The Stovebolt Site Forums The Parking Lot Big Bolts Rear axle questions - which one do I have?

I have a 1950 4100 with a 235 and a 4-speed and what I believe is an Eaton H072 axle, however I am not sure. What axles were in use in these trucks and what are the available gear ratios? Mine is 6.17, I checked it. I have located a 2-speed axle from a heavier 6000 series truck that appears to be very similar. I am wondering will the 2-speed third member out of that axle bolt into my axle housing and work.

Upon further investigation it looks like my truck probably has an H110. Doesn't appear to be a whole lot of good, organized information about these axles online.

unless you are hauling a lot of weight or want the lower rear ratio for pulling power, I would stay with the 6.17 gears. The 2-speed is 6.40 and 8.75. That is nice for pulling a lot of weight because you have more gears but, it has a slower top end. My 1958 6400 spins about 3500-4000 going down the freeway. (depending on how fast I push it), 34-3500 I am getting passed by everyone, 3600-3700 I am keeping up with traffic. if I want to get in front of a slower moving vehicle, I am pushing the 4000 mark.

The 2-speeds were 6.10 and 8.10 from what I am reading. However I guess that depends on which axle you have. There were several different manufacturers. I'm just having a hard time nailing down model numbers and application charts.

I don't have a good reason for wanting one other than I just want one - and that's all I need. lol

wanting a 2-speed is plenty of reason to switch!

I think it also depends on year. Looking again, the 55.2-59 shows 2 ratios, 5.83/7.95 and 6.40/8.72 earlier probably uses a different rear.

Rookie here and don't mean to steal your post but how do I tell what gear ratio I have and what axle? I have a 68 2 ton with a 5 speed tranny with th 2 speed rear axle. And side open in high does about 50 and sounds like it's gonna fly apart

Sometimes there are numbers stamped on the housing out near the spring hangar. To find ratio, jack up one wheel, count driveshaft vs wheel revs., make sure you know hi or low.

Ed

There's a couple ways to tell. You can located ID info on the axle and research it and find out - or you can open it up and count gear teeth (divide the number of teeth on the ring gear by the number of teeth on the pinion) Or you can jack it up and turn the axle one revolution and count how many revs the driveshaft makes. This last method can be complicated if you don't have a posi unit in the diff. What I usually do is jack it up and block one wheel - then turn the other wheel TWO revolutions and count how many turns on the driveshaft. The result will be the same because of the gear reduction through the differential. I'd say your truck probably has at least a 6:1 final in high range.

Yes, the earlier ones did use lower ratios because of the smaller, less powerful engines. The 261 was available by 1955 so the final drive ratios got a little steeper.

Still waiting on someone to provide some ID data on these axles. I haven't been able to find anything definitive yet.

I went through this with my 52. Since you have determined that you have a 6.17 single speed H110 (standard for the 1.5 tons), about the only easy option is the optional 5.43 ring and pinion set. Much is said here about rarity but I found a set( most recent part# 2352908) with a few phone calls.The set was made by Cobra Gears. I had it installed with all new bearings and seals and can say that it makes a big difference for me. With 7.5x20 tires/235 engine/SM420 trans it does 50-55 without screaming.

Thanks for that post Andy. How did you go about finding a set? Were they used or new?

I googled Cobra Gears and all I got was Ford Cobra's and Mustang stuff. Jeffrey

Me too, however if you also include that part number he listed there are few results on down the list that are pertinent.

I called a truck parts dealer that I plucked off of Google. He found a set from one of his suppliers and had it shipped direct to me. The rebuilder threw my paperwork away (which I left in the parts box)and I cant recall who the dealer is. This is a new set that was on a shelf. I don't think they are still available from Cobra. This ring/pinion set was used in military 4x4s as the front differential, by offroad truck builders,and in some Ag equipment, so there must be more out there. I'll post more info if I find it.

So anyway, I recently located a brand new set of 5.43's for this truck. I reckon I am going to purchase them. I figure those, together with a fresh 261 in this truck will make it a whole hell of a lot more useful to me. Should be able to attain 55mph with it without any trouble and will still be able to pull heavy stuff.

Does anyone know what the ring and pinion ratio on a 2 speed is before the double reduction. I know my two final ratios are 8.10 low and 6.13 high but I am wondering if that can be changed by changing the ring and pinion in the 2 speed.

I believe it's 6.13 Kenn. It's not plausible that there would be double reduction in both ranges. One range - the primary range - is likely just single reduction. Otherwise there would be too much heat generated all the time in the gearbox and it just wouldn't be reliable over the long term.

And I think you have it wrong - high is 6.10 and low is 8.13.

My shop manual shoes the ring and pinion as the first reduction and then either high or low speed second reduction. The manual also shoes the ratios as low 8.10 and high 6.13. I went out to the cold shop and 8.10 and 6.13 are stamped on my case. The manual does not show what the ratio is for the first reduction (ring and pinion) and I believe the 8.10 and 6.13 are a combination of the first and second reduction.

