Auto center diff

badhuis · Post by **badhuis** » Wed Apr 29, 2009 12:22 pm

I think the center differential on my 93 auto Wagon is broken.
Anybody knows where to find a replacement?
Are all the center diffs in auto transmissions the same (1.8 litre, 2 litre, I have a 2.2 litre)? Up to what year? Is it used in other (Legacy 2) transmissions as well?
I could not find much info about the automatic central differential. The online WSM is of course just missing these pages (3.2) and there isn't anything in the Haynes.

Any help much appreciated!

kimokalihi · Post by **kimokalihi** » Wed Apr 29, 2009 2:30 pm

What is wrong with it? Why do you think the center diff is bad?

PhyrraM · Post by **PhyrraM** » Wed Apr 29, 2009 2:53 pm

The autos do not have a center diff. They use a clutchpack controlled by a duty cycle soliniod.

The soliniod is known to have problems. Try searching for "soliniod c" (?), maybe b.

badhuis · Post by **badhuis** » Wed Apr 29, 2009 5:59 pm

Reason why I think it is the central "differential" is because of the change in behaviour when the engine / tranmission is cold or warm / hot.
When cold, there is NO problem with the car. Runs smoothly, picks up speed fine, no rumble in the corners. If the engine (transmission) is hot, it is very different. Severe shudder / judder when accelerating, in slow corners, when moving from standstill. Maintaining a speed, there is no unbalance but there is when accelerating. Sometimes it is so bad it seems the whole drivbetrain is in unbalance. I had the car on a 2 post lift, and checked the axles for unbalance (engine running and car in D).

Tha nk you for clearing up that it is not a real diff but a cluchpack (like motorcycles have). And that these are acted by a solenoid. Now the tip from someone else makes sense that the fuse can be removed, forcing FWD only. I think I will try that and see what happens then.

Thank you for the tips / reactions - keep them coming.

log1call · Post by **log1call** » Wed Apr 29, 2009 9:28 pm

transmission manuals are here... http://cid-4ca3c3459aaa7f7f.skydrive.li ... px/.Public

Those symptoms don't sound like tranmission problems, not the "centre clutch" or the main transmission assembly.

First off, are you sure it's not a missfire in the motor?

If it is a vibration from the driveline it should be obvious by it's frequency. I'd be looking at the front axles and especially the inner ends where they fit onto/into the gearbox.

ericem · Post by **ericem** » Wed Apr 29, 2009 9:32 pm

Are all your tires the exact same size and are they inflated equally?

Also did you try putting the fwd fuse in place near the passenger side strut tower when warm to see if the "binding" goes away?

kimokalihi · Post by **kimokalihi** » Wed Apr 29, 2009 10:55 pm

Just make sure you do not leave the car in FWD mode for very long. Do not drive it around all the time in FWD or you will destroy your duty c solenoid.

Post by **Legacy777** » Thu Apr 30, 2009 6:43 pm

To clear a couple things up.

The first thing I would suggest is checking your transmission fluid. Is it at the correct level? The engine must be running, the trans up to temp, and you have cycled through the gears prior to checking the level. Check if the fluid smells burnt.

If that is alright, I'd suggest installing a fuse in the FWD fuse holder to disable the AWD. Yes you need to install a spare fuse, not remove one to disable the AWD.

It is recommended not to run extended periods with the fuse installed, but I wouldn't say it will destroy the duty c solenoid.

If your problems go away with the fuse installed, you either need to change the trans fluid, or may need to replace the clutch packs on the rear transfer clutch.

If your problems do not go away, it may point to a problem with another part of the transmission, duty c solenoid, or possibly some other component on the car.

Try performing some more tests and see what you find out.

log1call · Post by **log1call** » Thu Apr 30, 2009 8:51 pm

Tune your motor!

badhuis · Post by **badhuis** » Mon May 04, 2009 5:44 pm

Thank you all for your reactions.

So, I put in the fuse, there's a FWD light on the dashboard I've never seen before and yes, no more shudder / troubles. The car drives very normal in FWD mode. Although I can feel the steering is a bit different as compared to running AWD.
The trans fluid is clear, does not smell burnt, and there's enough of it in on the dipstick.
Tyres are the same make and dimension all round, good profile.
So it is the clutch pack. Glad to know what the cause is of the problems.

