Joey Mack Posted Thursday at 12:16 AM Share Posted Thursday at 12:16 AM Not sure what country your in, but , 4:17 are plentiful.. Quote Link to comment https://www.bigmacktrucks.com/topic/40341-regear-options/page/2/#findComment-576152 Share on other sites More sharing options...
880joe Posted Thursday at 01:22 AM Share Posted Thursday at 01:22 AM I was always told that the 3.86 was tuffer than the 3.87 Quote Link to comment https://www.bigmacktrucks.com/topic/40341-regear-options/page/2/#findComment-576157 Share on other sites More sharing options...
terry Posted Thursday at 02:47 AM Share Posted Thursday at 02:47 AM 9 hours ago, Outbehindthebarn said: What's your 'go-to' for an E9 12 speed OD with 11r24.5's in a road tractor? It currently has 3.87's, but I've never worked it... yet. Found metal on drain plug on the crdp92, so I pulled it... gear set is toast. Rebuilder is shying away from replacing the 3.87 ratio. He called it a "weak gear set". I have zero experience with that sort of thing. He's steering me towards 4.42 or 4.17. That's the reason I asked about the closeness of the 3.86-3.87. .. and why he calls it a "weak gear set". With that set up a 4:17 would be ideal, i once had a DM dump with a 285 engine, 12 spd od mack with 4:17’s and 22.5 tires, engine would turn 2300, and bury the 80 MPH speedometer. It was quite the sleeper! Terry 1 Quote Link to comment https://www.bigmacktrucks.com/topic/40341-regear-options/page/2/#findComment-576159 Share on other sites More sharing options...
Geoff Weeks Posted Thursday at 01:09 PM Share Posted Thursday at 01:09 PM I don't know about Mack's gearing on the two in question. Rockwell went from 3.70 (37-10 tooth) to 3.73 (41-11 tooth) to have greater tooth contact, back in the early 80's when power started increasing. I lost a 3.70 set not from anything with the ring & pinion but because a thrust washer came apart and past through the pinion, knocking off part of the tooth, drove it home. "weak" is a subjective and retaliative term. I have no idea how many miles were on my set, but could have been over a few mil. Still had the riveted on ring gear, so wasn't re geared in the field. I found another 3.70 set with a blown powerdivider and swapped the R&P and carried on. If it was made, and lasted until now, how "weak" could it be? Anything will break from abuse, and if operated by a careful operator, can take a huge "overload" without any damage, I put little stock in what someone calls "weak", unless there is a real obvious defect that shows up on just about every unit. Finer gearing with more teeth are going have more tooth contact then course gearing with fewer teeth, by this definition, slow gearing is weaker than fast, but "sees" lower sustained torque loads. It is the old trade off, and why multiple O/D gears were used of old. Spin fast and gear down at the back. Quote Link to comment https://www.bigmacktrucks.com/topic/40341-regear-options/page/2/#findComment-576165 Share on other sites More sharing options...
Joseph Cummings Posted Thursday at 05:54 PM Share Posted Thursday at 05:54 PM Low gears in the rear, and a double overdrive, and you don't abuse your frame crossmembers like this guy 1 Quote Link to comment https://www.bigmacktrucks.com/topic/40341-regear-options/page/2/#findComment-576178 Share on other sites More sharing options...
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