The Stovebolt Site Forums The Shop Area Engine Shop CRUSING SPEED WITH THE UPGRADED REAR GEARS?

hey guys, what do you guys get for a comfortable highway cruising speed in a 46 chevy 1/2 truck with the upgraded rear end gears like the sets from Jim Carters? 50-60mph?

50-60 is for the stock truck. You could cruise 60-70 if you trust the steering, brakes, and tires. Or you could just cruise at 55 and enjoy less noise and better fuel efficiency. I left my gears stock because I like the way it roars up hills fully loaded in high gear at 55mph.

I'd just like to point out that the gears are not upgraded... the ratio is higher. This is a trade off of sorts, but it is well worth the trade.

You didn't say your engine size or condition. I think with 3.55 gears & a stock 216 engine in good shape, 60 mph would be a good cruising speed with burst's up to 65 or so. Diameter of rear tires plays a part in it also.

I have a '37 Pickup with a '57 235. I'm running a 3.55 rear. I typically cruise at 65 and have run it at 75 for short sprints (with plenty of throttle left). It likes 65 and will run comfortably all day...

3:55 gears is one of the best upgrades that I have done. Like said above, whether this upgrade is for you or not depends on where you live, and your plans for the truck.

If you live in a hilly or mountainous region, and you tend to drive on short trips or just locally, with the 216 you may want to stick with the stock 4:11's. But if your plans call for long trips to meet other fellow Stovebolters, you will love the 3:55's

Seeing that you live in Texas, hills may not be your issue. On flat Texas ground you could get that 216 up to a speed faster than your brakes can stop. Make sure that you take the time to make upgrades to items like suspension and brakes and ensure other items like steering are operating in great shape to make your truck a good driver.

I have done three of these upgrades, if you decide to proceed or have any questions, just let me know.

How much difference does it make?
3.55 ÷ 4.11 = .864
Engine speed is reduced by 13.6% (3,000 becomes 2,591, etc.)
Engine torque is reduced by the same percentage, but only has a strong effect in 1st gear, 216 "feels like" 187".
MPH at the same RPM is increased 15.8%, 55 becomes 64, etc.

My 55.2 has 3.55s in it, installed by previous owner. With that and 30" rear tires it cruises comfortably at 62 mph. It will run faster, but I don't feel the need to push it. It's running about 2500 rpm, near torque peak.

Devin

SWEET if right, best thing you can do for the vehicle. Besides cruising speed you'll love the pick up in ALL the gears. I've gone to higher ratio in all my trucks and it's always been a good move. If I were in steep mountains I'd opt for an overdrive trans though, love the T-5 in my pickup.