Softer shifts at higher rpm's

[Marty85]

Have any of you 4L60E tranny people ever noticed that after you installed your shift kit or other method of making your tranny shift harder that while at first it seemed like it worked great and you noticed that even at WOT it shifted better but have you taken the time to notice the difference between say a 1/2 - 3/4 throttle shift is compared to a WOT shift. Well I have and I have found a reason why. In the 4L60E transmission there is a vane pump driven directly by the torque converter (ever noticed those two notches on the part of the torque converter that goes inside the pump body, those drive the vane pump). I noticed that my vehicle would shift great and shift firmer while at partial throttle but got softer at WOT. Well I read on different websites (cant rememeber them) that the reason for this is because the vane pump inside the 4L60E has a casing that is spring loaded and the vanes are able to slide outward in their rotor. What happens at high rpm's is that the vanes of the pump push themselves outward due to centrifugal force against the spring loaded vane housing which gives away due the pressure exerted by the vanes. When this happens it allows tranny fluid under pressure in the vanes to to leak behind them and around them lowering the amount of pressure that the pump is able to preduce causing softer shifts. I just thought id write that nice little peice of information in case anyone was wondering. I even think there is a website that deals with nothing but 4L60E trannys that sells all kinds of upgraded parts and shift kits and also sells a heavy duty pump assembly able to withstand higher rpm's and greater pressures.

[andrew.brandon]

hmmm I had wondered that also. I figured it was just the kit itself.

http://www.transmissioncenter.net/4L60E.htm