yet another tranny question

[lee]

Originally posted by gl1674
Lee,

Few more things more or less at random:

- it is quite possible that tranny does not slip at stall test, but still slips when driving - at stall RPM the engine revs are too low to produce enough torque, when driving the revs are higher and more torque is available.

- What is the mileage on the transmission and where was it rebuild (the question really is: did they change the solenoid pack or not). 150k is the ballpark for duty solenoids life, but it is very rough - a better measurements is hours of operation..

- Did you check ECU codes? A faulty TPS should also set the code in ECU. And the code is also 31.

- TPS should give you continuously changing readings as you slowly move throttle - any positions where resistance/voltage jumps or any noise when it is being moved are a problem.

Mileage on tranny is 127K miles, rebuilt 25K miles ago. I was charged for a new solenoid pack, but of course wasn't there to see it go in. However, the shop was recommended independently by three different people (personal recommendation, recommendation from place I had do my water pump - day after I bought it, and including the mechanics at the Air Force Base Hobby Shop - they won't let you do tranny rebuilds there, no idea why ).

I put back in a dropping resistor. Now I get no blinking power light on start-up. The stored codes are for TPS and Solenoid A, but I have no idea how old the codes are. The TPS was replaced, and without the resistor, well of course that one got set, so....??

I have checked the TPS voltage (at the TCU) with engine off and the voltage smoothly increases with more gas pedal. However, the value of this test is suspect because I'm using a digital VOM and doubt my movements are smooth enough or that the VOM responds fast enough, to see a spike/drop-out.

I drove to work and back today and the car still seems improved over a few days ago. I did notice one thing. The "slip" I have been reporting seems worse if the car is in "D" when the 3-4 shift occurs than if I drive off in "3" and manually shift to 4th. I tested this so the revs in third were the same at the shift point (about 3500). Both times were on flat ground about 1 minute apart, fluid warmed to about 160F.

[lee]

Originally posted by oab_au
Lee when you check out the TPS, check the resistance through the full sweep of the wiper. Hook up the meter either OHMs or VOLTs, ignition on, engine off. Move the throttle shaft slowly by hand, watch the meter , look for a spot where the reading drops. The reading should change smooth, to show no bad spots on the resistance track.

Did, but see my response to gl1964, wish I had an oscope as I don't trust my VOM to be accurate along the time scale given the coarse movements of my hand on the throttle.

...snip....


It is not the torque converter stator slipping or sticking as the stall test shows. A problem in this would happen in all gear positions. I would also disregard the A solenoid, for the same reasion. The shift solenoids don't actually shift the gears, they just operate the shift valves, other variables operate also.

There may be some "slipping" in all gears, it's just most noticeable when requesting acceleration in 4th at a slow speed, i.e., traffic slowing to 40mph, then picking back up again. The transmission shop told me the same thing about the stator slipping and said it should be the exact opposite, I should see it in 1st as the car tries to get moving from a dead stop (and I don't see this at all, 1st seems about at good as it's ever been).

The units that cause the different ratios are, the FORWARD CLUTCH, BRAKE BAND and the HIGH CLUTCH. The sequence that selects the ratios are;

1st. FORWARD CLUTCH applied.
2nd. FORWARD CLUTCH still applied, BRAKE BAND applied.
3rd. FORWARD CLUTCH still applied, BRAKE BAND released, HIGH CLUTCH applied.
4th. HIGH CLUTCH still applied, BRAKE BAND applied.

If you check this sequence against the shift solenoid sequence, you will find that they don't match up.

I think UberRoo was suggesting it was an easy test to make sure the systems were synchronizing their actions (maybe help eliminate a TCU problem?), but shouldn't speak for him. The test with a couple of bulbs is indeed easy and I've rigged up the lights in a little black box already, just gotta find time to install. Can't hurt to find out.

