I put an early 70’s mustang rear in my46 pickup. It measured the same backing plate to backing plate as the Hudson. I had to angle the spring mounts because the Hudson springs are angled. Had to get new bolts from a spring shop because the mustang has larger axle tubes. Same wheel pattern as Hudson, and had to have drive shaft shortened because I also have a 50 pacemaker O/D in it. The ford rears have a tag on them with the ratio. I used a 2.78, but I’m going to change it to a 3;55. I’m also running a Hudson straight 8.

I think it cost me about $30 for the 4 new U-bolts, lock washers and nuts. It took them about 10 minutes to bend up the u-bolts.
I took one of the original u-bolts with me for length and a mustang u-bolt for size..

Depends on what engine you have and where you are driving it. If you have the 3x5 then you have about 101 HP, not as much as an eight, so if you put highway gears on it, you may have trouble with the hills. If your area is hilly.

Also, what is your current rearend ratio? Didn't the trucks normally have a 4-5/9 rear, or worse? 4.11's were standard for passenger cars and once in awhile I can still find NOS ones at reasonable prices, so you could start out by simply changing your rearend gears.

Overdrive is always a "plus" because you can change ratios as you drive. If you only change the rear axle, you're stuck with that gear.

I have the 3x5 engine with the standard 4.1 rear and an overdrive, and can cruise at 60-65 (though I tend to hold it to 60 to spare the engine). The normal "factory" rearend gearing for OD, I think, was 4-5/9, but the 4.11 gets me down the road faster, and if I hit a steep hill I can always kick down to third gear.

Then too, as Ed indicates, a more modern rear axle (with a highway ratio) is a fairly easy installation and it means the parts will be easier to find if something breaks. Mustangs are a popular interchange for Hudsons, and Gus Souza (in the Chicago area) has actually prepared a whole instruction sheet on how to put a MoPar rear from the 60's - '70's into a Hudson. And with a complete axle, you can fairly easily unbolt and remove it and put back the Hudson axle, should you want to make the truck original again.

So, you have a number of choices and combinations of fixes.

Thank you. You've given me quite a bit to think about. I've been told by Aaron that the serial number on my engine indicates a 1946 3x5. I don't know what the gear ratio of my differential is. I live in NE Pennsylvania, so it is quite hilly terrain. It sounds like O/D may be a better solution for me. I really appreciate your taking the time to give me some great advice.

Thanks Ed. Appreciate your detailed response. Not sure which way I'm will go yet.

Jon, I think I will go with the OD route. Can you point me in the right direction on where to purchase the right OD kit?

There's no kit. Just look for a Hudson overdrive transmission, they're not hard to find. I'm a "pre-war guy" so not able to advise which year of transmission will fit your truck, but in general it would be 1941 through (I think) 1952. At that point (until the end of StepDown production) Borg-Warner started making Hudson's transmissions and they use a slightly different linkage, though in the end I think they can be made to fit the earlier ones. Of course Borg-Warner always made the overdrive unit, Hudson simply bought it from them and installed it on their own transmission (which uses the single-lever-plus-cable linkage) up to the changeover in 1952.

Someone more knowledgeable than I will jump into the discussion at this point, and give you a much more detailed answer. As to where to shop for an OD transmission: look in the WTN, on either of the Hudson forums, on the Hudson Facebook page, in Hemmings and on Ebay, once you know exactly which year of transmission to buy. I believe the bellhousing would have to mate correctly to both the engine and transmission.

When you purchase the transmission be sure to take it to a reputable mechanic and have him check it out internally. Perhaps renew any bad parts, put in seals, install bearings if necessary. And check out the electrical parts. It's also a good time to check out the condition of the clutch and replace any parts in that. You certainly don't want to install the transmission only to have to remove it six months later because something broke.

These OD transmissions have been interchanged between Hudsons for decades, so just sit tight and someone will give you the complete information.

1940 Hudson Big Body rear end. What happens when you get some ones unfinished project. 1965 Chevy 396 going thru the X fame of the Hudson to a 1960's Mustang rear end. The fun we having making this work. We considering going back to stock but a engine in hand is easer then finding a Hudson engine in the weeds.