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I've got a 1986 CJ-7 with the 258 and a 4 speed. The axles are geared at 2.73. Yuck! I am running 31 inch tires and will most likely never go any larger. I pull a 4x6 utility trailer and do some light to moderate 4 wheelin'. Would like to swap gears as it would, hopefully, make life a little easier when starting out in first gear. Not sure what ratio to go with. Maybe 3.73s or 3.54s? Any advice would be appreciated.

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1986 CJ-7
 

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Superfly
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It'd be easier to suggest something if you could tell us what rpm you'd prefer to be at, and at what speed.

Where does your 4-cyl make the most power?

...lars

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19911995409993004:144444.103512.58274



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Isn't a 258 the 4.2L 6 cylinder

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Sold 85 Toyota extra cab 4x4 2" lift 33" BFG M/T with lots of tire rub!
Wanted 84/85 4runner, needed a few more seats less rust, and a beter FRAME.
 

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actually pitter
only from 87 to 90 I believe the 258 is a 4.2 model
other 258 models exist but are not 4.2
(don't quote me i may be wrong)

Jason

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IF GOD NEVER CHASED MAN OUTTA THE GARDEN OF EDEN THE GREENIES WOULD HAVE
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Superfly
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Originally posted by pitter:
Isn't a 258 the 4.2L 6 cylinder
Oops...quickly scanned the msg and for whatever reason thought he said "2.5L" which is why I thought it was a 4-cyl.

So yes, the 258 will be a 4.2L, always (258 cu in ~ 4.23 L). The 4.0L is somewhere around 244 cu in. I don't think it was exactly 4.0L, though, which is why I'm saying it's somewhere around 244 cu in.

Well, given that the 258 is a low revving engine (no more than 3000 rpm), if you want a comfy daily driver, you really don't want to go too low.

A 31" dia. tire means that it would have to rotate at 653 rpm at 60 mph.

If you want an engine rpm of 2200 at that speed, then 2200 / 653 = 3.37 (assuming 1:1 tranny ratio which should be right for a 4-spd with no overdrive). So, something close to 3.37 will give you a decent rpm at 60mph.

At 60 mph:
3.54 gears = 653 * 3.54 = 2311 engine rpm
3.73 gears = 653 * 3.73 = 2435 engine rpm
4.10 gears = 653 * 4.10 = 2677 engine rpm

I've run 3.55 gears w/31" tires. Worked well on the hwy and the trail but as always, the lower the better for the trail.

...lars


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