Our available information indicates that '68 K-trucks came from the factory with a semi-floating unit with a 3,300-pound rating, which pretty much leaves you with the Saginaw Model 33 9 3/8-inch "big 10-bolt," a semi-floating design with a 3,300-pound GAWR and 17-spline, 1.28-inch outers. (You can pull a shaft and count the number of splines to verify this.) The only catch is that this axle was supposedly discontinued in Chevy trucks after 1964 or so, though it's possible that (a) a previous owner swapped it in, or (b) your truck rolled off the assembly line towards the end of a model year, when assembly-line workers would often bolt up whatever components were left over in the factory parts bin. (This was back in the day before companies like GM outsourced most of their axles to independent third-party suppliers.)
There's also a slim chance that the axle's a 10-bolt Dana 41, which is a direct precursor to the more famous 44-but this is an ancient axle that saw very little use in OE applications beyond the mid-1950s, though some Chevy C-trucks of the mid- to late '60s were rumored to have ended up with them. They ran 10-spline outers, so again, pulling a shaft and counting splines will confirm what you have. Or not. Hey, is owning an older truck fun or what?
Your axle should-repeat, should-have 3.73:1 gears (it was the standard gear ratio from the factory), but with trucks of this vintage, nothing is certain, and your best bet to determine what ratio you have is to consult the RPO sticker on the inside of your driver's side door. Look for a three-digit alphanumeric code starting with the letter "G," and you'll be able to ID your gear ratio from a number of Internet sources. Missing the RPO sticker after 40 years? More fun!
Okay, secure your rear axle on jackstands so the tires are off the ground. Chock the front tires, and put the transmission in Neutral. Turn the rear tires slowly, and count the number of rotations the driveshaft makes for every single rotation of the tires. Using a pencil or a piece of chalk, make a mark on the top of the driveshaft before spinning the tires to get the most accurate measurement.
Anyway, that's our best guess, though we have a funny feeling that Cameron Carlile might know more about this than we do. Readers, your best guesses?
Plug-In Hummer:
Fact Or Fiction?
Recently, as I was driving into San Francisco, I saw a Hummer H3 on the bridge. Nothing unusual there, but it had a "Hybrid" badge on the back. I looked into this and found there is a company in Utah that converts H3s into hybrid vehicles, claiming 100 mpg in the city and 33 mpg highway. Have you guys heard about this? Is there anything behind it?
Daniel Johnson
Petaluma, CA
Yep, it's legit. A company in Utah, Raser Technologies, has built a plug-in (120-volt) H3 hybrid in cooperation with GM as a rolling showcase of the latest green-vehicle technology. It operates on a similar principle to the GM Volt system, which means if you only drive it in-city for short distances and re-charge it regularly, you may never need to consume a gallon of fuel over the lifetime of the vehicle. Our own beloved governor Arnold drove it last year and gave it his thumbs-up as well. There's no word on whether this system will ever go into production on the Hummer platform (they do have new owners, or not), but such a system could certainly help to rejuvenate Hummer and/or SUV sales in the future. You can learn more about the H3 hybrid at www.rasertech.com.