MOloghauler Posted December 28, 2018 Share Posted December 28, 2018 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 1 Quote Link to comment Share on other sites More sharing options...
Mack Technician Posted December 28, 2018 Share Posted December 28, 2018 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. 1 Quote Link to comment Share on other sites More sharing options...
MOloghauler Posted December 29, 2018 Author Share Posted December 29, 2018 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! 1 Quote Link to comment Share on other sites More sharing options...
Mack Technician Posted December 29, 2018 Share Posted December 29, 2018 You out west? Assume MO= Missouri? Quote Link to comment Share on other sites More sharing options...
MOloghauler Posted December 30, 2018 Author Share Posted December 30, 2018 Yes Missouri Ozarks Quote Link to comment Share on other sites More sharing options...
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