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

[Dick Spellman]

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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