Clunk in Diff or Tranny?

1992 SVX LSL, on hard acceleration when the front wheels loose traction, there is a hard clunk coming from the tranny or diff. When I jack up the front end and spin the wheels slowly, there is no torq going to rear. If I speed up, then I get the loud clunk again and the rear wheels engage. Is this normal or is the transfer clutch in the tranny going out? Is there a fix without pulling the whole tranny out? Maybe its time for a 5 speed conversion??? Help.

Still no reply to this post.

Is it possible that this "clunk" I hear is the same as the rear end binding? If so is it possible that adding the LSD friction stuff will help?????

[lee]

I'm far, far from a tranny expert, but it seems likley to be the AWD transfer clutch pack. As I understand it, this repair can be done without removal of the whole transmission, but I'd search the forum a bit before taking my word for it.

[Earthworm]

Yeah I would say either the AWD transfer clutches or else the solenoid that controls them.

Me again,

I have only had this SVX a few months. Tranny was rebuilt or replaced just before I got it. How to I tell if the tranny is an SVX tranny or a Legacy Tranny and thus a "mismatch" causing the problem? I hope that isn't the problem. I will check the transfer case pressure first to determine solenoid vs. clutch pack. Can the transfer clutches be replaced without removing the whole transmission unit??

On a side note, I just replaced timing belt and front crank/cam seals, also rear wheel bearings. So far, this car is fun to work on and even more fun to drive.

Thanks for the input.

[lee]

again, not a tranny expert, but I don't think the type of tranny, SVX vice Legacy, would be the issue. I'm guessing the rebuilder never touched the transfer case part, instead just dealing with the transmission proper.

[Aredubjay]

If you have a Legacy tranny instead of an SVX tranny, with mismatched rear end, you'll know it when you pull out, quickly, from a stop, into a hard left turn. The shuddering is unmistakable. You'll have to remove the unit to replace the clutch pak, but, solenoid C can be accessed (I believe) without removal of the unit. I've got diagrams of the solenoids on my home computer, I can post them tonight, possibly, after I get home.

[want-a-fast-svx]

When i asked the mechanic a long time ago about the transfer clutches he said they just leave the tranny in and get at it on the lift from the back. They dont look all that bad if i remember from what i saw in the book but i would still imagine them not to be easy either. With a little hard work im sure they could be changed easily...Also you can check on the side for pressure to see if its the solenoid or not, which i believe the tranny does have to come out for....Someone who knows for sure will be able to help you, or when i go outside and work on the jeep ill take a look at the manual and let you know....

[Aredubjay]

Originally posted by want-a-fast-svx
When i asked the mechanic a long time ago about the transfer clutches he said they just leave the tranny in and get at it on the lift from the back.

Hmmm. Apparently, I've been misinformed.

[oab_au]

Originally posted by larry
1992 SVX LSL, on hard acceleration when the front wheels loose traction, there is a hard clunk coming from the tranny or diff. When I jack up the front end and spin the wheels slowly, there is no torq going to rear. If I speed up, then I get the loud clunk again and the rear wheels engage. Is this normal or is the transfer clutch in the tranny going out? Is there a fix without pulling the whole tranny out? Maybe its time for a 5 speed conversion??? Help.

Hi Larry, it looks like the C solenoid has failed. Yes the transfer case can be pulled off on a lift. Replace the solenoid and the clutch plates, not too costly.

I checked out the C solenoid out of Amuse's car when it failed, and found that the return spring in the solenoid had broken and jammed the armature, which stuck it in the on position. This seems to be a common cause of transfer failure.

Word of warning, don't let the front wheels spin, as it may cause the front diff to break, due to the shock loading from one wheel to the other. This can't happen if the AWD is working.

Harvey.

Thanks for all the input. I did check the numbers on the transmission to verify that it is not a legacy trans. It has the same numbers as the VIN number of the car. Hence I assume it must be the original trans. (relief over that one)

I picked up a transmission pressure guage. Any information on where the port is to check for solenoid C operation pressure would be helpful. Also, what should the pressure be under what circumstances? I suppose that info is in the manual, which of course will take days to arrive like any other SVX part. Nobody stocks anything. You drive a what? Hee Hee!! Sob Sob. You know, the car IS fun to drive, I just wish it worked right.

I can get clutch disks/valves etc. through subaruparts.com. Any idea whether this is a good source or is it better to go to my local uniformed subaru dealer????

If anyone has done a transfer clutch and C solenoid replacement I would appreciate some feedback. I have done my share of transmission overhauls. The worst was a W4AT in the mitsubishi/eagle summit AWD. Now that was a bear.

One last question. What happens when you run the car on regular? Just curious. This premium gets to the wallet pretty quick.

If I opt not to repair this tranfer clutch/solenoid problem, will it hurt the car to run it in FWD (ie with the fuse in)??? At least until I decide what to do with it? I know, it sort of spoils the fun of having an awesome performace car with AWD and limited slip rear though. Sniff Sniff. Especially going up a hill on wet leaves. That stuff is worse than snow. It makes a mess of the wheel wells too.

[gl1674]

Judging by the pictures in FSM the Test port for transfer pressure
is on the extension case. It is on left (drivers) side, it is angled 45 degrees up. It is very close to the end of extension case, but it is not on a rear wall. It is way up, above the drive shaft.

If anybody could scan pages 98, 108 and 121 of the section 3-2 of FSM, this would be quite useful.

The tightening torque for the plug is 12-14nm.

The pressures are supposed to be 7-11 psi at idle, 104-114 psi at stall rpm in either D or R in AWD mode. Always 0 in FWD mode. This is with ATF temp between 140 and 176 F.

Subaruparts is OK. Good service, reliable. Getting pricey though (I picked up water pump for $50, now it is getting close to $80). Still much cheaper than my local dealer.

You are not supposed to run transmission in FWD - apparently there are some problems with that. There is a note in some factory manual somewhere. Apparently something is not lubricated properly (transfer clutch?) or passages tend to get blocked with debris - this is not known.

OK, I have it up on jackstands and am getting ready to check pressures with a transmission pressure guage. I will get back with the results. Wish me luck.

Ok, here is the initial report. After removing the small catalytic converter and heat shield (a pain in the neck) I was able to get to the pressure test port for transfer clutch/C solenoid. At Idle, pressure is Zero. In Drive/Reverse at stall RPM there is a brief jump in pressure to about 100 lbs that corresponds to the clunk in the drive line (ie transfer clutch engages briefly). However, after testing for a few minutes, the only pressure I can get from that port is a brief spike at initial RPM increase. The rear wheels will not stay engaged for any length of time. I am guessing that this is a stuck C solenoid and will proceed to remove rear of trans. Any idea how to identify C solenoid once I am in there?

Also, when doing this test, there was a code 32 that was generated. I suspect this is a result of incorrect vehicle speed between front/rear wheels due to vehicle being up on jack stand and not on the ground.

If anyone else needs to do this kind of pressure test on trans, it is not difficult. NAPA sells the guage and all adapters for around $58. Subaru wanted about $700 to do any work on rear of trans, and AM---- trans wouldn't even touch it.