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Author Topic: 2003 Silverado 1500 4l60e harsh shift 1-2 & 2-3 slip??  (Read 3042 times)

Offline cw41

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2003 Silverado 1500 4l60e harsh shift 1-2 & 2-3 slip??
« on: September 08, 2009, 10:26:52 AM »
I've encountered a harsh shift from 1-2 and especially while going uphill, when shifting from 2-3 it acts like it tries to slip into 3 prematurely and happens under partial throttle and especially under full.  I've changed the fluid and filter no contamination refilled with the correct GM fluid and have no codes set.  I've heard that these 4l60's have had a problem with shifting and do they make a improver kit to help this problem or is there another issue elsewhere?  Thanks again for any replies!
Chuck
BTW when I search 4l60e, nothing comes up???

Offline Transman

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Re: 2003 Silverado 1500 4l60e harsh shift 1-2 & 2-3 slip??
« Reply #1 on: September 08, 2009, 09:05:09 PM »
What kind of mileage is on this vehicle? Any addons or extras? Last "Flash" from the dealer? There were problems with the EPC solenoid (pressure control) as well as alternator problems. Disconnect the 4 pin elec. connector at the alternator and drive, is the problem gone? If not reconnect the connector. There have been problems with the input speed sensor AND the wiring harness to it. Are you able to see the datastream for the trans? Post info and we can continue, Transman
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Offline cw41

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Re: 2003 Silverado 1500 4l60e harsh shift 1-2 & 2-3 slip??
« Reply #2 on: September 09, 2009, 10:49:14 AM »
Thanks for the reply.  It has 90k no add ons of any kind and I'm not sure what the Flash from the dealer is??  They looked at it showed no codes test drove and told me its normal.  I will disconnect the alt and see it the problem goes away.  I don't have any equipment to scan the system by myself so thanks for any help to keep me out of the shop again!
Chuck

Offline cw41

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Re: 2003 Silverado 1500 4l60e harsh shift 1-2 & 2-3 slip??
« Reply #3 on: September 09, 2009, 02:42:21 PM »
I disconnected the alt plug and went for a ride although could not duplicate the same uphills that are about 90 miles away that I frequent, but did notice some shifting improvement especially 2-3.  1-2 is still somewhat harsh.  What does the alt have to do with shifting its charging 14.2v?  Thanks again,
Chuck

Offline EricC

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Re: 2003 Silverado 1500 4l60e harsh shift 1-2 & 2-3 slip??
« Reply #4 on: September 09, 2009, 03:26:44 PM »
Take it somewhere and have it scanned for DTCs. While I wouldn't rule a possible engine problem out, many trans codes cause the PCM to
command maximum trans line pressure, resulting in harsh shifts. Most chain auto parts houses will scan for codes at no charge, and the
infamous P1870 will not always cause the SES light to come on.
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Offline Transman

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Re: 2003 Silverado 1500 4l60e harsh shift 1-2 & 2-3 slip??
« Reply #5 on: September 09, 2009, 09:43:23 PM »
The alternator makes AC current and it is changed to DC by diodes that basically cut the bottoms of the power off thus leaving DC current. The problems come in when one or more diodes fail or just get weak and don't effectively cut off all the bottoms. On older cars, this was not a big problem. On the newer cars, this is a big problem as all the computers on the vehicle can't deal with AC current, even slight amounts. It makes them go nuts. If your vehicle's shifting improved with the alternator connector unplugged then get the system tested by a shop that can test for AC ripple. Even if it isn't the transmission's problem, it soon will be. Please don't waste any time about it as the electrical damage can be considerable if the diodes fail completely. It would be like plugging your 12 volt appliance into 120 V outlet. Post results, Transman
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