[W126 Coupe] Transmission "Clunk" - But only when selecting Reverse Gear

[Dick Spellman]

Hi Carl,

No can't explain.  This is just the first thing to look at, there is 
more but, it's the easiest to check.  Could be some suspension problem 
in the rear as well or even the brakes slipping in the calipers. But, 
Mike describes a pronounced clunk and in my few hobby hours working on 
MB's the drive shaft flex disks have more often than not been the problem.

Regards,

Dick

Carl Hansen wrote:

> Perhaps you could explain why it only makes a "clunk" in reverse and 

> not in forward?

>

> I do not believe the drive shaft discriminates between forward and 

> reverse.

>

> Carl H.

>

>

> ----- Original Message ----- From: "Dick Spellman" <spell.yy at verizon.net>

> To: "Mercedes Coupes Mailing Lists" <mbcoupes at mbcoupes.com>

> Sent: Wednesday, January 02, 2008 2:53 PM

> Subject: Re: [W126 Coupe] Transmission "Clunk" - But only when 

> selecting Reverse Gear

>

>

> Hi Mike,

>

> See if you can get the SEC up on a lift. Grab a hold of the driveshaft

> while it's in Park. Roll the driveshaft from side to side while

> observing the front and then the rear flex disks. If you see cracks in

> the flex disks or their bolt holes, this is the likely 'clunking'

> problem you describe.

>

> If the flex disks need service, I would go ahead and replace the center

> support bearing and rear pinion seal while the drive shaft is down for

> this service. Any exhaust work should be done at this time as well.

>

> Regards,

>

> Dick

>

> Mike Taylor wrote:

>>

>> On my 1988 560SEC the auto transmission (original) works great in 

>> forward gears, with very smooth change-ups. I’ve had the trans fluid 

>> changed at recommended intervals. But on selecting reverse gear there 

>> is a big clunk and the car initially jolts backwards, sometimes quite 

>> violently, with or without the brake pedal pressed.

>>

>> I’ve searched the archives and can’t see anything specific to reverse 

>> gear. Does anyone know if there is an adjustment or anything to 

>> remedy this ?

>>

>> I’d not want to do anything that may affect the forward gears as they 

>> are currently very smooth, but appreciate any help if anyone else has 

>> had this.

>>

>> Cheers,

>>

>> Mike

>>

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