I'm looking at buying a 1930 model A and the owner (not the builder) says he thinks the rear end was out of a 1947-1948 Ford. I'll post a pic. My real concern is the availability of parts and am also curious what the gear ratio should be assuming it's stock. Anyone have any ideas?

 

Unless it's from a truck, it's not 47-48 Ford (passenger car). Those still had the banjo style and torque tube rear ends. I wouldn't worry too much about parts availability. As long as you have grease in them and don't abuse them, rear ends rarely fail. Bearings and seals can usually be found even for the most obscure of parts, and if that is some type of Ford, it wouldn't be that obscure. Worse case scenerio; it does grenade and you swap it out for an 8". No big deal.

 

Yea, he specifically said it was from a Ford Truck. He has no clue what the gear ratio is. I would really like to know because due to the age, I'm sure finding an assortment of gear ratios is not an option. My only concern is that it may have a steep enough gear that cruising rpm on the highway is too high with the lack of o/d. A problem that's easily solved but I would like to know what I'm getting into first.

 

Is it drivable? Can you take it for a cruise and see how it runs, and what rpms it runs on the highway? Unless there's an ID tag on it, you'd have to pull the back cover and count the ring and pinion teeth for an accurate assessment on ratio. Like I said before, for little money and effort, swapping the rear is no big deal, if you like everything else about the car. I wouldn't let that be a deal breaker. It does look like an old Ford truck diff, which means it's probably in the ball park of 4.11:1

 

see below.

 

Cool guys thanks for your help. I just want to make sure gear sets are available for it. the car doesn't have a tach or speedo installed. Owner says cruising rpm is around 3k. Changing gears is no big deal. I would like to avoid having to swap in another rear end due to the cost.

 

Looks like the F1 rear - Dana 41. Clean off the webbing on the lower right corner of the housing - you should see a cast-in 41. As far as I know there aren't gear swaps available. It's slightly different than the D44

Stock ratio was either 3.92 or 3.73 (early and later F1's) or the optional 4.27:1

edit: evening Havi!

 

Don't listen to me, but listen to Tim.

 

You could get an 8" out of a Maverick, Granada, or early Mustang for the same or less than a set of gears for a Dana 44. Cost really isn't a factor.

 

You probably don't have a DANA 60, but these photos from my 1956 F-250 will give you an idea of what to look for on the casing. The first photo is the whole unit from the rear. The second is the lower-left corner showing a metal tag with 41/9 stamped on it. As the fellas said, that's the gear ratio - in my case, 41 / 9 = 4.56:1. If you're lucky, you might find the original tag on yours, but they are often not reinstalled if someone does service on the unit and removes the rear cover. I don't see anything on the photo you posted to make me think you are going to be lucky. The third photo shows the lower-right corner with the model number cast in as Havi mentioned. Remember, this is a DANA 60 and you probably should see a 41 or 44.

If you don't have the gear ratio tag, there is an easy way to check the gearing. Block the front wheels and one rear wheel. Put the tranny in neutral and make sure the parking brake is off. Jack up the unblocked rear wheel and count the ratio of drive shaft revolutions to wheel revolutions as you rotate the wheel. Multiply that ratio by 2 to get the axle ratio. On mine, just a little over 6-3/4 revolutions of the drive shaft gives three complete revolution of the wheel. So 6.75 / 3 = 2.25 and multiplying by 2 gives 4.5, pretty close to the actual ratio of 4.56. If I had taken into account the fact that I got a little over 6.75 drive shaft revolutions I might have gotten something like 6.8 / 3 = 2.2667 x 2 = 4.53 which is even closer. The more revolutions you count the more accurate an axle ratio you can calculate.

If the axle is not on a vehicle just keep one wheel or hub from rotating with a clamp or bar and use the same process.

 

In theory, yes. However, the rearend would have to be the right width to start. Then fabricating the brackets for the suspension and shocks would add to the cost since I cannot do that myself. I'm sure that rearend would not be compatible with the current brakes on this car, I do not know that for sure so add to the cost a set of new drums/pads/wheel cylinders and probably wheel bearings. If I was going to go through that hassle I would just go with a 9 inch for slightly more money.

 

I found this chart:

Axle Identification Chart

Check out the pics of the D41 vs D44, the D41 looks much more round. I will ask the owner to verify the number on the casting since I have not yet had access to the car to inspect it myself.