Want to bet on my luck? (atf to "save" transmission)

[Snoman002]

Originally Posted by nascarnation

If the engine and chassis are still solid, I'd say this is one major repair that is worth it.


And that is the rub. I'm $6k in to a rusty $5k pickup. Im not too broken up over that since it is a Quadrasteer (rare), in an 05 a silverado (more rare), in a special order color (you get the point).

 

[Snoman002]

Easy enough to test....Unpin the Yellow wire out of the MAF connector, Let the PCM set P0101 & all the line pressure calculations will work off the MAP sensor values (Speed Density)

Unpinning the signal circuit is very easy with an Awl, You don't want to simply unplug the MAF as the IAT is built in.

In an act of laziness, I'll simply provide a link to something I posted a couple years ago...
https://www.bobistheoilguy.com/foru...-on-3rd-to-4th-05-solara-5at#Post4784036

Hope it helps and that a rebuild isn't necessary!

Changed the fluid with little to no change and the issue getting worse by the day. Cleaned the MAF as well with almost zero change.

Today, in an act of desperation, I just unplugged the MAF. The transmission is near perfect.

Now, my question. With the MAF disconnected there was no code thrown. More importantly the shifts were NOT hard. What are the chances the MAF is bad and changing it will fix the issue. Vs the likelihood that maxing line pressure just covered up the problem?

 

[clinebarger]

It should set P0102.......You may have to kill & start the engine a few times. I meant P0102 not P0101 in the other post!
I don't recommend unplugging the MAF because the IAT sensor is incorporated into it. Unpinning the Yellow wire is pretty easy!

Defaulting to the Main VE Table which is what the PCM will do when P0102 sets Does Not max out line pressure, The PCM is simply using a backup source for calculating engine load/air flow. Will it raise line pressure a little from a normally functioning MAF calculated load?........Sure, But nothing drastic.

Further diagnosis will require a good scan tool that can read engine load & MAF values.........Short of throwing a MAF at it.

 

[Snoman002]

It should set P0102.......You may have to kill & start the engine a few times. I meant P0102 not P0101 in the other post!
I don't recommend unplugging the MAF because the IAT sensor is incorporated into it. Unpinning the Yellow wire is pretty easy!

Defaulting to the Main VE Table which is what the PCM will do when P0102 sets Does Not max out line pressure, The PCM is simply using a backup source for calculating engine load/air flow. Will it raise line pressure a little from a normally functioning MAF calculated load?........Sure, But nothing drastic.

Further diagnosis will require a good scan tool that can read engine load & MAF values.........Short of throwing a MAF at it.

Understand on the yellow wire and that was my intent after your previous comment. I only unplugged the MAF here as I was at work and did not have access to my tools. I had driven it in hopes the new fluid would offer some differences but within minutes 4th had basically started to disappear and I was getting up to 1000 RPM slip with just lite throttle changes.

Thank you for the info on the Volumetric Efficiency table and line pressure. A few internet posts had indicated to me it would just default to a "safe" mode and max line pressure, if it is just calculating engine load in a different manner then it makes sense the transmission would go to switching more "normal". And "normal" it seems in this state. There is still a slight delay in the 2-3 but much less flare and 4th actually engages and locks in now.

I will fire up a scanner and get a better look at the MAF readings but I expect we have a good lead on the issue.

 

[Snoman002]

It should set P0102.......You may have to kill & start the engine a few times. I meant P0102 not P0101 in the other post!
I don't recommend unplugging the MAF because the IAT sensor is incorporated into it. Unpinning the Yellow wire is pretty easy!

Defaulting to the Main VE Table which is what the PCM will do when P0102 sets Does Not max out line pressure, The PCM is simply using a backup source for calculating engine load/air flow. Will it raise line pressure a little from a normally functioning MAF calculated load?........Sure, But nothing drastic.

Further diagnosis will require a good scan tool that can read engine load & MAF values.........Short of throwing a MAF at it.

Interesting results today. I finally pulled the yellow wire and plugged the rest back in. Sure enough the problems resurfaced. Granted, to a far lesser extent, but the 2-3 flare is back and the soft lockup in 4th is there. Unplug the MAF fully and the transmission is back to perfect.

New MAF should be here this afternoon.

