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4.56 gears & 31's


 
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Ptown_bogger
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PostPosted: Wed Mar 14, 2007 5:03 pm    Post subject: 4.56 gears & 31's Reply with quote

Ok guys im sure this is a dumb question but i gotta ask. Im running 4.56 gears and 31's on my daily driver. i drive about 40 miles free way everyday. How bad is it for my motor/drive train to be running those gears with the small tires?
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ehirner
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Joined: 01 Jan 2004
Location: Eastern PA

PostPosted: Thu Mar 15, 2007 1:07 pm    Post subject: Reply with quote

It's probably just fine. What RPMs are you running on the highway?
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Ptown_bogger
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PostPosted: Thu Mar 15, 2007 1:48 pm    Post subject: Reply with quote

with the automatic at about 60-65( speedo shows 70) the rpms are around 3000rpm
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hutchman
Captain Kirk
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Joined: 07 Feb 2007
Location: Kennewick, WA

PostPosted: Thu Mar 15, 2007 3:11 pm    Post subject: Reply with quote

I would think it should be fine.

Peak torque is achieved at approximately 3100 rpm on the 4 liter, so you are operating in the area of peak efficiency on the torque curve. The materials use in the crank, rods, and pistons are suitable for operation at those levels with no issue. The only downside is that the faster you turn the engine for a given speed, the more wear occurs. But I just can't imagine this being too much of an issue.

I would much rather have the driveability of the lower gears versus the lower engine wear. My guess is you can do much more damage to the engine by lack of maintenance than with the lower gears.

Hutch
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Bruce McMurtrie
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Joined: 28 Jul 2007
Location: Blue Mountains Australia

PostPosted: Sat Jul 28, 2007 2:42 am    Post subject: Reply with quote

Ptown_bogger wrote:
with the automatic at about 60-65( speedo shows 70) the rpms are around 3000rpm
I have just bought a second hand 1994 Cherokee Limited 4.0 auto. I get 75 miles per hour at 3000 revs. I suppose there is some tolerance in both the speedo and the tacho.
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