AW55-50SN has no gears after 3 seconds

[jim9fisher]

Good afternoon all, I am new to this forum, but was sent here because I was told you were the keepers of the truth in the Volvo world. I am afraid I have killed my daughter's 2000 S70 N/A (214K miles).

The story:
In 2013 we had a flashing arrow and intermittent speedo, so I swapped out the ABS module and all was well.
In November 2014 she came to me with a flashing arrow, and a P0740 code. I reset, and all was well until she got to 50MPH, when the P0740 returned. After a lot of research, I rebuilt the linear solenoids and flushed the system with Mobil 3309 fluid. This did not solve the problem. I was not able to get the transmission into Adaptation mode because I did not have VIDA and a DICE, so I ordered one from China.
And waited......... for a while.
I got impatient and pulled a valve body from a junkyard and installed it into the S70. I was able to back out of the driveway, and then lost all gears, maybe 30 seconds of total movement. I reinstalled the original valve body, and have the exact same symptom.
here is what I have done:
I have rebuilt the valve body with new accumulator checks, gaskets and a shift kit. - then took it back apart and back together to make sure all is correct...
I have changed the linear solenoids
I have changed 3 of the shift solenoids (even though they all test good)
I have replaced the O-rings (seals) behind the valve body
I swapped out the TCM with a unit from the junk yard. (besides a boot reset with the VIDA and DICE, no help)

Besides getting really good at getting the valve body out of the car, I am not making any progress.
When the car is stone cold, I can put it in reverse and smoke the tires. No slipping or anything.
I can then put it into Drive and do the same. ------ for about 30 to 60 seconds. Then nothing. I put it in Drive, and there is no gear engagement, no rpm drop, nothing. it is like the pump has stopped working or has been switched off.

The default opinion is 'Change the Transmission', and that may be the answer, but I would like to understand why. I don't just want to start throwing $$ at the car, it is not worth that much.

Keepers of the truth.......what have I done?

I was told to reach out to Astro-14......but I have read much wisdom from others as well. Any wisdom would be appreciated.

[howardc64]

Just a random guess, I recall reading someone who replaced valvebody on this tranny and the o-ring (the 2 o-rings for the channels that runs into the gear housing) fall out during install. This person lost reverse as I recall.

Not sure what those channels are for but one would guess pumped hydraulic fluid must come through at least 1 of them?

[Astro14]

Interesting story!

First, the disclaimer: I am a DIY Volvo owner. I fly airplanes for a living. I've pulled apart a few transmissions, and wrote up my experience replacing the valve body on this one. If you've read this: http://www.volvoxc.com/0/resources/h...ment-Notes.pdf then you've seen it. I wouldn't say that I am wise, just skinned a few knuckles on this beast...

So. My approach to your problem would be to check cheap/basic first. What is the fluid level? Are you checking it cold, before you move the car?

Next, I would go back into the valve body. Make certain, in the multiple changes, that the slider to the gear selector lever is engaged. Howard makes a good point on the o-rings - were they to fall out, there wouldn't be line pressure to be shifted in the valve body, which would cause the problem. I used Vaseline to keep them in place while installing the body.

But if the O-rings were missing, then I would think that you would never get any gear. Your problem sounds like the car doesn't know what gear to be in.

It's also possible that you have an unrelated (to the valve body) electrical failure that's causing this.

In your car, which is a lot like my much-loved 1994 850 Wagon, I believe that the battery sits above the Neutral safety switch. That switch can get corroded, and fail, causing all sorts of issues. Perhaps yours.

Looks like this: http://www.ipdusa.com/products/6217/...e-light-switch

[howardc64]

Reread OPs efforts, there are a lot of variables at this point. Perhaps its good to confirm current status

- Original VB (home rebuild with Transgo kit) back in the car
- Original TCM back in the car? Probably want to make sure original TCM back in the car if not already.

I wonder if the gear loss in 30-60s has to do with catalytic converter startup mode? I don't know if the TCM changes out of that mode by ATF temp or coolant temp (I'm guessing ATF?). VB change requires pulling the temp sensor on the TCM/VB cabling. I recall how the temp sensor removal and install is rather tricky. There was that metal key that slides in side ways to lock it down and most people wouldn't know how that is assembled on first encounter.

