The Stovebolt Site Forums The Shop Area Driveline Taint no such thing as new 3.90 or 4.10 gears!!!

Jim Carter’s tech section has some interesting tips in it but I wish some one who knows
Jim would have him tell one of his staff to remove or modify this paragraph in his tech
section:
“For those wanting a new 4.10 ring and pinion, production was begun again in April
2000 (at this time they also produced a 3.90 ratio). In order to use these assemblies in the
1940's and 1950's truck, they must be attached to the differential carrier from a 1964-72
3/4 ton. Only then can the complete pumpkin be installed in the older truck.”

It should read:
“At one time early in this century a run of 4.10 and 3.90 ring and pinion gears
were made but the supply was exhausted in short order and are no longer available.”

I have been asked many times about this and have seen this misinformation repeated often
on this and other forums. Those of us with stock ¾ and 1ton trucks would kill
for either one of these gear sets but the fact is that no vendor is willing to make the
investment to have a gear manufacturer run off a few hundred or a few thousand of them.
It simply amazes me that no one has picked up on this hole in the supply chain. This is
the one item that almost every owner of a ¾ or 1ton asks starts looking for about the first
week that he has been driving his truck. In other words out of the hundreds of thousands
of these series trucks still on the road that were built from the 50’s thru the early 70’s
surely there is a huge market for these gear set.
I’ve written to every US gear grinder that I could find and have never gotten one single
response back so it‘s clear that the US manufacturers cannot produce this item even at an
inflated cost. China’s industrial machine is still in its infancy and they could produce
these gear sets rather inexpensively now. As unfortunate as it is, in a decade or so China
will take over as the worlds industrial leader and as the American dollar continues to
loose more and more ground the cost to us will really be out of the reach of most average
restorer here in the States.

But right now, I would be willing to take out a mortgage or come out of retirement to
acquire a couple of sets of 3.90 gears. I might even consider renting my “big old wife” out
for domestic chores in order to get a couple of sets of new 4.10 gears.
Denny Graham
Sandwich, IL

Denny, I know of 2 guys that found 4.10 gears at places I had overlooked within 50 miles of where I live. I think the customers didn't spec pickups back then, but the dealer did. Apparently the Chev dealer here must have ordered several of them. Most pickups of that vintage died within 100 miles of where they were first sold. I haven't been looking very hard because I plan on putting a Saginaw OD in my 3/4 ton. My cousin's parts man found 3.90 in the parts book for limited applications, but I don't think I have ever seen one that actually existed.

Denny, a quick look on Ebay shows several sets available.

I still got the 3.90 out of my 59. Figured I could not just throw it out. Could get rid of it if some one wanted it. I got the 3.38 now

I think Denny is looking for 3/4 ton gears. The gears on eBay are not for 3/4 ton and the 59 3.90 gears were in a half ton. The gears Denny is looking for are extremely rare, but they do exist.

The 4.10 gears just happened to be ideal for people running 1.88:1 2nd. gear Muncie 4-speed transmissions on 1/4 mile dirt tracks back in the late 1970's. The Chevy 3/4 ton rear end with the full-floating hubs was a favorite with those of us who ran roundy-round cars. Running 2nd. gear against a 4.10 rear end gave us a 7.70:1 final drive ratio. That was just right for coming off the turns at 3500-4000 RPM, and hitting 6,000 by the end of the straightaway. We snapped up every 3/4 ton 4.10 gearset we could find, along with the special-offset carrier that it needed to fit the pinion gear right. Then the axle gears and spider gears got welded together for a locked rear end, and we went racing! Lots of gearsets got trashed that way.
Jerry

Wouldn't it be nice if they re-run the 4.10 or 3.90 gears, and make them fit the older carrier? A guy can dream.

I don't think it's possible due to the dimensions of the housing. When I say "carrier" I mean the part that the ring gear bolts onto, the one that's held between the two side bearings. The left-right spacing of the flange where the ring gear bolts is different than the one for the 4.56 ring gear.
Jerry

So the 3 gear sets I have are all 3.90.

The numbers on the housings are:
one has 1797310
and 2 have 3707340

I was told these are all from '58.

How do I determine 1/2 ton from 3/4 ton?

3.90 is the standard 1/2T ratio, and 58 didn't have a 3.90 in the 3/4T, they were 4.57

Bill

Yeah this is always what happens when we open this discussion. Someone reads 3.90 and
insists that their truck has one in it but they are always getting the half ton gear set mixed
up with the HO52/72 axles.

But the question was why JC doesn't up date his tech notes. Every newbie with a 3600 or
3800 that reads that note has this false hope that he's gonna be able to find on of those
new gear sets only to find after months of searching and 29 pages of us explaining that
there are no mo of those around and haven't been for a decade. I'm running a 4.10 in my
'50, 3604 and have been searching for a donor for my newly acquired '54, 3604. Even the
used 4.10 axles are getting almost impossible to find now.

Iin the six years that I've been back to the hobby I've yet to hear from anyone that has
ever had one of those new 3.90 gear sets for an HO52/72 axle.

