This would also be a good point in our story to mention that either the TKO-500 or the TKO-600 has a lower first gear than a Muncie or a BorgWarner four-speed close- or wide-ratio transmission, which in effect is like installing lower differential gears for a quicker launch.
The same holds true for a Tremec TKO versus an original equipment three-speed stick transmission. The second-gear ratios for the Tremec TKO-500 and TKO-600 are 1.98:1 and 1.89:1 respectively. Third gear comes in at 1.34:1 for the TKO-500 and 1.28:1 for the TKO-600, with both transmissions utilizing 1:1 for fourth gear. This brings us to where a conventional three- or four-speed transmission is stuck with whatever final-drive ratio might be installed in a vehicle, and where the Tremec TKO's fifth-gear overdrive ratio kicks in. With a reduction of .68 for the TKO-500 and .68 for the TKO-600 the Tremec, TKOs offer up to a 36 percent reduction in rpm while in fifth gear. What all this wonderful information means on paper is that any vehicle equipped with such a transmission should offer, in addition to higher cruising speeds and lower interior noise levels, a noticeable increase in gas mileage.
But as they say, the proof is in the pudding, so what did we find out when Classic Chevy 5-Speed's "GM" Jim Goodlad finished installing the Classic Chevy 5-Speed Elite kit into our '66? Well, for starters, we ended up choosing a TKO-600, which is rated to handle 600 lb-ft of torque, while the TKO-500 is rated at 500 lb-ft of torque. To say we were happy with the conversion to a Classic Chevy 5-Speed would be to put it very mildly. We just couldn't get the smile off of our face as we ran the '66 up through the gears. The TKO had the right gears at the right time, and no matter what speed we were at, the little stock 327 was punchy as all get-out. Not wanting to jump to any premature conclusions, with a smile still on our face we failed to show up for work the next day and continued to put miles on the truck. With the 4.11:1 rearend, the '66 ran out of gears at the end of the freeway on-ramp, but now we can scream up the ramp, shift to fifth gear, and cruise all day long with the big dogs.
It might sound kind of dumb, but we really had no idea that swapping out the stock transmission for a Tremec TKO would have made such a radical improvement to our C-10's performance. Not to make a pun, but it really transformed the truck into a hot rod. As far as an improvement in gas mileage is concerned, we have been having so much fun blowing the doors off of our friend's trucks that used to be able to beat the '66 that we haven't done any serious fuel-mileage loops yet, but offhand it looks like our "10 mpg no matter what" truck is hitting at least the 14-mpg mark on the highway. Naturally, since "Farm Fresh" is one of our ongoing projects, we'll get some solid mileage numbers to confirm our suspicions before we move on to the truck's next modifications.
Removing the stock transmission, bellhousing, and driveshaft was a simple matter of unbolt
...and replaced it with a needle-bearing pilot bushing included in the Elite kit.
Classic Chevy 5-Speed produces their own "precision" version of GM's 621 aluminum bellhous