Repair-It

Oh yes. It started as increasingly firm shifts when hot. Of course this is compounded by my completely failed engine mounts, But still, I think something is up with the trans. That's why I checked the fluid the other day (the level was fine).

I drove it today and it actually felt like it was consistently slipping on the 1-2 shift. Not a regular slip but more like a shudder/judder. I saw zero RPM flare but it did not feel good, either. For what it is worth, as I was driving around I was like, if this needs a trans, I am probably getting rid of the car. Just saying.

When I got back I pulled out the Tech 2 and looked at stuff. Zero transmission codes (good I guess). However the first thing I noticed is the transmission doesn't seem to be getting up to operating temp. Granted it is only 35F today and I didn't go on the highway but I was driving around town where you'd expect trans temps to climb without too much issue due to all the shifting and torque converter action. But the temp was like 135F or something while the engine was 190F or so.

At one point I just did a rolling brake torque in 2nd gear at like 3000 rpm. Temp didn't really budge. After I stopped, the temp started climbing and hit a peak of 150F before cooling back down again. Is this right?? I don't know. I found a bulletin in my FSM titled "#PIP3434A: Transmission Oil Cooler Lines - Deletion of Cooler Thermal Bypass Valve - keywords 5L40E 5L50E automatic bypass chafe fitting leak rub - (Nov 3, 2005)." Interesting. The fix is to use second design lines and get rid of the thermal bypass valve which I take means some kind of thermostatic control of transmission fluid. I don't recall seeing this valve on the side of my transmission so I think mine was built without it anyway. But it's interesting because I guess GM had originally intended to thermostatically control trans temp but then when this issue happened they were like "forget about it." So the fact that it seems to run cold may just be normal. Maybe this is not the smoking gun.

Not to be deterred, I decided to use my IR temp gun and check the pan and compare to the sensor. Well, the pan was about 5 degrees cooler than the car reported which means....that's all working fine, or at least the temp is probably being reported accurately. Moving on....

Then I looked at some other screens, like the shift info stuff and shift adapts. I figured if something was worn out I'd see some crazy numbers in here. Here's what I found:
What stands out is the negative pressure correction on the 1-2 shift in the light to medium throttle where the shifting was nasty. I also drove around and did some WOT shifts (yeah I know). And they didn't feel any worse. Very harsh and quick but no slipping really. What's going on? As I continued to drive and as it learned some of the cells, it was continuing to pull pressure out to slow down those 1-2 shifts. Also the 1-2 and apparently also the 2-3 is the only thing to have negative correction. The 3-4 and 4-5 have positive which you'd expect for a higher mileage transmission. Negative correction does not make sense. And the 1-2 was nasty. The 2-3 was also quick and harsh but did not do that shudder/judder, fwiw. Also notice the 1-2 on heavier throttle goes back to positive correction. If it was mechanically wearing out, I would think it would just correct across the board, and maybe even WORSE in higher cell areas. Not convinced this transmission is done. But what could it be?

Did some more research and found this:
https://axleaddict.com/auto-repair/The- ... n-Problems

Scrolled down and saw this:

Harsh Gear Changes
Symptoms

Harsh gear shifting
"Trans Failsafe" mode
When an automatic transmission like the GM 5L40-E changes gear, oil is fed into a sealed chamber, forcing a piston to push against a stack of clutch plates. If the oil were just shot into that chamber all at once, the clutch pack would apply with a harsh thud and make for a very unpleasant driving experience. The 5L40-E gets around this problem with the use of a number of accumulators which allow the oil to be fed in gradually until the pressure is sufficiently high.

The accumulators work by sitting a small sealed piston on top of a spring so that when the oil is fed into the chamber, it pushes the piston against the spring. These springs, however, have a nasty tendency to break. Fortunately, repairing this problem is (relatively) easy. You don’t need to remove the transmission, just the valve body which can be found inside the sump at the bottom of the transmission.

Hint: Be extra careful when removing the accumulator housings so as not to rip the gasket. If the gasket rips, the valve body has to be completely stripped down to replace it.

5L40 broken accumulator spring.PNG

This picture shows the four accumulators removed from their housing. The accumulator spring on the far right has broken in two.

Range Rovers.net

Ah, NOW we're getting somewhere. Theory: if I have a broken 1-2 shift accumulator spring, and maybe a broken 2-3 shift accumulator spring, the shifts are way firmer/quicker than they are supposed to be. So it pulls pressure. But when cold, this is now way too little and it actually could cause a slip. So it tries to correct this as well, which then makes the hot shifts too harsh, until it relearns those. The cycle repeats. I think I might have a broken 1-2 and maybe 2-3 shift accumulator spring!! Especially if this is a "common" issue, at least on the 5L40 as used in many European cars.

Only problem is, I cannot source ANYTHING. All I can really find is an entire valve body.

