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Old 09-17-2008, 11:44 AM
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Too many Rpms - Convertor slipping or stall speed too high?

Our 39 Willys pickup has 3.73 gears and rear tire diameter of 28". At 50 MPH I am at 3000 RPMs. My calculations say at 50 MPH I should be in the 2200 RPM range. My TH400 transmission is shifting into 3rd and does not seem to be slipping. I have no idea of the convertor stall speed. Engine is a 396 bored .030 over. I don't know anything more about the engine.

Is it possible that the stall speed is too high or the convertor is slipping?

Would a transmission shop be able to determine the stall speed?

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Old 09-17-2008, 12:09 PM
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Sure sounds like your converter stall speed is too high. Probably in the 3500 range. You'd be better off with about 2500 stall on the street.
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Old 09-17-2008, 01:32 PM
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Yep my calc's show 2238 rpm, if you're sure about the 3.73 then it could be the converter or a faulty tach. Most tach's can be set for 4, 6 or 8 cylinder engines, you might want to check that first. You may have a bad trans. pump but that would usually slip all the time.

If you want to check the converter just do a power brake test, put it in gear with your foot on the brake and gently start giving it some throttle, watch your tach (if it's working right) and you'll be able to feel when the conv. really wants to lock up. It's not a perfect test but it will give you an indication on where you're at.
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