Trans slipping in od 4l65e
10-08-2015, 08:17 PM
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Trans slipping in od 4l65e
06 Silverado 4x4 4l65e Trans runs perfect for the first 10 minutes you drive the truck then after it warms up the trans will slip when it's in lock up and throw a po894 code. Going up a slight hill it will stay locked the whole time until you top the hill and right at the top (when the load on the trans is decreased) the trans slips about 3-400 rpm. Any idea what it is? Thanks guys!
10-10-2015, 12:23 PM
#2
If it's only slipping by that much it sounds like it could be the toque converter lockup clutch. A slipping 3-4 clutch pack in a 4L60/65/70 feels more like going from fourth to second gear - it freewheels, not just the 300-400 RPM you've described.
With the assumption it's got to do with lockup there are two causes I can think of off the top of my head.
1. TCC Apply valve wear - a well known problem in these transmissions. This valve modulates the line pressure to the torque converter clutch. Over time the valve wears out in its bore allowing excessive bypass resulting in lower than expected line pressure delivered to the TCC. The Sonnax TCC apply valve kit is a fairly easy fix - only valve body comes out, trans stays in truck.
2. Torque converter clutch wear - could just be the clutches in the converter are finished. Solution is to drop the trans and replace the converter.
There are a few things you can do to confirm it's in the lockup circuit. TCC lockup can be inhibited by activating the brakes, so if you just barely have your foot on the brake pedal enough to activate the lights but not actually apply the brakes it will inhibit lockup. In that scenario if you repeat your throttle test and don't experience the slipping you'll know what you were feeling normally was the converter unlocking unexpectedly.
With the assumption it's got to do with lockup there are two causes I can think of off the top of my head.
1. TCC Apply valve wear - a well known problem in these transmissions. This valve modulates the line pressure to the torque converter clutch. Over time the valve wears out in its bore allowing excessive bypass resulting in lower than expected line pressure delivered to the TCC. The Sonnax TCC apply valve kit is a fairly easy fix - only valve body comes out, trans stays in truck.
2. Torque converter clutch wear - could just be the clutches in the converter are finished. Solution is to drop the trans and replace the converter.
There are a few things you can do to confirm it's in the lockup circuit. TCC lockup can be inhibited by activating the brakes, so if you just barely have your foot on the brake pedal enough to activate the lights but not actually apply the brakes it will inhibit lockup. In that scenario if you repeat your throttle test and don't experience the slipping you'll know what you were feeling normally was the converter unlocking unexpectedly.
10-10-2015, 08:13 PM
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Yea I took it to the transmission shop and got it back like this, took it back they replaced the converter and it does the same thing. Took it back a third time and supposedly the replaced the tcc valve and they said it was fixed. It still isn't. He said he never saw a pressure drop but he isn't driving it for 15 miles and letting it warm up then looking at the line pressure
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