Reading the write up somewhere else on this BBS, it is mentioned that it could be replaced without pulling the transmission. Although this was for the manual trans with the viscose "diff".
Does anyone know changing the clutch pack can be done with the transmission in the car?

Post by **Legacy777** » Mon May 04, 2009 6:23 pm

The rear transmission housing can be removed and the clutch packs changed without removal of the transmission.

I'd suggest changing the fluid once or twice to see if things improve.

badhuis · Post by **badhuis** » Sat Oct 03, 2009 10:15 pm

A post to conclude this.
The rear case of the AT was removed, and the clutches were looking fine. Next step was to investigate in the software that steers the central diff. And yes, after hours of reading and searching the problem was found: a faulty throttle positioning sensor. Exchanged it for another one and problem is solved!
Who would have thought that - not me! (or anyone else on this forum....)

So I am happy that this problem is solved. Now only the next one to solve, this one looks to be even harder as I've seen several postings with the same question but not one resolution to it.
Sometimes only, and over a period of over a year, with a fully warmed up engine and AT, a slight shudder of the front end and bad, very bad vibration when stepping off the pedal, or accelerating at/from around 60 mph.
This has become worse over the months, the strange thing is that it is not always the case. Now it is so bad there's always judder and shimmering.
Checked and replaced one CV. Next to do on the list is to change the front diff fluid.

93forestpearl · Post by **93forestpearl** » Sun Oct 04, 2009 7:45 pm

When the duty C solenoid goes bad, it doesn't usually just stop working out right. They often get a bit funky in their operation, and symptoms like this are a possibility.

Lunatech · Post by **Lunatech** » Sun Oct 04, 2009 10:21 pm

Is the duty solinoid the only thing that takes beating from doing this? Running in FWD mode that is.

Lunatech · Post by **Lunatech** » Fri Oct 09, 2009 3:04 pm

Is the duty solinoid the only thing that takes beating from doing this? Running in FWD mode that is.

ericem · Post by **ericem** » Fri Oct 09, 2009 3:45 pm

Yup pretty much the clutches SHOULD be fine technically always pressurizing them with trasmission fluid.

tturnpaw · Post by **tturnpaw** » Fri Oct 09, 2009 8:30 pm

Mine had a similar issue, jerky shifts, and sometimes the reverse wouldnt engauge much. It acted as if it was slipping. The fwd fuse was in because of torque bind.

tahiti350 · Post by **tahiti350** » Sun Oct 18, 2009 5:21 am

Not sure whether to post this in drivetrain or engine, but figured here since it's the center diff (clutch pack/dutyC) that is really actiing up.

Car just came out of summer storage (winter beater), and was running fine, but doesn't seem to be transfering power to the rear wheels, lot's of Front wheel spin on take off even with moderate throttle. Then today I fueled up at the local AM/PM (BP) and within a couple of miles it seemed to bve running weak, not missiing or stumbling, just not making normal power unless I get the RPM's over 4k.

It was raining pretty hard today, and there were a few times I had to kick it down to 3rd to maintain 60-65 on hills and when it shifted down it would spin the front tires (RPM's jump to 4k and making power).

I did some searching and found that teh duty C solenoid may be an issue, and that others had found the TPS to be part of the problem.

Where do I start?

ericem · Post by **ericem** » Sun Oct 18, 2009 5:44 am

Maybe time for a tranny oil change. Hopefully it is one of those problems that will fix themselves with some more driving. When you take off foot to the floor with the power light kicked on do you still have wheel spin? If not doubt its a TPS issue.

tahiti350 · Post by **tahiti350** » Sun Oct 18, 2009 5:50 am

ericem wrote:Maybe time for a tranny oil change. Hopefully it is one of those problems that will fix themselves with some more driving. When you take off foot to the floor with the power light kicked on do you still have wheel spin? If not doubt its a TPS issue.

I'll have to try that, but I think it just spins the fronts. I know if I stomp it while rolling and get the power light it spins and torque steers backand forth as power transfers from one side to the other...

Fluid is red, not burnt, and is just shy of the full line when hot and on level ground. I never have done a fluid and filter job on it, and I've beat the snot out of it for about 30K now. Currently at 204K miles.

ericem · Post by **ericem** » Sun Oct 18, 2009 3:25 pm

What is the longest you have tried driving it steady?

tahiti350 · Post by **tahiti350** » Sun Oct 18, 2009 4:13 pm

damn it, just realized I tagged onto onther thread, gonna split this off and start my own....

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