RPM drop at 45 MPH

Rclarkson62

Member
Joined
Nov 11, 2020
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29
Location
Connecticut
I just filled an almost empty transmission in my 4.0 6cyl 4spd auto 04'. When accelerating I feel it down shift ok. But rpms climb to 2500-3000rpms then drop only about 1-200rpms and at about 43-45mph rpms drop to 1500 . Is this normal? I feel it's not. I drive a lot . Just honestly never paid attention. Bleh.
 
Dropping the rpms way down is normal with that particular transmission, especially with bigger tires if the axles haven't been regeared to match the larger tire size.

What size tires are you running?
 
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Dropping the rpms way down is normal with that particular transmission, especially with bigger tires if the axles haven't been regeared to match the larger tire size.

What size tires are you running?
That's so crazy. I'll have to believe you. I just don't think the Jeep did this 3-4 months ago when I first bought it. You don't think the transmission is slipping? I thought it was because I filled the tenant from bottom to top
 
It may be that it is making the last transition a little more firm or solid now that you have enough fluid. Not "slipping" into OD.
 
It may be that it is making the last transition a little more firm or solid now that you have enough fluid. Not "slipping" into OD.
It's still doing it. On the highway my rpms are at about 2100 rpms at 60-65 and about 2700-2900 at 75 mph. Is this really normal for a 4 speed auto?
 
Dropping the rpms way down is normal with that particular transmission, especially with bigger tires if the axles haven't been regeared to match the larger tire size.

What size tires are you running?
31in tires no lift. At highway speeds rpms are in the range of 2000-3000rpms. Rpms only drop drastically once I hit 45mph
 
It's still doing it. On the highway my rpms are at about 2100 rpms at 60-65 and about 2700-2900 at 75 mph. Is this really normal for a 4 speed auto?
Well, I have a 3spd auto and am clipping 3k at 65mph. She has done 75, but only on a trailer.
 
31in tires no lift. At highway speeds rpms are in the range of 2000-3000rpms. Rpms only drop drastically once I hit 45mph
The rpms drop from whatever they were at to 69% of that when it shifts into Overdrive which doesn't occur at any specific speed. It shifts into Overdrive once you either drive fast enough or when you stop accelerating and are at a suitable cruising speed.
 
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Are you sure it’s not the torque converter lock up your seeing? It should drop 200-500rpm at about 45mph. You asked about slipping - this would display as the opposite and you’d see a increase or flare in the rpm.