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#1
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1979 300D transmission shifts late.
Hey,
I'm relatively new to Mercedes' though I've had my fair share of experience with Fiats, Lancias, Renaults and most notably Alfa Romeos. Anyhell, yesterday I purchased a 1979 300D from the original owner. I'm thinking of replacing my 300E with it. It's an absolute dream, a real time capsule (despite the 194k miles) but it has one issue-- it likes to hold 1st gear too long. Above 20mph if I take my foot completely off the throotle it'll shift hard, otherwise it'll hold it until 25-30mph and then shift (once again rather hard). I've read that they're supposed to start out in second gear but that doesn't seem to be the case, unless I'm missing something. All the other gears are just fine. I've spent the last half hour or so using the search function but I still have some questions.. 1) From my reading, I think it's a vacuum leak. My door locks are slow as sin too so I guess that would back that up. However, the engine turns off just fine so no vacuum leaks there. If it is vacuum related, what would be the first thing to check? Cracked lines, loose connections, etc? 2) If it's not vacuum related, what could it be? I read something about the bowden cable but I also read that some cars don't have it.. keeping in mind that mine is just a standard diesel, not a turbo, will it still have the cable? This car has been meticulously maintained (I have all the records from new), the trans fluid is good and topped up though I'm tempted to have it flushed to see if that helps. Thanks. |
#2
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go here and sam ross's "it's critical..." post will describe vacuum testing for the transmission: http://www.peachparts.com/shopforum/showthread.php?t=142395 i wouldn't bother with a flush until you've looked at the vacuum profile. also definitely read this: http://www.mercedesdismantlers.com/722.118_transmission_adjustments.html since i think your transmission is probably a 722.118 (see stamp on passenger side pan). no, you don't have a bowden cable unless your 1979 is different than my 1980s, which it could be since you never know... good luck
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1980 300D (non-turbo, 421k miles) 1984 300TD (turbo, 305k miles) 1985 Vanagon (170k miles) |
#3
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Thanks a lot, I'm looking into it.
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#4
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Anybody else want to chime in on what the first thing I should check is on my vacuum? I have a vacuum meter and what not, I'm just unsure about what to check. The line going to the transmission?
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#5
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Okay, the car is 2 days old? Reminds me of buyin 1980 SD in Sept. Kicked like a mule in between shifts until I got used to feathering the pedal after couple of weeks. It always holds gears waay high into rpm's over 4,000 and starts out in 1st. But can control shifts myself using hammer down then release on accelerator pedal. Must always anticipate every shift ye make.
It's got no bowden cable but long steel rod from accel linkage on valve cover, correct? From what I'm seeing, characteristics of primitive German 4 speed automatic especially combined with diesel engine is hard shifts that work driver's to death. Thought I'd hate the automatic after 4 yrs with stickshift 240D, but am now loving the hard shift 4-spd auto trans because it requires tremendous skill to operate. Far cry from typical brain-dead slush box auto transmission. You'll also find "S" and "D" very useful for manual shifting between 3rd and 4th. Generally I drive in S below 55-60mph. And frequently drop from D into S for climbing hills even at 65. According to speedometer marks 3rd tops out at 75. And the primitive automatic always takes lower gears up around their speedo marks before grabbing the next gear. I've seen all of the symptoms you describe, Alfa. Even consulted with mechanic to soften adjustments for smoother shifts. His advice was leave it alone, you want it shifting hard and NOT flaring in between shifts. Finally 194k miles is NOTHING. Mine had 260k when i bought it. Am thinkin about cyl head and valve work between 280 and 320k, expecting engine to reach 480k well maintained. Consider replacing time chain at about 220k and measure timing chain stretch next time you adjust valves. Timing the Injector Pump compensates for 4-6* degrees stretch. Being a diesel it will tolerate up to 10* stretch though most people replace chains at 8. Going from Alfa Romeo to MB diesel, huh?? Yer in for culture shock like you wouldnt believe. Zero gasoline logic applies to diesels and no 2 vehicles could be further apart.
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'80 300SD/ w116 '79 240D 4-spd '71 750cc Guzzi previously owned: '83 240D 4-spd '77 280SEL 4-spd '74 280/8 '72 250/8 '65 220Sb 4-spd '63 220Sb 4-spd '63 190c 4-spd '61 220Sb 4-spd '60 190b 4-spd |
#6
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I had the same problem
This summer at times my would shift that way. Then again it would do ok. Mine is a W123 300 D Turbo. When doing some serious checking with Bajaman a couple of weeks ago, we found out that the small vacuum pickup off the mainline between the pump and the booster was not pulling any vacuum. Mine has two vacuum pickups close together and the first one was just plugged up. I had a spare line from an 83, put it on and problem solved.
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Junqueyardjim Christianity, if false, is of no importance, and if true, of infinite importance. The only thing it cannot be is moderately important. C.S. Lewis 1983 Mercedes W123 240D 4 Speed 285,000 on the road with a 617 turbo, beautiful butter yellow, license plate # 83 240D INDIANA 2003 Jaguar Type X, AWD. beautiful, good mileage, Mom's car, but I won't let her drive it! |
#7
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DieselDog-- thanks for the reply. My main concern though is that it shifts late. And luckily, I'm not coming straight from an Alfa to a 300D, I'm coming from a 300E. But last spring I regularly went from my '62 Bug to my '92 300E (both cars sold now), now THAT was something .
Jim-- thanks, I'll look into it. |
#8
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Quote:
What's the next step from here? |
#9
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Uh oh..
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#10
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Purple would be EGR temp sensor vacuum line, according to vac schematic my car's got on sticker attached next to radiator. Coulda been discarded there if replaced earlier.
An excellent thing to do is cut back vacuum rubber elbows and joints 1/4" to give fresh rubber that tightens up connections. Basically go from one to another with razor blade cuttin back rubbers and reattaching. You will see how it tightens em up with first one you do. Returning to transmission, if fluid's overfilled even slightly then will shift harder than normal. Oughta be at bottom line on dipstick when cold, as I'm sure you know. I check tranny fluid level with car idling in gear and emergency brake on. |
#11
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Probably a dumb question but hell, I'm new to these cars-- what's the line going into the airbox?
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#12
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I'm still trying to figure this out-- any help would be appreciated.
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#13
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got a picture of that line? what i'd look at, in terms of vacuum: check and see if the modulator is holding vacuum--a new o-ring is probably helpful--just pop off the modulator cap and replace, if needed. i like to check the vacuum right at the transmission's modulator by putting a three-way connector with long vacuum line attached to gauge, then check while parked and look at the profile while revving--should drop at higher rpms--opinions on profiles vary but something like 10" vacuum at idle down to zero at full throttle with a more-or-less linear drop with respect to rpm. (you can also T into the line in the engine compartment, obviously; should be the black line.) maybe that helps? at least for starters...
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1980 300D (non-turbo, 421k miles) 1984 300TD (turbo, 305k miles) 1985 Vanagon (170k miles) |
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