[W126 Coupe] 7" of play in park

[Elm Zobens]

That is one of the main reasons why we (I) don't use them in the Midwest as well (other than it's totally FLAT here). The road salt from the winters have frozen many a cable and cooked many brake shoes/pads in my years but I have yet to experience a parking pawl failure.


--- On Tue, 9/15/09, Dean Slone <daslone at saber.net> wrote:


From: Dean Slone <daslone at saber.net>
Subject: Re: [W126 Coupe] 7" of play in park
To: "Mercedes Coupes Mailing Lists" <mbcoupes at mbcoupes.com>
Date: Tuesday, September 15, 2009, 10:28 AM





Any chance that the pawl might be sticking and not engaging into the first available notch?  
 
As far as using the emergency brake, I was raised in New England and we never used the emergency brake during the winter (and consequently NEVER bothered to use it at all).  New England winters and salted roads are harsh on the equipment.  With emergency brake use when parked over night the brake pads would be either frozen to the drums the next morning.  The emergency brake cable could also be rusted tight refusing to release the brakes.  Maybe this doesn't happen with disc brakes but I have not been retrained.  I park with my tires pointed toward the curb in the down hill direction, in Park without the parking brake on.  Never got out of my early training.  BTW when putting the car in Park the foot brake is released slowly.  The vehicle will roll and you want the pawl to engage smoothly, easily and completely.  
 
Dean 
Eureka, CA

----- Original Message ----- 
From: FPecar4525 at aol.com 
To: dan at landiss.com ; mbcoupes at mbcoupes.com 
Sent: Tuesday, September 15, 2009 7:52
Subject: Re: [W126 Coupe] 7" of play in park



In a message dated 9/15/2009 6:20:00 A.M. Pacific Daylight Time, dan at landiss.com writes:
So let's see if some arithmetic works.

8 teeth = 0.125 turns maximum of the drive shaft before engagement

2.47 axle ratio so 0.125/2.47 = 0.0506 turns of the rear tires

0.0506 turns times 80 inch tire circumference = 4 inches of travel maximum (2" average) before a tooth falls into place

That's to GAIN locked position. Anything after that has to be drive line free play?

And herein lies the problem.  When this happened on all the MBZs I have owned from the day they left the dealership new, I never got out and measured the distance the car rolled nor did I keep a log to determine if it occurred each and every time I parked the car in my garage.  It could have been only 4" but since most cars I owned up to that point did not do that, I noticed the event and it "felt" significant and unusual.  
 
What I am saying is that this discussion has evolved to where numbers are being thrown around between 4" and 12" and solutions being provided that are making assumptions about a disaster scenario.  It would appear that proper troubleshooting procedure would have the actual travel distance measured and disregard as a problem if it is 4" or less.
 
My thanks to Dan for doing the math on this issue.
 
Frank Pecarich
Ventura



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