Jerry I do have an early and a late pumpkin here and I had both of them apart next to each
other on the bench. I matched up the early and the late differential carriers and they are
the same dimensionally and they will interchange as do the spiders and I also swapped the
ring gears from one to the other, both were 4.57 ratios and I saw no difference between
them.
The problem comes in with the pinions, they are different. The early and late housing is
cast different internally in the way their pinion is supported and you can't exchange the
pinions.
Denny Graham
Sandwich, IL

Denny, the problem arises when you try to install the 4.10 ring gear on the carrier made for the 4.57- - - -it doesn't mesh with the pinion. Thge offset of the mounting flange is different when the ratio is changed, because the thickness of the ring gear and the root diameter of the pinion is also changed. Unless you have a 4.10 ring and pinion handy, the difference can't be observed. The carrier MUST match the gear ratio.
Jerry

Sounds like others have had the same fantasy I've had, but with even less hope for a ton-and-a-half. Just ain't no such critter as "highway gears". And I agree with the poster that there is indeed a fairly fat market for them given the number of units on the road and the expense of the other options. I would happily pay pretty dearly for a 4.10 or so that would fit my punkin.

When Jaxed was working I used to search for these. Used ones can be found from $150 - $800 but are limited. Here's a post that I compiled from Denny and others: HO52 & HO72 EATONS

Denny,I forwarded your concerns to Jim.
Lets see what happens.

Tim

Well thanks Tim, that really should be updated, it's given a lot of us false hope
over the years. Of course what would really be nice is if Jim would contract a
gear grinder to make up a batch of those in a 3.90:1 ratio. But I'm sure that taint
never gonna happen again.

Denny Graham
Sandwich, IL

I can't imagine doing this would be a technical challenge so does it really comes down to the initial cash investment it would take? I dont have a stake in this particular game but im just curious to the reason.

I would say it's due to tooling costs and agreeing to buy however many sets the manufacture makes.

Tim

Why not start a section or forum here on the board where folks who are interested in buying one of these gear sets could make a pledge to buy one (or more) once enough interested parties expressed interest?

It should be easy enough to get a quote. Might be a nice little investment opportunity, as I imagine that they could be sold for a profit on down the line once the initial run is finished.

Just a thought.....

Kurt

To get a gear grinder to commit to setting up a short run would probably require at least
an order of several hundred sets. The setup wouldn't be all that hard with the CNC
equipment available today but I would think that would be a minimum any of them would
commit to. The cost would have to come in somewhere between 500 to $800 a set. So
you see your getting into some pretty big numbers and you won't find any vendor that is
willing to tie that much up on one item.

Denny Graham
Sandwich, IL

I poked around on some of the racing forums, and it seems that folks were talking around 100 units would need to be ordered.

Don't you think that there are at least 100 folks would want one?
I'm thinking co-op here rather than vendor.

Kurt

Ive seen on other forums that they do a poll and see how many people are interested.. Things such as HID Headlight Plug and Play Kits for ATVs and such.. But with items like that your looking at maybe 150 a set.. Not 500 to 800 like Denny said.. So im sure there will have to be a big demand to get something put into production. But if this gets pushed through i will be in line to buy a set of 4.10s for sure..

Patrick Dykes out at Casa Grande had the tooling done for his 3.55 half ton gear sets about 20 years ago. I was doing quite a bit of business with him at the time and I had quite a few discussions with him on the subject at the time. I doubt that he would have interest in 3/4 ton gear sets in today's economy. I would think one of his first suggestions would be to get a large deposit from the guys who express interest. With no deposit, guys with interest seem to evaporate when they are asked to fork out cash.

That I would agree with Ken. If someone put this on his credit card with the promise that
your buddies are gonna come across when the parts are delivered you could get caught
with a bill in the tens of thousands of dollars real quick.

In the half dozen years that I've been back into the hobby I've seen a bunch of big ideas,
some of which took deposits that never yielded any fruit for one reason or another, and it
left a lot of tee-off guys.

The only way this is gonna ever get accomplished is if someone made the investment and
was willing to stock and distribute them.
The most logical one would be one of the gear makers but I've contacted all of them that I
can find and none of them are interested in the project.

Denny Graham
Sandwich, IL

none are interested because they know the number of 3/4T truck's "restored" is a drop in the bucket compared to 1/2T's, and of those, the number of owners willing to drop over a grand on gears to replace what are likely already functional originals wouldn't move a dozen sets in the next dozen years, folks that make this stuff aren't ignoring you guys, they just know the market

I'd expect when Patrick got the original order of the 1/2T gears the tooling info was still in the system, only recently 'out of production', so not as spendy - like the 55-59 1/2T 3.38 set, which can still be found at some rear-gear places - but at that, how long did it take to sell off his original purchase, or has he?

Bill

Denny,
maybe some day we will able to buy some made in China gears for a really good price so that we can replace them once a year or so, when they go bad!

Speaking of the JC website, do you really want him to make a change. Do you remember the last time they made changes to it?

