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1979 300SD weird trans problem
I hope Stretch will chime in on this one. On a 1979 300 SD, the trans goes into neutral after stopping. It shifts the rest of the gears great, but I have to put it in neutral and then back into drive after stopping. If I shift it down into second before stopping, it seems to start in first ok. I adjusted the modulator pressure a little tighter thinking it has low pressure, but that did not help. The modulator holds vacuum, and the VCV tests good (full vac idling, gradually decreasing to zero at a little before full throttle). The fluid level seems a tad over full cold, have not checked it warm (have not had the car long enough). The previous owner said it has been like this for many thousands of miles, and he just dealt with the hassle. Any ideas?
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All Diesel Fleet 1985 R107 300SLD TURBODIESEL 2005 E320 CDI (daily) LOTS of parts for sale! EGR block kit http://www.peachparts.com/shopforum/diesel-discussion/355250-sale-egr-delete-block-off-plate-kit.html 1985 CA emissions 617 owners- You Need This! Sanden style A/C Compressor Mounting Kit for your 616/ 617 For Sale + Install Inst. Sanden Instalation Guide (post 11): http://www.peachparts.com/shopforum/diesel-discussion/367883-sanden-retrofit-installation-guide.html |
#2
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Shifter bushings?
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I don't believe so. Something is happening hydraulically causing the problem, but what exactly, I have no clue.
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All Diesel Fleet 1985 R107 300SLD TURBODIESEL 2005 E320 CDI (daily) LOTS of parts for sale! EGR block kit http://www.peachparts.com/shopforum/diesel-discussion/355250-sale-egr-delete-block-off-plate-kit.html 1985 CA emissions 617 owners- You Need This! Sanden style A/C Compressor Mounting Kit for your 616/ 617 For Sale + Install Inst. Sanden Instalation Guide (post 11): http://www.peachparts.com/shopforum/diesel-discussion/367883-sanden-retrofit-installation-guide.html |
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Stretch? Anyone?
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All Diesel Fleet 1985 R107 300SLD TURBODIESEL 2005 E320 CDI (daily) LOTS of parts for sale! EGR block kit http://www.peachparts.com/shopforum/diesel-discussion/355250-sale-egr-delete-block-off-plate-kit.html 1985 CA emissions 617 owners- You Need This! Sanden style A/C Compressor Mounting Kit for your 616/ 617 For Sale + Install Inst. Sanden Instalation Guide (post 11): http://www.peachparts.com/shopforum/diesel-discussion/367883-sanden-retrofit-installation-guide.html |
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Normally I am about the last to offer transmission advice, but seeing as you seem to be getting an echo....
I have no idea if this behaviour is actually linked to the operating pressure, but I'll go with that for now. You say you adjusted it a bit, did that make any difference to the shifting otherwise? If it did not, I wonder if the modulator is set way too low. How does it shift otherwise, firm or what I call slithering through the shifts (I hate overmodulated setups)? If the modulator way off the correct setting, you will need many turns. You can either go ahead and just try one turn at a time, to see if anything changes. Or you can try to put a gauge on to test the operating pressure, to see if modulator adjustment is indeed the tree you need to bark up. To do that you will need to confirm which is the correct test port (there are probably three or more choices and they are apparently different on the later trans, so beware hooking up a gauge based on info from archive posts).
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Mac 2002 e320 4matic estate│1985 300d│1980 300td Previous: 1979 & 1982 & 1983 300sd │ 1982 240d “Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22 |
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Indeed a strange problem. An incorrect vacuum can cause all kinds of shifting weirdness, but I never heard of a transmission slipping out of gear because of it.
First start with the basics: when was the fluid and filter last changed? The fluid level should be below the marks when cold. Best way to check fluid level is when the transmission is warm. I believe the 1979 300SD has a shift rod to control the shift points and the first gear take-off. Is the linkage adjusted according to specs? A small investment in a pressure gauge and pressure line should be made so that you can measure the oil pressures inside the transmission. In that way you can correctly set the modulator. Does the modulator hold vacuum? You can also use a T piece and a long vacuum line routed to the cabin and connected to a vacuum gauge to measure the vacuum to the transmission during driving. |
#7
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Quote:
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All Diesel Fleet 1985 R107 300SLD TURBODIESEL 2005 E320 CDI (daily) LOTS of parts for sale! EGR block kit http://www.peachparts.com/shopforum/diesel-discussion/355250-sale-egr-delete-block-off-plate-kit.html 1985 CA emissions 617 owners- You Need This! Sanden style A/C Compressor Mounting Kit for your 616/ 617 For Sale + Install Inst. Sanden Instalation Guide (post 11): http://www.peachparts.com/shopforum/diesel-discussion/367883-sanden-retrofit-installation-guide.html |
#8
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Quote:
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All Diesel Fleet 1985 R107 300SLD TURBODIESEL 2005 E320 CDI (daily) LOTS of parts for sale! EGR block kit http://www.peachparts.com/shopforum/diesel-discussion/355250-sale-egr-delete-block-off-plate-kit.html 1985 CA emissions 617 owners- You Need This! Sanden style A/C Compressor Mounting Kit for your 616/ 617 For Sale + Install Inst. Sanden Instalation Guide (post 11): http://www.peachparts.com/shopforum/diesel-discussion/367883-sanden-retrofit-installation-guide.html |
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