The Stovebolt Site Forums The Shop Area Driveline 1970 gmc half ton gearing

The obsession with running engines just barely above idle speed while highway cruising began back in the late 1980's when a bunch of government bureaucrats with no engineering and/or manufacturing experience started telling car manufacturers how to build their vehicles. Setting outrageous standards for both exhaust emissions and fuel economy forced them to build cars and trucks with completely inappropriate gearing so they could meet the requirements of chassis dyno simulations that had no resemblance to real world operating conditions. The penalty for failing these tests was severe- - - - -the manufacturer's entire production run of all vehicles- - - -not just the ones that failed the test- - - -could not be sold anywhere in the USA. Standards set by California were even stricter. Naming the California standard setting group C.A.R.B. (California Air Resources Board) was no accident, I believe!

Those kinds of requirements compel manufacturers to redesign everything- - - -combustion chamber shape, compression ratio, camshaft timing and lift, ignition timing, computer programming, etc. Trying to make a 1970's engine without computer controls function at those artificially low RPM numbers is not only virtually impossible, it's downright foolish. Gas mileage will drop precipitously because the engine is lugged down all the time and the power valve in the carburetor will stay open virtually constantly- - - -spark plugs will foul out quickly, and there's a distinct possibility of piston and ring damage from detonation. Performance will also suck like a Dyson ball vacuum cleaner because the engine will be running far below its efficient torque range.

Other that those minor concerns- - - - -there's no problem with running a stupid-high rear end gear!
Jerry