Differential gearing by counting

[Hedgehog]

So, there is an axle, I do not have it to work with, the owner is long distance. He counted 1.7 turns of the yoke for 1 turn of the hub. The math should be easy, but hey I know my limitations. He thinks it's a 3.42:1, but would be an odd ratio. I think it must be a 3.54 or a 3.31 can anyone help me out here?

 

[Hedgehog]

Okay I think I've got it. essentially with one wheel locked it will take two turns of the hub to make one evolution. Or 1.7x2=3.4:1

So 1.77 = 3.54 he could be off 0.07 in his guess at the number of turns or it could be 1.655 or off by 0.045 for 3.31:1

Both off by ~0.05 turn .... Could be either one

 

[shum8]

Okay I think I've got it. essentially with one wheel locked it will take two turns of the hub to make one evolution. Or 1.7x2=3.4:1

So 1.77 = 3.54 he could be off 0.07 in his guess at the number of turns or it could be 1.655 or off by 0.045 for 3.31:1

Both off by ~0.05 turn .... Could be either one

My coffee hasn’t kicked in enough yet for this...... any chance he’d pull the cover and count ring and pinion teeth?

 

[Peanut Butter]

Are we talking about the AMC20 here? If so have him look for the stamp on the passenger's side of the pumpkin for a letter. Here are the codes:
Narrow Track AMC20 Code Gear Ratio Diff Type
AA 2.73 Open
DD 2.73 Trac-Lok
BB 3.31 Open
CC 3.31 Trac-Lok
A 3.54 Open N 3.54
Trac-Lok GG 3.73
Open Q 3.73 Trac-Lok
L 4.10 Open
M 4.10 Trac-Lok

Wide Track AMC20 Code Gear Ratio Diff Type
D 2.73 Open
DD 2.73 Trac-Lok
B 3.31 Open
BB 3.31 Trac-Lok
A 3.54 Open
AA 3.54 Trac-Lok
H 3.73 Open
HH 3.73 Trac-Lok
C 4.10 Open
CC 4.10 Trac-Lok
Not 100% fool proof way of telling, but might take the error factor out of the equation.

 

[Hedgehog]

That is in the works for today. Not just to get the tooth count. but to see what is inside. A big mess can easily hide inside a differential cover.

This is something I frequent ponder in threads like this. Almost always folks suggest counting the teeth, but I haven't seen a ring gear that doesn't have the tooth count stamped prominently on it. Are thee ring gears without this seemingly basic information right there for everyone to see? The birth date, serial number and tooth count should be on the gear. I seriously doubt it has ever been stamped wrong.

The sad part is:
1 - He doesn't know what he has, it was loaded in his vehicle when he bought it, he thought it was an old two piece axle shaft Dana 44 Willys Wagon rear axle, when in fact it is a newer one piece Dana 44 Scout II axle. The Scout axle has many plusses, stronger, better brakes, better gearing.

2 - I already paid for a Scout axle. On the outside the axle looks good and clean. On the inside it's a mess, rust, the wrong gearing 3.09:1, the shims are rusted out on the pinion. It will cost less money to buy this clean, painted, properly geared, smooth and free spinning axle than it would cost to repair the old one. Essentially $250 wasted.

PB - Valuable information. Unfortunately no its a completely different animal. From the measurements I've had him take it is a rear Scout II Dana 44 . Its for a Willys Wagon project. Unfortunately he is in Flagstaff, a couple hundred miles north of here so it's a long distance conversation.

 

[shum8]

Highly doubtful gears are incorrectly marked, but I have found it’s much easier to get people to count teeth than rely on them being able to find the marking, read it, and reliably forward the info. They may be able to take a few pics, but I have found counting to be the easiest route for most folks.......


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[Lumpy Grits]

Can he send pictures?
Have him do a tooth count of the R&P.
The tooth count might already be marked on the outside of the ring gear.
LG

 

[Hedgehog]

Good point, I will have him take some pictures. I think he's fairly competent though. He was able to properly count turns and come up with a fairly close number to what the gearing more than likely is. I can read numbers on a ring gear, but had to research how to come up with the gearing by turning the yoke and hub revolutions.

Hello Lumpy, good to see you this morning. We are covering that very same ground.

 

[shum8]

Maybe it’s just me, but I never underestimate people’s ability to screw up seemingly simple stuff. Heck, I can do it if I give it a bit of a try


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[Hedgehog]

He just sent some pictures, the guts look nice and clean. No pictures of the numbers on the gear, but he is willing to give me anything I need so the numbers and pictures are probably on their way.

Unfortunately it's an open differential with nothing special in there. Darn, I was hoping for at least some sort of Limited slip. Can't win'em all.

 

[Hedgehog]

Well darn it! It's a 3.31. I have to praise the fellow, he did all he could to help with this, but the gearing isn't what I'm looking for. So, the chain reaction would be to get new gears and upgrade the carrier to an Eaton torsion locker. This would be what would need to be done to upgrade the axle I already have. Well. at least the axle I have wasn't a total waste of money.

 

[Lumpy Grits]

You could go with a Power Lock LSD. About the very best 'clutch-type' LSD ever made.
LG

 

[Hedgehog]

Lumpy - We have talked about this before. I really don't like the clutch driven Limited Slips, but have heard great things from those that have Eaton (Detroit Locker Fame) torsion lockers. They don't use clutches, don't wear out and are very solid. I put one in the front of my CJ5 and have been VERY impressed with it. I haven't heard any negatives about these lockers, except that some folks have blown them up, but supposedly Eaton worked out those problems. I absolutely don't want a clutch driven carrier, but I don't want or likely need a true locker for the Wagon.