Problem after transmission fluid change

[mercuric]

Time to get a look at what's on the transmission side... and if there's even lines.. If you got extremely lucky, they installed an aftermarket transmission cooler, as some folks in hot climates do -- Better cooling and no chance of mixing engine coolant into the tranny.

Running without a cooler in Texas would likely result in really high fluid temps. That should have triggered DTC 235, High Oil Temp, which causes a warning light.

However, if they disabled the oil temp sensor, that should have triggered DTC 142, however that code won't throw the warning light.

Be aware neither 235 or 142 appear to have an ODB-II equivalent code, so if you're using a plain ole ODB-II scanner, you won't get either of these codes. Since you have a 97, which doesn't have the diag box (as far as I understand), you'd need a volvo scan tool, VIDA/DICE, etc, to get them. There are a lot of volvo-specific DTCs that don't have ODB-II Pxxx codes. These are two of them.

http://www.volvoclub.org.uk/tech/servic ... gnosis.pdf is probably worth a look over to get a better idea of the entire autobox system.

Based on the fact that a fluid change exposed the issue, I'd suspect your damage is hydraulic related, with the valve body being the prime suspect. Lots of moving parts including multiple rubber check balls to control fluid flow. I'd suspect clutch damage would have shown up regardless of fluid quality. In case you're curious about the mechanical naughtiness of the valve body, here's some diagrams: http://www.fichier-pdf.fr/2009/08/16/gv ... ervice.pdf

If the slippage is only occurring in certain gear(s), this document contains a chart of which elements are applied based on shift selector and running gear, and might help you understand what's borked (or what paths in the valve body are SOL) : http://www.fichier-pdf.fr/2009/08/16/6h ... enance.pdf -- It also contains expected resistances from the oil temp sender and solenoids should you have electrical curiosities.

Whatever the case, if you've indeed been running a while without a cooler in Texas, you are probably best off just swapping the sick thing with a good used box... At least that's what I'd be thinking of. Unless I had a ton of cash, and wanted to keep the car a long while, then I'd hunt down a reman. It's possible you may have a valve body or solenoid issue that could be repaired without replacing the whole box, maybe even without dropping the box, but with such high temps, I'd expect your wear rate to be higher -- So if you plan on keeping the car, I'd be thinking about cutting my losses on the tranny rather than investing time and money trying to patch it up only to find out you did other damage and need a new box in the near future anyways.

If you really want to go the route of trying to get the tranny back in order, a trip to a transmission shop capable of testing hydraulic pressures is probably your next step. However, the general answer I've got from local shops on this tranny is internal problems = swap the box.

Fair warning: I'm a bit knowledgeable of A/Ts in general, but don't have significant experience with the AW50. I've just started to learn the gory bits of this FWD autobox myself.

[Francois850]

At this point I am so bummed out, I have no idea what to do.... I am sure at some point everyone has experienced this with their car. I don't just drive my 850, I love my 850.
Tonite I drove it after it sat 2 hours and the first minute or so It was flying.... then went back to its usual issue.... this is just too strange.
Btw, do you think a trans shop would be able to pull Volvo codes...? I understand that a standard OBDII reader may not be able to read such codes but wouldn't the C.E.L. of the car come on?

[Francois850]

http://www.ebay.com/itm/190787480868?ss ... 1438.l2649
http://www.ebay.com/itm/190787480877?ss ... 1438.l2649

Not showing as fitting my 850 NA 97, but, this would fit my car right?

[erikv11]

For sure those lines will fit.

I agree a trans codes should throw a CEL that is not readable by a standard OBD2. There are a lot of scanners that can retrieve trans codes, I have one (Autel EU702) so yes, many shops should be able to read trans codes. DOes not require a trip to the stealership. If there are any stored. Definitely worth checking.

The lines won't solve the present issue, I'm sure you have already considered that. I know you've already done it once but maybe another trans swap is in order. In general these transmissions are very hardy so for example I would not hesitate to pick up and install a used one that wasn't even remanufactured. Will be much cheaper than a rebuild, as mercuric alluded to. If you do go that route, best bet would be to find one with a known history. The whole sequence of events is puzzling but so far does seem to point toward cooked hydraulics.

[Francois850]

For sure those lines will fit.

I agree a trans codes should throw a CEL that is not readable by a standard OBD2. There are a lot of scanners that can retrieve trans codes, I have one (Autel EU702) so yes, many shops should be able to read trans codes. DOes not require a trip to the stealership. If there are any stored. Definitely worth checking.

The lines won't solve the present issue, I'm sure you have already considered that. I know you've already done it once but maybe another trans swap is in order. In general these transmissions are very hardy so for example I would not hesitate to pick up and install a used one that wasn't even remanufactured. Will be much cheaper than a rebuild, as mercuric alluded to. If you do go that route, best bet would be to find one with a known history. The whole sequence of events is puzzling but so far does seem to point toward cooked hydraulics.

I fully agree and thank you for the info. It's kind of late and I am tired... Thank you so much to all of you, you guys are so kind and helpful! I know the lines won't fix the issue but since I don't have them... may as well see what's out there.
Later and have a great night!

[mercuric]

I'd be bummed too!

The CEL (or maybe blinking arrow?) will come on for some codes, not for others. Look at that PDF linked above from volvoclub, it shows which throw a warning light and which don't.

