The Stovebolt Site Forums The Shop Area Engine Shop gear change I want to know some personal experiences

Those that have changed gears, give me your opinion on the drivability like the rpm at 55 or maybe 65. I already read the tech thread on it. I just want to know from your personal experience. Thanks.

Spencer

What year? What gears?
More info, please.

I believe that he's talking about a '53 3100. I also think that he's talking about the gears in the axle. But I just guessed on the last part. I do know that he has a '53 3100.

Spencer,
I did an overdrive transmission swap in my 59. My rear axle was leaking so after the transmission I had the axle overhauled, and the gears changed from 3.90s to 3.38s. I should have kept the 3.90s as my truck has a flat spot around 2000 rpm. In short The 3.38 gears are almost to tall to use with the overdrive.

My truck before would do 65 mph at about 3150 RPM
with the overdrive it would do 65 at 2300 RPM
With overdrive and gear change I can do 65 at 2000 RPM, but it has to be pretty flat.

I have the stock V8 in my truck, and not the 6 banger. If all you are doing is swapping the gears, I think you will be pretty happy. Changing gears from 4.11 to 3.55 would effectively give you an OD ratio of .86. Or in other words your RPM will drop 14% in your top gear.

John

Thanks for the reply. I forgot to put it is for the 53, and I'm thinking about the 3.55 swap along with a good running 235 that is taking up space and needs to go somewhere.

Spencer

I'm in the process of restoring the stock drivetrain on my '51 and started with the rear end. It's now completely rebuilt with a 3.55. I have the SM420 4-speed transmision and I noticed the old 216 was a bit happier at speed but she's tired and will be coming out to be replaced with a rebuilt 235 so I can't be of much help on high speed impressions. One suggestion that I will offer is to look into some large-diameter LT tires. The ones on my truck now are only 26" in diameter and aren't helping the high-speed cause.

Driving around town, the change is dramatic and I think a lot of guys are overlooking the drivability of the SM420/3.55 combination. Essentially you have a fully syncro 3-speed and you never go wanting for a gear to downshift into. Dump a load of mulch in the bed and pull off in first gear slick as can be. The "granny" first is a lot more practical now... no more instant red line but still stump pulling power.

A lot of bad mouthing goes on about the stock drivetrain in these trucks but I, for one, just happen to think the 3.55 gear and the rock solid SM420 make a very drivable combination. I'll be glad when I get my 235 in so I can hit the 55mph roads. I'm not interested in expressway cruising at all. Where I live, it's mostly back roads anyway.

I put a 3:55 gearset in my 52 last year and am happy with the results. The one thing that needed some getting used to was starting off from traffic lights. With the stock gears I could gently let out the clutch without touching the gas and now I have to gently touch the accelerator to prevent stalling. The only time I drove it on the highway was to take it to storage last fall. I asked the wife to follow me and note speed so I could determine comfortable crusing speed as well as top speed. I did'nt get any data as she said after I passed several cars I was gone like Jack the bear. I have a stock column shift 3 speed and the tallest 15" radials (255-70-15). I put on the tall tires before changing gears and now realize I could have gone with a bit shorter tire.

Spencer, I have done the swap in my 41 1/2 ton to the 3:55 gear from Patrick's and I am more than pleased with how the truck runs now. 235 (63) stock 4 spd trans and 3:55 gear with stock tires. Runs well at freeway speed of 65-70 at 2000rpms. No down shift to climb a fairly good grade abt 6% gas milage has improved and I still have the stump pulling power in first gear and great driveability on the highway. Also went with a front disk brake conversion to help with the stopping. Going fast is great but stopping is a whole lot more important.