The Stovebolt Site Forums The Shop Area Engine Shop Rear replacement

To everyone who has seen this question before from 4 million folks, I appologize pro-foosely!

That said, my '53 pickup has a rear from Lord only knows what. I could pull a light standard out of 20" concrete in first, but can't drive more than 30 feet. I also want to get rid of the Huck brakes hooked up to it. SO, what kind of rear would make my super 235 engine and trans happy? I have four-speed, and would like to make it just a bit more highway-worthy.

Thanks!!!!

Shmoo-

There are dozens of thorough and thoughtful threads on this topic on this forum. Check out the 'search' button at the top right of the forum home page. There are also tecnical articles on the transmission upgrade.

Basically they'll tell you that your problem isn't necessarily the rear differential, its the gear ratio in your transmission and rear differential. So, you've got some choices, improve the ratio at the rear diff or improve it in the tranny.

First option: Change the ring and pinion gears in your existing axel to something a little more friendly to modern speeds. I think Patrick Dykes of Patrick's Trucks sells the ring and pinion plus the kit to install it (shims, bearings, bushings, gaskets...) All you'll need on top of that is a tools. There are several other vendors who sell the stuff, but it lately they've all been on back order. Total cost, probably between 1,000+ (parts are $600+)

Second option: Get a rear differential with the gear ratio you'd like to have AND also replace the torque tube with a driveshaft.

Third option: Do something about your transmission to get better gear ratios there. There are bolt in kits to swap your existing SM420 to a Saginaw 4-speed, which has a much more useable gear ratio. To use the Saginaw and keep your torque=tube you need the rear housing off a 3 speed, a shifter (the saginw is NOT a toploader like the SM-420), and the Saginaw itself, a very common tranny.

Fourth option: A combination of both- Upgrade your transmission to a modern 5-speed and replace the rear differential and drive shaft. I paid $100 for a rear differential at a junk yard and spent $200 going through the brakes and differential. The drive shaft cost me $25 and I spent $100 on new u-joints, balance, etc... The T-5 tranny cost me $100 and I'll probably spend another $150 on a 'short thow shifter' for it.

The SM420 you've got is probably 7:1 in first gear, combine that with 4.11:1 in the rear end and you turn the engine a lot to get the tires to go around once, and max out your speed in that gear pretty quick. That was great for pulling stumps but for driving in todays traffic...

My t-5's first gear is 3.76, combined with a rear diff ratio of 3.72:1 I'll be going 30 in first before I have to shift and in overdrive will be crusing at 75 at the start of my engine's powerband with plenty throttle left to pass cars or speed up. Plus, I'll get much better gas milage.

However late, I wanted to say thanks for insight into the rear issue. Lots of valuable information. Gonna keep my eye out for the right replacement when the time comes; I can only pull so many stumps out around here.

i'm tring to find info about changing huck brakes to 'self energising'. i found a thread on this site about using 54's backing plates. i haven,t tried it as finding old parts around here is dificult.

Is this truck a 1/2 ton or 3/4 or 1 ton.

go to SEARCH @ the top area (right) of this page and type in rear end
you will get SOOOOO much help your head will spin

SCHMOO, i put in a nova rearend the size is right and they are many available. be sure and check the gear ratio, mine is a 2.73 which suits me fine. you can go to www.randysringandpinion and play around with the calculator on his site and figure out the tire size and the gear ratio that best suits your needs.

It is a half-ton, with a rear that we cannot identify. That's the big problem.

shmoo, you do know 1st gear is just for hauling a load or creeping?

for around town driving, treat your 4 speed like a 3 speed by only using 2,3,4.

i would make it highway speed stop friendly before you make it highway speed driving friendly.

how about describing the rear to us or even better a picture. how do you know it has huck brakes? who would have put an earlier rear end in a 53 half ton? since it came out of who knows what you, are saying it is not stock?

Thanks for the great questions. Yeah, I do know about the use of first gear; drove a 1946 Mack Firetruck for several years that acted just like this guy.
I know it has Huck brakes because of the "Brake Institute" specialist that provided me parts when I first rehabed the rear brakes. We do seem to have some difficulties figuring out why anyone would put an older rear in a '53, but it does work and is very clean (we had it open to replace the gasket--that we made.)
The problem with the emergency brake has been resolved--we put in a hydraulic brake, and, as you would believe, the install kit had a bad engaging switch. But, now I do not have to worry about leaving a chock at the side of the road.
The brake system works well now, but there will come a time when the rear must go and take its brakes with it. I will let all the bolters know that it will be available! :-)
Thanks for your help.
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