My '87 4000Q is nearly ready for the road, thanks to suggestions/advice/etc gleaned from this message board.

Question of the day. Can I move the diff-lock control while the car is moving ??? Assuming I'm on a snowy road (coming soon) and I want to lock the center diff, do I have to stop the car ?

Oh, does something light up to show the diff is locked ?

I don't have an owners manual and Bently doesn't discuss user operation of the diff lock.

Thanks,
Dave

I have an 87 and I can turn my diff on and off when ever I want to. I have two lights tha light up to let me know that the diff if locked.

and you can turn them on and off as you please and at just about any speed. the rear diff lock is only good for low speed stuff like crawling up walls and driving at the bottom of the ocean where the sand is soft and its easy to get stuck. at high speed i really dont trust it. the center you can use all the time in the snow, even in heavy rains if you dont feel comfortable. it makes highway driving at 80 or 90 mph through 6" of fresh snow in a blizzard much more comfortable. the car will feel a little stiffer on turns when its dry if you have it on and itll wear your tires and reduce gas mileage. thats what ive gathered anyway, if something in there is wrong someone please correct me.

Nothing wrong with that post! You hit the nail on the head. Sometimes the diffs take a second or two to lock or unlock after turning them on or off. Rocking the car back and forth with help them along some.

I was just waiting to finish cleaning my 86 4000cs, before I start autocrossing it. I might debut it in the San Diego autocross on Oct 20.


RObert
86 4000cs
98.5 A4 2.8qs TIP

A couple of things. Sure, you can lock/unlock while driving, but be SURE your tires are all the same diameter. Don't put different size tires on, and make sure they all wear the same otherwise driving in the snow will be dangerous as one axle will rotate at a *slightly* different speed and slip a bit (found this out the hard way last winter). Second, don't unlock while turning as this will put undue stress on the gearsets. I wouldn't recommend locking the center in the rain either, but to each their own.

I've been following this thread and just can't keep silent anymore. You can lock the center diff at pretty much any speed yes, but you drive 80-90 mph in 6'' of snow, you better not be on any highway, interstate ot whatever you want to call it. The center diff is an added stability feature at normal driving speeds. If you are driving 80-90 mph in 6'' of snow, you are well above that. Anyone here ever try to stop at 90mph in the snow? Avoid an accident? Hitting a non moving object or slow moving object in inclimate weather at 90mph is no fun. You can see my recent post at audifans if you think my remarks are unfounded.