97 4L80E dropping out of TC lock up

[mannebk]

how about i throw a new harnesses at it the next time i pull the pan? cant be that crazy expensive.

and probably that shift detector forward next to the plug and all coils as well?

what would that cost? is it worth a parts cannon shot with known good quality sources?

and ehat else is "know" to fail from the OEM stuff that was installed by GM

 

[mannebk]

while under it i checked again, my cables go right into the big harness and up on top of the gearbox, over the driver's side valve cover then all the way up front over the radiator to the PowertrainControlModul.

So I don't have en ECM and seperate TCM.

I have one unit; a PCM.

i also checked for loose cables or damaged plugs, couldn't find anything obvious.

 

[mannebk]

let me also add, I'm currently traveling from Salt Lake City to Seattle. Im just into Washington (just made it onto I82 west), so if you know a good trans shop on the way, speak up pls.

And i do have some serious mountains ahead of me, but ive been through Sequoia NP and passed through Telluride multiple times way earlier in the year and including snow covered roads, so I'm not scared. just an other test drive for the trans, now that the engine finally is all fixed right now.

 

[mannebk]

okay, plaid some more.

coolant plug off, -40c in odb, dash showing real temp. no change in Transmission behavior. plug back on.

tps plug off, boy what a change. transmission feels like a manual, switching real hard like a double clutch transmission but without the enfine adaptation to it, the whole powertrain jumping in the engine bay. especially the shift to 4th is real hard. 1-3 all normal, 4th, switch happens and after about 3 seconds it starts slipping like almost no contact on the band anymore.

i plugged the tps back in while driving, no change, fault reset while still driving, transmission tries to re-engage 4th but fails like usual.

so what makes the 4th come on real hard but start slipping after 2 seconds??

sounds to me like. a blown seal on the 4th hydraulic circuit.

when it goes on its got the required pressure, but when it stays on the pressure drops away gradually.

its worse when hot, and sometimes its there and other times not...

im bewildered, to put it mildly.

 

[dbrannon79]

What does your trans fluid look and smell like? sounds like 4th is about to leave the chat. you might look into dropping the pan for inspection of clutch material in the pan and magnet along with a fresh filter and new fluid.

use only dextron 3 not the 6 like GM wants you to use. you can add with I call new clutches in a bottle (Lucas trans fix) with the new fluid and baby it if your traveling, but from the sound of it, I think 4th is going out.

 

[mannebk]

i changed fluids about 2k miles ago.

see for yourself, i think i was the fist in there, at least its 20 years and 6k miles old, cause thats what i did drive with it.

filter looked like brand new, not dirty at all.

i just discovered that my MAF goes bonkers in rain....

i think i have an electric issue.

i also discovered that on similar condition

same speed
same throttle position
same engine load

uphill i have like 3 seconds of 4th gear

while downhill i have like 30 seconds of 4th gear, of if i roll out of downhill, respectively earlier.

and if i take the food off the pedal downhill the 4th stays engaged as long as the downhill lasts or until i apply throttle, then counting down about 30.

r respectfully i disagree, its not the 4th being in its way out. its som electrical issue, i just don't know what.

 

[jrsavoie]

how about i throw a new harnesses at it the next time i pull the pan? cant be that crazy expensive.

and probably that shift detector forward next to the plug and all coils as well?

what would that cost? is it worth a parts cannon shot with known good quality sources?

and ehat else is "know" to fail from the OEM stuff that was installed by GM

I would only use a GM or ACDELCO harness.

There might be something better. But not that I've heard of

 

[mannebk]

I would only use a GM or ACDELCO harness.

There might be something better. But not that I've heard of

you wouldn't happen have a parts number for me, would you? O'Reilly's couldn't even find it last ai was in and asked, not that im going to order it there.... was just a while i buy oil and filter for the tans, do you happen to have that too? idea.

