Highway RPM seems high. Lockup not engaging?

[wmorrison65]

'01 GTP. Correct me if I'm wrong: Final drive 2.93:1, 4th gear 0.7:1. Tires 225/60-R16, 26.6" diameter. Right?

Plugged those figures into the calculator here:

http://www.crawlpedia.com/rpm_gear_calculator.htm

If I calculate correctly, at 65mph in 4th gear with the lockup clutch engaged, shouldn't I be at around 1684 RPM? That seems low to me, but I'm used to driving cars with smaller engines that need to rev higher.

I can hear it shift into all four gears, but I'm cruising at about 2500 RPM at 60-62 mph, going easy on the accelerator. Is that normal? It's about what I would expect for a much smaller engine, but I'm surprised a 3.8L needs to rev that high just to cruise.

Highway MPG is 24 if I'm lucky, but usually lower.

Does it seem like I should be looking into the lockup clutch? Or a solenoid, or bad connection, or something? Or is this normal highway RPM, and I calculated wrong?

[BillBoost37]

Nope, you'll see around 1800-2000 on the tach at 70mph.

Since you are seeeing 2500 at 65mph but you feel all 4 gears, run a little test.

Driving along at 65 with your right foot on the throttle nice and constant, tap the brake pedal just enough to get the brake light to turn on with your left foot. If the rpm jump ~500 rpm then what you thought was 4th was really the torque converter locking up and you have lost 4th gear based on the splines wearing.

There's a how to for replacing the 4th clutch hub (work part). It's by me in the how to section.

[wmorrison65]

So I think what you're saying is, if the torque converter locks up in 3rd gear, it might kinda sound like a shift to 4th. If the torque converter is locked, tapping the brake signals the car to unlock it, and if you're still holding the accelerator steady, RPM should jump up.

Took a 2-3 mile loop and tried that, several times. RPM held steady when I tapped the brake.

[Scottydoggs]

you do that test at highway speeds, and light on the gas pedal. over 50 is best. dont know what speed you were going.

also if your driving along at say 65 mph and your showing 2500 rpm, if you drop the shiftier to 3 rd the rpm's should go higher as its leaving od. if the rpms stay the same you lost 4 th gear. and your in 3 rd already.

[wmorrison65]

60 to 65 mph, light on the gas pedal. RPM didn't go up when I held the gas pedal steady and tapped the brake with my left foot. I'll try shifting down into 3rd tomorrow.

[BillBoost37]

2500 still feels a little too high to be just converter, but it's kinda one of those things you gotta do both. Leave it to Scott to fill in the gap.

[wmorrison65]

BillBoost37, I think you're right, not getting 4th gear. Probably not locking up, either.

Tried the shift-into-3 test this morning (cruising 60 mph, keep foot on gas and shift from D to 3) and generally RPM didn't rise. Once or twice it blipped up a hundred RPM or so, but it didn't sound/feel like it downshifted.

[Scottydoggs]

no 4 th gear then. the part is like 40 bucks. to bad you need to open up the tranny to fix it. can be done tho.