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Got my 4L80E 10.5" single-disc stall today and a red spring came with it with instructions for the pump modification (install the supplied red inner spring on the Converter Limit Valve). I believe this spring raises the pressure that is sent to the stall. Instructions say the line pressure must be at least 180 psi at max throttle opening. Not sure what the stock pressure is...Is the installation of this spring absolutely necessary? Has anyone ran it with the stock spring that comes in the 4L80E? Anyone have instructions on how to do this or is this something a trans shop needs to do? Car is a 2000 Z28, Procharged, ~650 rwhp.
Last edited by mike135531bubba; Nov 8, 2018 at 06:34 PM.
You'll need to pull the pump to replace this spring.
What brand 10.5"?
Yank - Pro Yank Series. Previously, I ran a Vigilante triple-disc stall in a Procharged Fbody w/ 4l60e and was never sent a spring by PI, never had issues with that car.
Well that was a 4l60e and now you have a 4l80e. They are not apples to apples comparisons.
the 4l80e has a little different theory on lockup control. Stock converter pressure is regulated with the spring from 93-107 psi. A stiffer spring will raise this pressure.
That's what the book says anyway. In reality it's not. I wouldn't install a stiffer spring.
I'm gonna definitely trust that you know how the converter pressure works...can you explain for me how the stiffer spring wouldn't raise the pressure? You're right...I study the book fairly often...and that's what it says.
I called yank today, they claimed the spring was needed for the line pressure. Should I just slap the tranny in without worrying about the spring?
After extensive testing on a transmission dyno over the years, I can safely say, you don't need to raise the converter charge pressure in a 4L80E. My shop as well as a couple of other shops that make specialty 4L80E parts have done in depth testing of this.
If the converter supplier knew what the actual pressure was in the converter, they wouldn't want any more.
Initially I never even installed the spring. However, upon start-up of the new motor/trans, the trans pump seal was shot and was leaking fluid everywhere. I pulled the trans and it turned out the used trans I got on CL that supposedly ran well needed a complete rebuild. At that point since the trans was apart, I had my trans guy install the red spring. He also recommended installing it. It is what it is at this point.
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4L80E Pump Modification 