I still believe that the band is slipping as it tries to hold the front sun gear, if it does, then it will go to 4th, if it slips, it goes back to 3rd. The brake band may be out of adjustment, or there is a line pressure problem at that particular point, caused by the TPS.

Will readjust this weekend. If the problems aren't gone then I will either buy the gauge or pay for the test (about the same price so I'd like to have the tool, but then again I have no idea what the data means if it needs interpreting, so...?)

...snip...

All the best Harvey. [/B]

[UberRoo]

I hindsight, I might suggest that you tap all six control wires for all six solenoids. I've been driving around like that for several weeks and I've found it interesting to note exactly what the transmission is doing. Most of the time I already know what's going on, but sometimes I look down at the lights only to see that it snuck something by me. I'm probably far more in tune with my transmission than anyone because I've been watching those lights like a hawk.

My point about hooking up the other lights is because the overrunning clutch light may also play an important role for reasons yet unimagined. It's also possible to observe the torque converter lockup (solenoid B) by observing the bulb's increase in brightness. I foolishly elected to use LEDs which don't modulate their brightness very effectively with respect to the duty cycle of the duty solenoids and I haven't been able observe any modulation of solenoid A nor C, though generally when solenoid C changes state, I'm watching the road.

When I first got my car, I thought the transmission was buggy. Sometimes it would slip, and/or buck at the most inconvenient times. I'd think about passing someone and just as I was about to begin the maneuver, it'd loose power as though the clutch was slipping. After it did this a few times and I started to drive the car more aggressively, it became apparent that it was always changing gears at the wrong time, often jumping the gun, choosing the wrong gear, and changing it's mind. Eventually the car either got smarter, or I learned to dumb down my driving.

A confused ECU will leave you tearing your hair out, and it can be caused by strange things like driving too carefully.

[lee]

Originally posted by UberRoo
...snip...A confused ECU will leave you tearing your hair out, and it can be caused by strange things like driving too carefully.

Now that's an interesting, and plausible, idea I hadn't thought of.

For some reason my negative battery cable terminal decided to crack where the bolt goes through to tighten it on the post. I removed the cables long enough to change out the terminal. I wonder if the ECU got "stuck" in "never never land", just at the point of losing the memory. That might explain why it seems to be doing better, learning with more driving cycles and being put through it's paces by the transmission tech guy.

If this (confused ECU) turns out to be true I will be giving myself the DUH slap to forehead (and promising a cold one to you all for helping out the village idiot). I should have mentioned this up front, but just didn't think about it.

[lee]

Another update.

Did a band adjustment. Reset the ECU by removing the battery for awhile. No codes are presently being set. Went back to the tranny shop that did my rebuild and they gave it another road test. Said there is no slipping in the transmission. Ran a stall speed test and gave me a file they pulled from the net somewhere (I'll attach it below - said it was on Subaru's but not the SVX specifically). Since the stall speed was if anything slightly low in D, 2, & R, they infer that the road test is correct, no slipping of bands, etc. I asked again about a slipping stator and they said no, as I would be experiencing poor off the line performance, and in all gears, not just trouble in the higher gears.

They said they would do a line pressure test (for around $100), but thought I would be wasting my money. I think they think I'm a bit daft over this transmission (maybe I am, but I don't think so, transmission behavior is definitely different in the last few weeks from the 20 months preceding).

So, as I see it, I could get a gauge and do a pressure test myself - but don't know how. Will a pressure test reveal if the solenoid pack is going bad? I'm about out of ideas. EDIT: I previously reported that the slip went away during the time I had TC lock-up. That seems no longer to be true, if it ever was. From this I infer the band is slipping. But since it passes the stall test, I'm now guessing I have a problem with the A solenoid. END EDIT

So, at this point I see two likely alternatives: a) solenoids failing gracefully (can they do that?), or b) lee is an idiot. Safe money would probably be on choice b.

[lee]

sorry, forgot the file I said I'd attach.

