Help with transmission diagnosis

[FirstVolvo]

There are test strips you can use to determine if coolant is contaminating the ATF. How does the coolant level and color look?

https://www.ebay.com/itm/ACUSTRIP-71...IAAOSwNZtZ2B7W

[Xfingers]

Preliminary results:

Took a test drive today after replacing the contaminated ATF. The shifting was verrrry smooth which makes me think the strawberry milkshake stuff I removed was causing some slightly jerky shifting with the new VB. I guess it's good I overfilled it the first time or else I probly wouldn't have thought to check the condition since I'd replaced the fluid about a week before starting the repair.

Now for the not so good news. The car was driving/shifting as well as it ever has since I've owned it. Took it on the highway to get the speed up to 60mph. Code thrown again: P0740/TCM-002F (Lockup function slipping or not engaged) and also TRANS SERVICE REQ'D message. I drove home in Limp mode and checked the fluid level at 80C. It was just below the bottom of the HOT range so I added 150ml.

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:

Engine speed: 6000 rpm
Speed calculated by output sensor: 57 mph
Input speed sensor: 1963 rpm
Output speed sensor: 1932 rpm
Oil temp: 66C
Pedal position: 22%
Torque from engine: 500 Nm

According to VIDA: The automatic trans checks that lockup is not engaged or slips by comparing the rpm signal from the trans speed sensor to the engine speed. Signals must then show the same calculated speed. If TCM detects that the engine speed signals do not correspond with the programmed values, it means that lockup is slipping or does not engage in the locked position. The DTC is stored.

Looking at the frozen values above, I'm focusing on the Input speed of 1963 rpm vs Output speed of 1932 rpm. This difference (31 rpm) is greater than the accepted programmed value so therefore limp mode? This same code has come up once previously since doing the repair. I don't remember the exact frozen values but I am pretty sure that I looked at the input and output rpms and once again the difference was 31! Is this why the TCM is throwing the 002F code?

As I was driving, I was looking at the Amperage signal being sent to the SLU solenoid responsible for lockup. Prior to getting on the highway, I was in 5th gear and was seeing a reading of 1.0A for the SLU solenoid which I believe indicates full engagement of the Torque Converter Clutch. So signal is being sent for the Lockup to fully engage. Does the fact that output and input speed sensors are not equal in 5th gear at highway speed indicate the clutch is worn and slipping when it shouldn't be? I'm telling you, the car drives great so if the TCC is malfunctioning, it sure ain't noticeable to me. Also, I can't have my eyes glued to the SLT amperage while I'm driving so maybe the amps dropped slightly while in 5th, thus causing the output speed to drop and code thrown?

There's discussion online about this exact same problem - many apparent fixes but no surefire cure from what I can tell. Here's my game plan going forward: check the wiring harness connection for the linear solenoids at the airbox. I added 150ml ATF because the level was below the HOT minimum value but not getting my hopes up this will correct the issue. Do the adaptations even though the car seems to be shifting fine. Check with a local indy to get the TCM software updated to 30677036. Dealer is farther away and would require highway driving.

This car doesn't get a lot of use. I may have to become the ultimate back roads driver since running at highway speeds throws car into Limp mode. Apparently, some people have been able to avoid the TCM code by putting the car in cruise control at hwy speeds. I've yet to use cruise so I'll have to read the owner's manual. Sounds very dangerous during rush hour!

[Astro14]

Let's go back to this question, from your very first post:

"2. Tackle the new GM valve body replacement procedure. To me, this is the real crux of the issue and reason for this post. Can my shifting problems be cured with a new valve body or is there significant damage to the transmission internals - bands, clutch plates, etc.? Again, the trans is slipping in all gears above a fluid temp of 55C. "

You had been driving a car with a slipping trans for a while...so after a month of work, and 9 pages of thread, the TCU sees a 31 RPM difference between input and output.

I hate to say it, but it sounds to me like...

The trans is slipping. Which, since you've got a new valve body, is due to excess wear in the torque converter lock-up.

Which means the fix is, in fact, a rebuild of the worn friction materials in the transmission, starting with the torque converter. Parts are readily available for this, but it might be worth pulling it yourself (thus saving all the labor) and finding a local shop to rebuild it. It's not rocket science, but there are some specialty tools involved, I think...

