4l80 jumping back and forth 3/4

[RDF1]

oh yah one thing you can be sure of is good grounds. every single one was removed cleaned and reinstalled, then i even added some extra ones. im actually pretty good at electrical

Email them to me at [email protected]

 

[PEIslander]

The 4L80 uses solenoids to shift. I'd verify they are working and also check the harness from the solenoids to the PCM. When I bought my 94 it wouldn't shift at all. I build a little stand alone box with toggle switches and plugs for the transmission and a cig lighter plug to feed it 12V. That isolated the shift solenoids from the PCM. I could then manually activate the solenoids. On my truck they were fine. It turned out I had a bad PCM. There's lots of plans online for making these test boxes.

 

[ncnichol]

Where do you live? I know lots of good tuners in Alberta

i live on vancouver isl in bc..... guess where my tuner is from ? alberta lol

 

[ncnichol]

Try this little test. While driving when it does this lift up slightly on the shift lever. Not enough to change gears but just a little bit toward neutral.

i will try that for sure, pretty simple right? although i have been underneath and cheaked for perfect shifter cable alignment. but i will try it

 

[ncnichol]

This is the most likely explanation.

In short:

No blower - trans worked
Blower - trans doesnt work (at least not normally).

@ncnichol - Take it for a drive with a bi-directional scan tool with trans and engine data displayed and see what's up. Then go from there based on what you see/find.

ok so, sorry for having slow responses, first problem is waiting for good weather to test then life keeps getting in the way lol. ok, so here is where im at, 1st thing i did after your last post was cheak tps, it failed...here's what i did, tested tps with multimeter slowly increasing throttle with eng off. was good untill about 1/4 way then voltage was jumping all over the place. ok so then i connected hp scanner and did same test watching tps voltage on scanner, failed again. this is great. at the same i was looking at iac position becouse eng had been surging at idol. thought maybe idol screw had backed off, sure enough it had so i adjusted that and got iac position back between 80 and 90, while adj it watching tps voltage, it didnt change at all, another indication bad tps, so i now change tps for one i know is good then did a tps iac reset and then cheaked everything all over again on the scanner.... perfect, everything was right on point. all issues in spec and passing tests. great!!!! time for road test, no frigging change, trans still acting exactly the same. that was discouraging to say the least. so a couple days later i drive it and it throwes a front speed sensor code, YES!!! that could defiantly affect shifting. so i put the truck up in the air and didnt just cheak speed sensor but every plug and connection, found green corrosion on the larger plug on the switch on the shifter shaft. ( dont know how i missed that before ) anyway. got that all cleaned up. tested speed sensor... probably had the decimal point in the wrong spot but reading was 1.47 ohms. i think thats ok ? so anyway get it all back together time for a test drive. hi hopes again, i have solved issues on other vehicles becouse of that same green corrosion. so off i go.... no change. trans still has same issue. are you kidding me ? grrr!!! so that is where im at now. i am going to try and figure out how to put a scanner recording log together to data log all the trans info. i must say though i sometimes struggle with the scanner, hp has not made the scanner as easy to understand as the editor. there is one thing thats been in the back of my mind, when i drove it and manually locked the converter and then locked it in 4th and it still did it how could that be? it doesn't take imputs from anywhere is locked through scanner.... unless there was a pressure leak internally ?