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**pjmoreland** · 11-03-2005, 04:52 PM

Diff. Ratio = Engine RPM x Tire Dia. x .002975 / Speed / Transmission Ratio

Engine RPM = 3500
Tire Dia = (2 x .75 x 265 / 25.4) + 16 = 31.65"
Speed = 70 MPH
Transmission Ratio = .7

Diff. Ratio = 3500 x 31.65" x .002975 / 70MPH / .7

Diff. Ratio = 6.72

There's no way your differential ratio is that high.

I'm guessing one or a combination of things are happening.

1) Speedometer is wrong (check with a stopwatch on the road)
2) Tachometer is wrong (compare against an engine analyzer)
3) Transmission is not shifting into OD
4) Torque converter clutch is not locking
5) Differential gears are not what you think they are

Maybe the torque converter clutch is locking in third gear, making it feel like you are in overdrive.

I would definitely check your speedometer and tachometer first before disassembling anything.

11-03-2005, 04:52 PM	#9
pjmoreland Senior Member Join Date: Jan 2005 Location: CA Posts: 5,347	Re: My motor RPMs don't seem right Diff. Ratio = Engine RPM x Tire Dia. x .002975 / Speed / Transmission Ratio Engine RPM = 3500 Tire Dia = (2 x .75 x 265 / 25.4) + 16 = 31.65" Speed = 70 MPH Transmission Ratio = .7 Diff. Ratio = 3500 x 31.65" x .002975 / 70MPH / .7 Diff. Ratio = 6.72 There's no way your differential ratio is that high. I'm guessing one or a combination of things are happening. 1) Speedometer is wrong (check with a stopwatch on the road) 2) Tachometer is wrong (compare against an engine analyzer) 3) Transmission is not shifting into OD 4) Torque converter clutch is not locking 5) Differential gears are not what you think they are Maybe the torque converter clutch is locking in third gear, making it feel like you are in overdrive. I would definitely check your speedometer and tachometer first before disassembling anything.