Clunk in Diff or Tranny?

Is there anybody out there familiar with the innards of this transmission? The C solenoid seems to be fine. It actuates, allowing passage of air, when activated by a 12 volt signal. There do not seem to be any clogged passages. On inspection, the Transfer clutch seems to have normal wear. I don't know what the specs on the clutch pack are, but there is about .036 thousanths clearance in the pack (using a feeler guage set). This transmission was rebuilt about 5,000 miles ago, and I thought that maybe the rebuilder had missed the transfer clutch section. I'm scratching my head at this point. I guess I need to bounce some of this information off someone familiar with working on this transmission. Any information would be appreciated!!! Thanks.

[gl1674]

Larry,

1. The code 32 is vehicle speed sensor - and it is quite likely it is triggered by wheels spinning in the air.

2. Duty Solenoid C is normally closed and in this position the clutch should be engaged giving the max rear end torque - this is a fail-safe design, intended to give you maximum driveability. This means if you disconnect solenoid C wiring you should see maximum pressure.

3. The spec on clutch pack clearance is 0.008 - 0.024 "standard value" and 0.063 is the "allowable limit", so you seem to be OK there.

4. You might also try blowing compressed air to see if the clutch works - just to make sure...

5. I've had a very similar failure of the duty Solenoid A (note it is also a duty solenoid - subject to continuous wear as it cycles 50 times a second). My solenoid would open and close properly when I played with it out of transmission, but in the transmission it would stay wide open all the time there was any signal coming from TCU. It would stay shut if I cut the wire from TCU. A new solenoid pack had solved my problems and the transmission has done another 12k since then without any new problems.
If you do not see anything else wrong - just do a leap of faith and buy a new Solenoid C. It's listed for about $80 on subaruparts.com My theory is that the moving cores of duty solenoids wear out and ATF pressure begins to push them fully open. Or the return springs get weaker.

Thanks for the reply. I did assemble the transfer clutch into the rear extension housing and then used compressed air to activate the clutch through the C solenoid valve assy. With the C solenoid inactive (no voltage to solenoid) the clutch pack actuates fine. With voltage to solenoid, the clutch does not activate. This seems normal to me. At this point, I am about to reassemble the whole thing and test the pressure before the C solenoid. I would assume that is "line" pressure, but I need to get a transmission manual from Subaru that has the diagrams of the hydraulic circuits. If I have normal pressure at that point, then I will go for the C solenoid replacement. It should only take about 15 minutes to put the extension back on the tranny. Wish me luck. This thing is turning into a nightmare.

Oh, one other detail. I put a meter on the wire coming out of the tranny to the C solenoid. With ignition on, there is about 7 volts to that wire. With FWD fuse in, there is about 12 volts to that wire. Don't know what normal is, I guess tranny manual will tell me that too, unless somebody there knows. Thanks again.

[gl1674]

Larry,

12 Volts with the FWD fuse on is normal.

The voltage in AWD mode is a bit more difficult to measure - TCU does not feed a constant voltage, instead it uses 12 volt pulses of variable lengths. What you actually measure depends on how your meter averages up the pulses.

However the voltage you measure should depend on the throttle position. No need to run the engine, just ignition on is enough. With full throttle the voltage should drop, probably not to 0, but to somewhere around 1 volt.

In my case that 1 volt was enough to keep the solenoid open. You should probably check that clutch pack still activates with compressed air when the solenoid is connected to TCU and TCU is in full-throttle mode.

Yes it is all based on line pressure with two valves in the extension housing controlling it. The first is pilot valve that reduces it to some constant pilot pressure. This fluid passes a small calibrated opening and Solenoid C sits after the opening and can keep the pressure when it is closed or drain it when it is open. This pressure moves the transfer control valve that actually supplies line pressure to the transfer clutch.

I'm pretty sure you have the line pressure, at least in the transmission body.

OK, hopefully I am nearing the end of this process. I took the assembled extension section under the car and hooked ground wire between it and tranny. Then I ran jumper for the hot of the solenoid. I put a meter across the solenoid. With key on, I read 5 volts. Air pressure does not activate clutch. With trans in 1st, pedal to metal, voltage is about .5 volt, air pressure activates clucth. Letting up on throttle slowly, clutch stays activated until pedal is about 3/4 of the way up, then clutch deactivates. This all seems like normal type operation to me, but maybe in the car? I will take the leap of faith and go ahead and replace the C solenoid.

