2004 xc70 jerk shifting into reverse, with new valve body

[arrrxivvv]

So while waiting for the pressure gauge to arrive I used VIDA to read the solenoid currents, diagrams below. It seems like the SLS current curve is not the same as the one shown in the reference provided by firstv70volvo. The wave form is the same every time I shift N-R. Not sure it's normal, hopefully someone who shifts smoothly into reverse can provide the reading to compare. Also the jerk occurs well before S5 solenoid comes on, which I believe means that the jerk comes before C2 clutch is applied? That would point to B3 as the problem, as firstv70volvo predicted. Unfortunately there doesn't seem to be B3 pressure tap outside the transmission, and I haven't found information about its operation, for example which solenoid engages B3 clutches, though I guess maybe S3 and S5 together does that, or maybe S3 alone, since they are applied at reverse. If that's the case then I guess I can observe S3 on/off wave form as well, and should verify that B3 engagement coincides with the jerk.


The above picture shows the current of the three linear solenoid, where I shifted from N-R-N. The green line is SLS current, as well as the on/off of S5, the purple-ish line. Each line has a different y-axis shift though.

The above is a better picture, but without S5 on/off data. Shift sequence N-R-N-R-N-D-R.

The above is the reference waveform from firstv70volvo's reference.

If I remembered correctly the jerk happens at the peak in the green line.

To firstv70volvo, what are the main worn components when you took apart the transmission? In Hiram's youtube video of an AW55 tear down, the B3 clutches are in pretty good shape for that particular unit. I suppose it's pretty reasonable, since B3 only applies for reverse and so is not really used often?

Right now there are also some small kicks in all my downshifts, especially 2-3, though they are pretty small, do not depend on temperature and do not seem to be getting worse.

I've spoken with Sonnax and a Valve Body Pro's tech guys and both have heard of this problem after torque converter rebuilds and recommend trying an additive. The Sonnax tech person also said this condition may go away in time.

Did you buy parts from them so they provide technical support? Or do they answer consumers' questions in general? Just curious.

I have seen on a Saturn forum that for some models the reverse-related oil channels get clogged up more easily because it's not used often, so putting the car in reverse for say 15 minutes, by applying parking brake and wheel chock, simulating sitting in traffic in reverse, cured transmissions that slam into reverse but shift fine otherwise. Not sure what you guys think about it.

The man in a wheelchair (Rcflyer) story is really inspiring indeed.

[firstv70volvo]

If I have some time tomorrow I'll see if I can get solenoid current readings from my car. The B3 Low/Reverse brake doesn't have an external pressure tap, it's one of the two fluid paths between the valve body and case where the two o-ring type seals are needed. Solenoids S3 and S5 turn on for reverse although I don't know the timing of S3 and but it doesn't look like the application of the B3 clutch is a controlled application like C2 clutch. The jerk before S5 is likely the C2 clutch applying with something wrong with the pressure control during the servo or torque engagement phases. It will interesting to see what the pressure gauge readings look like for the C2 clutch.

About contacting Valve Body Pros and Sonnax
I was referred to Bob at Valve Body Pros by PDQparts, which is the placed that rebuilt my torque converter. I wanted find out what could be causing the slight shudder with the torque converter. Bob was very helpful, he's spent a good deal time answering my questions and he was very busy, he's a good guy. I just wrote to Sonnax and Jason responded several times with very good information.

Regarding what I found when I rebuilt my transmission. Badly worn friction material on the 1-2/Reverse Brake Clutch (B5) and the Low/Reverse Brake (B3). What I don't know though is what was replaced during the previous rebuild, this was a dealer installed transmission 105K miles ago so this transmission had been apart before. The Low/Reverse B3 clutch isn't applied much since it's just for reverse and it's a static type engagement so the wear on these frictions doesn't make a lot of sense unless they friction can wear just from spinning between the steel plates a lot of time. The filter was clogged with the friction material and I've heard this can be from the torque converter lock up clutch coming apart but I didn't have the original torque converter rebuilt so I don't know if that's the case. It could have just been clogged up from the other worn clutches. Other than that nothing else look worn or damaged.
Like I mentioned before when the filter clogged up I also had a harsh reverse shift but also had delayed slipping forward engagement when cold and when hot I got a torque converter lock up code. Prior to these problems I started hearing whining noise form the transmission when cold.

[arrrxivvv]

Now that I pay attention there is a whining/grinding sound at cold start, that increases when revving the engine.
The sound recorded in the following video, may need to turn up the volume a bit.
https://youtu.be/cUzagCjNDz0

After driving a few minutes I park the car and do the same test, the whining sound definitely goes away, leaving only the deep and sonorous inline 5 engine sound. I wonder if it's the whining sound of the transmission pump, as I never really paid attention to the sound of the car.

