Re: 1971 F700 Does it go over 40MPH

Posted by Hal/WA on January 06, 2007 at 17:41:23 from (66.45.175.118):

In Reply to: 1971 F700 Does it go over 40MPH posted by David on January 06, 2007 at 08:15:48:

If it struggles to go over 40 unloaded, I would suspect a problem with the tune-up (maybe stuck advance plate?) or maybe a plugged exhaust system. If you have a tach, that engine should rev fairly easily, and I would expect it to have no problem going over 4000rpm.

A friend of mine had a 68 Galaxie with a 302 that got rotten gas mileage and would not go over about 70mph. He had the problem analyzed and learned that the exhaust system had collapsed inside. A new muffler and tailpipe upped his gas mileage by about 5mpg and his Galaxie would exceed 100 with ease.

If the engine is screaming at 40mph, at like 3500-4000rpm, then it may just be geared very low. Or, like the others wrote, you might have a 2 speed rear end in low.

Lots of the old grain trucks had very low gears, and worked pretty well with 6 cylinder engines, for the purpose they were built for. But those trucks were not intended for ever going fast. My 36 Chevy was flying at 45! And I think that trying to go faster downhill might have blown up the engine.

But I would expect a truck that new, with a fairly large V8 engine to be built to go down the highway at a decent speed. But all sorts of rear end ratios could have been ordered...so you probably want to check what you have.

Good luck figuring it out!

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