Question: 4l80e high line pressure in park and neutral

[rick67]

The truck is a 1997 GMC 3500, 5.7, 4l80e 71k.
Since we have owned this truck it has a very soft shift, especially into reverse.
I ran pressure tests, all were in normal ranges. I pulled the valve body and found the seats in the spacer plate were worn, so I ordered a transgo spacer plate and sg1 shift kit. I installed the kit and spacer plate. I have installed a lot of kits in 350 and 400 trans , but this is my first 4l80e
When I fired it up, line pressure is high [around 400 psi] in park and neutral, but drops in any gear. Also drops with throttle opening.
I am thinking I don't have the pressure regulator installed correctly. The instructions that came with the kit did not match the info in the video on the transgo site.
Anything else that I should look at while I am back in it?
Should I just put the original pressure regulator pieces back in?

 

[Mike L.]

The truck is a 1997 GMC 3500, 5.7, 4l80e 71k.
Since we have owned this truck it has a very soft shift, especially into reverse.
I ran pressure tests, all were in normal ranges. I pulled the valve body and found the seats in the spacer plate were worn, so I ordered a transgo spacer plate and sg1 shift kit. I installed the kit and spacer plate. I have installed a lot of kits in 350 and 400 trans , but this is my first 4l80e
When I fired it up, line pressure is high [around 400 psi] in park and neutral, but drops in any gear. Also drops with throttle opening.
I am thinking I don't have the pressure regulator installed correctly. The instructions that came with the kit did not match the info in the video on the transgo site.
Anything else that I should look at while I am back in it?
Should I just put the original pressure regulator pieces back in?

Sounds like you did a few things wrong. There are 2 different PR setups. Also you were suppose to drill some holes through the casting and install a blow off valve. 400 psi will crack the case in short order and could spike to 900 psi.

 

[rick67]

Thanks for the reply.
I did install the blow off valve.
I was just watching the video again, and I think I may have misidentified which style of valve I actually have.
I did not let it run long at that high pressure, and did not have it off of the lift.
I may run over to the shop tomorrow and pull the regulator back down. I don't want it to bug me all weekend.
Thanks again for the reply
Rick

 

[rick67]

I pulled the pressure regulator back down, removed the spacer, and pitched it. pressures good.
Trans shifts good.
Thanks for the reply Mike.
Rick

 

[Mike L.]

I pulled the pressure regulator back down, removed the spacer, and pitched it. pressures good.
Trans shifts good.
Thanks for the reply Mike.
Rick

Good man.:thumb: