CQ rear diff stuck on....

MS-L · 14-06-17, 02:15 PM

As above.
I've not driven the car for ages and took it for a little spin to today to check everything works ok before I put it up for sale.
Anyway the rear diff engaged as normal but wont disengage.
Any thoughts?
Something stuck maybe?

Thanks

Hanuman · 14-06-17, 03:19 PM

The locking mechanism is vacuum operated. It's possible that it can't move against a build up of crud around the shaft.

Is the operating rod intact? Due to the build up of crud, the shaft can be prone to rotting through.

(The two above are easily checked within a couple of minutes on ramps)

Sticky internals. I've not come across a rear diff doing it, but several centre diffs had played up unlocking, until the transmission is unloaded. Usually going in reverse a few feet.

MS-L · 14-06-17, 03:32 PM

Thanks. I'll have a crawl about underneath later and see if the rod is stuck.
It engaged ok but won't free off.

MS-L · 15-06-17, 09:12 AM

Right then.
The lever moves back and forth but is rather stiff. I'm assuming that with the switch set to off the vacuum fades away and the lever moves back to off under it's own steam as it were, or should the vacuum pull it back?
There is loads of pressure to push it into the on position but nothing pulling it back.

Any ideas?

msh · 15-06-17, 09:22 AM

Quote:

Originally Posted by MS-L

Right then.
The lever moves back and forth but is rather stiff. I'm assuming that with the switch set to off the vacuum fades away and the lever moves back to off under it's own steam as it were, or should the vacuum pull it back?
There is loads of pressure to push it into the on position but nothing pulling it back.

Any ideas?

Yes. After all, there is no spring pulling it back, both outside and internally, so it's up to actuator to do that. Check the switch and hoses, presuming we're talking about B2.

MS-L · 15-06-17, 09:26 AM

B2. Yes.
Thanks. So the actuator pushes and pulls? I think mine may have stopped pulling.
Plenty of push but no pull.

msh · 15-06-17, 03:45 PM

Actuator has two hoses connected because each is connected to one side of diaphragm or whatever is inside. Like I said, check if the diff lock switch puts vacuum to correct output when lock disengaged and if there isn't a leak in the hose between switch and actuator.

MS-L · 15-06-17, 03:59 PM

Thanks.
I'll check to see if all the pipes are still in one piece. It has only just started doing it after quite a long lay up.

14-06-17, 03:19 PM	#2
Hanuman Trickster Classic Audi Club Member Join Date: May 2009 Location: Heckling from the cheap seats, Phnom Penh, KoW Posts: 7,006	The locking mechanism is vacuum operated. It's possible that it can't move against a build up of crud around the shaft. Is the operating rod intact? Due to the build up of crud, the shaft can be prone to rotting through. (The two above are easily checked within a couple of minutes on ramps) Sticky internals. I've not come across a rear diff doing it, but several centre diffs had played up unlocking, until the transmission is unloaded. Usually going in reverse a few feet. __________________ I wish they would keep the damned Chinese away now that I can go home, so that I can enjoy Fish amok and a draught Angkor

14-06-17, 03:32 PM	#3
MS-L Grown up member Join Date: Jan 2016 Posts: 77	Thanks. I'll have a crawl about underneath later and see if the rod is stuck. It engaged ok but won't free off.

15-06-17, 09:12 AM	#4
MS-L Grown up member Join Date: Jan 2016 Posts: 77	Right then. The lever moves back and forth but is rather stiff. I'm assuming that with the switch set to off the vacuum fades away and the lever moves back to off under it's own steam as it were, or should the vacuum pull it back? There is loads of pressure to push it into the on position but nothing pulling it back. Any ideas?

15-06-17, 09:26 AM	#6
MS-L Grown up member Join Date: Jan 2016 Posts: 77	B2. Yes. Thanks. So the actuator pushes and pulls? I think mine may have stopped pulling. Plenty of push but no pull.

15-06-17, 03:45 PM	#7
msh 4 ring whore! Join Date: Jun 2008 Location: Rucava, Latvija Posts: 3,816	Actuator has two hoses connected because each is connected to one side of diaphragm or whatever is inside. Like I said, check if the diff lock switch puts vacuum to correct output when lock disengaged and if there isn't a leak in the hose between switch and actuator.

15-06-17, 03:59 PM	#8
MS-L Grown up member Join Date: Jan 2016 Posts: 77	Thanks. I'll check to see if all the pipes are still in one piece. It has only just started doing it after quite a long lay up.