[UberRoo]

Yes, the solenoids can fail gracefully. They just sorta wear out slowly. As much as I hate giving advice that costs money, I think that doing a pressure test would be prudent. If it turns out to be a pressure problem due to a solenoid, it'll save you the cost of replacing your clutches when they finally wear out. If it's due to the pump or some of the clutches themselves, at least you'll know you can stop worrying about the solenoid.

I wouldn't necessarily say that the safe money is on choice 'B', but less money is on that choice, and that makes it a good choice. The way I see it, the pressure test will tell you if you just need a solenoid, or if you have a clutch problem - with a cautious fear that we may still be overlooking something - but I'm beginning to doubt it.

I'm not sure where the pressure ports are, but I doubt they're terribly difficult to get to. It requires a banjo bolt of the right size and a gauge with plenty of hose. I've never priced the pressure gauge (and parts), but I've heard that unless you plan on using it at least twice, you're better off having a shop do it for you as it'll cost less (and safe you the trouble to boot!)

I'm not certain if you need to pull the valve body in order to change the solenoids. I'll try to find out for you...

[lee]

thanks UberRoo.

[oab_au]

Hi Mate, the sarga goes on.

First the stall test does not clear the band from slipping, as it is not applied in first, only the Foward clutch is applied. The band can still be suspect.

Yes I would go for the line pressure test. I think it would be best for you to do it yourself. Beg, borrow, or steal a gauge, fit it so you can watch the line pressure as you drive. The test that the Auto shop does, is to check the idle and full throttle pressure. This may test OK but it is in the operation of the changes, that will show any problem that you are having.

The pressure is controlled by two sorces, the throttle movement varies the pressure in line with the engine load. The harder the pedal pressure the higher the line pressure. So as you back the throttle off the pressure will drop.

The other sorce of line pressure change is preformed by the TCU, in line with the memory map that is written for every gear change and operational condition, temp, mode (cruise control, power mode), kick down, manual shift etc. The TCU will vary the line pressure to suit the type of condition that the box is experencing.

The pressure that you will see on the gauge, will go up and down, as the throttle moves up and down. But even if the throttle is held steady, the TCU will still vary the pressure. So what you should look for is a drop in line pressure, that should happen as the gear change takes place, that is a lot lower during the 3/4 change, than the 2/3 change.

It can be a combination of the light throttle pressure and the drop in the TCU pressure, that causes the band to slip. As you say, the slip is not as bad in a manual 3/4 change as the auto 3/4 change. This is a sign that it is a line pressure problem as the TCU is providing more line pressure for this change, than it does for the auto change.

You may have to run the gauge on the car for a while, to get use to the way the pressure changes. Then you can look for the cause. As you have eliminated the band adjustment, the line pressure is the last check.

All the best.
Harvey.

[lee]

Harvey, et al,

I didn't get to watch them run the stall test. Do you reckon I could put the transmission in manual mode, select "2" and run a stall test myself? That seems like it would check the 2nd gear holding - which if I understand it, involves the band clutch.

I'll be looking for a gauge set soon. I noticed JC Whitney has one for $62.99 online, but I'd like to get a local purchase.

[oab_au]

I guess you could do that, though I would be a bit reluctant to do it, in Manual mode due to the lower pressure that this mode would use. To give the band a test, just kick it back from 3rd under full throttle. This will test the bands grip under full power, as it has to be applied to get 2nd.

I was thinking, that another way to see the line pressure performance, would be to connect a DVM up to the A solenoid to watch the level of the modulated signal, that the solenoid is receving. It won't rule out any problems with the pump or line pressure leaks, but I don't expect the problem to be there.

If your meter has a duty cycle mode, you can connect it to the GREEN/YELLOW wire from the dropping resistor, to read the total signal that the A solenoid is receving. The other side of the dropping resistor, the GREEN/RED wire, will show just the throttle pressure, componet of the signal. The percentage at idle is ~95%, full pressure is ~5%.

