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 https://www.bigmacktrucks.com/topic/55140-new-gears/ 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 https://www.bigmacktrucks.com/topic/55140-new-gears/#findComment-412053 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 https://www.bigmacktrucks.com/topic/55140-new-gears/#findComment-412095 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 https://www.bigmacktrucks.com/topic/55140-new-gears/#findComment-412097 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 https://www.bigmacktrucks.com/topic/55140-new-gears/#findComment-412202 Share on other sites More sharing options...
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