decoupler troubleshooting

[kguarnotta]

A little background - I've got a triple knob '86 syncro with a subaru 2.2 in it. I had to replace the transmission over the winter. I also have the decoupler with solid shaft.

After the transmission was installed - the middle knob seemed backwards (ie pull knob, light goes off, push knob light comes on). initially I thought it was wired backwards, and tried reversing wires. This didn't help. I brought it back to mechanic who replaced transmission - and he said that he probably reversed the vacuum lines. He would fix it when he was doing some other things. He did it, but he told me there was still something not right, as it seemed to take a really long time for the actuators to engage. I said - yeah that does not sound right, they used to be instantaneous.

Now I can't get any lights to come on - going through the troubleshooting from here - http://www.syncro.org/DiffLock.html

I get a hissing noise when I disconnect line right after check valve, and can feel vacuum with my finger.

The connection at the reservoir does not seem great. It looks like a rubber grommet on a metal tube that goes into reservoir. This slides right out - so I'm thinking that I don't have a good enough seal at this grommet, and therefore the reservoir is not holding a constant vacuum...I could just silicone this in place, but it appears to have originally been a grommet - so maybe I should not do that. Is this a special grommet - or should I be able to find at any FLAPS or hardware store?

When i go up to the dash knobs - to try to troubleshoot vacuum leaks there - everything looks in good shape - no obvious cracks, or loose connections. Also a million connections - quite intimidating -as I imagine getting those connection crossed would be a nightmare to get straight.

Any further tips or suggestions?

_________________
-Kevin
Lincoln, MA

'86 Triple Knob Syncro w/EJ22
'78 Westy
'69 Single Cab
'65 Kombi - EZ-Camper

[michaelasnider]

Mine recently started taking longer and longer to actuate until it eventually would not actuate and was stuck in 4WD. The flexible lines connected to the vacuum actuator had started splitting. Just cut the splitting section out and reconnected and back to quick actuation (shouldn't really expect instantaneous, depends how things are lined up in the transmission).

[kguarnotta]

I'll check where you are suggesting - If I were to just replace that hose - (ie the little flexible connector) what size hose should I be looking for?

I've got some windshield washer fluid hose - looks to be the same size.

As far as instantaneous, I may have been overstating - I meant it was within a couple seconds of pulling the knob.

I understand that opening the system may cause it to take a while to re-pressurize (or re-vacuumize?) how long should that take - ie a couple minutes or more than that?
_________________
-Kevin
Lincoln, MA

'86 Triple Knob Syncro w/EJ22
'78 Westy
'69 Single Cab
'65 Kombi - EZ-Camper

[michaelasnider]

I'm not sure on the size, I just cut about 1cm off where it was splitting, and reconnected. If the engine is running it should basically have vacuum again immediately (someone can feel free to correct me there though).

As far as the grommet on the reservoir, I just cleaned mine up and jammed it back in there, seems to be fine as all knobs are functioning as expected (light for the front as well as the display illumination is a different story though).

[Howesight]

On my three-knob system, the diff locks started taking longer to engage and disengage. Turned out, one of my vacuum valves (the business end attached to each of the three knobs), was leaking internally. It did not hiss and I had to diagnose it with my vacuum pump and gauge, after first spending hours testing the actuators, checking for line leaks, etc. I replaced the dead vacuum valve after destroying it trying to get it apart. The other valves also leaked, but had very slow leaks. After servicing (see below), no valves leaked at all.