I've rebuilt a bunch of 2 speed rear axles, and the higher ratio is always the ring & pinion reduction. The lower ratio is obtained by engaging a planetary gearset built into the carrier which slows down the axles after the ring & pinion does its thing.
Jerry

Have a look at the shop manual for the two speed axle in question, a double reduction unit as mentioned and explained by Kenn.
http://chevy.oldcarmanualproject.com/shop/1948_51truck/51ctsm0428.htm

The ring and pinion come first, then it uses either of two final reduction gear sets. Nice picture in that link.
No planetary gears (as in later 2 speeds), and always double reduction.

Would be interesting to know then what the primary reduction ratio is on one of these axles and whether or not that ratio could be changed - effectively changing both secondary reduction ratios. I never had one of these old axles apart before and did not that they worked in this manner.

When you get one apart, or if you can research in the parts book might show tooth count so you can do the math.
Being that they didn't offer alternate ratios I'd guess that no other ratios are available even today. Unless perhaps that ring and pinion is borrowed from one of the smaller trucks that did have alternate ratios available, and perhaps they fit or can be made to fit in the double reduction housing.

Some hunting in the parts book might answer some of those questions.
Picture
http://chevy.oldcarmanualproject.com/parts/1929_54/334.htm
Page with ring pinion, section 5.529
http://chevy.oldcarmanualproject.com/parts/1929_54/353.htm

Hard to read that scan but might be 23:8 teeth, or 2.875:1 ratio. In which case, being rather fast for a single ratio rear (if that's the hope for a donor) unlikely you find anything faster that fits, pretty sure nothing faster for GM from that time period.

Man, that's a lotta torque transfer going on in that rear. Surely it can't be very efficient. I reckon that's why they don't still make them like that today.

I still can't believe I was able to buy a brand new rare ratio set of gears for an axle that has been out of production for more than 40 years.

Have you checked, do the gears fit?

The single speed, double reduction units that the military trucks use is a complex, very inefficient setup, but it's similar to what Mack used for a long time on their big rigs. The monster truck guys love those military surplus axles, also some of the truck/tractor pullers.
Jerry

Not yet, I dont have them yet. Should be here Monday or Tuesday.

I just wonder if they will or if some confusion and they're for something else.
Let's hope they fit. If so please share some part numbers.

I made sure I could return them before I bought them. They cost me $395.

I bought them from Inter-Continental Gear & Brake in Grand Prairie, TX. They're made by Cobra Gear. The application is Eaton H110.

My gears came today, they are beautiful! And clearly 'new production'. They have modern stamped or etched numbers on them. Look to be done with a laser possibly, so they are definitely not an NOS item.

Get those shiny metal parts moving. Let us know how it goes. I got my truck to drive for the fun of it, and the new gears did help.

I can almost hear the RPM's droppin already.

Yep, I'm excited. Now the only thing I am worried about is whether or not I am going to be able to locate a replacement pinion seal. I'll make the other gaskets, no problem. However I believe I recall reading somewhere that the seal for the pinion on these axles is no longer in production. Seems to me that I recall some folks ended up having to make a bushing to facilitate the use of a different seal with a smaller OD.

Try Timken 411330N for the seal (Replacement for GM 3653618/719373/3879527- superseded part numbers)and National 5M89 for the felt. Both are available from R*ck A*to for about 15 bucks for the pair. *(I'm fairly sure of it, but will not be held financially responsible for this info.)

Thanks for that info Andy - I looked at the spec for the lip seal on RA and it looks like it's pretty close! I haven't got mine apart yet so I haven't measured it yet.

I wonder what the odds are of finding gaskets for the hogs head?

Yes! I found the gaskets on RA also - the listing is for a '69 C30 pickup. The H110 was available in that chassis. The FelPro pn is FEL-PRO RDS5049


So I ordered all the parts - a new pinion seal and the felt, gaskets for the center section and two new axle seals. All of it from Rock Auto for $32 delivered. Great score! Thanks again Andy.

Started installing these gears today, they fit just fine - or at least they will fit just as soon as I can get my hands on a thin wall 1 5/8" socket to get the pinion nut off with. Already got the diff and the housing cleaned up and reassembled with the new ring gear. The chunk is unbelievably heavy and is almost unmanagable when its fully assembled. I bet it weighs 175lbs.

Got this all back together. Just gotta install the chunk in the axle housing. I ended up having to make a socket to get the pinion nut off with. There isn't one made that is thin enough. I had to turn one down on a lathe to get it to fit in the bore.

Not sure how I'm going to get this heavy bastard re-installed. I may drill through one of the ribs and put a small clevis on it and use my hoist.

Just use a strap/sling around it.

I would, but it's not possible to rig to it in its center of gravity because of the way it is made. Even if I put a clevis on it it won't be at the CG - at least with the clevis the rigging point would be secure and I could work with it. I'm planning to reinstall it tonight after I get home from work. I'm already working on my list of new and especially offensive cuss words and phrases to dispel the first time I gom up the gasket while I'm struggling with getting it lined up to the bolt holes. I'm sure it would be entertaining for bystanders.