The Stovebolt Site Forums The Shop Area Engine Shop What rearend for better gear in a 1957 3100?

Hey guys, I have an original 1957 3100 with a 235 and 3 on the tree. Top speed is only about 50-55 and she's topped out. I want to change the rear out to be able to cruise at highway speeds. I believe the flange to flange is 62" (feel free to correct me if I am wrong). I have researched a ton of info on this and there are so many opinions its confusing. I would like to know what is the best swap out. It would be nice if this was a straight forward swap out. Any detailed info would be great because I am ready to get it done.
Thanks for any info in advanced.
Later

What is best depends on you and how you plan to use your truck. My opinion it is not necesary to change out the rear. Try a t5 5 speed transmission

Another option would be to swap for the factory optional 3 speed with the Borg-Warner overdrive, which would also keep the column shift in tact.

Putting a longer rear axle will make the truck go faster, but will also make the first 2 gears longer, the truck will be more sluggish in town, it may also end up taking a looooong time reaching that new top speed... Also, be careful, how long a gear ratio can the engine pull (enough torque?).
OK, now that you are a bit more confused, my recommendation would be to look into an overdrive trans, a modern 5-speed or original OD: this way, you have a fairly short 1st gear for getting the truck moving, and also a longer 5th speed to go faster.
On a lighter side, you realize that if your truck goes faster, it will be more noisy... Do you really want to be noisier? ;-)

Then when it goes faster you need better brakes to stop it, and better steering to control it, and the list goes on......
Fred

You have some real good sugestions here. Another one is to get a 3.38 rear end gear set from one of the specialty suppliers & change the gears in your rear end.

Thanks to each of you that responded. I will keep you posted on what I do.
later

A Dodge van rearend would fit just about perfectly. It is also 62 inches to flanges. A Ford van is 64 to the flanges. I'm not sure about the GM rears. The problem with the Mopar or Blue oval is the 5 1/2" bolt pattern. An S10 rear with a 3.42 gear is pretty easy to come by. It might fit the bill fairly well.

S-10 8.5" out of the ZR2 off-road packages would work and give you a 5 on 4.75 pattern if that is what you are looking for, however I would swap out the trans first and go that route.

alan,
for whats its worth, i have a rear out of a 1980 full size chevy 1/2 ton truck.
not sure what the measurement is from plate to plate, but it fits nice and on the original leafs.

i have 15x7 wheels with 4.5 back spacing with 225-70-15 tires.
but that full size rear is 5 lug with 5 inch bolt pattern.

the gear ratio is somewhere around 2:80-1, and with my 350 / th350 at 60-65mph i am right at 2200rpm.

if you need measurements, let me know and i will get them for you.
leonard

I have a 1957 3200, and I used to drive 45-50mph and the engine was screaming with high rpm's. I simply changed my ring and pinion gear inside the stock 4.11 to a better gear of now 3.38
Yukon gears out in California has the ring and pinion set for about $400. I purchased them through classicparts.com
GOOD LUCK - J.R. in VA

I must have had a different model 56 3100 with a 235 and a granny box trans, than everyone is talking about. I drove it on the freeway all the time here in SoCal. It was never topped out at 50-55 MPH. I have had many 3100s over the years and never had any trouble keeping up with the traffic. These trucks all had 3.9 gears and stock 235s.