Quote:
Originally Posted by jocko
I think you may be misreading the chart - staying with TH350 and swapping rear from 4.10 to 3.54 will absolutely drop highway rpm. (2713 to 2330 at 65 mph for comparison). Drops it by almost 400 rpm.
It does so at the expense of bottom end torque multiplication though (10.33:1 final drive changes to 8.87:1 - so less accel off the line). Not "that" noticeable, unless your favorite passtime is doing burnouts. I'd say the highway rpm reduction is worth the tradeoff. Keep in mind, it's ALWAYS a tradeoff, unless you upgrade to an overdrive trans - doing that (without changing the rear gears) normally means increased acceleration and decreased highway rpm because of the additional gear allowing for a more optimal spread.
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Jocko,
I agree, your chart shows the highway rpms dropping about 400rpms. I was trying to say that I was hoping they would drop more than that.
I'm concerned about losing the bottom end torque, but it sounds like that isn't too big of a concern for normal truck operation.
The message I get from your chart is to change out the transmission if possible. Keeps the three lower gears almost exactly the same, and drops the highway rpms way down toward 2100rpms. That sounds like the perfect setup. I need to look into the details of what is involved to change out the transmission.
Take care, JP