Nube transmission question: 1987 Turbo Diesel (w124)

[littlerobot]

I recently purchased a 1987 300td with only 109,000 miles on it. It initially changed from 2nd gear to 3rd way to quickly. I wanted to check the fluid level and noticed the dipstick was broken at the top. It would no longer "clamp" down by flipping that little plastic thing on the pipe. I put more transmission fluid in, which changed the cars behavior dramatically. It now shifts much more roughly. Too roughly. I'm wondering if:

a. the cap on the dipstick has to be locked on to get normal shifting, because the system is hydraulic.

b. the shifting is a vacuum problem.

c. the problem is unrelated to either of these.

Where is the best place to start? Is part a. true, meaning that the dipstick cap must be airtight? My gut says yes, but my brain hasn't a clue.

[Jeremy5848]

The dipstick isn't related to the premature shifting problem. You need to tighten the Bowden cable that runs from the throttle linkage to the transmission. The tighter the cable, the longer it will hold the transmission in each gear before shifting to the next. The vacuum control valve also needs to be correctly adjusted but that affects primarily the firmness (or not) of the clutch action.

[compress ignite]

1.Drive for approximately 20 minutes.
2.Park on UBER level spot. (I use a 4 Ft. carpenter's level)
3.Idle for 5 minutes total.
4.Run the gear selector through all the gears.
5.Check the Transmission Fluid Level on the Dipstick (with the engine running in, Park).

You Do Not Want to Operate a Mercedes transmission in an OverFilled State!

[littlerobot]

Originally Posted by compress ignite

1.Drive for approximately 20 minutes.
2.Park on UBER level spot. (I use a 4 Ft. carpenter's level)
3.Idle for 5 minutes total.
4.Run the gear selector through all the gears.
5.Check the Transmission Fluid Level on the Dipstick (with the engine running in, Park).

You Do Not Want to Operate a Mercedes transmission in an OverFilled State!

What are the dangers of running the transmission in an overfilled state?

[littlerobot]

Is the Bowden cable to be adjusted from above the engine, or below? I'm unfamiliar with this model. And- which vacuum valve has to be adjusted? Is it the larger green vac pod?

[babymog]

Originally Posted by littlerobot

What are the dangers of running the transmission in an overfilled state?

... and which states are considered overfilled? New Jersey? Florida?

I would go in this order:

1)If the fluid mileage is un-known, change the fluid and filter, do NOT go to a place that "flushes" transmissions. If fluid and filter are fresh, check fluid level and correct as necessary.

2) Look for and correct any vacuum leaks. This will (as stated above) be necessary for proper firmness of shifts, even a minor vacuum leak will cause harsh shifts.

3) Search for "bowden cable" and adjust. This will affect how early it shifts, also adjust the throttle cable as necessary (before bowden cable adjustment). Too loose is early shifts.

4) Search "ALDA" and "alda adjustment" as well as "switchover valve" and "overboost protection valve". Either of these not functioning correctly will reduce your power, which causes the pedal to be down further for enough power, the pedal position will cause firmer shifts as the transmission is expecting to be shifting under more power.