No, the Step-down rear ends are hypoid, that is the pinion is set below the centre line of the crown wheel. Not sure if the whole unit would fit in the housing, but I'm sure the splines are the same. The drive shaft would be out of alignment.

Thanks Geoff,
That's the info I need ,, Do you know of any other make rear the will fit the '42 ?
Cal

None that I know of. Local member here in N.Z. fitted complete Holden rear end in his .37 T, but had to modify the wheel studs and spring pads. Gave him a ratio of around 3.5:1 width was similar. Drive shaft was at a greater angle and would occasionally scrape on the X member. Step-down rear ends are narrower. Chrysler models had same bolt pattern I believe, so there are options for complete replacements, but nothing that I know of that will just bolt into your housing.

I was thinking changing the whole assembly if there is one that would fit. I have access to a 1956 ford rear assembly. Haven't done the measuring yet
Biggest problem is that it is winter here, and we just got 20 inches of snow last week.

Thank you Geoff. Please accept my condolences on the loss of your son.

I have a 1953 Hornet with 308. The engine was replaced with a 308 from a later car (it has the 1/2" studs on the head, rather than the bolts). The engine is plenty torquey, so I've pondered replacing the diff with a lower ratio. I think the standard ratio was 3.08 or thereabouts. Are there any reasonable swaps to get into the 2.8 range?

Is your car an automatic?

Yes, dual range HM.

Check the rear first and make sure which ratio it is. It should be a dana44 rear end with 19 spline axles. Im not sure how high they (dana) went with their gear ratios. Also there are case sizes that work with different ratios. I think 3.90 and up "numbers and then down to around 3.00 the case works.

The Dana 44 is the same gears as a 70's/80's AMC Grand Cherokee/wrangler. We put a set of 2.72 gears in my brothers 54 Hollywood. New gears are no longer available, but a used set off of Ebay. I recommend getting a installation kit to do the job(new bearings and shims).

I installed a posi unit from a mid 60's ac cobra into a 52 dana rear.
Here is a decent how to video
https://www.youtube.com/watch?v=OurJHaiy6kI

Gents: Thanks for the info. I'm familiar with the Dana 44 diff, as my previous 1961 Studebaker Hawk had the "Twin Traction" Dana 44 rear too. I'm also seeing several other parts that are common to Studes and Hudsons. If I recall correctly, the Dana 44 in the Studes was also 19-spline.

I failed to mention it earlier, but part of my reason for considering a diff swap is to gain the positraction feature too. I wouldn't go to the cost and trouble of swapping the diff without getting positraction in the process.

Tom, thanks for the reference to putting a 2.72 into your brother's "54 Hollywood. That would be about the ratio I want. Did you replace only the gearset, or was it the whole carrier assembly? I assume that you kept the case/axle tubes because those are narrower than other cars. Was that a posi diff too?

I've done several flanged axle conversions on Studebakers with dana 44s. The Hudson axles and bearings are bigger and no one offers a conversion for it.

Just the gear set and re-shimming to set it up right.

Kerry and Tom, if I understand you correctly, that means that I can't get any old 44 positraction carrier and bolt it in. I would have to find a Hudson posi, then disassemble that, then put in the lower ratio gears, then shim everything for proper gear lash and engagement pattern, then put it all into my axle housing. And while I'm at it, I should replace bearings and clutches. That might be too much effort to make it worthwhile. Or I'll have to collect the parts over time before I do it.

But Kerry, you also said that you put a posi unit from a mid-60's AC Cobra into a 1952 Hudson--how did you do that? I assume the carrier with the posi clutches must use the same bearings as the non-posi unit, but you also said those bearings are different. I must be misunderstanding something.

Has anyone transplanted a complete rear axle out of newer car or light truck? I know it would require considerable work to narrow the rear axle to fit inside the skirts of the step-downs, but someone might have found a good way to do it. You could get a lighter rear axle assembly as a result, with rear disc brakes.