4.1 Rear Axle Ratio

[cbody70]

Once I get over 55 mph on the highway the 318 sounds like its reving a lot. Is it a difficult job for the do-it-yourselfer to change to a lower more highway friendly gear? Are specialized tools required? Are parts available. Keep in mind I have zero experience with this kind of job.

[wideblock]

its easier to swap the whole rear end on a 200 series truck. the half tons are cake, but the 3/4 ton requires at least a little experience, a lot of patience, and a good selection of tools to get it all set up right. what size tires are you running? mine has 4.10s as well, and although it may sound stressed at 55mph, she will run 65-70 all day if you have the proper tire size. get you a tachometer, then youll know for sure whats going on. the 318, in good tune, will run good up to 3000rpm for extended lengths of time. i ran my poly at 3000-3400rpm for better then 18 hours straight on one of my houston trips, only stopping for fuel. it does take some getting used to, hearing the engine like that. but if your in good tune and not about to blow a rod on a worn out block, youll be sailing down the freeway at 70 without issues.

[Jeffc]

Changing a dana60 ring a pinon are not a "backyard"
project.
The easy swap is to find a higher geared axle
and swap it in, or run taller tires.

[cbody70]

The tires are 7.5 X 16LT on split rims. The LA 318 is recently rebuilt and stock except .30 over. The Polara with the same motor 2.76 rear and 235 R15 tires doesn't make the same fuss until you get over 80. Trey while the commotion is disconcerting I'm inclined to go with your advice since the 318 is in good shape. Don't like the idea of a tach spoiling the stock look of the dash but I might rig up something temporary just to see whats happening.

[wideblock]

on my 66 i hung the tach under the dash, out by my right knee. it was down out of the way, but visable for monitoring the engine. and that 2.76 rear is a beast, i put one in my 66, to replace the 3.91, thought it would be a great hiway gear. and it was, but anything below 80mph and the motor was lugging. a gear like that requires an auto or a big block. LOLOL great thing was it would run 100mph without breaking a sweat. you pass a bicyclist doing 100+ in a swepty and watch thier reaction as they get blown side ways then sucked back in by the wash. LOLOLOLOLLLLL

just to give you an idea, my tires are a shade taller at 33" but, 2900rpm is 70mph on the balls. 2300rpm is 55mph. go to randy's ring and pinion web site. http://www.ring-pinion.com and play with the calculators. best i can tell, your tires are about 31.5 inches tall. so 55mph=2400rpm, 60mph=2600rpm, 65mph=2800rpm, and 70mph=3000rpm. all these are + or - 50 rpm, i just rounded it out. in any case, assuming your speedo is accurate, 70 all day wont be a problem. you wanna test the speedo, put her dead nuts on 60mph, then time yourself between mile markers. 1 minute between markers is exactly 60mph. the calcutaltor section can save you hooking up a tach if the speedo is accurate. i made a posty note for mine, ran with it in the glove box for a while till i had memorized what was what

[cbody70]

Thanks for all the info. Its a great help