This is starting to sound like a funky computer issue or problem in the tune. Have your tuner send me the tune file (if it is in HPT) and I'd take a look at it.

 

As I read through the 4L60e service manual that I have, geezzz! It is a much more complicated process than I had expected. I was hoping for an answer like 'this solenoid is off in 'D' but on in '2' ----- But gear position '2' engages all sorts of things: D2 - D3 - D4 lines, both A & B solenoids, 1-2 shift valve, 2-3 shift valve, accumulator, servo, over run clutch...etc. I mean almost everything is in play when the transmission is in '2'. So,essentially unless a good idea comes up that component (whatever) is the culprit and can be replaced without dropping the trans....(sigh)....(something about a goose being cooked)...

 

Thanks Man - Let me see what I can cook up!

 

There are actually many more leak paths in D2 than in normal drive.
That's why I'm currently heavily leaning towards this being a tune/commanded pressure issue.

Also...if you can take an HPT log while driving, monitoring all the "normal" things like tps, map, maf, coolant, yadda yadda but ALSO force motor stuff and shift pressure stuff. That would be cool too

 

Is there any way that this could be something as stupid as a bad 2-3 shift solenoid or something similar? Should I drop the pan and look around? Maybe test a few solenoids?

 

No. Not a shift solenoid issue. 99%

You need to get a scanner put on the car and watch the EPC current. Both commanded and actual.

This will show if the pressure is being commanded differently

 

Ok, thanks for the help. The issue that I have is the following: I'm not close to anyone who has a pro grade scanner and I don't trust the truck to make a lengthy trip.
What I have in terms of diagnostic tools here at the moment is:
- a Foxwell NT510 scanner (with BMW diagnostic software - the GM software can be added for $70)
- An OBD to USB plug (so if I can get a complete software pack for my laptop, maybe that can be an option) + a pretty good laptop.
- Couple 3 year old android tablets
- Recent LG cell phone.
If none of those will do, then I guess I'll need some advice as to what to do or get so I can move to the next step in this magical-mystery journey.
Thanks guys!

 

Hi guys, still no real advancement on the tech side of things. It would be great to see what the ECU is sending out as data, so I'm still working on that. But I did do a few things today:
I drained the fluid and pulled the pan. I noticed that the 2-3 shift solenoid was loose and had a crack on the plastic part of the body. So I replaced it with one that I had on the extra 4L60E in the shed. (the problem with that 4L60e is that it was dead the day I bought it and I never had an idea what was wrong with it. It never moved the truck, all gears were dead, so it will probably be a parts donor).
Back to my slipping transmission: The fluid seemed relatively clean. I put everything back together and filled the fluid gradually as I did a few test drives. At the end I got it to about half quart over full when hot.
Now, for some results:
For some strange reason the PSI is always at about 60psi no matter what gear I'm in and no matter how many RPMs I'm doing. It will move around a bit but not that much, like 10 psi here or there. Maybe my gauge is broken but I undid it to clean out the inside and even started the truck while the gauge was undone to get some fluid to flow through and no, it wasn't clogged. It goes back to 0 when I turn the truck off. (So it might be working fine) - I don't know what's up with that but it is really down from previous PSI numbers.
The transmission still slips at around 1900rpm and then it re-engages around 2600-2700rpm. As if it hits a flat spot. It seems to be getting better but still not 100%. It did go through all of 2nd gear WITHOUT slipping but that only happened twice out of many 1-2-3 gear upshifts. So it is still has an issue somewhere...I was thinking of swapping out the pressure control sensor and/or fluid pressure switch assembly.
If you have any ideas, I'd love to hear them.

 

If the transmission is not holding (or producing) the necessary line-pressure, then slippage will occur...

There is no way around it.
The line pressure is needed to hold the clutch plates applied and/ or the band applied.

