill both mating surfaces to tolerances much closer than original specs to accomplish the task. This can become a very expensive proposition, depending upon the rarity of the vehicle/parts in question, the amount of distortion to be compensated for, and the desires of the person contracting the repairs. What it boils down to is this:

(1) Old vehicles leak oil.
(2) The leaks can be cured.
(3) Are you willing to foot the (possibly expensive) repair cost?
(4) If not, can you tolerate a little seepage?

If your answers to (3) and (4) above are "no," you're in the wrong hobby.

MSeriesRebuild wrote:

Nickathome wrote:

MSeriesRebuild wrote:Well folks, drips & leaks are par for the course on trucks that haven't been rebuilt correctly. We have built many that were leak free & this experience has given us opportunity to learn how to stop it. Really it amounts to this, if you want to put up with it, fine. If you don't like drips & leaks you don't have to put up with it, they can be stopped by doing repairs correctly & replacing junk NOS seals with modern sealing technology, it's up to the individual.

Well, considering my truck hasn't been rebuilt at all, other than the few things I've done to it, I guess the above is a moot point....

I used one of those "NOS Junk Seals" as you call it. I went from a good sized leak to a few drips a month. I consider that pretty good considering the age of the seal.

Just sharing experiences, if you are happy, GREAT. I was sharing a totally different point, you are speaking of slowing the leak to a minimum, I'm speaking of leak free. Most of our customers don't want to see leaks after they pay us to rebuild a truck, thus we have endeavored to learn how to build them without drips. When you get her on the road & are able to log a few hundred miles, give us a drip report at that time, I imagine you will better understand why I made the comment then.

I agree that once I have my truck on the road and start logging miles, I may see more of a leak build, and also may see leaks develop that weren't present before. I don't doubt that will happen at all. However, even then if the leak doesn't get to the point that it was previously, I will still have no problems with it. I'm not one to be ableto afford the type of rebuild you speak of anyway so I guess my choices have pretty much been made for me. If this seal fails, then I will go with the more modern alternative.

If have it right these old girls were built before the space shuttle and If I recall it had a leak as well. Caused a major problem. Any liquid in a dry world will find a way I always say. Sooner or latter everything will leak a little, I know I am and I am about the same age as my ride.
Tim