4l80e problem

[Houseofperformance]

i´m in need for suggestions from the 4l80e gurus.
i´m running a built 4l80e with a new 2800 stall lockup conv. and the first generation tci wp ecu with george blakes harness.
finaly i´m even able to comunicate with the tci, after finding 2 wires of the comunication cable beeing switched.
now for the problem: the tranny feels like it is sliping or it has some internal resistance from a dead stop or slow speed - engine revs, boost builds, but no go at first - then it slowly catches up, engine power is there, but it gets lost somewhere in the tranny.
it might be a oil pressure problem - so i need to know where to get a line pressure reading, and what line pressure is normal.
i had to completly dissasemble the trany to change the output shaft - maybe i made a mistake when reasembling, but the trany shifts, has reverse and all gears, oil looks good....
any suggestions what the problem could be and where to get a proper line pressure reading?

 

[JSM]

Re: 4l80e problem

there is a plug on side of trans you can remove and put a line pressure gauge on.

In the TCI keep in mind line pressure is reverse of what you would think. If I remember on older TCI 0% is actually full line pressure, so your curve for line pressure -vs- tps will start up and get less as TPS increase which in turn gives you more line pressure.

 

[TYTILIDIE]

Re: 4l80e problem

If you bought it from Blake, why not just ask him?

 

[Windedv6]

Re: 4l80e problem

If you bought it from Blake, why not just ask him?

Good luck with that idea...

John

 

[Six-is-Enough]

Re: 4l80e problem

Good luck with that idea...

John

Yes George is tough to get ahold of........

 

[1BADV6]

Re: 4l80e problem

I would say almost impossible......

 

[MRKING]

Re: 4l80e problem

When you are driving , look at the dash on the tci program and verify you are starting out in first gear . Also is the correct configuration file properly loaded ?

 

[Houseofperformance]

Re: 4l80e problem

thanks guys!
i didn´t start this topic to get a "george did or didn´t thread", i just started it to get help, and as far as i remember george was always willing to help!!
jeff: where exactly is that plug? - i got the model with both coolerlines in the front - i know about the reverse pressure programing - the tci was programed by george with some standard program that should get me driving - starts out with about 50% dc on the pressure valve and flattens to 0 in first - so the configuration should be ok.
i´ll try to get a datalog today and will upload the file, maybe there is something obvious i don´t see!
thanks

 

[Try Me]

Re: 4l80e problem

There should be a brass plug on the drivers side of the trans about half way back from the bell housing where you can hook up a gauge. I have the same early case 80e with the cooling lines up front together similar to the 700.

To check line pressure once gauge is installed start the truck and put it in reverse. Make sure to go into Operational Parameters and change the "Rev LP Kick %" to 0. This way you should see what your max line pressure the trans is making at 0% duty cycle (like you would be under wot).

Max line pressure should be somewhere between 200 and 240 on a performance built trans. "They say" (i hate that phrase) you should never have more than 240psi or it will cause damage to the trans. I know my transgo shift kit had a vavle you install that is a pressure releif incase it gets too high so your trans probably has something similar.

 

[Houseofperformance]

Re: 4l80e problem

thanks - i´ll do the pressure test today.
also loged a file while cruising but i´m not abel to save it as a .log file - guess i´m on the demoversion of the wp software.

 

[Houseofperformance]

Re: 4l80e problem

pressure tested - lp kick set to 0.
on the economy mode i just get about 130psi in reverse - when hitting the performance switch pressure rises to about 260psi (the programing says 25% perf.kick) - but the sluggish feeling when taking of is present in both modes.
just no go till the truck hits about 20mph, then the trany seems to grap and of it goes.
i´m lost here

 

[Houseofperformance]

Re: 4l80e problem

when looking at the tables it seems, that the trany just starts to grap when it sees 100% line pressure in first, that can´t be right, i don´t belive the trany was built to see 100% line pressure all the time - what could be the mechanical cause for this? maybe the pressure is bleeding of somwhere on the way? please give me some hint

edit: i think the trany doesn´t grap at all in first, it´s only sliping and barely moving the truck till it shifts to second, than it gets grip and the truck starts to pull as it is supposed to.