[FirstVolvo]

Xfingers, Here are some notes from a Sonnax paper. This won't fix internal wear and slippage but it's something you could try with the two hall effect input/output sensors. Pull them out and make sure they're clean. I would expect you'd be seeing multiple codes if there was a problem with these sensors but it's not too difficult to pull and check them.

AW 55-50SN / AF 23-33 Diagnosis and Valve Body Information
Presented by
Bob Warnke
ATRA Powertrain Expo 2008

Rebuild Comments:

Input & output speed sensors are Hall affect.
Be sure to clean them and keep away from stray frequency.
Harsh shifts, high line pressure & TCC concerns can be caused by input contamination,
also Gear ratios, TCC cycling, 3-5 shift, phantom codes.
Add ground straps & distance the sensors from Linear solenoid wiring.

[pbierre]

The "pink milkshake" finding on page 7 is a major finding. The most likely route of contamination is a leak in the radiator from the coolant-water into the tranny-oil chamber. Unless you have another explanation for how your ATF got contaminated, this is the showstopper, and you'll have to start with a new radiator to save the car. The lack of viscosity in the pink milkshake might have seriously damaged the metal parts in the tranny. It usually costs less to just replace the transmission. Am I missing something? I didn't see a strong reaction to the pink milkshake observation.

[Xfingers]

Well, Astro, that slipping I was experiencing in all gears above 55C was actually cured (I think, don't want to speak too soon, only 2 test drives) by the new VB. Also, that slipping condition had only just started as I was trying to diagnose the P0735 incorrect ratio code which was throwing the car into Limp mode. When I was caught in limp mode I had to get up small hills or start from a stop, and the trans complained a little. This added strain may have caused the second condition of slipping above 55C which made the car undriveable. Hopefully the new VB has fixed this problem, so far so good after 2 test drives. The crazy thing is I still have the original problem of car going into Limp at highway speeds but this time (with the new VB) I get a P0740/TCM-002F Clutch Lockup System code. I realize this indicates the TCC is not doing its job but to drive it you'd never guess anything's wrong til all the sudden you get a yellow triangle and TRANS SERVICE REQD. Then you see -.- and you hear a clunk and you're in 4th/Limp mode.

So you guys seem to think that difference of 31 rpm is what's triggering the TCM code. I read some posts where there was some later trans software which possibly gave larger leeway before throwing this code to accommodate Torque Converter wear. I'll check again but I think VIDA said there was a software update available for my trans. If you could change the software code to wait until a difference of 10,000 rpm (i.e., never throw the code) what might be the danger? Does the TCM put the car in Limp mode to force you to deal with the problem now when it's small, before things get progressively worse?

I think thru VIDA you can put the trans in Test Mode. Instead of "D" you see the gear displayed and the yellow triangle stays on when the TCC is in full engagement and blinks when the TCC is slipping. When the code is stored, you'd expect to be in 5th with the triangle lit on but instead the triangle would be blinking, indicating the TCC is slipping when it should be in full lockup. If the TCC can't maintain full engagement, it shouldn't be due to inadequate line pressure because I just put in a new VB. Therefore, TCC wear would be suspect.

Thanks, FirstVolvo, I'll look into that info.

[FirstVolvo]

Preliminary results:

Took a test drive today after replacing the contaminated ATF. The shifting was verrrry smooth which makes me think the strawberry milkshake stuff I removed was causing some slightly jerky shifting with the new VB. I guess it's good I overfilled it the first time or else I probly wouldn't have thought to check the condition since I'd replaced the fluid about a week before starting the repair.

Now for the not so good news. The car was driving/shifting as well as it ever has since I've owned it. Took it on the highway to get the speed up to 60mph. Code thrown again: P0740/TCM-002F (Lockup function slipping or not engaged) and also TRANS SERVICE REQ'D message. I drove home in Limp mode and checked the fluid level at 80C. It was just below the bottom of the HOT range so I added 150ml.

