The Stovebolt Site Forums The Shop Area Engine Shop Can I cruise 65 w/ 3.90 rear end?

I have a '59 chevy apache 1/2 ton with a 3.9:1 ring/pinion. Do you guys reccommend swapping that w/ a 3.38 or lower? I'm not looking to haul [censored] around town, but I would like to cruise without putting excess ware on my soon to be rebuilt 235. The tranny is a 3speed...thanks
pork

To answer your initial question...

Sure you can. With overdrive!

But changing to a 3.38 or numerically lower would work too. I have a 3.73 rear end in my '66, but the overdrive in fourth gear puts me at 2200 rpms at 70mph. To me that's cruising.

-ftyler

My 59 panel truck has a 235 with the stock 3.90 rear end and 3 sp tranny. It will cruise at 2800-3000 rpm max. A freind followed me on the freeway and said I was doing 63mph. I have 235 75 15" tires about 29" tall. I am looking for some tall skinny tires 33" I should be able to do 70mph if I can find some that fit without rubbing.

http://www.gearvendors.com/cg2wdt.html

theres some great overdrives for Muncies and Borg-Warners.

I know of one person (F-150 Lightning) who put a Gear Vendors Overdrive unit behind his E4OD and had 3.73 gears in the back. When he was going to Lightningfest in Kansas in Sept, he was cruising at 70-75 most of the way, and his engine was practically idling at about 1700RPM. After a couple years I think the money you save on gas would easily pay for it.

Drew

I have 3.08 gears in my 55 1st Suburban. It cruises at 55 turning about 1500 RPM. I don't remember what the tach says at 70, but with the GMC 270 it will easily run 70+.

pork chop,,,, Go to the RPM Calculator on the Randy\'s Ring & Pinion Page..

Enter your tire size, final tranny ratio, then you can try different rear end ratios to see determine your final RPM's..

I still have the stock 3.90 in my 54 with 235 and 30 inch tires and am barely able to attain freeway speed without the engine sounding like it will self distruct.

I already have the 3.55 ready to go in but even with that it will not be a freeway cruiser.

thanks for the input guys. What I think I'll do is put the 3.90 back in since I have never driven the truck and see how she runs after the restoration. If I'm satisfied then I'll probably just leave it in and if not it's a pretty easy swap I'll just replace it. My 3rd gear ratio is 1:1 so i'll check out that website that calculates rpm. To be honest I'm only going to drive the truck to cruises and shows so I might be worrying for nothing...thanks
pork

First thing, do you want to be going 65 MPH on 45 year old drum brakes and straight axle?

My 59 runs a 235 and 3 speed with a stock 3.90:1 rear end and it screams at anything over 60 and seems to be best driven at 55 MPH.

I routinely cruise my 56 3100 at 70mph with straight axle and drum brakes. That's Sierra mountains, flat valley lands as well as bad California traffic. If your truck is well maintained and in good condition, no problem. Never had brake fad and have always had the truck under control. I have had this truck since the 70's -- no crashes. Do not tailgate, drink, eat or yak on the cell phone while driving. Trucks take longer to stop than a Honda Civic, so think defensively.

I used to have 3.90 gears with 650x16 tires. I now have 235x15 tires and 3.38 rear gears, much nicer at 70mph.