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

Pope, I sent you a PM. Thanks Jerry

Achip --- Excellent...I am still convinced there is enough pent up need that someone could make pretty good money fabbing highway gearing for these old girls. Especially given the new cad/cam capabilities. It's pretty much plug in the specs and hit the switch. Good luck with it and many thanks for the ground work.

Sorry Tango they are form 72's one set came from a 4 speed c30 dually and another from a c20 suburban. I just sold 1 Set and have 2 more, but 1 set is pretty rusty and I need to get it cleaned up to be sure that it is ok.

Bump...any word yet on gear sets?

...plans are to go by there mid day tomorrow. I'll return and report. Sorry its taken so long guys but my days are pretty full. Tomorrow is my day "off". Biscuit at 9am then Griffin Gear afterwards

Return and Report:

Well, Griffin Gears turned out to be a bust this morning. I can't remember the guys name that I talked to but when I mentioned "...ring and pinion for a truck rearend" he just flat told me they did NOT do them. He said "they require a very precise cut"...blah blah blah. I had a few questions to ask him but when he said they would also be quite expensive I decided I was wasting my breath. I could tell he had no interest in what I was saying so I bid the gentleman goodbye and drove by to Boiling Springs!

Sorry guys. It was a good thought/idea but just didn't pan out.

Hey Chip --- thanks for the effort bud. Sounds pretty much like what I have heard here, but I'll keep trying.

Well, I'm still curious. When I mentioned this to one of my hot rod buddies he told me his girlfriend's brother worked at Griffin Gear!! I'm going to ask that guy for the "lowdown" on this situation. I'm just curious.

What peeved me was the guy said they couldn't do it but then wanted to pass it off as being expensive. Heii, I could have been a millionaire and he passed up busines...Oh well, time to moooove on.

I know we all want made in America, but here is a Chinese manufacturer that seesm like they will make them, Minimum order is 10 sets.

Custom Ring and Pinion.

May be total BS, but could be worth an inquiry...


Kurt

That would be doable if someone was willing to gamble five or six grand on a short run
of ten sets.

I’m sure that a manufacturer could bring them in for around $500 to $600 a set even in
this country. In the US there wouldn’t be enough profit to pay the electric bill but in the
far east I’d bet you could bring them in for a third of that which would leave plenty of
room for mark up.

I’m not sure how you would engineer it. I would think that they would have to work off
of drawings and gear drawing are quite complicated. I don’t know if it is possible to take
a 4.57 or 5.14 gear set and scale the teeth to a 3.90 ratio. If that were the case there are
plenty of them around that could be sent as working samples.

I really don’t have any problem buying non-American products that we are unwilling to
make in this country. Any company that is set up to manufacture ring and pinion gears
should be able to give you a reliable product, it‘s not like something that can be produced
out back of the house in a make shift shop like a lot of the simpler items. Gear
manufacturing is really a specialized business that takes a lot of know how.

I can say this for sure, that anyone willing to pursue this can put me at the top of the list
for a couple of sets when they receive their shipment. For the life of me I don’t
understand why one of the vendors doesn’t take a chance on a test run. If I weren’t retired
living like a pauper I thing I might even take a stab at it.
Denny Graham
Sandwich, IL

My bet is you could tell them the critical dimensions or even ship them a differential and say what ratio gear set you want in that case, and they would do the engineering.

Kurt

Exactly, no need for us to guess how the pro's might go about figuring tooth geometry and such or telling them how to make the gear.
Anyone with the machines to make them and willing to do the job should have the know how and understanding to tell you how they'll do it and what info they need.
I suspect the offset between carrier and pinion centerline (they don't intersect) as well as offset between mounting surface on the carrier and pinion centerline are the critical dimensions.

Hey Denny...you can add me to that list as well.

