View Full Version : too much line pressure?!?


lt170chevelle
06-10-2008, 07:33 PM
i have been having problems pecking the rev limiter in 1st to 2nd for a while now .i have a shift kit in a 4l60e and upped the line press in the table by 5 psi. my question is..is there a chance i am getting too much line pressure? also when i replaced the tranny about a year ago, i was getting a very delayed shift through all gears and was told to turn the torx something on the valvebody to increase line pressure to compensate i think was an 1/8th to 1/4 of a turn.could i have too much now? i have been gradually lowering the shift tables with no luck yet.will too much pressure make it hang in gear in between 1st to 2nd shift?:confused:

JimsWS6
06-10-2008, 07:43 PM
I have a vette servo, changed the pressure valve spring, and vette 1-2 spring and if i horse my truck alot she'll shift 1-2 around 4500 WOT. I have to disconnect the battery and then it'll go right back up to 5300.

But my truck will churp the tires sometimes in the 1-2 shift under WOT. Probly not too good for it, considering it has 220,000 miles


So I think it is possible, it backs off some pressure to help reduce stress I feel. We'll wait for a pro to jump in on it

performabuilt
06-10-2008, 08:26 PM
Yes excessive line could cause a no shift issue at WOT this can happen when so much fluid is be sent to the solenoids that they cant vent fast enough. And is you have the line raise both electronically and with the PCS screw and with a boost valve from the shift kit its very possible this is the case. I would disconnect the harness from the trans with a pressure gauge installed and see just what the max line pressure is, IMO it should never exceed 230 PSI

lt170chevelle
06-10-2008, 09:36 PM
ok thanks. when i can get my hands on a guage i will definitely have to see what its doing. About when would max line pressure kick in? in gear revved? Or certain rpm in neutral?what will happen if i drop max line pressure in my tables by like ten psi?

02c6ss
06-10-2008, 09:42 PM
Is it a weak 1-2 shift kind of like it slides in? Once it goes in 2nd does it hold or slip?? I had a problem that sounds like yours. I decided to install the trango hd kit with the fairbanks super servo and aluminum 1-2 and forward accumulator pistons. I ended up that one of the factory plastic accumulator pistons had a crack in it which was bleeding off the pressure and causing the weak 1-2 shift. Now the thing shifts better than ever and saved myself 1800 dollars. The pistons were only 20 bucks off ebay for both of them so its worth a try. Hope this can save you some cash!!

performabuilt
06-10-2008, 09:46 PM
ok thanks. when i can get my hands on a guage i will definitely have to see what its doing. About when would max line pressure kick in? in gear revved? Or certain rpm in neutral?what will happen if i drop max line pressure in my tables by like ten psi?


You can adapt and old A/C high side gauge to work and to see max line simply unplug harness from trans with it running and test line. I usually test in OD position and at idle it should not rise with engine rpm with harness unpluged.

And whats mentioned above is also a distinct possibility

lt170chevelle
06-10-2008, 10:01 PM
well it shifts good unless im at wot.quick shifts under normal driving conditions and doesnt slip.also when i installed the shift kit i noticed all of my pistons are aluminum no plastic ones.but maybe a bad oring..no tellin at this point. i will see if i can find a guage laying around and go from there.

Jeff 97 Formula
06-19-2008, 09:16 PM
I hear it's not good to increase line pressure and shift kit (do one or the other, not both).

Vince @ FLT
06-19-2008, 11:04 PM
I hear it's not good to increase line pressure and shift kit (do one or the other, not both).


I wish I had a dollar for every time I have said that on the phone to a customer. One or the other not both. :nod:However tuning will not effect max line pressure. Meaning how much pressure the trans is capable of making. The trans depending how it is setup, will only make so much pressure. I feel that 210-220 max psi is perfect when hot. Most builders will crank the epc up to get more pressure and IMO you will yield to much pressure when doing this. Vince

98 T/A raptor
06-20-2008, 12:55 PM
this is good to know