4L80E Shift problem - Diesel Truck Forum - TheDieselGarage.com
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post #1 of 3 (permalink) Old 06-04-2009, 10:18 PM Thread Starter
 
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4L80E Shift problem

Hope someone can help, been scratching my head for a couple days now. In a '99 truck, it start shifting out of first way late, unless you let off the gas. and the shift was harsh. Had the codes pulled and it said "Mechanical Failure". A guy I talked to said it could be the 1-2 shift solenoid or a problem with the valve body. Just to be safe we replaced the whole valve body with an AC Delco reman, and we still have the same prob. Short of the pump going out, there shouldn't be too much else that could cause a late shift, since the electronics control it all, or am I missing something?
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post #2 of 3 (permalink) Old 06-28-2009, 12:39 AM
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VSS can cause this. It did in mine but it also threw a code for it. Check for historic codes.

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post #3 of 3 (permalink) Old 07-22-2009, 04:33 PM
 
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Check the sensor and its connection closely before replacing it. Around 1350ohms both directions. Just got done chasing mine down after having the trans out, and completely tore down.
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