I think you are being very naive here. A minimum casting run is usually 1000 pieces.

of course Mr Arthur Cheng doesn't state what the design and setup fee and shipping from China would be, and ya hafta join AliBaba to learn more

Bill

Tks Bill, I think you missed that part Charlie. As I said, it would be a worth while project
for someone that was willing to gamble a few grand and the time to jump thru the hoops
of off shore manufacturing and importing.
We need someone like Counterpart Automotive out in CA to take an interest. They are
familiar with the import business since it appears that the vast majority of the products
they sell come from China.
DG

That same website says they make brake drums and rotors. How about the 3600/3800 drums that are so hard to find? Some enterprising entrepreneur with a big sack of money he needs to invest might corner the market on some of that stuff. Anybody got a rich uncle? Mine died, and didn't share anything with me!
Jerry

you'd think that if it really was possible to procure small lots of correctly made parts at a reasonable cost with no further commitment, and if there was really any market for them, that Patrick would have done it already or at least investigated the possibilities .... anybody talk to him?

Bill

Just a thought, but I would think a 3.73 ratio would be better than a 3.90 ratio if I was going to try to have a set of gears made.

Don't quote me on this but I think I'd read something somewhere
in the past about there being a limit on the way the gear sets
physically will fit in the HO52 carrier and 3.90 was the
highest ratio that would fit in the space.

Denny G

Never thought about that..

Denny, could you tell me exactly what and where the identifying markings are on an HO52 carrier. I'm looking at a rear end out of a '70 chevy c20,but not quite sure what to look for. Also, does it matter whether it's equipped with coil or leaf springs. TIA.
Terry

Upper right hand side of the differential carrier you will find the code. A series of
numbers designating the ratio TAA,THU,TJU,TLN,TMZ,TNA,TNB,TOT,TTF,TWI,
were all 4.10. A fourth letter which tell the plant it was built in G,W,B or K followed by a
series of four numbers telling the month built and day built:
http://www.pbase.com/dennygraham/eaton_ho52

I'm unsure of the coil/leaf thing, I've heard conflicting information about that and would
check both relying on the code.

Denny Graham
Sandwich, IL

From what I have seen the spring type really didnt matter. I have found both from the factory with the 4.10 gears. The option varied through the years though, depending on the model. Earlier ones could be ordered with 4.11 gears which had 9 tooth pinions and 37 tooth ring gears, while the later 4.10 were 10 and 41 tooth

The rumor has been that they were only in the coil suspension
trucks but I think you are correct Ryan, it was not that
consistant.
And not to cornfuse things, the 4.11 rear options were not the
Eaton HO52/72 units.

Denny G

Thats what I had thought but according to the 65&66 chev literature that I have there was 4.57, 4.11, gears for the C and P 20 & 5.14 for the C and P 30. Could have been a typo.. All of the 4.10's that I had were from the 70's, so I figured they had made a change at one point in the late 60's. Have you got some option specs for the mid to late 60's trucks?

The only thing I've got Ryan is the information that's available in the parts books, that
which is in the "Catalog of Chevy Truck ID Numbers 1946-1972" and the findings that
people have reported to this and other forums over the past seven years.

The ID Catalog only lists the C & K truck types up to the 3000 series and there are no
4.10 gears listed. Which indicates to me that the 4.57 & 5.14 were the only Eaton gears
used. It makes no distinction as to the suspension.

My 1946-1972 series 10-20-30 parts book show this listing:
Ring and Pinion gear assembly (not sold separately)
68-69 Ser. 20-30 w/4.10 ratio (exc 4/WD)
70-72 Ser. 20-30 w/4.10 ratio
71-72 G-30 w/4.10 ratio
Part number 3933960 gear assembly (41-10T--hypoid) (3934647-3934641)

I did talk with someone this weekend that said he got a 4.10 out of a junked van which must have
been as the parts book indicates, a 71-72 G-30 w/4.10 ratio. But those are quite rare I’m sure.