 

[BlakeB]

Interesting results today. I finally pulled the yellow wire and plugged the rest back in. Sure enough the problems resurfaced. Granted, to a far lesser extent, but the 2-3 flare is back and the soft lockup in 4th is there. Unplug the MAF fully and the transmission is back to perfect.

New MAF should be here this afternoon.

 

[Snoman002]

New MAF installed today.

Issue is greatly improved however there is still a small slip in 4th. Unplug the MAF and the slip goes away.

Unless there is any other advice I'm guessing 4th is done and I'm on the edge of it failing completely. Looks like there is some free tuning software for this ecm, I might just boost line pressure and send it.

 

[clinebarger]

2nd & 4th use the same Holding Member (2-4 Band)........

You can check the 2-4 Band Clearance by pushing on the Servo Cover, Anything over 3/16"-1/4" indicates the band is likely worn pretty bad. The 4th servo piston will also bottom out before the 2nd servo piston.

Installing a Sonnax Extended Length 2/4 Servo Apply Pin "may" buy you some time, It will need to be ground to fit. And if you want real cheap......Flip the 4th Servo Piston around to where the "Knob" on the piston faces the apply pin snap ring. This will extend the range of the 4th piston.

 

[Snoman002]

2nd & 4th use the same Holding Member (2-4 Band)........

You can check the 2-4 Band Clearance by pushing on the Servo Cover, Anything over 3/16"-1/4" indicates the band is likely worn pretty bad. The 4th servo piston will also bottom out before the 2nd servo piston.

Installing a Sonnax Extended Length 2/4 Servo Apply Pin "may" buy you some time, It will need to be ground to fit. And if you want real cheap......Flip the 4th Servo Piston around to where the "Knob" on the piston faces the apply pin snap ring. This will extend the range of the 4th piston.

Ha!

Went to install a corvette servo and the cover is stuck solid. I will try again and see if I can get it lose.

Thanks for the advice, I'll give it some more effort.

Any simple way for a home jobber like myself to monitor line pressure?

 

[clinebarger]

I don't live in the rust belt, So the cover generally moves quite easily, But......I've gotten some cores from up north before.....Gotta smack the cover a few times & some penetrant doesn't hurt.

A mechanical pressure gauge is the only way to monitor line pressure outside of a pressure transducer. A interesting hack is to use a A/C Pressure Transducer (Same as the one on your truck now) & run a jumper whip up to the existing A/C Pressure Transducer connector......This will allow you to monitor line pressure with a scan tool. You just can't use the A/C during testing. Not at all worth the effort with the adapter fitting & wiring whip you got to build....But interesting nonetheless.

 

[bdcardinal]

I love watching their videos.

 

[Snoman002]

Quick update.

Kept the MAF unplugged and it started to slip again. In a last ditch effort I installed the servo and adjusted the EPC valve to up line pressure at light load. It holds great in 4th for the moment (only a few miles on it) but the combination of one turn on the EPC and the corvette servo is too much, its going to break hard parts. Right now the 3-4 shift is as firm as I want my 1-2 shift. So back in and I'll crank it down to 1/2 turn over stock.

 

[clinebarger]

Using a 093 (Corvette) Servo requires hydraulic calibration changes & a second cushion spring in the servo.

At the very least.....Install the secondary cushion spring GM part# 8681195 & tighten the Band Clearance to @ .060".
I've had to explain the importance band clearance to experienced trans builders.......It's like having a Running Start at hitting a brick wall, Your going to hit it HARD!
But if you stand right next to the wall.....You can't hit it as hard.

That's exactly how the Servo reacts to band clearance!

Grinding or Cutting 4 oil exit slots in the steel cushion spring retainer/cover also helps. Fluid gets trapped behind the cover....Hydrolocking it thus reducing the effectiveness of the cushion springs.

 

[Snoman002]

She still lives!

There is something that is causing a bigger issue, not sure if it's the cheap MAF or a lazy MAP but you can feel that it doesn't want to lock in like it should. That said, it still lives and drives fine. Im not going to pull a trailer with it, but it keeps limping along.

 

[Crash Bandicoot]

It's a bit of work to get the unit out of the truck, but it's not rocket science to rebuild.
Cleanliness and attention to detail plus a good manual should get you there.

The 4L60 is one of the most common units out there.
Rockauto has re-mans for 1100 bucks and there are a lot of other sources.
If the engine and chassis are still solid, I'd say this is one major repair that is worth it.

You means it not as easy as Richard makes it look?