The Subaru parts dept. here has been a real help. The parts guy went out to the shop and got the manuals for me. He let me study them for about 45 minutes and then made copies of the key pages. I have a C solenoid/transfer valve assembly on order, should be here in the morning. Everything seems to be working out of the car, but maybe in operation it fouls up. Will let you know tommorow if this fixes it.

[lee]

Larry,

Sorry I'm late to the party and from reading your posts it's a cinch you know much more about auto boxes than I do. Can I ask one question as it seems to had some bearing on a clunk on my own tranny.

Have you measured the rolling circumference of the tires. I have approximated this by measuring the radius. I used to trust the factory recommended pressure differential, but I now believe that to be brand dependent. I'm running 31 and 42 psi (rear & front respectively), but of course some of that difference can be attributed to tread wear depth/difference as well.

Anyway, after adjusting pressures, my transmission seems to have gotten quieter, but I don't think it was ever as bad as you initial complaints. Just an idea.

[gl1674]

Now I'll have a sleepless night worrying whether the new solenoid C will fix your problem.

Wow, it is nice to have AWD again. The C solenoid/valve assembly fixed the problem. $105 plus gaskets and fluids. The strange thing is that everything checked out fine on the bench. The clunk is completely gone. I am one happy SVX driver. I was thinking about going to a 5 speed, but now will keep driving the automatic. One last question, what happens when you put regular in the tank? Does it really do damage to the engine like the manual says it will? It puts a real crimp in the pocket book to keep putting high test gas in it.

Again, for all you folks who helped me figure this thing out, many thanks. This is an awesome web site.

[gl1674]

Larry,

Congratulations. Impressive work, especially without looking into the manuals!

Can you cut your old solenoid C open and see if you can find anything wrong with it? This thing still bugs me - I've opened mine and could not find much wrong with it.

[Jamsvx]

Glad to hear that the SVX is back to normal, but, I was having an embolism reading the posts...when I hear/feel strange sounds, bangs I am not able to pull over, pull it apart and fix it but rather...


"Oh dear gawd, no" - ripping hair - "why, why I ask have you done this to me" followed by plan: bread and water for food free $$ for Subaru thieves



Harvey, next time you are down I would be obliged if you could drive mine and perhaps comment on whether there is anything unusual....especially the throttle response

[LarryIII]

Larry,

Nice to see another Larry SVXer on the board.

[oab_au]

Originally posted by larry
Wow, it is nice to have AWD again. The C solenoid/valve assembly fixed the problem. $105 plus gaskets and fluids. The strange thing is that everything checked out fine on the bench. The clunk is completely gone. I am one happy SVX driver. I was thinking about going to a 5 speed, but now will keep driving the automatic. One last question, what happens when you put regular in the tank? Does it really do damage to the engine like the manual says it will? It puts a real crimp in the pocket book to keep putting high test gas in it.

Again, for all you folks who helped me figure this thing out, many thanks. This is an awesome web site.

Gid'ay Larry, top marks for a good job.

Running low octane is possible, the car will do it , the knock sensors will pull the spark back when detonation is detected. The problem is that detonation has to occur for the sensors to detect it. This depends on how hard you drive it.

Performance and gas consumption will be affected.

Harvey.

[svxistentialist]

Originally posted by larry
Wow, it is nice to have AWD again. The C solenoid/valve assembly fixed the problem. $105 plus gaskets and fluids. The strange thing is that everything checked out fine on the bench. The clunk is completely gone. I am one happy SVX driver. I was thinking about going to a 5 speed, but now will keep driving the automatic. One last question, what happens when you put regular in the tank? Does it really do damage to the engine like the manual says it will? It puts a real crimp in the pocket book to keep putting high test gas in it.

Again, for all you folks who helped me figure this thing out, many thanks. This is an awesome web site.

Hi Larry and welcome, you are new here, I can see by your low post count.

You are obviously well clued up on transmissions, good job and well done as Harvey says.

I have run mine on regular for over two years with no ill effects. So has Arthur610 in the UK, his is a 95 or 96 model I think. It is difficult to impossible here to find high octane gas, 95% of pumps are regular. It is a bit down on power, but I can't honestly say it is worse on consumption, seems about the same to me.

I drive it a lot in 3 rather than D, so that possibly cuts down on potential pinking. The ECU and TCU has a "learning" mode, so I would not be surprised if it kept the ignition cut back all the time when fed a diet of Regular. But maybe not. At any rate, mine does not pink.

Last point, the price of your gas is way cheaper than over here. If I could get high octane, I would use it. Unless it is a significant percentage more expensive, stay using the good stuff, but don't be afraid of it if you have to fill regular somewhere.

Joe