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MACK MAN

1998 E-427 and rear end ratio question

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I need a local truck bad,I have found a nice 1998 CH,E-7 427,eaton 10 spd,not a super 10.The truck has 11;24.5 tall rubber with 4.42 rear ratio,at 65 mph the truck is turning 1675 rpm.I run 50 miles one way empty one way loaded,total 300 miles a day,when loaded gross 80,000 to 91,000lbs.With this engine being a 1800 rpm will I be killing it running 1675 to 1700 rpm when on the hiway? can this engine be turned to 2000rpm?I would love to find one with 4.17 ratio but not having any luck,I can change the ratio to 4.17,but that would run about $ 5,000 to $6,000 and really don't want to go that way.

thanks Al

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Perhaps find a cut off set of tandoms in a junk yard, swap gears, re-sell the taller gears an eBay? What brand rears does ithave? 2,000 rpms would make me nervous.

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My 01 is set up similarly with 4.42 rears and tall 24.5's. The difference being mine has a Mack 2180 trans now. According to the mack parts computer mine was born with 4.17's and an Eaton 18. I don't know why all the changes, but I do like the setup. The eaton od ratio isn't as "tall" as the mack (.73 or .75 vs .71)

I run 63 at 1500 rpms, 68 mph at 1600. Odd as it seems 1600 is one or two tenths better on fuel than 1500 on the turnpike. Having a cruise rpm closer to 1700 like you said might be past any fuel sweet spot though. If your grossing up to 90k you will probably want your rpms to be in the 15-1600 range. If mine pulls much under 1400, its flat on its face.

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I don't know any prices, or what shipping would be, but Roy's enterprises in Hayward Wi. has many 4.17 gear sets in his salvage yard. google the name and you'll find his number. very easy guy to deal with. never had a bad deal from them yet. and just to be clear on this, I am talking about Mack drop ins.hope this helps.

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This thread is interesting to me, good info! My 2007 Mack Granite, which I have yet to even see, has a 4.42 rear end and 22.5 tires. I will be using it to run around hilly/mountainous Idaho doing taxi crane work. It has a 30 ton National crane mounted on it, no cargo other then a few spreader bars and rigging. It should weigh around 52K I'm thinking. I have no real need for speed, 60-65 is plenty, as I get paid travel time so no real benefit in going 70..... As of now, I'll cruise it at 1600 rpm on the long drive back this weekend from Wisconsin. 10 speed Fuller BTW. Anyone want to hazard a guess, or know the math, on what speed I can expect? 60 or a bit above is my guess.

Edited by SCS

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As of now, I'll cruise it at 1600 rpm on the long drive back this weekend from Wisconsin. 10 speed Fuller BTW. Anyone want to hazard a guess, or know the math, on what speed I can expect? 60 or a bit above is my guess.

62 mph at 1600

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Today I was driving 60 miles back from what turned out to be my last job with the current rig I have operated for 6 years now. A Sterling truck with a 22 ton Manitex rider crane. A CAT C-7 engine. I made a note: at 62 mph the rpm was 2100. If I make that same speed at 1600 RPM, I'll be a happy camper.

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442 rears here too and i turn 1800 at 65 mph. 1600 gets me about 58mph i believe. 1900 gets me 70 :)

22.5 tires here

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