I am trying to figure out at what vacuum level will 123 & 123 trani shift up and down smoothly.
If your car is shifting up and down without banging. What is your vacuum gauge -pressure.
Thanks a bunch

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1984 300SD turbo 126
"My true love"

God made me an atheist and who am I to question His wisdom

From an article on Mitchell:

HARSH ENGAGEMENT WHEN SHIFTING GEARS
Incorrect working pressure. Check and adjust modulating
pressure. Check vacuum line and connections for leaks. On vehicles
equipped with diesel engines, check vacuum control valve. Coolant
entering transmission oil cooler and contaminating transmission fluid.
Replace radiator. If necessary, replace all friction linings and/or
replace transmission.

HARSH ENGAGEMENT WHEN SELECTING "D" OR "R"
Idle speed too high. Check pressure receiving (pick-up)
piston in valve body for ease of operation and correct installation.
Replace valve body (if necessary).
NOTE: Pressure pick-up requires a running period of approximately
2 seconds. Harsh engagement may occur during repeated shifts
between "N" and "D". If harshness takes place within 2
seconds, condition is considered normal.

HARSHNESS ON 4-3 DOWNSHIFT
Sealing ring on release end of band B-2 worn or damaged. Band
B-2 piston worn or damaged. Band B-2 thrust body damaged.

Also: Mercedes-Benz Transmission, Steve Brotherton, ImportCar, February 2002

and see attached. P2 has modulator pressures. Trans number is on passenger side right above pan gasket.

Some sites say idle pressure is close approximation of driving pressure. I haven't compared (yet).

Attached Files

TransTec-722.3-722.4.pdf (436.0 KB, 82 views)

__________________
85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

Transmission Vacuum and adjustments
Mercedes-Benz Transmission, Steve Brotherton, ImportCar, February 2002

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84 300D, 82 Volvo 244Gl Diesel

A quarter with a 1/8" hole works as an approximation of 10mm spacer for VCV adjustment.

__________________
85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

It is not useful to compare vacuum levels from different vehicles. The reason is the fact that no two transmissions have the same level of wear internally and no two transmissions have the same modulator pressure.

You must take your own measurements of vacuum to the modulator and adjust that vacuum to your specific transmission. Raising vacuum will result in softer shifts with a possible flare developing on 2-3 if the trans is worn. Lowering vacuum eliminates the soft shifts and usually eliminates the flare, but not always. Sometimes, once the vacuum gets unrealistically low (below 5" at idle), the modulator pressure needs to increase slightly. Several members were quite successful in salvaging a really annoying flare by simply turning the modulator one or one and one half turns clockwise.

I currently operate the SD from a maximum of 8" to a minimum of zero. It's far below specs, but the unit works perfectly.