So as far as reading codes goes, indeed a proper professional scanner as many shops have will read them. But now I'm curious... Even with the ODB-II post-95 volvos, some modules still can be read with a LED/switch combo, like as jreed shows on thread: https://www.matthewsvolvosite.com/forums ... =1&t=50443 (look towards the bottom of the first page).

Is it possible to use a similar method to retrieve transmission-related codes? I am now curious

EDIT: It appears, according to the wiring diagram, the transmission ECU uses K-Line (digital data), along with the seat controllers, instrument panel, and ABS module. Scanning these will require one of the various compatible tools -- VAG-COM + VOL-FCR is probably the cheapest. I'm going to have to play with this someday

It appears Motronic 4.3 (pin 3), electronic climate control (pin 6) and cruise control (pin 13) are readable via the blinkly-LED/switch combo.

[mercuric]

The whole sequence of events is puzzling but so far does seem to point toward cooked hydraulics.

Indeed, but I am a bit puzzled by the "happy when cold" factor. There are a bunch of variables here, including electronically controlled ones -- I'm guessing hydraulic line pressure changes significantly as the transmission heats up, either by mechanical malfunction or intentional control of the line pressure solenoid by the TCM as it senses the oil heating up. I don't have all the variables to piece it together, but I'd guess we'd either see the main pressure or the pressure to the various elements drop significantly after warmup... Then we slip.

I assume it slips in all gears? Then again, I suppose once it starts you're not going to go fast enough to get out of 2nd with much throttle, as i believe he said 40mph was tops.. which means 2nd gear, maybe 3rd with lighter throttle...

Also of note, this tranny does have a line pressure solenoid (#4) but doesn't appear to have a line pressure sensor or anything of that nature... So the TCM would have no clue that pressure problems exist. It appears it simply assumes the valve body and associated components are doing their job. It does, however, have a pressure test port for a technician to validate the system line pressure. Seems like if the pressure is within spec and there's no mechanical issues, the TCM knows how much to open the pressure solenoid to achieve it's programmed goal. As such, there are no pressure-related codes listed.

[Francois850]

I don't know if this helps and I probably already wrote it:
-When I select any gear, it never hesitates, engages smoothly and properly and near immediately, cold or warm.
-The car never slips out of gear, cold or warm.
-I could probably achieve better than 40 mph but most likely would damage something and I don't want to.

Also, I did some reading yesterday about someone who had experienced similar issues and the faulty part was some kind of transmission speed sensor. Anyone knowledgeable about such sensor?

[mercuric]

Also, I did some reading yesterday about someone who had experienced similar issues and the faulty part was some kind of transmission speed sensor. Anyone knowledgeable about such sensor?

The parts diagram shows two speed sensors on the transmission: One that measures engine speed and the other that measures drive shaft speed.

From the volvoclub PDF:

ENGINE SPEED (RPM) SENSOR
Electromagnetic RPM sensor, mounted in transaxle housing, is
activated by a toothed impulse wheel. Sensor is an input device which
delivers an engine RPM signal to the TCM. By comparing engine RPM and
vehicle speed, TCM can determine amount of torque converter slippage.

VEHICLE SPEED SENSOR
Vehicle speed sensor, mounted in transaxle housing, is an
input device consisting of speed sensor rotor and speed sensor. Input
signal is delivered from speed sensor to TCM with each revolution of
axle shaft. TCM uses speed sensor input signal for controlling
transaxle operation.

Diagram: http://i.imgur.com/AJdjnez.jpg

DTC 311 / ODB-II P0705 and a warning light are set if these signals are missing
DTC 312 / No ODB-II and a warning light are set if for "RPM signal incorrect"


VEHICLE SPEED SENSOR (VSS) DIAG:
1) To check speed signal, connect measuring unit to TCM. See
g. 8. Raise and support front wheels of vehicle. Set shift lever to
N" position. Turn ignition on.
2) Connect voltmeter between measuring unit terminals No. 20
d 48. Battery voltage should be present. Block one front wheel and
in other wheel rapidly. Voltage should be 4-7 volts. If voltage is
consistently high or low, check wiring for an open or short circuit.
If no fault is found, replace TCM.
3) To check speed signal wiring to instrument panel, connect
measuring unit to instrument panel 30-pin connector. Ensure ignition
is off. Using a DVOM, measure resistance between measuring unit
terminal No. 6 and TCM connector "B" terminal No. 18. See Fig. 10.
4) Resistance should be zero ohms. If resistance is not as
specified, check wiring circuit and repair as necessary. If resistance
is as specified, check for incorrect installation of wiring which may
cause interference, such as ignition wiring, mobile phone, etc.

- So, it sounds like if your vehicle speed sensor is broke, you'd know it because it apparently drives the instrument panel speedo.

RPM SENSOR DIAG
1) Ensure ignition switch is off. Connect measuring unit to
TCM. See Fig. 8. Using a DVOM, measure resistance between measuring
unit terminals No. 1 and 2. Resistance should be 300-600 ohms. If
resistance is as specified, sensor and wiring are okay. If resistance
is not as specified, go to next step.
2) Measure resistance between transaxle 26-pin connector
terminals No. 16 and 17. See Fig. 9. Resistance should be 300-600
ohms. If resistance is as specified, sensor is okay. If resistance is
not as specified, replace sensor.

[Francois850]

Good info, thanks!