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Old 02-03-2003, 09:03 PM
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Question 1989 300SE Auto Transmission slips

I have recently purchased 1989 300SE 6Cyl auto non-turbo with 130 K miles. It slips when shifting up into next gear (all) on acceleration. Fluid is clear.

I can replace myself ( I think) with a salvaged one, rebuilt, or would like to try some things first.

Also, I assume this is 4 speed with lockup converter. How many RPMS should I turn at about 60. Does ~2800 sound right? Is Dextron the correct fluid.

Any suggestions appreciated.
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Old 02-04-2003, 07:50 PM
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Also are there any inherent problems to this model Mercedes. This is the first one I have owned.
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Old 02-05-2003, 01:55 AM
haasman's Avatar
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Join Date: Jun 2001
Location: San Francisco, CA
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there was just a bunch of postings regarding this type of problem. Do a search using the word *flaring* I think you will find what you need.
'03 E320 Wagon-Sold
'95 E320 Wagon-Went to Ex
'93 190E 2.6-Wrecked
'91 300E-Went to Ex
'65 911 Coupe (#302580)
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Old 02-05-2003, 08:16 AM
Registered Diesel Burner
Join Date: Aug 2001
Location: Northern Virginia
Posts: 2,911
The first thing I'd recommend is a fluid and filter change. If the filter is clogged a bit with use and age, I think that can lower the system's hydraulic pressure. And I have had excellent results with synthetic Dextron-III ATF - currently using Quaker State 4x4 fluid.

I had a problem that started showing up in cold 3-4 shifts. The shift would not execute and the car would just rev. New fluid and filter completely eliminated the problem.

(refers to my 1982 300D)

(also have a 1987 300D)
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Old 02-05-2003, 09:03 AM
it leaks, its german
Join Date: Mar 2002
Location: raleigh nc
Posts: 1,111
bump the modulator pressure and drive it, if the slip is consistent in all shifts, sounds like low apply pressure.

the modulator is on the l/h side of the box in front of the manual valve arm. (shifter) pop the little rubber cap off and turn the enclosed key clockwise 3 turns, put the cap on and drive it..... too firm, back it off in 1/2 turn increments.

if the shifts are late or early, adjust the bowden cable (under the air filter behind the a/f sensor) longer housing, later shifts, shorter housing, earlier shifts.

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Old 02-05-2003, 08:25 PM
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Wink 89 300SE Modulator adjustment

Thanks for the advice. I adjusted 3 and seemed like it was still not enough so I went 4 1/2.
This seems to have solved the problem! I hope it holds up. The 1st shift is not as crisp as the others but is very good compaared to what it was.

Do you 4 1/2 was to much and should I consider modular change out, etc.

I also am turning ~2400 rpms at 50. Is this correct because I really can't feel it go into 4th but when I go to 3 it does downshift.

Thanks for all your help.
John L
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Old 02-05-2003, 11:34 PM
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Join Date: Feb 2002
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Our trannies start in 2nd gear... maybe thats why you don't feel it going to 4th.
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Old 02-06-2003, 01:24 AM
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Have you replaced the trans filter? When you do be sure and drain the torque converter as well.

'03 E320 Wagon-Sold
'95 E320 Wagon-Went to Ex
'93 190E 2.6-Wrecked
'91 300E-Went to Ex
'65 911 Coupe (#302580)
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Old 02-06-2003, 04:31 PM
sixto's Avatar
smoke gets in your eyes
Join Date: Jun 2000
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There's no torque converter lock up.

If the transmission is responding to the modulator adjustments, it's likely not a bad modulator.

91 300SE
87 300SDL
83 300SD
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Old 02-06-2003, 04:46 PM
Join Date: Mar 2000
Location: Gainesville FL
Posts: 6,844
If you had to go 4.5 turns something is big time changed. Could be the modulator. I would verify that the vacuum to it follows manifold vacuum (goes to zero at full throttle).
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician
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