The Stovebolt Site Forums The Shop Area The HiPo Shop '42 panel truck differential replacement (restomod)

Hello all!
I'm in the process of a resto mod on a 42' Panel truck. I have the original axle with what I have accessed to be a 4.56 ratio. That won't cut it for highway speeds. I've looked into a 3.55 rebuild but it may be beyond my abilities and darn near the price of a remanned diff with a warranty from Powertrain products.
Axle measures 60.25" from hub to hub. Anybody know of a make and model that would fit well under this truck?

What bolt pattern do you have on the wheels and what is your use case? The main use case question is if you need an industrial strength axle or if a lighter duty one would do the job.

42' panel truck,

You haven't given us enough to go on to really give you the best answers possible. According to this resource document 1942 Chevrolet Truck Data, there were at least 4 different sized "panel trucks" offered in '42.

Can you let us know which one you have??? A rough guess based on your current rear axle ratio being "4.56" would seem to indicate you have a 3/4 Ton on first look (but there are actually 3 different 3/4 tons including the standard 3/4, 3/4 Heavy Duty Equipment and a 3/4 "Special").

Please come back and provide more info on what truck you actually have so folks can better try and answer your question.

Dan

What do you mean by "highway speeds"?. I have a '41 3/4 ton with the factory 4.56 rear gear. I swapped in a T-5 transmission with overdrive 5th and regularly do 55-60 on the highway with no problem. I don't drive on the interstate. Probably easier to swap the transmission than the rear.

I'm new to all this. That document link makes it simple. I have a 115" Wheel base. According to that it's the 1/2 ton "light delivery" model.
6 lug wheels although if I am to replace with a different differential, I'd like to go 5 lug to match the Mustang 2 kit I'm putting on the front.

Take a look at the 93-98 I6 grand cherokee rear axles. Disk brakes, 5x4.5 bolt pattern, 60" WMS/WMS.

Multiple ratios are available with and without posi.

I will be running a 700 R4. I would like to cruise at 70 without running high RPM. According to the chart I have, with a 26" tire and a 4.56 at 70 MPH with a .7 overdrive I'd be running at 2,900 RPM. That sounds a little to high to me. Not terrible just seams a touch high. Again, I'm new to this
Thoughts?

26" tires are really small. What size are you planning to run?

What engine are you looking at putting in? The power band of your engine will drive what rpm you want to cruise at.

What are the benefits and draw backs of Posi VS without Posi?

The ride height will drop 4" with the mustang 2 front. I'm concerned a tall tire won't clear
Running a 250 I6 mated to a 700R4

As far as posi: https://www.speedwaymotors.com/the-toolbox/what-is-positraction-and-do-you-need-it/53704

Hot rodders generally consider posi a desireable thing. Is it really necessary? Up to you.

Is your 4" drop frame to ground? Frame to body?

You might consider looking through some of Coilover's old posts to see if he has a recommended tire size. His shop does a lot of mustang 2 conversions.

Frame to ground.
Thanks

Lugnutz has a good writeup on picking a rear end ratio. For the I6, you might want to be revving pretty high because you need to keep it in its power band. These trucks are bricks, so you need a decent amount of power to make them cruise at 70.

If you are lowering the frame to the ground, not the body to the frame, then you won't need smaller tires. The max tire size is a function of frame to body spacing.

Edit to clarify this comment: if you are keeping the same upper suspension stops, that will keep the tires at the same place at maximum travel.

You might consider putting the M2 front end on, then seeing what size tires you like with it. Are you planning to run the same size front and rear? Doing staggered sizes with the M2 front end is fairly typical.

It's been suggested to move this to HiPo forum. I guess the "restomod" should have been our first clue. You'll get some good input there.

Here is where Lugnutz has the recommended overdrive/axle ratios by engine (bullet point 4).

https://lugnutz65chevystepside.weebly.com/thinking-about-installing-a-t5-read-this-first.html

I believe he said he is running 28"-ish tires, but I can't find that post at the moment.

Do you have an adapter for the 700R4 already? What are you planning to do for the TV cable?

I'm running a 12 bolt posi in my 1946 1/2 ton panel. It's out of a 1967-69 Camaro/Firebird. Bolts directly on to the stock leaf springs, with lots of room for wide wheels and tires. These 12 bolts have become quite pricy, but the 10 bolts of the same genre can often be found for reasonable prices, and should hold up fine behind a 6 cyl.

Great stuff. Thanks.
With regards to the TV cable I haven't gotten that far yet. My neighbor sold me the trans. It's being rebuilt. He's giving me a lot of guidance. He's been an old school hot rodder for 50+ years. I'll pull him in when it comes time to install.
Thanks ironhead, I'll check those out

check out Bowtie Overdrives they have some good info on the lockup kit for those....