[W126 Coupe] 87 SEC hard shift

[Dick Spellman]

Hi Rick:

A couple of similar events to the one you described:
I've experienced a firm hard shift in all gears when the vacuum to 
modulator is lost or absent.  In my case the vac line was disconnected.  
This would be easy to check visually and with a vac guage in line while 
driving.  I imagine you could put a vacuum on the modulator to see if 
the diaphragm is holding the pressure too.

I am experiencing in another MB a firm hard shift from 2nd to 3rd and 
suspect it is the B2 piston.  In my case when slowing down but not fully 
stopping and then accelerating again I get a pause then the hard shift 
from 2nd to 3rd.  I do have the procedure for replacing the B2 piston 
and the nylon sleeve with the transmission mounted to the car chassis.  
It looks like very tight quarters to me so I have waited until I do the 
front engine mounts where I can tilt the engine up and lower the 
transmission valve body in the hopes the B2 is accessible from the side.

I 'd be very curious to learn what you discover on your SEC and maybe 
you can ask to see if the B2 is even a factor on your model year.

Good luck, Dick

Richard Hesek wrote:

>  Hi Coupers,
>  My '87 560 has developed a firm, even hard, shift from 2 to 3rd gear
>under normal acceleration. This happens only when warm and after driving at
>least 20 miles.
>My transmission fluid and filter have right around 7k miles on them.
> I suspect the modulator has failed and I will pull that out and test it.
>I just wondered if there were any other thoughts as to what might cause
>this.
>
>Thanks,
>Rick Hesek
>Northboro, MA
>
>The MB Coupes Website!
>W126 SEC Mailing List
>Postings remain property of MB Coupes, L.L.C.
>
>  
>