 

[Houseofperformance]

Re: 4l80e problem

got a log file saved, but i´m not able to upload it on here - i can send it via e-mail, if anyone is interested.
truck pulls great in every gear, except first - and i have no lockup, eventhough the tci seems to comand lockup, and i checked the tcc solenoid and it´s o.k. could this 2 problems be related?
help me out, please!

edit: got the file uploaded here:
http://www.mediafire.com/?sharekey=224df2af3e0f56cf61d4646c62b381cbe04e75f6e8ebb871

 

[Houseofperformance]

Re: 4l80e problem

found the lockup - the connecting pin on the trany plug was pushed back so it didn´t make contact.
now show me where to find my first gear, please - when manualy downshifting i can feel every shift except the one to first

 

[Houseofperformance]

Re: 4l80e problem

question, to interrupt my monolouge here a bit:
is one of the braking bands activated in first gear, that might need to be adjusted?

 

[DaveP]

Re: 4l80e problem

First gear, D4, is using the direct clutch only. If you have "slipping" in first, D4, there is a problem with direct clutch, or line pressure.

First gear, D1, applies the rear band for engine braking. The rear band is also used for Reverse. If Reverse is OK, the rear band is probably OK as well. Go back to first paragraph.

My Helms Manuals calls for 35-171 psi line pressure in P,N. Is there a way to increment the pressure regulator within the TCI to check the pressure at each 'percent' level available? Then watching PC DC in each gear might reveal a problem in first, D1.

 

[Houseofperformance]

Re: 4l80e problem

thanks dave!
i just tried a reverse boostlaunch - it works.
so the band seems to be ok.
i guess it activates the band when manualy downshifting to first, but i´m not able to feel it because of the sliping direkt clutchpack.
i could check the pressure increments by connecting the pressure gauge to the trany output while changing the settings of the pressure valve dc - but i have no way for telling if the pressure makes it to the clutchpack, i guess. asuming that the pump delivers pressure, and i have correctly assembled the clutchpack, where would be the most likely place for the pressure to get lost on the way to the clutch - blown gasket, sticky valve...?
sorry for this questions, but automatic transmissions are like brain surgery to me.

 

[DaveP]

Re: 4l80e problem

thanks dave!

i could check the pressure increments by connecting the pressure gauge to the trany output while changing the settings of the pressure valve dc -

I would do this. Now you know what the pressure is at a particular duty-cycle. Then you can look at the 'dashboard' DC and compare dc's in different gears.

, where would be the most likely place for the pressure to get lost on the way to the clutch - blown gasket, sticky valve...?

Separator plate or gaskets. Not sure if there is a forward-clutch accumulator or not. My buddy the builder was talking about a 4L80 he did recently that didn't work correctly upon installation. They pulled the valve body, and found a cracked case that he missed when it was on his bench. Ooops. It's also easy to cut a piston seal during assembly. But this should result in slipping in third.

actually, anything that is related to the forward clutch (I was calling it "direct clutch" in earlier post, but that is incorrect term) slipping should be more apparent in higher gears where the torque levels on the clutch are higher than they are in first.

edit: I don't have any experience or knowledge with the TCI controller or programing, so I can't make suggestions for where to look within the program.

But you can do this to see if you have a problem with the forward clutch or rear band circuit:

1. Read the pressure (on the gauge) and record the dc in neutral.
2. Put the trans in D4. Set the dc to the same as step 1. Pressure on the gauge should be the same. If lower, there is a leak in forward clutch circuit.
3. Put trans in D1. Set dc to same as step 1. If gauge is lower, but step 2 was OK, there is a leak in rear band circuit.

 

[Houseofperformance]

Re: 4l80e problem

that´s wiered, since mine will only slip in first and works great in every other gear - i´ll do the pressure test tomorrow to see how changes in the settings influence the actual pressure.
the tranny also has a shift kit installed (transgo 2), but i guess that doesn´t matter for my problem.
thanks a lot!

 

[Syclone#892]

Re: 4l80e problem

House of Performance send windedv6 a message about the shifter problem you have.

What he found was the linkage bracket that george supplied with the trans is incorrect for the shift detents on the shifter itself and that is why you can not get it into first.

He made a new one and I think he may have given the drawings etc to someone to make some for the community.

I bet if you safely had 2 people you could disconnect the shift linkage and manual shift at the trans to get it in first gear and it would work great.

If you keep operating it the way it is you run the risk of messing up the trans because it never fully goes into a gear its always between 2 gears.

Good luck