Why do 4l60e's lose 3-4
 

What makes these transmissions lose 3rd and 4th gear. I just lost 3-4 and I have a couple of buddies that have had the same thing happen to them.. In every case we have experienced 1-2 have been alright just no 3-4.

Typically the cause is a 3-4 clutch pack failure. This can happen several ways. 1- the 3-4 clutch pack just wears out it has the smallest friction area of any upshifting clutch set in the 4l60e.2- Another reason is loss of line presure such as a bad PCS since this pack has the lowest friction surface it tends to suffer the most damage first from slipping. 3-The snap ring breaks out of the input drum this is the comon cause of a sudden loss of 3rd and 4th basically the snap ring either comes out or breaks through the drum, This can be caused by several things, Improperly installed shift kits,Too much line presure,Excessive 3-4 clutch clearance either during a build or because of wear or just a weak drum. There are other possible causes but the main reason this is the first area to fail is because its the area with the lowest overall friction area and the largest fluid presure and volume demand during apply in the 4l60e during and upshift.

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