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Posted by CharlieT (75.30.228.42) on 12:31:25 07/10/08
Finally got around to taking it to the dealer for harsh shifting after it had been sitting for several weeks. Had this problem since new but it always fixed itself after a few miles so low priority. According to the tech the problem is caused by the torque converter draining down. The only fix is to allow a few seconds for the TC to fill before putting it in gear after prolonged sitting. Below is the Bulletin describing the problem.
Document ID: 1846766
2004 _Chevrolet Chevy Suburban- 4WD I Avalanche, Escalade, Suburban, Tahoe, Yukon (VIN C/K) Service Manual Transmission/Transaxle ~ Automatic Transmission 4L80E/4L85E Diagnostic Information and Procedures Document ID: 1846766
#PIP3857: Harsh Shift After Cold Start - keywords DTC MIL P1810 - (Jul 11, 2006)
Subject: Harsh Shift After Cold Start
Models: 1998-2007 Light Duty Trucks and Vans Equipped with a 4L80E/4L85E Transmission
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:
A 4L80E may intermittently set DTC P1810 and exhibit harsh shifts. Freeze frame/ fail records may show the vehicle was in reverse and the P1810 set shortly after a cold start. The vehicle may also have not been started for an extended period of time.
Recommendation/ Instructions:
This condition may be inadvertently induced by starting the vehicle and immediately shifting the transmission into a drive range or reverse. If the PCM does not see a PRND43 input from the transmission fluid pressure switch before the customer shifts into a drive range or reverse, the PCM will assume the TFP is malfunctioning because the PCM did receive a signal from the PRND43 switch and set the code P1810. This condition would occur more easily if the vehicle has not been started for an extended period of time because of torque converter drain back. DTC P1810 does not turn on the MIL the first failure, but does store the code and it commands maximum line pressure. The customer will probably notice only the harsh shift.
Currently, there is no fix for this condition. The dealer can advise the customer to start the vehicle and allow it to run for a few seconds before selecting reverse or selecting D4 before reverse.
CharlieT
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