[W126 Coupe] Re: Transmission Shift Question

[Richard Hesek]

Hi Richard:

I've got 6 meters of MB vac line due here tomorrow with some other gear
to shim the new hood latches.  I can set up my other vac guage easily.
Not sure what I'd be looking for other than high vacuum when this
problem occurs.  But, I should be able to see the vacuum decrease as I
adjust the modulator on subsequent drives.  Not a bad idea.

Dick

Richard Hogarth wrote:

>Have you tried "T"ing off that hose and putting a vacuume guage on that
hose
>during normal driving?
>That may give you some interesting results.
>-RPH
=======================

Dick,
 The modulator will not change the vacuum level. The modulator is a spring
loaded plunger that exerts a force on the
shift spool valve in the tranny valve body. The available vacuum unloads
the spring based on the variable orifice (T adjuster) position.
  The above experiment will tell you if you are losing vacuum when you
should have vacuum. If that were happening, you would be experiencing a
poor engine running condition. A vacuum leak.
 What you need to be aware of is the modulator pressure or fluid pressure
on that spool valve. That WILL change as the modulator is adjusted.
The factory spec for the SD transmissions is @45 PSI. I don't remember off
the top of my head. And the gas engine is most likely different.
Too high a pressure and seals could be blown out.
  The 2 to 3 shift quality is modulator dependant. A 1 or 2  notch
adjustment should be noticable. More than that and you should measure the
fluid pressure at the modulator fluid port.

Rick Hesek