Help with transmission diagnosis

[Xfingers]

When I drained the ATF to do the VB repair, the fluid looked bright and red (no strawberry milkshake). I replaced this same fluid after completing the repair and topped up with another 400ml for all the additional ATF which had drained from the hoses and old VB. Did a few test drives with the new VB, got the ATF up to 80C, checked the level and found it to be overfilled. I drained 500ml from the drain plug. I looked at this fluid and this was THE FIRST TIME I found it to be pink and milky. Did a Gibbons flush of 12 qts. and the old fluid looked like a strawberry milkshake.

I have two possible explanations. I damaged the radiator during the repair or water got into the radiator/trans during the repair. I did not have the radiator ports completely plugged nor the trans housing sealed airtight while working. The car was sitting for a week with rain, snow, large temp swings so maybe there was condensation? Of course I'm gonna monitor the situation, make sure I'm not losing coolant. With the new flush, the shifting is noticeably smoother than the two test runs with the pink milkshake so if the ATF becomes contaminated again I expect I'll notice the rougher shifts. Still, once the ATF has been contaminated the damage may already be done and I think I noted this in a previous post. This is why I flushed the fluid ASAP. Keeping my fingers crossed and watching the coolant level.

This car doesn't see a lot of use and mostly gets driven around town. If I need to keep it under 55mph to avoid Limp mode, it can be done. The dealbreaker was the slipping trans when the fluid got warm. So far, this condition seems to have been corrected with the new VB. I've still got more testing to do and options to explore. I just added 150ml ATF so need to confirm level is correct at 80C. When driving at 55+ mph, I can possibly use 4th in Geartronic or cruise control. I still have not done the adaptations for the new VB. I don't think I have the latest version of the trans software.

Thanks everyone for the guidance and support!

[Brett San Diego]

On the other hand, a new radiator is not that costly, ~$115, just to be sure.
Brett

[Xfingers]

R & R the radiator? Are you guys sure you can take another 10 pages added to this thread?

Took it for another spin today. Got the speed up to 50mph with no problems. Checked the fluid level at 80C and it was below the minimum mark. Added another 200ml. The coolant level is at the FULL mark in the reservoir.

[Rabid Koala]

This has been a very interesting thread! I look forward to more updates.

[FirstVolvo]

Preliminary results:

The car is basically doing the same as before the new VB. When traveling in 5th gear at higher speeds, without any noticeable driveability issues the trans is going into limp mode. Now here's what's a little strange. Prior to the new VB, trans would throw a P0735 5th gear incorrect ratio code. With the new VB, car goes into limp mode but throws the P0740 Lockup function slipping or not engaged code. Here's some frozen values from when the code was stored:

Xfingers, I've reread your previous posts of the original problems (P0735 and slippage in all gears) with the old valve body and the new P0740 code with the new valve body and I've looked at my ATSG manual for this transmission to see if there's anything in common.

With the P0735 5th gear incorrect ratio and the slipping in all gears problem you described is one or more of the clutch packs in the transmission is slipping and you've mentioned with the new valve body these problems no longer exist.

With the new valve body the P0740 code is TCC slipping or stuck off and this is only the torque converter lockup clutch, I don't think it has anything to do with any of clutch packs in the transmission itself. Basically a very different problem than with the old valve body.

If there were a problem with the torque converter clutch I would expect you to have seen this problem with the old valve body too, in addition to the other problems. I'm wondering there is a problem with the TCC control (SLU solenoid) connection. You can unplug the 8 pin connector and measure across the SLU solenoid to check and I wanted to attach the connector pinout but it exceeds the file size. I'll see if I can do it another way.

Just wondering does the P0740 code occur right away, the first time it expects TCC lockup?

https://app.box.com/s/erubrjw9e3z13h9vov7ppbpl46ca7u5u

[Xfingers]

I was thinking about that black connector to the SLU solenoid as well, FirstVolvo. But it's the first (top) of the linear solenoid connectors, the connector position was not changed with the later VB design (no lengthening of wires required), and I absolutely remember it making a clicking noise when re-connecting the wiring harness.

