4905 slack adjuster linkage

3408cat · September 20, 2009, 04:18:21 PM

On the right rear brake, the clevis for the slack adjuster has a lever-type part that seems to cam over and lock if you push it - it also has a spring steel clip. Can anyone tell me what its for

Should there be one on both sides

Thanks for any help with this question that can be offered, Bill.

roadrunnertex · September 20, 2009, 04:40:40 PM

These mechanical release yokes are installed on some coaches as special equipment and should be "released" only for their inteded purpose.

The purpose of this release mechanism is to allow the release of vehicle brakes in an emergency situation and there is insufficient air pressure to release the brakes.

Using a hammer strike the release lever of the yoke.This will bend the retainer tabs,perment the lever to turn approximately 90 degrees and alow movement of the slack adjuster 21/32".
See Section 4 page 32 of the P8M4905 GMC Coach maintenance manual X-7564 01/1975.

buswarrior · September 20, 2009, 04:43:16 PM

And if any of the parts appear to be decayed by the passage of time, best to think really hard to replace them with a traditional clevis.

If it somehow releases while under way, you'll increase your brake stroke by that same amount, rending that brake pretty much useless at stopping you.

happy coaching!
buswarrior

3408cat · September 20, 2009, 05:09:37 PM

Thanks for the info, where could I buy one for the other side ?

buswarrior · September 20, 2009, 05:19:10 PM

I haven't heard of anyone locating a source for those quick release clevis'.

Doesn't mean they aren't out there, but no one has shared it on the boards.

happy coaching!
buswarrior

roadrunnertex · September 20, 2009, 05:38:23 PM

Call Luke,
1-888-262-2434
Luke is a good parts source for our GMC Coaches.
jlv

3408cat · September 21, 2009, 03:00:16 PM

Thanks for the info, I would like to buy one for the other side - I don't think I could fit under our bus to key the cans off if she was dead and out of air, but with a set of quick release clevises, I could carry a long rod that I could reach under with to unlock them. What a great idea.

belfert · September 21, 2009, 04:21:58 PM

Quote from: 3408cat on September 21, 2009, 03:00:16 PM
Thanks for the info, I would like to buy one for the other side - I don't think I could fit under our bus to key the cans off if she was dead and out of air, but with a set of quick release clevises, I could carry a long rod that I could reach under with to unlock them. What a great idea.

It sounds like you need more than a rod to release these as they would seem to have locking tabs per Roadrunnertex. You sure wouldn't want them to release accidently as BW wrote.

3408cat · September 21, 2009, 05:10:19 PM

I think that the one that is on the bus now is complete and working correctly. It did not release very easily, but if you were to put reach under and put something against and push really hard it will open. I would most likely safety tie it closed with some soft copper wire that would break when pushed open.

roadrunnertex · September 21, 2009, 06:00:10 PM

To gain access to the release cam's.
On the back bulkhead of the 3rd baggage bin you will notice two smaller panels that you can remove on each side in front of the DD3 rod ends.
This will let you release the brakes with out getting under the coach.
jlv

buswarrior · September 21, 2009, 07:58:15 PM

If there is no air to release the parking brake....

Why do you want to start moving?

How are you going to stop?

Careful here, Darwin might show his ugly mug!!!

happy coaching!
buswarrior

3408cat · September 22, 2009, 02:08:48 PM

I think that being able to release the brakes might be very helpful if one were towing a dead vehicle