 

I am thinking about my now low line pressure...A couple weeks ago I did the line pressure test and the numbers seemed pretty good (see post #35). Then I read somewhere that maybe when I drove the truck home on the night the cooler line let go, maybe the computer made some compensations or collected data that screwed things up a bit...Maybe even limp mode (but I doubt it because it was still shifting)...Seeing as I had left the battery hooked up since that night, I unplugged the battery for a few days to get a deep drain and see if the computer would reset. I think since I re-connected it, I've had low line pressure. Like around 60-70 psi and no line rise. Every gear registers around 60-70 or so PSI - And that certainly cannot get the trans working right. Is there any chance that could be a contributing cause? Because, stupid as this may sound, yesterday it did go through 2nd gear while in 'D' twice without slipping, it slipped on 98% of the 2-3 up-shifts but it got it right twice.
Thoughts, Prayers and Donations are welcome.

 

60-70 psi is darn near minimum regulated line if you have a large ratio boost valve.
You need to look into the pressure control system as a whole.
Seeing the computer commanded epc amperage
ensuring the epc is good
wiring
boost valve
afl

it all works as a team. And you need to look at all players on the team.

I don't think there's a whole hell of a lot more we can help with until you start looking at more of the data and info

 

I think ECU may be the issue here.

 

Can anyone recommend a cheap software/scanner setup that would be good enough to give me an in-depth live view of my transmission components and my ECU? I need to see things like EPC, A & B solenoid, you know, the deep stuff...I have a Foxwell NT510 that has BMW software. I can add GM software for $70 but I don't know if I'll be able to get that deep into the transmission with it.
Thanks guys.
Edit: I ordered the GM software for my NT510 and when I get it, I will report back. In the meantime, still on the lookout for a system that can generate HPT files and give me a live snapshot of the goings on between ECU and Trans.

 

[QUOTE=Jimmys_Trix;20262418
Now, for some results:
For some strange reason the PSI is always at about 60psi no matter what gear I'm in and no matter how many RPMs I'm doing. It will move around a bit but not that much, like 10 psi here or there.[/QUOTE]

I found a few somethings worth thinking about:

I unplugged the trans wire harness to check whether the line pressure would rise to max level...It didn't! So I dropped the pan:

The filter was a cheapo paper filter that looked very dirty and looked better at stopping fluid than passing fluid. Will change it. I had heard that cheap filters can starve a trans of its fluid.

Also, I had a look at the PCS - It has 2 rows of screen filters to keep crap out - The one closest to the tip (that deals with incoming AFL) was full of crap. Nothing could flow through this thing properly. That may explain the 65 psi line pressure that I was getting and/or the drop from 125psi to 65psi (when I was in 'D' going from a 1-2 shift towards a 2-3 shift) (when I'd get to about 1900rpm the line pressure would drop from 125 to 65 and the flare would happen at the same time) .

And yet, even at 65psi, when I put it in '2', I don't get any slipping whatsoever...

While the pan is down, should I be looking at any other possible culprits that may be faulty? If there was crap in the PCS, where else is there going to be crap? I was even thinking of taking down the valve body to check the separator plate and check ***** and maybe clean up some crap, but I'd want to be confident that something could actually be gained by doing that. It is one of those moves that can totally change the direction of this endeavour, if done wrong.

So, I was hoping that the low line pressure and no line rise was due to the clogged PCS and the (previous) line pressure drop could be explained by something like a faulty check ball or clogged orifice that wasn't supplying or holding up enough pressure...And seeing as I'm making a wish list here (why not go big? and..) that was causing the flare...Call me crazy, I can take it!

 

There are 2 screens that snap into the separator plate. They protect AFL, PCS, and shift solenoids

 

Sometimes there are 3...

 

Yes! I saw them on the graphic that I have but hadn't realized that they were on the separator plate. Now, the question shooting around my head is, should I drop the valve body and poke around? Am I likely to find anything of value? Can I screw it up? Is it tough to get it back on right? Any pointers?