Author Topic: My DD-3 brake chamber experience.......(1964 PD4106 GM Bus)....  (Read 12973 times)


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Re: My DD-3 brake chamber experience.......(1964 PD4106 GM Bus)....
« Reply #30 on: December 29, 2010, 04:47:20 PM »
Jim, if you look at this link....

the two diaphragms at the bottom are the ones needed for the rebuild. Looks like I could've saved a few bucks over Luke's price. By the way, thanks for the link....

luvrbus, I sure would like to put the spring cans on there, but in addition to the plumbing issue, I'd of had to cut my current brake chamber mounts and fab up some new ones. Wouldn't have been a difficult job, but I have to take into consideration what would happen if, God forbid, I get in a wreck and someone gets injured or killed by my vehicle. When the lawyers got finished running me through the ringer, I wouldn't know up from down....

EDIT: After rereading this post, I realized that Barn Owl suggested a few posts back that I change to spring brakes. Barn Owl, I surely don't want you to read this and think that I disapprove of your tactic. I just felt it easier and simpler (although more expensive) to go with the rebuild option on my current brake configuration.....again, no disrespect meant at all.....I certainly appreciate your input
« Last Edit: December 29, 2010, 06:21:15 PM by bwze »

Offline rv_safetyman

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Re: My DD-3 brake chamber experience.......(1964 PD4106 GM Bus)....
« Reply #31 on: December 29, 2010, 05:11:03 PM »
Billy, thanks for the link to the two diaphragms.  The service one is a very deep (tall) unit.  We used to make brake diaphragms at Gates (I used to run the test lab that fatigue tested them).  I can appreciate that it would be a difficult piece to make.  That coupled with a low volume would drive the price up.

I probably got confused in the details along the way, but I though your DD3s were a modification on your bus.  It looked to me like one of the brackets was a bit home brewed.  Probably my imagination.

If the DD3s were a modification, then all bets are off when it come to liability.

Jim Shepherd
Evergreen, CO
’85 Eagle 10/Series 60/Eaton AutoShift 10 speed transmission
Somewhere between a tin tent and a finished product
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Re: My DD-3 brake chamber experience.......(1964 PD4106 GM Bus)....
« Reply #32 on: December 29, 2010, 05:24:32 PM »
Jim, I can't say for any certainty that the DD-3's were original equipment because, like you, I thought the mounting plates looked pretty flaky too. That being said, I do know that at some time later in the service life of the 4106, DD-3's were standard equipment (I think RJ may have stated around '63). There was an addendum to the original manual that included a section dedicated to the DD-3's (I need to buy one of these by the way) along with some other later additions. I have to admit, that link you found with those diaphragms has really got me thinking though. I may end up going ahead and biting the bullet and getting those babies.

Offline luvrbus

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Re: My DD-3 brake chamber experience.......(1964 PD4106 GM Bus)....
« Reply #33 on: December 29, 2010, 05:30:31 PM »
GM  buses had ICC brakes till 1966 or 1967 if my memory serves me and it doesn't sometime RJ or Teke would know for sure

good luck
« Last Edit: December 29, 2010, 05:47:12 PM by luvrbus »
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Re: My DD-3 brake chamber experience.......(1964 PD4106 GM Bus)....
« Reply #34 on: December 29, 2010, 05:45:24 PM »
Here's the quote from RJ's reply in my original brake post....where he states that the 4106 came with the DD-3's as an option around mid 1963. So I still don't know it mine were original or not ?????? .........from the look of those mounting brackets though, one has to wonder. Guess I'll never know.

Billy -


Before you try what Robert suggested, take a look at your rear brake cans.  There are two different types of parking brakes used on buses, DD3 and Spring.  Spring brakes were not an option on 4106s, but DD3s became optional long about mid-year of 1963 production.  A previous owner may have installed either type, so you need to determine what you've got, because the release procedure is different between the two types!

How can you tell what you've got?

Simple - look at the rear brake cans.  How many air lines do you have coming off the cans - 2 or 3?

If two, you have spring brakes.

If three, you have DD3s.

Release Procedure - Spring Brakes

1.  Build coach air pressure up to governor cut-out (approx 120 psi).

2.  Lightly cover service brake with foot - do not apply, just cover.

3.  Push in on parking brake knob until it seats.  Wait 3 -5 seconds.

4.  Put coach in gear and away you should go.

Coach should roll after #3.  If not, then pull knob back out to reset brakes and repeat steps 1 - 3.  If coach still doesn't roll when put in gear, something is wrong and needs to be looked at.  Make sure coach wheels are properly chocked, preferably front and rear, before doing any investigative work.

Release Procedure - DD3 Brakes

1.  Build coach air pressure to governor cut-out (approx. 120 psi).

2.  Lightly cover brake pedal - do not apply, simply cover.

3.  Push in parking brake knob to release parking brakes.

4.  AFTER pushing in knob, apply a FULL service brake application (FLOOR IT) and hold for 3 - 5 seconds.

5.  Release service brakes, coach should roll when put into gear.

6.  If coach doesn't roll, lightly cover service brake again (do NOT apply - just a light touch).

7.  Pull knob to reset parking brake.

8.  Repeat steps 1 - 5.

As stated above with spring brakes, if the coach doesn't roll after steps 1 - 5 are repeated, there may be a problem that needs investigation.

Setting Spring Brakes for Parking

1.  Once parked, lightly cover service brake sufficiently enough to just keep coach from rolling.

2.  Pull parking brake knob to set brakes.

3.  Release service brake - coach should not move.

4.  If coach will move with parking brake set, have brakes looked at immediately!

Setting DD3 Brakes for Parking

Procedure is basically the same as for Spring Brakes, but the critical point here is that you LIGHTLY hold the coach with the service brakes before pulling the knob to set the parking brake.  You should ONLY apply enough service brake to keep the coach from rolling, no more.  The harder you have the service brakes applied, the more difficult it will be to release the DD3s. 

FWIW & HTH. . .


Offline Dreamscape

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Re: My DD-3 brake chamber experience.......(1964 PD4106 GM Bus)....
« Reply #35 on: December 29, 2010, 06:48:18 PM »
I had DD3's on our 1968 Eagle 01 and decided after many phone calls to various vendors and of course my buddy Clifford, I changed out to 30/30 Spring brakes on the rear axle. I had one DD3 leaking real bad and to fix it cost more than two new Spring cans. It's not that hard to do, but then again it was on an Eagle. In your case I'm not sure. The Spring brake can has the same bolt pattern as the DD3 and they bolted right up.

The availability of DD3's is going south, so the price goes up! Spring brake cans are available at almost anyplace they sell truck parts.

Yes, you do have remove the inversion valve, add a QRC1 and plug one line, but not hard at all. After all I did it!  ;D

Becky and Paul Lawry, On The Road
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Our coach was originally owned by the Dixie Echoes.