The Stovebolt Site Forums The Parking Lot Tons 'o Fun anyone change out their 5.17:1 diff gears?

Hi all,

I need help finding a way to change out the 5.17:1 gears in my diff. Anybody know how? I heard about the Eaton ho72 4.11:1...can this be swapped into my 10 bolt rear end?

Sucks to only go 40mph!!!!

1949 3800 1 ton, 216cu.in., 17 inch wheels, single wheel axle.

Much appreciated

I have a 1941 long bed 1 ton and shared your frustration. I ended up having a new rear end built for $1,800.00. The new rear end has 3.73 gears and larger more modern brakes.

I also added a stock SB350 engine and 700R4 overdrive transmission.

I now get 70 mph at 2,000 rpm. You will not be happy until you make the change.

Go for it, Find that elusive 4:11 Eaton HO72 gear set from a 67-72 Chevy 3/4 ton truck with an automatic transmission. When you have that, unbolt the rear axles from your truck, and pull them out a few inches. then unbolt the 5.14 gear set from your truck and remove it. Then lift your 4.11 gear set up and install it into your rear axle housing, reinstall the axles, add gear grease and go for a drive, now able to keep up on the highway.
The real challenge is to find that 4.11 gear set as a lot of them were snatched up by the circle track dirt racers thru the years and also a bunch succumbed to the price of scrap. You wont find that gear set cruising down the interstate but get out and beat the bushes in rural areas and you will find them.

Thanks 1951Chevy1Ton!
I just need to locate one of these beasts now!

Easy to swap to 4.56 which was common in the 3/4 tons.

If you still need faster gears and after you give up looking for the elusive 4.11 consider a 14 bolt axle swap. I think swapping to a 14 bolt from under a cab and chassis GM truck is a very good option. Need to move spring pads but otherwise it's a good match, width is the same or within an inch or so.

Grigg

Thanks Grigg & Murraydave ......

I wonder what the improvement would be going from 5.14 to the 4.57 in terms of top speed in mph?

I made that change in my 52 1 ton and it was great for around here where we have hills. If you gear it too fast you loose the ability to haul lots of weight with a small engine, or even just the truck empty if geared real fast and you have good hills to climb.
On the flat I could easily travel 50-55 mph for hours and hours with a 55 model 235 and 4.56 gears, made an 8,000 mile trip in 28 days counting stops.

Grigg

I found a set of 4:11 s and switched out my 5:14s in my GMC 1 ton firetruck. WHAT A DIFFERENCE!. Not as good going up hills, buy what a pleasure to drive. The previous comment, 68-72 H072, out of a 3/4 tom Chev/GMV is what I found. Locally, expect to pay 500 bucks if some shop can locate one. My truck is stock with the 228, 6 cyl. I found mine here on the For Sale forum and bought up! Good luck

Thanks guys!

It doesn't look so bleak anymore! I will post for a 4.11:1 gear set and cross my fingers......thanks for the encouragement!

Do the math 5.14 divided by 4.11=1.25or 25% increase in speed per rev of engine 5.14 divided by 4.56 = 1.127 or 12.7% increase per rev of engine.
If this math is flawed, let me know the error of my logic.
Jerry

My truck has the 4.10 gears. I don't really think they are hard to find; both my trucks actually already had them. If you post a wanted ad here you should be able to pick them up for $100-200 IME.

I drive my truck everywhere as my daily driver. (I've logged hundreds of miles on it just the last few days.) I run 32" tall tires on later 16" wheels, and it works pretty good for me. Here's what my speeds work out to (approximately):

45MPH=2,000RPM
50=2,200
55=2,425
60=2,650
65=2,875
70=3,075

Not too bad, IMO. (My truck is a later '65 with a 283/SM420 combo, btw.) Hope this helps.

I put a 4.10 set in mine from a 71 3/4 ton. I am able to cruise at 60 mph with my 216. I have 16" wheels that are around 31" in diameter. I found my replacement at Minakers. Their yard is cleared now but I believe they have several buildings full of parts.

Thanks truckernix

I just sent an e-mail to them. Great to see another maple leaf & bolter in the area! I am near woodstock down south. I have had luck at Bill's truck stop out Courtice (Oshawa) way for some parts. Mainly I order all from Classic Chevy. Any Stovebolt get togethers up our way?

P.s: What did you do with your old gears set? Were they 4:57:1's?

Large

Thanks 66submarine! I love the idea of even going 60mph! But ya, it is very hard to locate the Eaton ho72 4.11:1 rear ends.