I agree the new P0740 code would suggest a different problem. Funny thing is the car seems to have the exact same issue - going into Limp mode while driving in 5th gear - that it had previously with the old VB/P0735 code. The P0740 code does not seem to occur right away. I can drive in 5th gear/1.02 gear ratio at lower speeds of around 40mph with Amps to the SLU showing 1.0 with no DTC. I'm thinking this info demonstrates that TCC full engagement/lockup is being requested by the TCM? I'm still a little confused about the VIDA documentation on the TCC operation.

The car threw the P0740 code again yesterday and went into Limp mode. I've got the frozen values from VIDA which I think you'll find interesting. First I want to do another test drive today and focus on some specific parameters. Then hopefully l can write a more complete report tonite, rather than throw out a few hunches now.

I do have an ATSG manual for this trans after you suggested reading it in your thread. It's like 170 pages.

[Xfingers]

Although it wasn’t my original intent, I’m glad people have found this thread entertaining. I guess file this next part under I’d Rather Be Lucky Than Good.

Update:
The car threw the same P0740 code again yesterday and went into limp mode. Here’s some of the frozen values:

Engine speed: 6000 rpm
Speed calculated by output sensor: 47 mph (Gear 5)
Input speed sensor: 1618 rpm
Output speed sensor: 1591 rpm
Oil temp: 46C
Pedal position: 21%
Torque from engine: 500 Nm

FirstVolvo, I think you nailed it in one of your previous posts. There's that Engine speed value of 6000rpm again which you flagged on my previous set of DTC values. There’s no way the needle of my tachometer was ever pointing to the 6 on the dial, nowhere close. Also, to get a dead on the nose reading of 6000 even, twice in a row, seems very suspect.

From VIDA: The ECM transmits the engine speed rpm on the CAN from which the TCM retrieves the signal which it then compares with its own speed sensor signal....Depending on slippage in the torque converter the gearbox speed and the engine speed will differ when the lockup function is not engaged. With lockup engaged the gearbox speed should be the same as engine speed (RPM).

Looking at the frozen values above, if the TCM is comparing the 6000rpm engine speed with the 1618rpm value from the input speed sensor and expecting them to be equal (5th gear, lockup engaged), it’s no surprise it would throw a P0740 code, Lockup Slipping or Not Engaged. So I took it for a test drive today and monitored the engine speed parameter. But first, there’s a little bit of info I’ve been withholding.

You may remember I reported that on one of my test drives I got the speed up to 50mph and no codes were thrown. What I didn’t tell you is prior to that drive, I’d been checking the trans electrical connections in front of the airbox as recommended in the fault-trace for both P0740 and P0735 codes. For easier access I disconnected the cold air duct from the grille to the airbox and also the MAF sensor. Well, I was only able to get the A connector (for the speed sensors) to separate. Everything looked clean and bright silver inside, with no rust or oxidation, so I hoped the other 3 connectors were in the same condition. Closed everything back up and took that successful 50mph drive. When I got back in the driveway, I popped the hood to check the ATF level and there was the MAF sensor - disconnected. (There was also a small screwdriver nearby but we’ll overlook that for now.) I cursed myself for being an idiot and plugged in the MAF sensor. The car had thrown a P0102 MAF Signal code and Engine Service Required message. I was surprised that the car had run so well with no noticeable problems.

This got me thinking, did the MAF being disconnected have something to do with the TCM not throwing codes? I’d read a post where one guy had finally solved his P0740/TCM-002F issue by cleaning the throttle body. So on my test drive today, I monitored the Engine Speed parameter and decided to unhook the MAF sensor. Had the car running at 60mph for about 5 minutes with no codes and never did the engine speed value go above 2800 rpm. Until now, driving this section of highway had consistently triggered a DTC/limp mode.

What I should probly do next is drive that same stretch of road with the MAF connected and watch the engine speed. I just hate going into Limp Mode if I can avoid it. The fluid level is now within the HOT range at 80C. I definitely want to give the adaptations a go; the 2-3 engagement is a little harsh at times and I notice a bit longer delay shifting between P and D than with the old VB. Now I’m going to research the MAF cleaning procedure - I believe there’s a special spray to use.

