I recently purchased a 1985 300SD W126 and I'm have shifting problems. Occasionally, I noticed that while driving that the transmission would not shift. I would manually down shift and return the shifter to D, only then it shifts. This would happen say twice a week. Recently some one bumped me in the back and the trany is acting up more often. Sometimes taking up to three to four minutes before shifting and sometimes not shifting at all. I am planning to change the trans. oil and filter. I have read other posts which taks about the vacuum modulator. Would adjusting this help? and if so, where is it located and what does it look like.

I would start with the fluid and filter change. Do not forget to drain the torque convertor, or you will leave old fluid in the system. In addition to searching this forum, do a Yahoo search for "diesel page" . I have forgotten the new name of Omar Sidiks page, but it is one of the first listings under that search parameter, and the page has a detailed tutorial on adjusting the vacuum modulator. There is also another excellent link for this proceedure I found by searching here at MB shop. Is your transmission flaring, and slipping, or simply refusing to shift? I am assuming it is refusing to shift, since you say it takes "three or four minutes" to do so. I would hate to think the discs are slipping all that time, or you'd need the fire department!

Luke

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'78 300D 310K Maple Yellow / Bamboo
'87 300D 81K Barolo Red / Safron (RIP @ 113K)
2003 E320 34K Pewter/Charcoal
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It seems to shift o.k when cold, however, when it warms up, it sounds like its shifting but does not actually shifts, sounds like it is in first gear and refuses to shift thereafter.