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:

Engine speed: 6000 rpm
Speed calculated by output sensor: 57 mph
Input speed sensor: 1963 rpm
Output speed sensor: 1932 rpm
Oil temp: 66C
Pedal position: 22%
Torque from engine: 500 Nm

According to VIDA: The automatic trans checks that lockup is not engaged or slips by comparing the rpm signal from the trans speed sensor to the engine speed. Signals must then show the same calculated speed. If TCM detects that the engine speed signals do not correspond with the programmed values, it means that lockup is slipping or does not engage in the locked position. The DTC is stored.

Looking at the frozen values above, I'm focusing on the Input speed of 1963 rpm vs Output speed of 1932 rpm. This difference (31 rpm) is greater than the accepted programmed value so therefore limp mode? This same code has come up once previously since doing the repair. I don't remember the exact frozen values but I am pretty sure that I looked at the input and output rpms and once again the difference was 31! Is this why the TCM is throwing the 002F code?

As I was driving, I was looking at the Amperage signal being sent to the SLU solenoid responsible for lockup. Prior to getting on the highway, I was in 5th gear and was seeing a reading of 1.0A for the SLU solenoid which I believe indicates full engagement of the Torque Converter Clutch. So signal is being sent for the Lockup to fully engage. Does the fact that output and input speed sensors are not equal in 5th gear at highway speed indicate the clutch is worn and slipping when it shouldn't be? I'm telling you, the car drives great so if the TCC is malfunctioning, it sure ain't noticeable to me. Also, I can't have my eyes glued to the SLT amperage while I'm driving so maybe the amps dropped slightly while in 5th, thus causing the output speed to drop and code thrown?

There's discussion online about this exact same problem - many apparent fixes but no surefire cure from what I can tell. Here's my game plan going forward: check the wiring harness connection for the linear solenoids at the airbox. I added 150ml ATF because the level was below the HOT minimum value but not getting my hopes up this will correct the issue. Do the adaptations even though the car seems to be shifting fine. Check with a local indy to get the TCM software updated to 30677036. Dealer is farther away and would require highway driving.

This car doesn't get a lot of use. I may have to become the ultimate back roads driver since running at highway speeds throws car into Limp mode. Apparently, some people have been able to avoid the TCM code by putting the car in cruise control at hwy speeds. I've yet to use cruise so I'll have to read the owner's manual. Sounds very dangerous during rush hour!

For the P0740 code I would expect the engine speed and input speed sensor to be used to determine if there's a problem with TCC lockup. Engine RPM should be the 1:1 with the transmission input speed sensor. In the freeze frame data the engine speed is 6000 RPM. This doesn't seem right unless you had a major slip/flare going on and you've not indicated this is happening. At 57 mph the engine RPM in 5th should not be anywhere near 6K. This doesn't make sense to me. The torque value doesn't look reasonable either. When driving the car can you feel and see (with the tach) TCC lockup? I know when I drive my car at cruising speed in 5th and over 50mph I notice TCC lockup and can see it on the tach.

[2002V70XC]

Very sad to hear the news Xfingers.
Sorry i can't offer any advice on your current issue.

[Brett San Diego]

The "pink milkshake" finding on page 7 is a major finding. The most likely route of contamination is a leak in the radiator from the coolant-water into the tranny-oil chamber. Unless you have another explanation for how your ATF got contaminated, this is the showstopper, and you'll have to start with a new radiator to save the car. The lack of viscosity in the pink milkshake might have seriously damaged the metal parts in the tranny. It usually costs less to just replace the transmission. Am I missing something? I didn't see a strong reaction to the pink milkshake observation.

I agree that you seem to have ignored this finding, xfingers. It seems very likely a new radiator is needed, or you will continue to contaminate the ATF with coolant.

Brett

[Astro14]

If you've still got pink fluid, you need to correct that before anything else can be done. I would flush it first, before anything else.

I find it hard to believe that rain and/or condensation added that much water to the transmission...so, it may be time for a radiator as that's the only way that water can get into your transmission once it's sealed back up. I don't think that you can tell if the fluid is good just by the tiny amount on the dipstick. Not enough of a sample to tell fluid condition.

If you flush it again, and there is entrained air, or water, you'll know. The fluid should be clear, bright red as it is discharged. If not, it's radiator time. Followed by a flush to get the fluid corrected.