I certainly don’t think I’m out of the woods yet but I feel like I’ve got a reason to be encouraged.

[FirstVolvo]

When you did get the P0740 code did you notice the engine RPM varying much prior to the code and when you were when in a steady cruise around or above 50MPH? Did is seem like the torque converter is locked up? Once in 5th and cruising I can notice the converter is lock when I press on the gas slightly or let off, the RPM doesn't noticeably change but if I press on the gas hard enough the TCC does eventually unlock and the RPM jumps up while still remaining in 5th; I check by going in manual shift mode to check the gear selected, it hasn't downshifted to 4th.

Having the MAF disconnected and not seeing the code is interesting, if this can be consistently duplicated that would good to know. Just don't understand the 6K RPM frozen value when the 740 code occurs. Engine RPM should be very close to input speed sensor value when TCC is locked.

If you do take another test drive with the MAF sensor disconnected and your engine is running well enough keep driving for a while to see if the code ever does appear. How's the transmission shifting otherwise, any noticeable problems when fully warmed up?

TCC lockup should also occur in 3rd and 4th gear at lower speeds so only seeing a TCC code in 5th gear means something.

[Xfingers]

FirstVolvo, I've never monitored the engine speed rpm before today. What I noticed is that engine rpm in VIDA is more sensitive/responsive than the tachometer. You'll see slight rpm variations up and down in VIDA while the tach needle doesn't move at all but nothing crazy. If I drive highway speeds with the MAF sensor connected and the TCM throws a code, will the VIDA engine speed vary by several thousand rpm? I have no idea but it may be necessary to try this to further diagnose the problem.

Some general info on MAFs indicated that if you disconnect a properly working sensor, your car should stall out. Not sure if this applies to Volvos. When I disconnected mine, the engine stalled for about a second then returned to idle. I should note that I've never noticed any idle issues or loss of power while driving this car. Should I have noticed reduced performance with the MAF sensor disconnected?

The transmission is shifting smoothly when I drive with an easy, light throttle. If I punch it a little bit, I get a bit of a jerk from 2-3. I want to do the adaptations with the MAF connected. Not noticing any shifting issues when the trans fluid is at 80C. I'll buy a can of MAF cleaner; at 130k mi. it may have never been cleaned before. But keep in mind, I've never gotten a MAF code except for the first time I drove around by accident with the sensor disconnected.

Could that 6000 rpms for engine speed be a "substitute value", a value the computer has been programmed to use if a certain fault occurs or data is missing? I need to spend some time in VIDA researching the MAF operation. I'm guessing there should be a way to monitor it in VIDA - maybe a voltage readout which should increase with engine rpms? We're due for some rain and snow so I'll give it some thought and have another go this weekend.

[FirstVolvo]

Below is a link about sensors and affect on transmission control. The MAF sensor is used to determine engine load and this can be used to change shift points and line pressure within the transmission so having the MAF sensor disconnected and no longer throwing a code is explainable. Not sure if this means the MAF is bad or not but it can influence transmission control.
Because you didn't see the P0740 code with the old valve body there is a chance this isn't an internal transmission problem with the torque converter clutch or other problem. I'd still like to know if you think the torque converter lock up is occurring when you're driving; is it working and slipping or not working at all?
Does lockup occur when you're driving with the MAF disconnected and it would be good to know with another test drive if no code is thrown with the MAF disconnected and an extended drive. Monitoring the engine RPM and torque for bogus values (6K and 500Nm) as in the freeze frame when the code occurs is something that needs to be understood too.

https://www.motor.com/magazine-summa...de-looking-in/

"Sensor Sensibilities

Throttle position sensors, MAP sensors, mass airflow (MAF) sensors and crank sensors make up a basic list of engine load devices the PCM/TCM uses to influence line pressure control, shift timing and converter clutch strategy. It stands to reason, then, that these items could cause harsh and/or flared shifts, bumpy coast downshifts, a sensitive passing gear, early or late shift points, no converter clutch apply or converter clutch cycling complaints."