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MOloghauler

New Gears!?

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Ok, I’m running a ‘93 RD688s and somehow the back rear end housing has got cracked and even has a couple chunks broke out of it. Obviously ruined, the 3rd member is still in decent shape but I’m replacing everything with a complete reman unit. The truck is currently running 4.64 gears, I found a good deal on a pair of 4.17 3rd members and am tossing around the idea of swapping them out to gain a few mph and maybe improve fuel economy. Question is: If I were to do that what should I expect performance wise? It’s got an E7 350 with an Eaton 13 trans. With the current gearing I have yet to find a hill it won’t climb, but am worried about over working the engine with that much of a change in gear ratios

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You won’t over-work the engine. You will be dropping out of the top hole more often and losing some of your low crawl. 

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Well i decided to stay with the original gearing. Being a log truck and crawling around through the mud and mountains I think having the low end “grunt” will do me more good than the extra 5 mph down the highway. Thank you MT for the input! 

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