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#1
05-15-2010, 09:25 AM
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1971 3.5 Coupe Transmission
The other problem area on the car is the automatic transmission. It has no kickdown, and I am not sure its getting into 4th gear. It seems to have its own mind about upshift and downshift.
I am not having much success getting basic information on it. Questions - What KC-xxx is it? Does it have a fluid coupling like the 113/108 or does it have a torque converter? Should it start in 1st gear? It seems to. 2000 RPM gets about 38 mph? Does this sound right?
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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 
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#2
05-15-2010, 11:11 AM
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Quote:
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Graham 85 300D  ,72 350SL, 98 E320, Outback 2.5
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#3
05-16-2010, 09:48 AM
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Thanks, at least a place to start.
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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
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#5
05-16-2010, 04:06 PM
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#6
05-16-2010, 08:59 PM
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And all other markets got both 4 speed with fluid coupler and torque convertor .Only 3 speed autos in other markets were in W107's .
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#7
05-17-2010, 07:40 AM
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And I found the following on the MBCA site from 2003. This car has the four-bolt pan, which would make sense for a 1971.
The fact that it starts in 1st and has no kickdown makes me think that the kickdown piston/solenoid/whatever is stuck in the "kicked down" position. ======================================================= What year is the car? The early W108 280SE used the K4A025, which was a very rough shifting unit. The later version, K4C025 was somewhat smoother, but a dinosaur by today's standards. Tom Hanson __________________ Hello, If the transmission has a four bolt oil pan it is the later version. On this version vacuume to the modulator and a linkage rod control the shiftting points. As mentioned make sure that there are no vacuume leaks. The position of the linkage rod going to the transmission can will change the shift points. This is the easiest thing to check or adjust first. In addition the vacuume modulator unit itself could be defective or incorrectly adjusted. The modulator can be adjusted but normally is just replaced (fairly inexpensive). I would check the linkage first! If the transmission pan has a sixteen bolt pan it is the early four speed automatic. This version has D 3 2 1 on the shift gate instead of D S L on the later three speed automatics (above). On this version there is no mechanical accelerator linkage going to the transmission, but rather a linkage rod controled electronically, by a three position solenoid on the transmission itself. This solenoid is activated by a switch on the intake venturi. If thethree position solenoid or its linkage rod is stuck the transmission will not shift properly. In addition if the venturi switch is not set up properly the downshifting will be very abrupt. These early automatics do have a vacuume modulator also, however the problem is usually at the three position solenoid or the venturi switch. Find out what version you have first, so we can advise. The change was made in early 1969. Joe Alexander
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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
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#8
05-17-2010, 08:34 AM
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But maybe yours is just stuck? - maybe pull it and check it on the bench. Mine showed zero resistance across the solenoid coil.
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Graham 85 300D ,72 350SL, 98 E320, Outback 2.5
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#9
05-17-2010, 07:22 PM
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Better information
Called the guy I go to for the hard ones. He is restoring a 3.5 cabriolet. He got out the book.
The 3.5 cars only came with one automatic, a K4A-040. It is designed to start in first gear. Shift points under very light throttle on level ground (in KM): 1-2 10 2-3 31 3-4 50 This one is about right.
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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
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#10
05-18-2010, 06:22 AM
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Linear Mode