Like I said earlier, They are NOT going to jump out of the woodwork and say, Here I am, You will have to get off the interstate and maybe even off the Information Super Highway and beat the bushes to find one. I am looking every time i travel.
I do think that the "Camper Special" trucks back in late 60/early 70's are candidates as well as some panel trucks, and maybe even some 1 ton or C30 model Chevy trucks. Also some Jeeps may have used Eaton gear sets. Checking in on a jeep forum may have rewards. Good luck
Jerry

Glad I could help. BTW; look for them in 67-72 trucks; that's where you'll find most of the 4.10 gears (from what I gather). They seem to be pretty common in that era.

Large,
I scrapped my original carrier. I was moving houses and some things had to go!

Have a look at this older posting. I am wondering if Mapleleaf has some leads. Posts about finding a 4:10 Pumpkin

I don't know of any Stovebolt get together happenings but I attend quite a few cruises.

One of the scrapyards may contact other yards for you. They are all linked by computer now.

My 69 1 ton dually 350 4 speed shows on the glove box sticker that it has 4.11 gears and posi. Would this rear be the same as my 52 1 ton DRW? I was looking at them a while back and the center sections did look close to the same. I will start looking for the 3/4 and 1 tons and see what rears and gears they have.

I would not speculate yes or no if that is the Elusive one. I am in fall harvest mode right now but I do have in my archives somewhere a digital picture of the ring gear showing part number. If some one knows how to post pictures I would send that photo to your email account. and ask you to post it. I also believe Denny Grahaam was dealing with a rear gear set with a 4.10 set up. I do not know if or how that one turned out. A review of his past posts may reveal that information. Maybe he will pop in here with info.Good Luck and poke me with a sharp stick in a few days for picture info I have
Jerry

Here's a big thread on the Pirate 4x4 board on the Eaton rears. http://www.pirate4x4.com/forum/chevy/771317-eaton-h072.html

A '69 and a '52 should both be the HO-72, and should directly interchange if they are. (At some later point a Dana rear was an option IIRC, but it won't look anything like the Eaton)

As with the thread on the pirate board, I don't think the 4.10 gears are hard to find at all. Most of the later trucks seem to have them.

You would think the 4.10s were common! Not so much for the HO72....I may hook up with another bolter who is willing to swap ring & pinions. Thanks JB!

When my truck is finished with its restoration, I'll let you know how it works. I was able to find a rear end from a 71 3/4 ton w/ 350 and auto transmission. Bought the whole rear end, took it home, and popped out the third member. It was a 4.10. I gave $250 for it. The guy who ran the junkyard specialized in 68-72 chevys. He's ran it for years. He was surprised by the concept.

They do exist, but as it was said before, they won't jump out of the weeds at you. You will have to hunt for them. Watch craigslist for parts trucks.

Large, I don't mean to hijack your thread, but my question fits nicely with this discussion:

My '59 has the dually HO72 with 5.17 gears. I want to swap to 4.57 gears and have located a 1958 3800 with single rear wheels. Unfortunately, it is parked so as to be VERY difficult to access the rear end (I will need to use a front-end loader to lift the truck). So, before going to all this trouble, I'm hoping someone here knows if it is likely to have 4.57 gears, or did all 3800s come with 5.17 gears?

Oldbolter....

Not sure of '58-'59, but in '49 the 3800's are listed as having the 5.14:1 (which is what I have). The 3600 is listed as having the 5.17 & 4.57. The 3100's have the 3.73 or 4.11.

When the cover is off....Look on the ring gear for the stamping numbers. Mine says "GM...... 7-36.." The 7-36 means 7 splines for the pinion and 36 for the ring gear. Divide 36 by 7 = 5.14:1

Update: I managed to hook up with another Bolter and am swapping my 5.14's for his 4.10's. I sure hope it is easier putting them back in!

Anything is better than a 5.17 but I have a 3.73 on 17 inch rims and a 700R4 transmission.

Result, 70 mph at 2,000 rpm using small block 350 power. I could not be happier.

"Well isn't that special?" Lol

For those that don't get the reference.

Gents, the elusive 4:11 is actually a 4:10 found in those 3/4 ton automatics through 72. Check out this website:

http://www.math-prof.com/Auto/Differential.aspx://www.math-prof.com/Auto/Differential.aspx

You can calculate your velocity knowing your wheel diameter, cruising RPM and final gear ratio,(usually 1:1 on an SM 420) It's a great site. Good Luck, Joe

Actually, there are both 4.11 and 4.10 Eaton gears. Earlier stuff is 9/37 4.11:1, and later stuff is 10/41 4.10:1. All SM420 are 1:1 in high gear, as are almost all older light truck/car transmissions. (The input shaft locks to the output shaft; no actual gears being used.)

