Forum Discussion
FishOnOne
Aug 17, 2022Nomad
Labman7 wrote:
Had a 1980 GMC 3/4 with the 292 six and 4:56 axle. I drove it all over the National Parks of the west for 4 years with a 9 1/2 Coachman truck camper on it. Never had any problems anywhere driving through the mountains or on the flat land. It was the same engine they put in school buses. The body was going with rust is the only reason I got rid of it. Oh, yeh. It got 10.6 mpg with or without a load, in the mountains or not. And top speed was 78 mph. I added a 32-gal aux tank and could go almost 400 miles with 39 usable gals of gas. Now I get the same mileage with my Duramax pulling 14,000 lb of toyhauler, with a much better top speed available.
I've never seen a 3/4 ton GM truck with a six.
I don't know what the rear end ratio was but I want to say around 70mph it was running pretty high rpm. Which reminds me it had the first gen overdrive transmission and you couldn't simply disengage OD with the column shifter, you had to disconnect a connector under the hood so that's how it stayed so that explains it not making 22mpg, which I still doubt it would make with OD engaged.
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