C5
Junior User
Joined: Dec 1999
Posts: 52
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From: Gustavus Township, Ohio
C5
Does anyone know about the C-5 tranny? I understand that it is supposed to have a lock-up converter.....how do you tell if it is shot? I'm getting horrible mileage (like 8-10 mpg) and have pretty much taken care of the "usual suspects"...I'm thinkin' the converter isn't doin its lock-up deal. Thanks in advance.
Posting Guru
Joined: Jun 1999
Posts: 1,525
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C5
Yes the C5 is the lockup version of the C4. I'm not positive if it's electric or mechanical lockup,but either way,once you reach 3rd gear and ease off the gas to begin cruising at 40-50 mph the RPM's will drop only about 200-300 when the convertor locks up.You should feel as well as hear the engine lug down a little when this happens.The lockup is not a great gas mileage saver, but it may add 1-2 MPG to your present,if it's not working,and you get it to work again.Make sure the vacuum to the modulator is good,as well as the modulator itself.Have the bands adjusted.If I'm not mistaken, the trucks equipped with C5 had the DuraSpark III ignition<3 socket module> which had a BARO sensor to control timing,and,the sensor could be faulty and you never really get timing advancement.
Phillip
Phillip
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