[firstv70volvo]

There's a good chance the sound is due to a mostly clogged and restrictive trans filter and this would explain the other problems you're having such as the harsh reverse. The gauge pressure readings will confirm if there's a problem with the pump pressure due to a restrictive filter.

Assuming the filter is clogged up you'll be facing the decisions of doing a long term fix that requires pulling transmission and rebuilding or replacing with a known good one or as described in the link below drilling and tapping the bottom of the case (clever idea, see link) to get access to the filter screen for cleaning or poking holes in it. This would be a shorter term fix where you're just trying to get some more miles out of the transmission. The condition of the rest of the car may help you decide what to do next if this is your problem.

Before I decided to rebuild my transmission I did go ahead and cleaned the filter screen because I was considering a rebuild down the road and didn't want unfiltered fluid circulating through the valve body and transmission with the poked holes method. I was successful in cleaning about 75% or more of the screen surface and I think this would have kept my transmission going for an extended amount of time but I didn't find out since deciding to just to rebuild it for an even longer term fix. With my car I had just done a lot of other maintenance work (tires, battery, PCV, oil pan reseal...) so decided to fix the transmission. I only put about 500 miles on it after cleaning the filter and it was working well. When I opened up the filter during the rebuild I was surprised how well I was able to clean it through the drilled hole opening. There was a very shallow areas where the case of the filter narrows down close to the screen that I could get completely clean as you see in the photo but overall I got most of the surface cleaned up,
[attachment=0]filter screen after cleaning.JPG[/attachment

my post about cleaning the filter is the March 22nd one
viewtopic.php?f=9&t=82841&hilit=clogged+filter

The thread is long and I recall Precopster mentioned something about blowing air through the trans cooler line to help verify if the filter is clogged. I didn't try this but it did sound like a quick and easy way to check if he filter is completely clogged. It's not a long lasting fix it sounds like it may blows just enough crud off the filter fo get some fluid flow. In your case though where the filter isn't completely clogged I don't know how effective this would be but it might worth a try before deciding on other courses of action, such a drilling a hole in the trans case.

[arrrxivvv]

Thanks, I'll check the pressure gauge when I get the tools.

I saw that a few years back you also suggested backflushing from the pump section port accessible after taking off the valve body cover and a cover plate. Haven't found anyone try that yet. Wonder what you think about it now that you have rebuilt your transmission so probably more familiar with its structure?

[firstv70volvo]

Thanks, I'll check the pressure gauge when I get the tools.

I saw that a few years back you also suggested backflushing from the pump section port accessible after taking off the valve body cover and a cover plate. Haven't found anyone try that yet. Wonder what you think about it now that you have rebuilt your transmission so probably more familiar with its structure?

I actually tried this method first and it only worked for about 300 miles before the filter clogged up again but I know I could have done a better job. When I had the small cover off the valve body I sprayed some transmission flush through the port and followed with low psi compressed air but the port opening was not sealed. I was concerned too much pressure in the port wouldn't be good yet doing it this way wasn't that effective. Even doing a better job with this method I got such good results using the new case hole with carb cleaner (with recommended hose) and bottle brushes turned out to be a known effective way to clean the screen although you do have drill and tap a hole in the transmission case.
If I were to try cleaning the filter again through the valve body port I would create a cover to seal the port opening and use a hose attachment to push a lot of transmission flush through the port to backflush the filter, high volume low pressure. It would probably work somewhat better but I think the other method of rubbing contact with the brushes over most of the filter screen surface and high pressure brake cleaner spray did a known good job. The downside is you have to drill the hole in the case to get access to the filter screen.

[arrrxivvv]

After replacing the front shock, spring seat and mounting plate the shifting became a little better. For the clunk into reverse, if I shift into D first before into R then the clunk is not too bad, while shifting from N or P into R is still not good, so now I just always shift into D first, and leave it as it for now.

[arrrxivvv]

Update. I brought the car to an independent Volvo mechanic and had him ride with me, he said that the shifting bumps are minor and nothing to worry about. They are very difficult to pinpoint and correct, and won't damage the transmission. So I'll just leave it as is.

[pbierre]

I think it would be worth getting opinions from a few reputable tranny shops. When you flushed the tranny fluid, did you filter the fluid looking for metal chaff? Did you inspect the VB you removed for chaff? Metal would indicate that this tranny cannot be made whole, as the mating surface tolerances are degraded. Better to know that before deciding to invest more.

[arrrxivvv]

I think it would be worth getting opinions from a few reputable tranny shops. When you flushed the tranny fluid, did you filter the fluid looking for metal chaff? Did you inspect the VB you removed for chaff? Metal would indicate that this tranny cannot be made whole, as the mating surface tolerances are degraded. Better to know that before deciding to invest more.

Thanks for the comment, I didn't notice metal when changing the fluid, but just by looking at the drain pan, not filtering it. Right now I'm relatively satisfied with how it drives so will not be touching the transmission at least for the time being.