What size of tire do you run? Also what are your rpm's at 60-65 mph? I ask because a good friend of mine with a 96 cc 4x4 srw is only running 1800 ish rpm at that speed. He's just running 285/75's which are a 33". His truck doesn't feel like it has the spunk it should and runs higher egt's than I'd like to see. It also feels like it's struggling to keep speed going up hills and such at highway speeds. Compared to my 95 with 4.10's and stock tires, there's a big difference in power. Also, Mine runs 400 to 500 rpm higher than his does at the same speeds.
Anyway to tell exact what it's got for gears other than the tag (if it's even there)?
I'm running 285/75's on mine with the 3.55's. The 3.55's did alright with the stock 235/85's on there but it lost power when I went to 285/75's.
Even when mine was a dually pushing 4 tires with 4.10's it seemed more powerful than it does now.
With the 285's I think i'm at about 1800 rpm going 60. About 2k rpm at 65 I think.
Just ordered a PHP chip from Rosewood Diesel though, that should help some!
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Brownie, Ooh-Rah! USMC Member of the NRA!
'95 F350 CC 4x2 - SRW Swap, E40D, PHP 6 Pos. Chip, 6637 mod, 3" D.P., Lost Kitty, 140v IDM, HPX Mod, FPR Shim (65 psi), T.C. switch, 3.55 gears
'88 F350 CC 4x4 - lots of dents, faded paint, old 7.3 IDI in pieces
Unless you change the magic number in the PSOM via the "secret handshake" with the odometer buttons, your relationship between RPM and MPH on the cluster won't change when you change tire size. Think about it; in your mind, jack stand the rear end and take the wheels off, and "drive" the truck. RPM and MPH will relate the same way, with a tire size of ZERO. Actual road speed will be about 3.5% higher with 285-75s vs. 235-85s. You'll feel a loss of power with bigger tires both because there's more rubber on the road (more friction) and because you're ultimately making the mass of the truck go a wee bit faster; IOW, the speedometer is a bit "pessimistic".
3.55 is def'ly the "economy" gearing. Both my wife's trucks run about 2000 RPM at 70 MPH, 235-85-16s, and the speedo is within a few tenths of an MPH compared to the GPS.
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1997 F250 HD XLT, 4x4, auto, 4.10 limited slip 265/75 KM2s approaching 300k mi
2002 Escape XLT, auto, tow package, Cooper disco STTs, ~80k mi
The years column of the code chart is pretty off though
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1997 F250 HD XLT, 4x4, auto, 4.10 limited slip 265/75 KM2s approaching 300k mi
2002 Escape XLT, auto, tow package, Cooper disco STTs, ~80k mi
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