I should mention that the Dana axle was available in a 4.10 ratio and is listed as;
69-70 Ser.20 w/127” W/B (4.10 ratio)
71-72 Ser. 20 (Conv) w/Dana Axle (4.10 ratio)
Part number 3965146 (41-10T) (Dana 24807X)

And again, every 4.11 gear that I've seen has not been an Eaton HO52 but a Dana and I think I
mentioned this before but the 4.10 gear ratio doesn't show up in any series until the 1968 model year
unlike the '67-72 that is often mentioned in the internet discussions.

Denny Graham
Sandwich, IL

Well thats what I had thought, never thought about the G series, though I havn't seen too many of them. What had me wondering was my 66 owners manual had 4.11 as optional for c20's, however that may have been a spicer axle it doesnt say, and my fault for assuming it was an Eaton. GMC liked to run the spicer axles in the 60's and they may have been offering them in the Chevs as the option to get the higher gears.. Good info Denny! Thanks for sharing.

You bet Ryan, but I'm just relaying what I found thru my search, I'm not an expert on
these and there may just be applications that I haven't seen the documentation on.
There isn’t a heck of a lot of information on the history of what rear axles GM used over
the years. Just try to find the background on the Eaton and you will see what I mean.

DG

Denny, May I send you an e-mail with some pictures attached and a couple questions?

Sure you can send me some pics but as I've said, I'm not an expert, just tellin' what I've seen and what my research has turned up.


DG

It doesn't look like it's been mentioned in here, but the gear sets are also marked on the edge of the ring gear. That's how I found my 4.11 pumpkin in a pick-n-pull junkyard years ago. The dome cover on the other side of the banjo axle comes off easily, and it's then simple to use one tire to spin the axle until you can find the markings - as long as the driveshaft is disconnected or the transmission is in neutral.

From what I've read, the 3.90 gearsets were only used in one fancy trim level truck for one year, and are consequently incredibly rare. The 4.11s, while not common, are far more likely to be located than the 3.90s. If you want to get really ridiculously rare, try finding a Detroit Locker unit. They went out of production as soon as the Eaton axle design was dropped in the early 70s.

The Detroit Locker was offered in the Spicer/Dana 60 and 70 in GM trucks well into the '70s. The "3.90" 3/4 ton axle doesn't exist as an oem option in GM products, only as an aftermarket gearset that's no longer made.

Detroit Locker units have been made for all sorts of axles, but the specific version for the Eaton banjo axles is difficult to find.

From the best information that I've found, there was a factory 3.90 gearset for the HO52/72 axle, but it's rare as hens' teeth. Supposedly, it was only available on 1970-ish big block automatic 3/4-tons. Long ago I spoke to someone who found one "in the wild," but that's the only one I've heard of. I'm sure that 1969/70/71 BBC 3/4-ton autos aren't exactly common.

Chev also use some spicer / dana axle behind the 396 / 402 in 1969/70/71

Just picked up my 4.10 gearset fron Ryan Pope. A nicer gentleman you will never meet.
Thank you very much, Ryan. Well worth the drive. :-)
Quite a nice yard (for a stovebolter, lol) with lots of projects. He likes diesels. Nice installs.

Hey Highflyer --- is that 4.11 set for your '49? And was it off-the-shelf or custom cut? Did a quick search but didn't see any other references.

Yes. They had a 3.54 gearset in them. The Heritage site also lists it being available in '68 in 3/4 tons with the 396.

Actually, the big block 3/4 tons are quite common. Especially in Camper Special form. Almost every single one I've seen had a Spicer rearend, oor the 4.10 geared Eaton. The only listing I've found for a factory built Eaton with 3.90 gears was for the '55 1rst and early '55 2nd Napco conversion for 1/2 tons, which used the 3/4 ton axle for the front. Otherwise, GM shows no listing for that ratio in 3/4 or 1 ton.

No, it's a normal center section from a 67-72 3/4 or 1 ton big block automatic.