Author Topic: Question about Shifting Problems with my 300SD  (Read 431 times)

avantbenz

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Question about Shifting Problems with my 300SD
« on: 13 October 2018, 08:30 PM »
I'm trying to diagnose an issue I'm having during shifting.

It doesn't seem like a serious issue and I've found a workaround but I'd like to get everything running well *without* applying my workaround.

The issue: If I start the car, put it in 'D', and drive she shifts fine. When I stop at a stop light or stop sign and put my foot on the brake long enough to come to a complete stop and then press the accelerator pedal it seems like the transmission slips. It feels like she's starting in 2nd gear but not really - there is a total lack of power. My workaround is that whenever I come to a complete stop I move the shifter from 'D' to neutral and then back again into 'D' and then proceed to drive with no issues.

Any ideas? Is it a vacuum issue? Throttle lingage issue? I just want to know what I should tackle first because it seems like adjusting the transmission shift points is a big deal. Also, I checked my transmission fluid and it seems like it's at the proper level although it looks a little dirty. I'll probably end up changing it and the filter soon but I don't know if this would actually have anything to do with the issue I'm experiencing.
Daily Driving 'Patience' ~ 1980 300SD

Diesel 617

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Re: Question about Shifting Problems with my 300SD
« Reply #1 on: 13 October 2018, 10:25 PM »
Hopefully others will chime in

First make sure you have the proper fluid level, it is unconventional and your need a ruler and mm conversion. Avoid getting any fibers whatsoever in the trans fluid or on the dipstick. Use a piece of cardboard or leather to wipe the dipstick see this procedure to check: https://handbook.w116.org/Maintenance/MY72/120.pdf The 78-80 300sd 722.120 transmission is W4B-025

Does the kickdown switch work? https://www.youtube.com/watch?v=nzBBHwX41mY and https://www.peachparts.com/shopforum/diesel-discussion/367833-order-troubleshooting-kick-down-switch.html

Do the RPMs/engine rev high then shift into gear i.e flaring? If so adjust the vacuum going to the trans: http://www.peachparts.com/Wikka/Trans722VacMod see post 51 and read the next two the Technical Data Manaual should have the correct spec as the FSM does not.
X3 1980 300SD Blown Heads, trans -Retired
1980 450SEL Parted out
1980 450SEL to Diesel Parted Out
1979 280SE Euro Spec Cloth Seats: Needs Rebuilt head and WUR
1979 300CD Daily Driver


Inventory of w116 Parts
https://www.ebay.com/usr/vintagepartsandstuf

daantjie

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Re: Question about Shifting Problems with my 300SD
« Reply #2 on: 13 October 2018, 11:20 PM »
Yup always start simple. Pan drop to check the sludge/debris situation. Then new Mann filter and good Dex III fluid. Measuring hot fluid level is critical to having a trans shift well.
Daniel
1977 450 SEL 6.9 - Astralsilber

Diesel 617

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Re: Question about Shifting Problems with my 300SD
« Reply #3 on: 13 October 2018, 11:55 PM »
Yup always start simple. Pan drop to check the sludge/debris situation. Then new Mann filter and good Dex III fluid. Measuring hot fluid level is critical to having a trans shift well.
On the note of trans fluid in the states Valvoline Dex/merc Max Life Fluid is what your after (red bottle), it meets the Mercedes specs
X3 1980 300SD Blown Heads, trans -Retired
1980 450SEL Parted out
1980 450SEL to Diesel Parted Out
1979 280SE Euro Spec Cloth Seats: Needs Rebuilt head and WUR
1979 300CD Daily Driver


Inventory of w116 Parts
https://www.ebay.com/usr/vintagepartsandstuf

gavin116

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Re: Question about Shifting Problems with my 300SD
« Reply #4 on: 16 October 2018, 06:45 AM »
Sorry posted answer on wrong thread...
« Last Edit: 16 October 2018, 07:08 AM by gavin116 »

avantbenz

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Re: Question about Shifting Problems with my 300SD
« Reply #5 on: 06 July 2019, 11:53 PM »
Dropped transmission pan and noticed no debris (yay!), popped in a new filter, changed transmission fluid using Diesel 617's recommendation, and she's shifting smoother but the problem persists. I'll probably update my custom project thread on the details - posting link here for ease of navigation: https://forum.w116.org/test-drive/the-patience-project-my-1980-300sd/msg142897/#msg142897

Next step - test kick down switch and see if I can adjust the vacuum. But first, gotta adjust my valves and replace my shift bushings (not sure if they're bad, doing it preemptively).
Daily Driving 'Patience' ~ 1980 300SD

OLDGOLD

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Re: Question about Shifting Problems with my 300SD
« Reply #6 on: 07 July 2019, 07:06 PM »
This is a long shot, but check your overboost protection device switching valve and your banjo bolt on the back of the manifold to make sure it’s clear. Ya never know!