Low fluid pressure 4l80e
Low fluid pressure 4l80e I have been having problems with my transbrake working so I took it to a local shop to have them look at it and try and figure out what was going on. After sitting on the phone with rossler most of the day and checking everything having to do with the brake they found the trans wasnt making enough pressure. They said the front pump was probably going causing the car to not make enough pressure.
So I took the car back to my dealership and had our transmission tech pull my trans and check my front pump. When he did he found the pump was trash in side was scoured housing was damaged. So I put a new pump and housing in the trans. After doing so the transbrake still does not work and I'm assuming at this point that it is still fluid pressure as when the transmission is put in reverse which demands the most fluid pressure it takes a few second for it to build pressure and the car to start moving backwards. My question is where do I go next with this? At this point ive spend 1100 bucks and still dont have this issue solved.
So I took the car back to my dealership and had our transmission tech pull my trans and check my front pump. When he did he found the pump was trash in side was scoured housing was damaged. So I put a new pump and housing in the trans. After doing so the transbrake still does not work and I'm assuming at this point that it is still fluid pressure as when the transmission is put in reverse which demands the most fluid pressure it takes a few second for it to build pressure and the car to start moving backwards. My question is where do I go next with this? At this point ive spend 1100 bucks and still dont have this issue solved.
So I put a gauge on the car today and this is pretty much how it went. At Idle and shifting though the gears it didnt move much above or below 60psi, I tried stalling the car up and around 2k-3k RPMS it makes and holds 150psi. I pulled out the tech 2 thinking maybe i had an amperage issue. I pulled up the data screen and shifted through the gears from park all the way down to manual first, the pressure control solenoid amps never changed from 1.0. So manually controlling the transmission pressure control solenoid, when I stepped the amps down to .10 each time i stepped it further and further down it made more pressure until it finally topped out at .10 and 150psi and held steady. So do I have a faulty pressure control solenoid or a bigger problem? Any further ways to test all of this would also be great.
Is it possible shift parameters and line pressures were never set when my car was tuned last? Im thinking its a control issue considering the amps never change when shifted, yet if I change the amps manually fluid pressure changes and will max out.
150 is a little on the low side. 180-200 would be more ideal.
Disconnect the trans connector and check line pressure again.
Although I don't think line pressure is causing your issue.
Disconnect the trans connector and check line pressure again.
Although I don't think line pressure is causing your issue.
TECH Enthusiast
Joined: Jun 2013
Posts: 513
Likes: 1
From: Moose Jaw SK, Canada
Had a friend chase a low pressure problem all last year with an 80e.
He eventually took my advice and had the brake removed. Turns out it was leaking internally through the TCI trans brake literally just shooting fluid out into the pan which made the trans have low pressures.
He actually couldn't get the car to go into reverse when the temps where warm. He had something like 150 PSI with some RPM and it just wasn't enough.
Slipping converter sounded horrible and made the car an absolute pig to drive. It felt like it was down 100 hp, also caused a lot of heat. Nightmare but finally got it figured out.
Not saying I have the solution to your issue but the more info we can get out there the better.. best of luck to you getting it sorted out.
He eventually took my advice and had the brake removed. Turns out it was leaking internally through the TCI trans brake literally just shooting fluid out into the pan which made the trans have low pressures.
He actually couldn't get the car to go into reverse when the temps where warm. He had something like 150 PSI with some RPM and it just wasn't enough.
Slipping converter sounded horrible and made the car an absolute pig to drive. It felt like it was down 100 hp, also caused a lot of heat. Nightmare but finally got it figured out.
Not saying I have the solution to your issue but the more info we can get out there the better.. best of luck to you getting it sorted out.
Last edited by SteenH; May 4, 2018 at 08:56 AM.
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Well I took it to work yesterday and checked to make sure the pressure based on the amps at the sensor is correct and it is. The fluid pressure control solenoid when I command it down to .1amps and hit the brake it holds just fine. So I'm down to it being the fact the solenoid isn't being commanded to charge pressure because the amps never change. Is there any way to use hptuners ot another program to have the module ask for .1 amps in manual 3rd and around .25 or .3 amps in reverse?
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