More info: https://www.transmissiondigest.com/iden ... ve-bodies/

I do see some springs on eBay under 5L40 applications: https://www.ebay.com/sch/i.html?_from=R ... tor+spring

But not sure if any of those are correct. You'd think I would be able to buy the accumulator as it simply bolts onto the valve body. Drop the valve body, replace accumulators, done. Not the simplest but nothing I shouldn't be able to handle. I sent a note to GM Parts Giant to help me locate these parts but they may simply not be available. A replacement valve body is $260 at Rockauto, though it says "RWD."

https://www.rockauto.com/en/moreinfo.ph ... 42&jsn=446

So that is a possible fix. GM may really not want to sell valve body piece parts because of warranty hand wringing. Well the warranty is over. Let me buy piece parts!

The other thing that is encouraging is I found this: https://www.amazon.com/dp/B0016IXT8U/re ... automotive

This is NOT the correct transmission and looking at the reviews it seems to be for the early to mid 2000s trucks with 4L60E. However, look at this review:

Eric
5.0 out of 5 stars Shuddering shift in second
Reviewed in the United States on October 8, 2019
Verified Purchase
Did some research because I was having transmission issues and came to this part being a possible cause of my shuddering (felt like slipping) shift into 2nd gear. The part was cheap enough it was worth a try and sure enough it fixed the problem.

I'll be damned if that doesn't exactly describe the issue and he claims it fixed it. This, and all of the other information I've collected, suggests that it is PROBABLY a broken spring (or two). I guess I could pull it apart and check but then I still have no parts to reinstall. Perhaps the logic is simple. Pull the valve body, inspect accumulator springs. If I do find broken springs, and the ONLY source of parts is to replace the entire valve body, then I would feel pretty encouraged at that point that the accumulator springs were causing my issue. If, however, I do NOT find any broken accumulator springs, well....then it's hosed?

I'd rather fix if it's this easy because I am not ready to put the E55 through winter (even though I have an entire driving season in front of me). Plus, I could still fix and sell. Just saying. Unlike many CL ads, if it's easy to fix, I always prefer that.

Called Herb Chambers. Cannot buy valve body parts, only the whole assembly. GM price is $543. No thanks. Rockauto for $260 seems reasonable. So now I just need to figure out my strategy for repair. Cross my fingers and order? Leaning that way....I just feel strongly about my theory and all of the data seemingly supports it.

Ordered the following from Rockauto: Says last shipment projected for 18 March so guess I'm driving the E55 for a while. Well, I could drive the STS but I don't want to do further damage if it's just an accumulator issue. $400 is kind of a lot to drop on a guess, but it's a very informed guess. I am 80-85% sure this is the issue. And if it doesn't fix it and there's no further hope then yeah I will probably get rid of the car. I'm probably not putting a trans in it. We shall see.

Got my 6 quarts of Dexron VI. Realized I forgot to order the Lubegard additive so I just ordered that and it should arrive tomorrow. Should be all primed to tear into this after tomorrow which means on the weekend. Need to get this functional because I need to start working on the E55 in preparation for the summer trip to NC.

I recorded 25GB of video for this job. I managed to condense 3 hrs 40 mins of video down to 2 hrs 12 minutes. Probably could have condensed more but I left some of my ramblings and trouble spots.

https://youtu.be/WCLOf1UxDRE

The result? I think this actually fixed the issue, after an extensive drive cycle to relearn all the adapts (after resetting them). I will test on the next cold start but it does feel completely cured. The area I had the most issue was light throttle 1-2 shifts. I had a really hard time getting it to learn those areas. Shifts were happening late and kind of firm. After I relearned, all values are positive and the shift point even cured itself. Like I said, it's possible the computer is chasing its tail or that I do still have some worn out clutches but the way it was driving at the end of my last drive cycle was 100% perfect. Like I say in the video, even if it does have some other issues (which may come with 156k and a very delayed first fluid change), it definitely needed this repair.

Also check out my use of video chapters. Helps guide through what would likely be a total non-starter for someone to watch. Really, only a handful of people who actually need to do this would consider watching. We'll see.

I can confirm it is fixed. New valve body and some time spent relearning as many TAP cells as possible, particularly the troublesome 1-2 ones that were originally presenting with an issue. The thing that threw me is the 1-2 AFTER I did the valve body was still bad, and I had reset the adapts. It took the careful relearning with a Tech 2 to get it all dialed back in right with the correct positive pressure corrections. Could I have done this without a Tech 2? Well, no not the reset part. It would have been even worse to recover from some bogus learned values. Technically, it would have relearned but would have taken even longer and without the feedback of which cell you are in, and whether it is learning. You basically would have to drive around and do 100+ shifts of each kind at different loads until it "shifts right." The Tech 2 made it much easier to see what it was actually learning (and when it WASN'T learning).

Nonetheless, it is fixed and I assume I saved the transmission by parking it as soon as I felt the issue. The valve body was the correct diagnosis. About 157k. Used Dexron VI and a tube of Lubegard Anti-shudder Fixx (for torque converter shudder), which also has proven itself. Kind of a relief.

It does make me wonder how many of these got scrapped for this, or sold a new/rebuilt trans, when it was just a valve body issue.

Picked Ian up from school. Thing shifts perfect!!

Posting here for someone who asked in YT comments.