Repair-It

Finally did this job. The car needed a sticker and we were having issues getting 4 of 6 systems "ready" w/o setting the code as pending. The code is a 2nd cycle code so in order to get this thing to pass in its current form, you'd need to get enough systems to set ready on the first drive cycle and not get into lockup conditions on the 2nd drive cycle (clear codes, cold start, drive to shop, hope for the best). We did some test runs and were able to get 5 of 6, but on inspection day it would only set 3 of 6. Two of them will only set ready on cold start (H-O2 + A.I.R.). The sticker expired in June so we were out of time.

The short story is the TCC is operated by a PMW solenoid. Unfortunately there are some case seals where the input shaft penetrates the case housing which wear. The internet theorizes this is due to "inprecise" machining tolerances during manufacturing. Once the seals are worn, they can't hold the required amount of pressure which causes the solenoid to run at 100% duty cycle. After a while the solenoid burns out and you loose torque converter lock-up entirely. This code had been appearing for the past couple of years for the previous owner but since he was bringing it to an independent garage, they were unable to properly diagnose it. The code sets with the slip RPM between the engine and transmission input shaft exceeds some value under certain conditions (I'll post the specifics later with the results).

The TSB for the issue says to replace the seals, solenoid, and torque converter for good measure. Fortunately none of those items can be replaced w/o removing the transmission from the car. It took ~25 hours with between 1-4 people actively working on it over this past weekend. Book time is in the 12-14 hour range for transmission R&R. I imagine the seal replacement could add another couple hours to disassemble and reassemble the transmission. Having now done the job, I think several hours could be removed from the repair time. I don't want to do this job again on one of these FWD Northstar G/K/H cars.

I will post pictures later.

Adam wrote:Once the seals are worn, they can't hold the required amount of pressure which causes the solenoid to run at 100% duty cycle. After a while the solenoid burns out and you loose torque converter lock-up entirely.

I am skeptical about the second part of that. It seems unlikely that the lockup solenoid cannot handle 100% duty cycle, a mode that many solenoids refer to as "on."

I don't want to do this job again on one of these FWD Northstar G/K/H cars.

I assume my STS would be even worse since the driveline is not confined to the engine bay. Good news: two fluid changes with Dexron VI fixed my torque converter shudder issue. I don't know if my TCC is the same style as the 4T80-E. Probably not.

Solenoid replacement is part of the TSB. The solenoid in this transmission was visibly fine. I watched some tear-down videos of the 4T60-E and some had solenoids with visible burns on them.

Time for pics.

Step 1, remove subframe. Step 2, remove transmission. Step 3, disassemble transmission.

The side cover comes off. You can see the main pump and the upper valve body. That's right, there's two valve bodies in this transmission. Pump removed. Upper valve body and plate removed. Both parts together. You can see the solenoid in the side of the valve body on the left. Center housing. Input shaft seal on the right. Main pump seals on the left. There is an inner and outer seal. Seal closeup. The white area on the upper seal is the wear area. You can see the wear is uneven. There is a rubber o-ring seal on the input shaft which seals it to the case. I replaced that while I was there. I didn't get a shot of it, but there are two large gears and a chain that mount over this to connect the input shaft to the main transmission components. Chain is pretty beefy. Installation is reverse of removal. The main filter is actually under the side cover (for convenience?). There are two pickup screens under the lower pan which I also changed. The fluid looked pretty dirty but there wasn't a large build-up of debris on the lower pan magnet. Filled up with almost 15 qts of Dextron VI.

During the initial test drive the maximum slip RPM when locked up in overdrive I saw was 66 RPMs. That's under what we saw during the initial troubleshooting of over 300 RPM.

Fixed forever?

Wow, you paid your dues on that car. Is there at least a noticeable improvement in how it drives?

I still haven't really looked through the pictures. Worst car forum owner ever.

And I think it drives exactly the same but with torque converter lockup.

Where did you do that job? Looks like it was on a lift.

Fast_Ed wrote:Wow, you paid your dues on that car. Is there at least a noticeable improvement in how it drives?

Yeah, the check engine light is off.

kevm14 wrote:Where did you do that job? Looks like it was on a lift.

Some friends up the street from us have a half-height lift. It gives you 48" of height. Good for low ceiling garages.

Also, they are big Toyota fans, so they gave Jenn some center cap stickers that they weren't using for anything. She installed one of them.

kevm14 wrote:I still haven't really looked through the pictures. Worst car forum owner ever.

And I think it drives exactly the same but with torque converter lockup.

The torque converter was locking up, but it couldn't maintain the slip RPM below the threshold, so CEL.