Here is another couple of experiments to consider

- shift P-R and keep it there instead of going to D. See if you loose reverse in 30-60s.
- shift from P to N and keep it there. See if you have any gears after 30-60s.

[coflynn]

Not mechanical but... you do have a DiCE setup then it sounds like? Does it have details of any logged errors?

Furthermore you should be able to go into the TCM and monitor line pressures, etc. See what changes when it stops responding.

I'd fully explore what troubleshooting you can do using the instrumentation already in the car.

[howardc64]

Furthermore you should be able to go into the TCM and monitor line pressures, etc. See what changes when it stops responding.

Actually, I don't think there are any pressure monitors internally to the transmission. It would be great if there was as it would make diagnosing hydraulic circult problem a lot easier. As of now, there are ports on the tranny which one needs to attach pressure gauges to to figure out whats going on. Here is a reference.

http://www.sonnax.com/articles/210-A...-Join-the-Club

And this might be useful for OP if it continues to be a mystery. It does require understanding the hydraulic circuits and monitor via these ports. Perhaps a tranny shop familiar with AW55-50 can determine the failed circuit quickly testing these pressure ports.

For diagnostic purposes, modern electromechanical valvebody transmissions usually have the following diagnostic capabilities

1. Quick open/short resistance test to check solenoid's wiring (external wiring harness and internally wounded electromagnetic wiring. But this doesn't test if the solenoids are mechanically moving smoothly.
2. temperature read
3. input and output RPM reads

#1 is cheap and easy, #2/#3 is required for the tranny to actually operate. Pressure monitors would be only necessary for pressure circuit wear diagnostics and I'm guessing they don't include for cost reasons. Manufacturer probably figures if there are any pressure issues, there are no cheap fixes anyways as labor charges are usually high just getting to the VB.

BTW, I recently did a TCM/VB diagnostic on a friends VW MK4 4 speed auto. The previous owner had 1) broken all the solenoid contacts while replacing the solenoids 2) fried the TCM by reversing battery polarity while monkeying around. We found all the faults with an OHM meter but of course a guru on this particular tranny had published where to check the pins on wiring harness+TCM. I haven't seen anyone publish this level of diag on the AW55-50.

[coflynn]

Actually, I don't think there are any pressure monitors internally to the transmission. It would be great if there was as it would make diagnosing hydraulic circult problem a lot easier.

Crap - you are right! What I was thinking of was the read-out of current consumption by each of the solenoid... I remember there being something to monitor, but it's much less useful than actual pressures.

However it would still be a worth-while check... as you could figure out what it's being commanded to do, and if the system is properly able to sense the current consumption when the solenoids are switched on. This does give you more than just a straight "short/open" test as the current is variable I think. A jammed or mechanically damaged solenoid would mean very high current consumption, which you couldn't detect with just an ohm-meter.

It also allows you to manually switch the solenoids on/off (while engine is off of course!).

If the system is disabling itself after that 30-60 second period, I would expect some sort of error message to be logged about what errors caused that.

Regards,

-Colin

[jim9fisher]

Great input, thanks everyone.

I have pulled the TCM and ohmed out the harness and the solenoids / temp sensor. I was able to get good info from Sonnax and Transgo with a simple registration. It does not look like I have any shorts or broken wires in the circuit. I put the original TCM back in as suggested.
interesting comment about the temp sensor..... I know it is keyed and locked in place and the DICE is showing the temperature with no error codes.

I have checked the park / neutral switch, and it does not appear to be acting up.

I have checked the solenoid schedule per the Sonnax table, and the solenoids are getting power in the correct sequence / combination for the gear selected.

I will check the P/R only next, to see if I go into reverse and don't loose reverse after 30 - 60s. I will update later today.

I think I will get a pressure gauge on this Tranny........ to see if the pump is 'shutting off'. Gotta find one. Anyone have more info on the catalytic converter startup mode?

More to follow.

[JRL]

I would not dwell on the solenoids.
Everyone of them would have to have failed at once for no gears at all, I think it's something else

[sjonnie]

I think he has an actual clutch failure, not a solenoid problem. New clutch packs would be the answer (i.e. transmission rebuild which is the same as a new transmission). If the OP is still around, do you still have reverse?