If the meter has a 'min/max' setting, you could press that button when the 3/4 shift is comming up, to capture the minmum and maximum pressure signal that the A solenoid is receving. Would be the same as looking at a pressure gauge, well allmost

The line pressure port is on the pump section, between the diff and gear box sections, just above the oil cooler outlet pipe. The normal pressure is 64 to 82 psi at idle, 164 to 182 psi at full load. Reverse is higher, 85 to 100 psi at idle, 206 to 230 psi at full load.

Harvey.

[lee]

thanks Harvey ( and others) for sticking with me as the saga continues. And a big thanks for the pressure numbers. I'm going to order in a manual, but that takes time and I worry about doing damage while I wait. Unfortunately, the SVX is my daily driver car for to/from work.

I ordered a line pressure kit from my local car parts house (less than $70). they tell me it will be in tomorrow around noon. I hope to get it after work and try a hook up that evening (if time allows).

I was hesitant to try the stall, and will avoid it based on your advice.

One thing I did try was to select "2", and put it in manual mode, while taking off from a dead stop. As expected for starting from a dead stop in second, there was a slower rate of acceleration. I did not try anywhere near a full throttle application, but gave it enough gas to wind the engine up to around 3000 rpm. It pulled quite smoothly with no sensation of slipping. I released manual mode and shifted into "3" and all went well. I will perform the suggested downshift trial, as it provides another vantage point for analyzing band engagement.

I do not have a very good DVM, but your suggestions are a good idea. It seems likely that between the DVM readings, and a pressure reading, I should be able to isolate the problem to either mechanical (solenoids) or electrical (TCU and/or wiring).

[oab_au]

I am not sure, but I would think that as the Manual Mode is for slippery surfaces, the TCU may tell the ECU to turn the power down, on the take off.

Sorry, I can't post the diagrams of the manual as my main computed has died, due to a servere virus.

Harvey.

P.S. Fluke DVMs are the best, bullet proof.

[lee]

I picked up the gauge set today, so hopefully I can find time to get it hooked up and report findings. However....

here's the kicker. I have been baby-ing the car, using "3" until I get to my desired speed, then shifting into "D" to minimize the "slip". Every once in a while (say every tenth go) I would leave it in "D", or give it some gas once in 4th, to see if things were better/same/worse.

So, on the way home from the parts house the darn thing shifted like the day it was first installed. No slipping - even going over the biggest hill we have around here - which always induced the problem before.

I told my wife the car is making a statement. As long as I buy new tools every week it will be fine. I don't think she bought into it.

Still, on the premise that car problems don't fix themselves, I will hook up the gauge and see what I get. I need to be prepared in case the problem comes back - which I'm sure it would about 5 minutes after I remove the gauge.

BTW, got charged $57.85 plus tax for a two-gauge pack (transmission 0-600psi and oil pressure 0-80 psi), 6 feet of hose, and about 10 or 12 fittings (both metric and US threaded).

edit: Most cars have a plugged hole for running the hose from gauge to tranny - if the SVX has one I can't find it - anybody know where it might be hiding?

[gl1674]

guess you could do that, though I would be a bit reluctant to do it, in Manual mode due to the lower pressure that this mode would use.

Harvey, why would that be? At full throttle TCU will give full pressure - no matter what gear you are in. At least my FSM gives the same numbers for all forward gears.

I was thinking, that another way to see the line pressure performance, would be to connect a DVM up to the A solenoid to watch the level of the modulated signal, that the solenoid is receving

That would prove precisely nothing. TCU does not wear out, it either work or it does not. But solenoids are mechanical things and they fail.
Mine came to a stage where it would stay closed as long as there were no signal applied to it. Any duty signal (even 5% ratio) and it would flip fully open. I don't know why it was happening, I cut it open and did not find anything obviously broken, but it was not working as it should.

the TCU may tell the ECU to turn the power down, on the take off

Hhmm, do you know this for sure?