|
|
|
|
|
#2
10-21-2003, 08:38 AM
|
|||
|
|||
|
This is usually a modulator problem, and the fix is to replace or adjust it. Best done by a dealer or an indie that knows this transmission.
__________________
Chuck Taylor Falls Church VA '66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe 
|
|
#3
10-21-2003, 03:11 PM
|
|||
|
|||
|
Which tranny? None of the '68 trannies, to the best of my knowledge, have modulators. They shift hard because they are designed that way, nothing you can do about it. The first MB auto to have a modulator was the WA3-050 in the 6.3/4.5 V8, all the six cylinder W108 trannies are the K4C 025 or 030. I'm not sure, but I believe the W114/W115 chassis had the same ones up to 72.
Mobl 1 synthetic tranny fluid may help, but by and large the old four speeds just shift hard. They also refuse to downshift at low speeds unless you floor them and engage the kickdown switch under the gas pedal, also normal behavior. Just the nature of the beast. Floor it on takeoff sometime and hold the kickdown switch down -- your head will snap back when it shifts into second! That is, if you have the never to let the engine reach redline first.... Peter
__________________
1972 220D ?? miles 1988 300E 200,012 1987 300D Turbo killed 9/25/07, 275,000 miles 1985 Volvo 740 GLE Turobodiesel 218,000 1972 280 SE 4.5 165, 000 - It runs!
|
|
#4
10-21-2003, 03:28 PM
|
|||
|
|||
|
I did look in the book before I wrote. The reason I suggested the modulator is that the book shows the 280SEL with a K4C025, same-o as my 250C, which definitely has (had) a modulator.
__________________
Chuck Taylor Falls Church VA '66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
|
|
#5
10-21-2003, 07:27 PM
|
|||
|
|||
|
When I first got my 280C, I thought the same that as you -- that it shifted hard and refused to downshift. People on this site set me straight, and they're right -- that's just the way the shift. One thing I've discovered, is that the harder you drive them, the better it seems to shift. In general, these old cars just like to be driven hard, and like to rev very high at speed. Oh, and I've gotten to be really good at downshifting manually when I need the extra oomph because they really, really don't like to downshift.
Catrinus 73 280C
|
|
#6
10-21-2003, 07:42 PM
|
|||
|
|||
|
Hmm. I didn't know the K4C had a vac modulator -- the K4A on the diesels doesn't, and that's the only one I've seen.
The modulator is adjustable, but should probably be set with a gauge and not by the seat of the pants. Shifts are HARD by American automatic standards, but so long as they are only firm and do not cause the driveline to thump I'd leave well enough alone. If you get a distinct clonk when shifting, examine the condition of the flex disks also, they may be shot. Peter
__________________
1972 220D ?? miles 1988 300E 200,012 1987 300D Turbo killed 9/25/07, 275,000 miles 1985 Volvo 740 GLE Turobodiesel 218,000 1972 280 SE 4.5 165, 000 - It runs!
|
|
#7
10-21-2003, 10:22 PM
|
|||
|
|||
|
You may also want to check the idle throttle switch on the side of the intake manifold (Fuel Injection-right?). This switch activates the pressure switch on the tranny and eliminates the hard down shift when coming to a stop.
__________________
Regards, Tom S. 1971 280SL Tunis Beige Metallic 1971 280SL Tobacco Brown (13K miles) 1970 280SL Deep Red 1994 E320 Cabriolet 1999 E320 Wagon 4Matic 2002 LX 470 1992 Land Cruiser
|
|
#9
10-22-2003, 09:53 AM
|
|||
|
|||
|
I know that they have a mod -- it is often the problem.
I like to call it firm - I agree that under full power they shift smooth. I also remember that I got good at letting off the gas just as it would shift - I have lost the skill since I do not drive them much any more. Also the down shift does work off the kickdown switch under the gas pedal -- you just have to punch it -- they let off the gas to the point that you want.
|
|
#10
10-23-2003, 11:48 AM
|
|||
|
|||
|
Chuck is right about the K4A025 used up until somehere in 69 when they went to the K4C025 in everything except the SL, because it wouldn't fit in the hole. You can which trans is in a 69 by looking where the window switches in cars with power windows. If the switches are mounted in the console , you've got the newer tranny. The modulator is a rubber diaphragm and is addjustable.
Peter, The diesel has a mechanical modulator, because there is no vacuum source to operate it. Tom is absolutely right about the switch on the intake manifold which controls the 3 position solenoid mounted on top of the tranny. If this switch isn't set up correctly you can have maximum control pressure on downshifts whish can jar you're teeth. Peter
__________________
Auto Zentral Ltd.
|
|
#12
10-23-2003, 07:16 PM
|
|||
|
|||
|
68,
Having been in this business for 30 years I get vibrations, and I don't think your dealer ordered the right part. The modulator is built into that tranny, and all you need to replace is the diaphragm which lists for $30.00 and the part # is 112-270-00-79. Peter
__________________
Auto Zentral Ltd.
|
|
#13
10-23-2003, 07:22 PM
|
|||
|
|||
|
Footnote to last post. I looked the part up on microfiche, but just for ****s and giggles I just looked it up on Fast Lane and they have it for less than $30.00.
Peter
__________________
Auto Zentral Ltd.
|
 |
| Bookmarks |
|
|
Linear Mode
