Rear end ratios

[Desotodav]

and some others...

 

[ggdad1951]

my rear diff had NO stamps...I understand your frustration, but most look to be 4.1.  Best to just to a rotation count.

[TrampSteer]

That last extra numbers look like a date. They all look like 4.1 IMO except for that one with just a triangle left on it (maybe a 4 also).

[Phil363]

I am still in the "very early" stages of breaking down my 52 Dodge B-3-B to the frame.  This thread and several others have me interested in going to a 3.73 diff from a '50 Plymouth in my truck as well. 

 

Just thinking it would be easier to acomplish with everything apart.

 

I attached my differential photo showing 4.1F .. no clue what the F means but the 4.1 mirrors what is on my chrysler build car for the axle ratio that was on the truck when sold originally.

[John-T-53]

_{Back in 2009 I brought up the same question and here's a reply I received from "DodgeB4YA" (Bob)...}

 

_{John,
You need to look for 1953 to 4 Plymouth rear end pumpkin-they use a 16 spline axle shaft which is what your 1953 B-4 1/2 ton has. Up to 52 they use 10 spline. You will have to swap the driveline yoke also. I say Plymouth because they are usually easiest to find. Dodge 1953 to 4 also will work as long as it's a 6 cyl. car-NO wagons or long wheel base cars. They use a bigger rear end (Pumpkin). On the bottom of the rear carrier is the ratio stamped on a 2" flat pad-need to clean it well to read for the ratio. The truck is the same.
Good luck, Bob}

 

_{I searched for a couple years and couldn't find any pumpkins out there. Maybe for 1952 and earlier years they are more plentiful. So I scrapped the idea and changed the tranny instead...}

Edited September 11, 2014 by John-T-53

[Desotodav]

Now I am just plain confused...

I chatted with a friend of mine who happened to have quite a few old MOPAR car diffs (8 & 1/4 inch Chrysler Royal) laying around, so he told me to come and take my pick. All going well so far... until I paid him a visit and inspected his diffs. I found a couple of them stamped 3.9 over 10... and then I spotted a few stamped 3.9 over 11. Could it be that the 3.9 over 11 (pictured) is actually a 3.54 ratio after one does the maths?... and that old mate in the diff factory got lazy thinking that rather than having to stamp a '.54' after the '3' that he'd just stamp an '11' rather than a '10' for the fraction number?... I'm sure hoping so as that might mean that I have a 3.54 diff rather than a 3.9 !!! I added some black ink to the numbers for the photos to make them easier to see.

Check out the fancy chrome one that I brought home also (pictured) which was just stamped '3.9'

Edited September 20, 2014 by Desotodav

[Young Ed]

The only way to know is pull the diffs and find the stamp on the ring gear or if thats missing count the teeth.

[Jeff Balazs]

Can't you just spin them and count the revolutions? It should be pretty easy to see the difference between a 3.5 and a 3.9. Might need to make a few reference marks but it should be doable.

Jeff

[Dodgeb4ya]

Look like 3.9's to me.

[Desotodav]

Thanks for the replies. The brakes are binding from sitting for too long so neither of the diffs stamped 3.9 over 11 will spin. I'll clean them up if I get time after the car show today and maybe pull the hubs. I suppose that 3.9 will be a little better than 4.1 if that is what they turn out to be.

[DJ194950]

Looking at my Hollander reprint for these years shows that any 49-52 Mopar 6 cyl.. motored vehicl should work. But, the exceptions are the 8 pass. cars and Suburbans(woody) only.

 

Now to find a 3.73 ratio.  Some 3.54 also out there - look for Chrysler 3rd. members. Common (standard) 3.73 ratio in 49-50 bus. cpes..

 

Your axles must be of the 10 spline type to work with these, but yours is supposedly a 10 spline stock.

 

If you pull one and it's a 16 spline axle, let me know. The interchange show other Mopar that use that. Mostly later models.

 

DJ

[DJ194950]

Desotodav,

 

If that 3-9 over 11 is on the ring gear the Hollander manuel says that it a 3.54 ratio, a 41-11 is a 3.73, 41-10 is 4.1, 43-10 is 4.3, 43-9 a 4.78.

 

Again the #,s quoted are on the Ring gear per book. Also used on the case?? Australian, and/ or export only??

 

DJ

[Desotodav]

Thanks for the replies gents.

I received confirmation today that the two diffs that I have which are stamped 3.9 over 11 are definitely 3.54 ratio. I must say that I consider it strange to see them stamped in that way rather than just plain old '3.54'. Needless to say that I am smiling like a kid with a new toy now knowing that I have 2 diffs with that ratio. I'll get them down to the diff shop soon for refurbishing.

[Dodgeb4ya]

Well I've junked at least 10-12  3.9's

Oh well live and learn.

[HanksB3B]

Thanks for the replies gents.

I received confirmation today that the two diffs that I have which are stamped 3.9 over 11 are definitely 3.54 ratio. I must say that I consider it strange to see them stamped in that way rather than just plain old '3.54'. Needless to say that I am smiling like a kid with a new toy now knowing that I have 2 diffs with that ratio. I'll get them down to the diff shop soon for refurbishing.

 

oooh,

 

Are they ten spline or 16 ?

 

Hank