 

[dbrannon79]

you mentioned it acts up in the same pedal position. have you tested your TPS with a volt meter while the key is on to see if it has any drop outs. or if you can see live data on the scanner for it? also check to make sure it's adjusted properly. it's possible there is an electric issue. you mention it sat for some time. is there or was there any evidence of rodent droppings anywhere? mice can wreck havoc and they love the plastic insulation on wires.

fluid and pan looks good.

 

[dbrannon79]

the trans will mainly use the TPS and engine RPM for shifts. since it has a MAF sensor, if it's flaky, it also can cause erratic trans behavior too.

what kind of scanner are you using again? I'm not familiar with the pic of that display you showed earlier.

 

[Will L.]

New parts does not mean good parts. New defective is a more common thing now than ever.
Loading the parts cannon is NEVER a good idea unless you are doing a full rebuild of a component. If you move forward with it, I suggest installing one part at a time, keeping the old one, and test drive between each part. Imagine part F is at fault.
You change abcdefg. But the problems persist or change slightly as you do it.
Because part c is completely bad and part d is intermittently bad. Change everything at once- you’ll never know.
Regardless- NEVER get rid of the old parts until a couple weeks of it working properly.

 

[mannebk]

im using an UltraGauge, similar to scangauge.

i can make the tps inctement at about 0.5% all the way from 0 to 100, no dropouts, no erratic behavior, pretty linear... was a test i did a week ago

also keep in mind i tried with tps unplugged, and the 4th still does drop out with tps unplugged while 1-3 are perfect.

no we did not have any sort of rodent damage, probably because the former owner has like 25 cat around his farm.

new evidence.

I'm on I90, just through Snoqualmie pass. its raining since 15 miles, quite substantially.

And now that the transmission has cooled down a bit in the rain and going downhill i have my 4th back up to the point where it shifts back into 3rd (about 50 % of tps (at 65-75 mog) so total normal behavior.

i roll out of the downhill, 4th drops out after a few seconds.

i go around a left hand curve in downhill, my 4th goes away.

i think the issue with neutraling in all gears that i have, and that i fixed for 1-3 by overfilling, is the same that kills my 4th.

but i dont know what would make the 4l80e suck air as soon as its out of level...

the only thing coming to mind is a failed valve body seal, so it won't suck from the filter but from inbetween. that would be wild.

 

[Will L.]

@Paveltolz does Bill know any good 4l80e trans guys up in his area of the country?

 

[mannebk]

check the time stamp, the rest

 

[mannebk]

and once more

 

[Glagulator]

Read this. Clinebarger is a 4l80 expert. Might be your problem?

4l80 overdrive problem, 4th gear kicks in, then drops out - LS1TECH - Camaro and Firebird Forum Discussion

Automatic Transmission - 4l80 overdrive problem, 4th gear kicks in, then drops out - hello, friends. I installed a 4l80 in an old chevy pickup, overhauled by myself, amateur me, hahaha. gears are controled whit switches, full line pressure, first three gear works fine, very fine, loved the...

ls1tech.com

 

[Paveltolz]

@Paveltolz does Bill know any good 4l80e trans guys up in his area of the country?

@mannebk On Edit. In Yakima…

The best is PacTrans. Ask for Al or Bryan.

 

[mannebk]

i could check that on the next oil change...

Read this. Clinebarger is a 4l80 expert. Might be your problem?

4l80 overdrive problem, 4th gear kicks in, then drops out - LS1TECH - Camaro and Firebird Forum Discussion

Automatic Transmission - 4l80 overdrive problem, 4th gear kicks in, then drops out - hello, friends. I installed a 4l80 in an old chevy pickup, overhauled by myself, amateur me, hahaha. gears are controled whit switches, full line pressure, first three gear works fine, very fine, loved the...

ls1tech.com

 

[Paveltolz]

sorry for any confusion as I updated my post after I initially hit send.

Repeating:
In Yakima, “The best is PacTrans. Ask for Al or Bryan.”

 

[mannebk]

sorry for any confusion as I updated my post after I initially hit send.

Repeating:
In Yakima, “The best is PacTrans. Ask for Al or Bryan.”

thank you, but unfortunately thats 2 h behind me