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#1
04-15-2009, 11:57 PM
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transmission slams into 2nd if I let up on accelerator pedal
I've noticed this on several MBs both w123s and my current w124. If I'm accelerating hard (half pedal or so) and then let up a little (maybe 1/4 pedal) it always bangs into 2nd gear. It's almost so hard I feel bad for the differential and it's mounts. I can hear a pretty good clunk back there.
The shifts are firm with no banging if I hold the pedal at any set position and of course softer if I'm light footed and firmer if I floor it like it should be. There is no banging if I keep it constant with pedal position. But, when I change my acceleration just before a shift point it bangs. Almost like it's confusing the vacuum modulator if I move the pedal just before a shift. It makes it pretty hard to drive normally. Either I have a super fast 0-45 MPH with a 1/2 pedal held constant or a super slow 0-45 if I don't want it to bang. It's hard to taper back as I'm accelerating because it confuses the transmission and bangs pretty good. Any explanation for this one?
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-E300d '99 350k -Suburban '93 220k -TDI Jetta '03 350k Sold -F250 '96 7.3 -Dodge Ram 12V -E320 '95 200k -E320 Wagon 1994 155k -300d Turbo '87 187k miles -E320 1994 200k -300d Turbo '84 245k (sold to Dan62) -300d Turbo '84 180k -300sd '80 300k -7.3 Powerstroke Diesel 15P Van 500k+ miles -190d '89 Non Turbo 2.5 5cyl 240k (my first MB) Tom's Imports of Columbia MO Ruined the IP in changing leaky delivery valve O-Rings - Refused to stand behind his work. Mid-MO MB drivers-AVOID Tom's. 
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#2
04-16-2009, 12:22 AM
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There is a good technical explanation for that behavior, but it escapes me at the moment. Many older transmissions behave in similar manner...........lift your foot and you get a very hard upshift.
Without dismantling the box, you're forced to make a VCV or an amplifier adjustment to soften the all shifts. It's not a perfect solution, but will probably offer a good compromise.
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#3
04-16-2009, 08:36 AM
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Is this something most of our old transmissions are having happen?
I've noticed it on quite a few of them. Seems like reaction time is not quick enough for the valve bodies or something.
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-E300d '99 350k -Suburban '93 220k -TDI Jetta '03 350k Sold -F250 '96 7.3 -Dodge Ram 12V -E320 '95 200k -E320 Wagon 1994 155k -300d Turbo '87 187k miles -E320 1994 200k -300d Turbo '84 245k (sold to Dan62) -300d Turbo '84 180k -300sd '80 300k -7.3 Powerstroke Diesel 15P Van 500k+ miles -190d '89 Non Turbo 2.5 5cyl 240k (my first MB) Tom's Imports of Columbia MO Ruined the IP in changing leaky delivery valve O-Rings - Refused to stand behind his work. Mid-MO MB drivers-AVOID Tom's.
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#4
04-16-2009, 09:13 AM
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Quote:
 There is something that wears in the clutch packs and causes the behavior. It's in the archives.............somewhere............
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#5
04-16-2009, 01:03 PM
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You could also try some Trans-X...
this stuff dissolves varnish which builds up over the years in those tiny holes with bb's used as one way valves ( gravity closing typically ) ... which are used with the automatic clutch hydraulic controls... so if they are working slowly or stuck... things like this can be the symptom. Cheap, no harm no foul if it does not work.... check the archives for more information....
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1980 240d , chain elongation, cam marks reference: http://www.peachparts.com/shopforum/diesel-discussion/10414-help-i-need-check-stretch.html http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html evap fin cleaning: http://www.peachparts.com/shopforum/diesel-discussion/156207-photo-step-step-post-showing-w123-evaporator-removal-1983-240d-1982-300td.html?highlight=evaporator A/C thread http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html
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#6
04-16-2009, 01:31 PM
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The things that wears and ages in the clutch packs are the seals. There are 3- one is a large o-ring that butts the piston mechanism against the back of the drum. This seal compresses and hardens and fluid gets around it. When you get a rebuild, I doubt that any shop ever replaces them because it requires grinding 3 rivets, tapping 3 holes countersinking the piston support and replacing the rivets with the proper screws (too hard pile).
The other 2 are lip seals that seal the piston to both the inner and outer walls of the clutch drum ( picture kind of a small bundt cake pan). When these seals get worn or sloppy, the fluid that enters the drum leaks around and compressing the clutches to the steels (the action inside the drum that makes it grab) slows down. Rick
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80 300SD (129k mi) 82 240D stick (193k mi)77 240D auto - stick to be (153k mi) 85 380SL (145k mi) 89 BMW 535i 82 Diesel Rabbit Pickup (374k mi) 91 Jetta IDI Diesel (155k mi) 81 VW Rabbit Convertible Diesel 70 Triumph Spitfire Mk III (63kmi)66 Triumph TR4a IRS (90k mi)67 Ford F-100 (??) Last edited by rs899; 04-16-2009 at 02:27 PM.
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#7
04-16-2009, 02:17 PM
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My car does the same thing, but not all the time.
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Dan 2005 E320 CDI - 246k 1987 300SDL TD05-16g, Herlevi pump, Elbe manifold, 2.47 LSD - 213k Past: 1987 300D - 264k 
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#8
04-16-2009, 03:05 PM
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Couldn't this be caused by a faulty VCV or restrictor valve?
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http://superturbodiesel.com/images/sig.04.10.jpg 1995 E420 Schwarz 1995 E300 Weiss #1987 300D Sturmmachine #1991 300D Nearly Perfect #1994 E320 Cabriolet #1995 E320 Touring #1985 300D Sedan OBK #42
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#9
04-17-2009, 08:16 AM
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My 124 does it too.
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 Muleears '07 E320 Bluetec 133K my DD '04 Jaguar XJ8 VDP, 34K '10 Hyundai Accent 60K Grocery Getter '02 VW Golf soon to be on the road again '97 E300 Diesel Son's DD '61 VERY tolerant wife Hampton Roads, VA USA Gone but not forgotten: '67 250S 95K '86 300SDL '87 300D Turbo, 364K! R.I.P. '98 E300 Turbodiesel, 213K '02 S420, 164K '01 Prius 138K
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