BTW, this is another good site (http://f-body.org/gears/)
If you're using the tire diameter to figure speed, remember that you need the theoretical "loaded diameter" (loaded radius x2). Making a mark on the tire and pavement and rolling it (while it's on the truck) is an easy way to get the "loaded circumference". Then divide the 63,360" in a mile by that, and you have your revolutions per mile figure.

Here's some of my own crap, FWIW:

Engine RPM x 60 / (final drive reduction x tire revolutions per mile) = MPH

MPH x (tire revolutions per mile x final drive ratio) / 60 = RPM

Also; RPM = (mph x trans ratio x gear ratio x 336 ) / effective tire diameter (loaded diameter)

235/85r16 MT @ 645RPM x 4.1 = 2,645 /60= 44RPM @ 1MPH
80@3,525
75@3,300
70@3,075
65@2,875
60@2,650
55@2,425
50@2,200
45@2,000
40@1,775
35@1,550
30@1,325

Thanks Sub, Can you tell us where those 4.10 Eaton gear sets can be found? I thought they existed but in what vehicles and years are they And are they a "Bolt In" swap like the 1967 thru 1972 Chevy 3/4 ton with auto trans. and a few other applications with the 4:11 gear sets. Thanks, Jerry

The 4.10 gears were what the 68-72 trucks had; IIRC the 4.10's in my '63 dually had 1972 stamped on them. The 4.11's were just an earlier version with a different gear tooth count; 9 pinion teeth and 37 ring gear teeth, where the later 4.10's were 10/41. I just thought I'd note that there were actually both 4.10's and 4.11's made for the Eaton rears.

AFAIK, the 4.11's were just a 63-67 3/4 ton thing. The GM docs from the Heritage Center site show them as an option through those years, with earlier stuff having no mention of them, and later stuff all being 4.10. In '68 they also show 4.57 becoming the standard ratio for one ton trucks, with the 4.10's being an option. (Prior years had 5.14 as standard, with 4.57 the only option.)

BTW, it's a neat site if anyone here hasn't seen it before:

http://www.gmheritagecenter.com/gm-heritage-archive/vehicle-information-kits.html

This should be Invaluable to those guys looking for one of these gearsets to "Jump out of nowhere" into your shopping cart. It will still take a little effort! Good Luck, You will NOT REGRET.
Jerry

Make sure to get the front bearing retainer when pulling a later 3rd member. My understanding is that they're different and needed to adapt the taller gearsets to the older axle housings.

I found a 4-10 diff out of a 69 chev van, I'm having the owner confirm some #s that were provided on here if it is correct 75.00 seems like a deal!

NOSbeast,
I don't understand your comment about the front bearing retainer.

One reason the 4.10/4.11 gears are scarce is the fact that a lot of us dirt track racers in the late 1970's scavenged them up to bolt into the 3/4 ton Chevy rear axles that were popular race options back then. The gears and axles were rugged enough to handle the power of a tight-winding small block Chevy engine making 500+ HP at 7,500 RPM and the rough surface of the dirt track. The earlier "full floater" Ford 3/4 ton rear ends from the 1940's got so scarce that a newer axle was needed and the Chevy axles were fairly common and not too expensive. A Muncie 4 speed with a 1.88:1 second gear working with a 4.10 rear end gear gave us a final drive ratio of 7.70:1, just right for coming off the turn at 3,000 RPM and winding up to 7,000+ down the straightaway. Do that twice a lap for 50 or 100 laps, and gears didn't last very long. We went through a BUNCH of ring and pinion sets!
Jerry

Just a thought, as I've done a few internet searches for these coveted 4.10/4.11 gears I came across a few references on 4x4 forums. A couple of posts led me to believe some are interested in getting the lower geared sets for their rock crawlers? Has anyone ever conducted a trade, your lower for their higher?

I once traded my 5.14 gears out of my one ton straight up for a 4.10 gear set. It was through the classified ads on pirate4x4.com
I've had several 4.10 sets over the years, a couple came from 3/4 ton automatic trucks, also pulled a couple from one ton trucks. It helps if you have a list of 4.10 axle codes so you can identify what you have. There is a stamped code on the axle center section.

I also once traded two 5.14's to someone in the New England states for one 4.11 gear set. We each paid the freight on what we received. I was happy, he was happy. His newly acquired 5.14's were going into Rock Crawler jeeps as I recall. This is why in some previous reply in a forum I mentioned possible finds in the Jeeps. Jerry

truckernix asked: I don't understand your comment about the front bearing retainer.
If you don't change out the entire third member and only get a later ring and pinion set to install in an older third member the front bearing retainer wont work on the new pinion apparently. I'll check the set i bought and see what is different about the retainer once my truck is back from the body shop.