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Jan 28, 2011 | 03:23 PM

jg96powerstroker

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From: Phill Mo

gears

ok guys my 96 cc has 4:10 in her as of now, i do have a lift and 5 speed and all my mods, i drove my buddys 2000 sd 4x4 with 6 speed same size tires and all at 75 mph it is at like 1800 rpms, i no he has 3:73, my ??? is can you get 3:73 for are obs?? and if not would going to 3:55 be good or bad?? plan on keeping the 37 cause a can get a set of 4 for 200 bucks, i no 3:55 will hurt my pulling, but thinking about makeing my 93idi cc drw long bed in to a ps and make it my work horse! and keep my 96 all nice and wear and tear off her, thanks guys

Jan 28, 2011 | 04:03 PM

strokin'_tatsch

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From: Austin, TX

You can definitely get 3.73's for your truck no problem. Just gotta buy the gears and since your in there you might as well change all the bearings/races and seals also.

http://broncograveyard.com/bronco/c-...g-pinions.html

http://broncograveyard.com/bronco/i-...build-kit.html

Jan 28, 2011 | 04:37 PM

redman84

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From: College Station, TX

Yep like travis said BUT they were not a factory option so don't go looking in wrecked obs trucks. Have you recalibrated your speedo? What are your rpms at? Those 4.10s should be pretty nice with 37s

Jan 28, 2011 | 06:31 PM

strokin'_tatsch

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I went and ran some calculations.. If i'm right then you should be turning ~2122 RPM @ 75mph with your 4.10s, 5 speed, and 37's. That is the correct ratio that you need for your truck IMO for best performance. Your buddy is running kinda low RPMs for optimal performance IMO, BUT the ZF6 has a bit different gearing in it than the ZF5 so it helps a bit. Just so you see the OD difference, if your buddy was to switch to 4.10's he would turn ~2011 RPM @ 75 mph.

If you were to swap to 3.73 gears then that would pull your RPMs down to ~1931 RPM @ 75mph.

Jan 28, 2011 | 07:08 PM

redman84

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From: College Station, TX

If travis did his math right then I definitely agree. I swapped to 3.55s but that puts me at 2000ish rpms @ 70 mph where I am almost always at. That gets me pretty good mileage and i don't have to downshift or anything to pass someone.

Jan 28, 2011 | 08:22 PM

jg96powerstroker

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From: Phill Mo

Quote:

Originally Posted by strokin'_tatsch

ok but i thought lower rpms would help in milage, highy way is 17 and 18 now my truck likes 6o0 and 65 but over that it dont like so much, lot of my driveing will be hiway for work now, was hopeing 3;73 might get me 20 or 21???

Jan 28, 2011 | 08:41 PM

strokin'_tatsch

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From: Austin, TX

You can get 20-21 with the gearing you have right now. I have 3.55's. I run higher RPMs at 75mph than what you do!! I get 18-19 normally driving 75mph or so daily... If I want to get 20-21 I have to keep speed down around 65-68mph tops. Keep speed down, you will get good mileage. There isn't really even much need in going any faster than that.