These vacuum valves do wear and can die. They cannot be disassembled for repair or service. I recommend injecting the oil of your choice (I chose ATF to swell the O-ring seals) into the valves when you are "in there", servicing or diagnosing your system. Use a syringe to inject oil in each of the three nibs, work the valve back and forth a few times, and you should be good. The oil will work its way through the vacuum system and not cause problems.
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'86 Syncro Westy SVX

[candyman]

Make sure your decoupler housing has the proper diff lock indicator switch installed and not the reverse light switch. More and more units are being shipped out using reverse light switches. This is a problem as those require much more vacuum to allow your decoupler shaft to engage. I had one on mine and it would not engage at all. I finally took out the switch and saw by the part number that it was a reverse light switch. I measured the pounds force to activate it and its like over 6 pounds of pressure. The diff lock switch works with under 3#s if i recall. One way to check is back out your indicator switch on the decoupler housing then pull knob and see if it will engage (you will have to drive a little). You will have to know if its engaging by feel since the light will not come on. Backing out the switch will allow the shaft to move freely to engage when prompted. Or you can just pull a vacuum hose and manually apply vacuum and watch the decoupler shaft move

[syncrodoka]

You could probably silicone it in place but here is a new one.
https://www.brickwerks.co.uk/seal-t3-syncro-vacuum-reservoir.html

[bajabones]

Gowesty sells the reverse switch as a locker switch
_________________
1990 Syncro Doka
2.1 DJ
Triple Knob
Solid shaft

[pemz0r]

You can easily check your decoupler shaft to see if it's moving by removing the switch and sucking/blowing air into the vaccum servo and watch to see if the shaft moves. Just a process of elimination.

[kguarnotta]

Thanks for all tips so far...I just wanted to update when I could - with 2 kids, it is hard to find time to work on this.

I checked all connections to decoupler actuators. The short piece of rubber vacuum line that connects the hard plastic line to the decouplers looked to be in good shape, but I replaced the ones on the decoupler for the main shaft and for the ones at the front differential.

Test driving - still no light, but I got a little adventurous and tried the front knob - and it was working (ie I could feel it engaging) but the light was not coming on. Back into driveway - check electrical connections - spray cleaner on main shaft decoupler switch - plug it back in, find the front one - it was knocked off completely! I rehooked that up.

Drive around a bit - and middle light works intermittently, front and rear light not at all. I think I need to clean connections again, and try again. If I had to replace this connector due to bad or worn out wiring - what is it called? Is there a standard IE the female connector for the switch.
_________________
-Kevin
Lincoln, MA

'86 Triple Knob Syncro w/EJ22
'78 Westy
'69 Single Cab
'65 Kombi - EZ-Camper

[kguarnotta]

update on this...(as you can probably tell, I'm slow on these things)

This is sort of hard to diagnose without a lift. I finally had some time - and my mechanic had some "lift" time.

This is where we ended up - mechanic thought the diaphragm in the differential lock actuator was torn and not holding a vacuum - I'm not 100% sold on this diagnosis. We were able to put another one on there.

The other thing we found - the decoupler switch for the rear differential was leaking - this I could actually hear - when we tore it apart, and put my ear to it. So for now - I've plugged the port for this switch. I'm going to get a replacement - although it looks as though original switches are NLA - anyone have experience with the GoWesty replacements?

As I'm writing this, I think i may switch the front and rear switch - and change over the tubing, as I think the likelihood of me needing the rear differential is much higher than ever needing the front.

Also - anyone ever rebuild one of these switches? I thought I'd read somewhere about rebuilding these - I now see what I read is that you cannot do so, but to try to put some oil on the shaft....
_________________
-Kevin
Lincoln, MA

'86 Triple Knob Syncro w/EJ22
'78 Westy
'69 Single Cab
'65 Kombi - EZ-Camper

[Sodo]

Link


If you have a hand vacuum pump you can test this stuff.
And test your decoupler and locker indicator switches, bulbs, wiring.

Looking at the actuator, the nipple pulls the plunger towards itself.
Imagine a diaphragm inside that actuator, with one nipple on either side of the diaphragm.
Vaccum on either nipple pulls the plunger towards it.

On the decoupler, vacuum applied to the forward nipple
slides the coupler sleeve off the pinion shaft and "decouples" the driveshaft.
Vacuum on the rear nipple slides the coupler rearward, bridging the gap between the cardon shaft and the pinion shaft, "coupling" the two shafts (makes 4WD).

The coupler switch indicates the position of the shaft coupler.
When the coupler is rearward, connecting the two shafts, the switch "closes" and the green light turns on.