Fred

My guess is that Patrick has gone through a few production runs. That is why it is not uncommon to have to wait a while for Patrick (and the many vendors who sell his 3.55 gear sets) to ship the gear sets.

We can talk about this till the cows come home but the only way we will ever find out is
to get a quote from a gear grinder. I've got a back ground in machine work and I'm pretty
sure you could bring this in well under a thousand dollars especially with the CNC
equipment available today. There are programs that pretty much do all the calculations for
you and tooling is pretty much standardized with this equipment so set up isn‘t a really
big factor. The billets and heat treat would make up most of the cost.

I’d have to disagree with ya Bill as far as selling these. Everybody, well at least 80 or
90% of the guys with 3/4 and one ton trucks would be more then glad to shell out five or
six hundred bucks for a 4.10 gear set and they would be beating down the doors if you
could squeeze a 3.90 in there. These gears used are getting harder and harder to find and
in many cases by the time you pay three or four hundred bucks plus freight your not that
far away from what a new set would cost you. And you would have the peace of mind in
knowing that your getting a new gear not one with X-amount of miles on it.

As far as Patrick selling his inventory of gears for the 1/2 ton, he's the only one that
would know how that’s going and I wouldn’t be surprised if he wanted to keep that a
secret from the competition. I'd bet a dollar to a donut that he doesn’t have them on the
shelf for very long. When there are tens of thousands of prospective customers and your
the only game in town your not going to have a hard time unloading a very popular and
invisible up grade item like this.

As far as the actual numbers of vintage Chevy trucks go, I don’t think anyone has been
successful in getting an accurate count of the registered vintage Chevy trucks still on the
road. But when you conceder that ½ , ¾ and 1-ton trucks from 1947 to 1972 could benefit
from one of these gear sets the numbers have to be staggering. Who would have thought
20 years ago that the hobby could one day support hundreds of vendors selling
reproduction parts for these vehicles.

Denny Graham
Sandwich, IL

Your in luck Patricks 3:55 have been made overseas for a couple years now.
Mike

Mike,
I was only having some fun there. I know that good stuff and bad stuff comes out of China.

Fred

...help me here. When you speak of gear sets your are talking about what....ring and pinion?
I'm curious as I use to get special gears made from a local shop (Griffin Gear) for the company I helped manage and while the cost was not cheap I was surprised several times at the quotes. They made many gears for us. Excellent quality and been in business for years.
I go down that way ever now and again and would just like to drop in and see the guys and maybe, just maybe get a ball park figure to see just how staggering it is?!

...there I go, thinking again.

Alvin you are right, Griffin is top quality stuff. Worth a call or visit if you have the time.

like this place Chip? seems a possibility

Bill

That IS the place,Bill. I drive by there quite often. I need to look in my old business cards and see who was my contact guys.
Maybe after the first of the year I can get by there.

....BUT, when/if I go I'd like to have some idea of what the heii I want. Thats why my question above...and of coarse I'd need more info. The more info the better they can give me an answer. There address is Roebuck just up from where Handdogg works but it is really just a stone throw from Downtown Spartanburg. Good folks.

Boy Alvin, that would really be great if you could get them to take a look at this project.
That's one gear maker that I didn't contact when I was looking into this project some time
ago.

Yes the "gear set" the we, at least me, have been talking about refers to the Ring and
Pinion. The late model (67-72) housings are plentiful but are stuffed with the 4.57 gear
set so finding a housing to install a 4.10 or 3.90 R&P in isn‘t a problem. I just scrapped
out three axles housings last year, all were complete with the 4.57 pumpkins. Keep in
mind now, we're talking about the Eaton HO52/72 axles used in the 3/4 and 1-ton trucks.

Any decent sized machine shop now days has a CMM and could copy the geometry off of
a stock GM 4.10 set of gears. A lot of the shops have software that will take the CMM
data and convert it to machine language that the CNC equipment can use. In other words
the programming is relatively easy in a modern shop.

Denny Graham
Sandwich, IL

There is a machine shop here with the capabilities and 3 years ago, they were so hungry they might have had interest in something like this. Now they are running 24/7 making stuff for the oil patch and wouldn't want to even talk about it. They even have 3 guys who once worked for me.

OK, guys. I will at least ask questions and see how they talk. It will most likely be Tuesday, right after I eat a couple hot dogs.....you all are invited. Anyone wanting a hot dog is always at my house Tuesday morning 11:15-11:30 Sometimes its just me an a friend, sometimes there is 4 or 5 that show up and we go

I don't know if you guys are still interrested in some 4.10 h072 and h052 eaton rears but I have a couple of sets laying around here. Send me a message if you would like more info and pictures, I am in MT so you'll have shipping from here.

Achipmunk --- any feedback from the folks at Griffin yet?

Pope --- what vehicle are those gears out of?

Tango, I have NOT forgotten it. Its been a hectic world here the past couple weeks but it IS on my "calender". I have another guy that is going to go with me so hopefully we can make it over there TUESDAY.