Like a moron I did some damage to my SDL tranny by running it with too much fluid. One day it would not do anything except in first and reverse. I have kicked myself for it many times. For a while I thought I had ruined it. But then after a year of sitting it I miraculously found it was working pretty well.

By then I had corrected the fluid level, I took it out on the freeway to see if it would slip - it never did. So I've been driving it more. A few days ago at a stoplight it would not move in drive. I put it down to low and took off - when I shifted up it behaved normally.

I checked the fluid while warm, it was a tad bit high, I siphoned off maybe 6 fluid ounces. It then read right at the add mark so I put some back in. I noticed it was not bright red. It was brownish red, which only makes sense.

I'm thinking new fluid and filter would be a good idea, but then I started reading that I might be disappointed. It will be a while before I buy a rebuilt tranny.

Any opinions?

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Te futueo et caballum tuum

1986 300SDL, 362K
1984 300D, 138K

I do a flush every 25K miles, around three years for me. If it starts to slip after a flush it needed a rebuild.

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1979 Black on Black, 300CD (sold), 1990 Black 300SE, Silver 1989 Volvo 780, 1988 300CE (vanished by the hands of a girlfriend), 1992 300CE (Rescue).

As Jorn says but the interval I run out to is 40k to 50k miles.

I would drop the pan/filter and then position the torque converter with the drain on the bottom and drain it too. It takes a while to drain the TC. You should find a magnet in the pan that will need to be cleaned off. Don't be alarmed by the debris on the magnet.

I would not as much "flush" it as drain everything and refill.

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Jim

I'd drop the pan, change the filter and drain the converter. I wouldn't do a flush with a machine. Exchanging the fluid through the cooling lines and changing the filter is ok but not with a machine and flush/cleaning chemicals.

When the fluid looks really bad and the transmission is presenting problems I'd leave it alone. If the fluid looks decent service it and continue to service it on schedule.

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

i read your signature. it says the sdl has 300k miles. NEVER had a trans rebuilt? NEVER changed the atf before? supposed to be every 30k miles. you're on fumes now.

try this. drain the pan and keep the fluid. refill with with 1 new atf. then refill with the used atf. this way you gradually introduce fresh fluid. gonna take a couple of years if you do this once a month. more work but cheaper that a trans.

me, i'd pull the trans and get it done. 300k is a lot.

You made a grave mistake.....

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'06 E320 CDI
'17 Corvette Stingray Vert

He messed-up BAD....

I'd of never done what he's done....

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'06 E320 CDI
'17 Corvette Stingray Vert

Oh hell yes, I effed up pretty bad. And you're a dumbass, I can fix the transmission, let's see you fix yourself.

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Te futueo et caballum tuum

1986 300SDL, 362K
1984 300D, 138K

It's not the original transmission. I bought it in 2017 with 303303 on the odo. I remember the figure because it was a palindrome. Who knows, maybe a sign.

It had a tranny fluid leak, seals no doubt. I had to check it every two or three days. In late 2019 I blew the radiator, luckily the idiot light caught my eye, I hadn't seen the needle going up to the red line. Popped the hood, it was all steam, at least it wasn't black smoke.

I put in one of those aluminum radiators, it ran fine until early 2021 when it started billowing white smoke, and finally gave up the ghost. I found out later it was a blown head gasket, it's what we all suspected.

I had gotten some prior work done on it that I couldn't do from a Vietnamese mechanic who cut his teeth on Mercedes diesels in the old country where they were pretty common. He's something of an OM603-ophile, owns two 350SDs. He somehow ran across an 87 SDL with 130 K, a really strong motor and a so-so transmission. I never did get the whole story. The body had been near totaled, but still drivable - he said the engine felt really good, and the compression checked excellent. He pulled it and the drivetrain, called me up, put it all in.

The fact that I blew it with the transmission haunts me, I don't know how I could be so stupid. I could try to make the excuse of the cancer treatment I was going through at the time, chemotherapy the whole works, but that doesn't really cover it. I've done pretty well with some other vehicles on maintenance. Took my 87 BMW 325I to 425K doing all my own work, changed the fluid, timing belts, etc. on schedule.

I'm healthy now, I just need to make the car healthy. A rebuilt tranny is in my future. But if I could get some service out of this one for as long as possible, that would help.

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Te futueo et caballum tuum

1986 300SDL, 362K
1984 300D, 138K

With installation I paid around $2500 for a rebuild transmission from Sun Valley Transmissions. My transmission blew up halfway to SF from LA, still made it to SF and back to LA without second and reverse.

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1979 Black on Black, 300CD (sold), 1990 Black 300SE, Silver 1989 Volvo 780, 1988 300CE (vanished by the hands of a girlfriend), 1992 300CE (Rescue).

In my opinion you probably didn't do damage by the slight overfill. It is possible but unlikely.

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

That would be an attractive price. I've seen accounts that have it $2500 just for the rebuilt transmission plus installation another $1200 perhaps by my guy.

In the old days, I would've changed the tranny myself. Various floor jacks, time, and stubbornness available. But I've heard the SDL tranny install is pretty tough. I did my last tranny quite a while ago, '02, my 325i E30. I thought that for only a 2.5 L engine it might be halfway lightweight.

OMG that was a tough one man job on the garage floor. And I was stronger then.

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Te futueo et caballum tuum

1986 300SDL, 362K
1984 300D, 138K

It's a dilemma. Not knowing is always tough. The business about the fluid being full of micro friction devices sometimes known as metal shavings is sort of a trip.

Here's a possibility. Drain all the fluid, save it and the old filter and put in new stuff.

If I suddenly get a wild increase in slippage, I'll drain it and put back the old filter and fluid. If indeed the micro friction from wear is real, don't need a nice clean filter extracting all of that from the broken-in fluid.

On a related note since the tranny started acting up two years ago I've seen two really clean SDL's at Pick n Pull, both with transmissions intact. There's something cruel about not being able to contact the seller, the last owner. I can only imagine they would be plenty happy to give some brief insight into the health of the transmission. I've tried it. The best answer I can get is I would need an DMV insider to get me that name and phone number just from the VIN. I might need to cultivate a Pick and pull insider, and offer them a not creepy bribe so that I could call some guy up and politely ask him if that tranny's still working.

Doing a flush and filter change would be a dress rehearsal for checking a boneyard tranny to see what the fluid, filter, and magnet looked like. I don't think they puncture the bottom of transmissions to drain the fluid the way they do on drain pans sometimes - very strange -I went looking for a drain pan. They all had big holes in them. But even if they did, I could use the cover off my existing tranny.

A tranny is $250 at Pick 'n Pull. I'm wondering if one that was clean inside is worth the gamble. Also, I would need to come up with some way to catch the fluid. Wouldn't want to be wallowing in it and wouldn't want to piss anyone off.

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Te futueo et caballum tuum

1986 300SDL, 362K
1984 300D, 138K

There are many different angles of approach...kinda have to pick one and hope for the best. My choice would be drop the pan, clean things up, replace the filter and fresh fluid. Lastly add a tube of Lubegard.

If the transmission is so worn that this makes it worse it was on its way out.

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

That does sound like a good approach. My only question and it might be a tough one to answer, if it makes it worse should I put back in the old fluid and filter? It's not running that badly now, I don't quite get it. There is a chance that new fluid might flush out valuable debris, metal filings, whatever and it will slip even with the old fluid put back in.

In a lousy dilemma, the cleanest boneyard SDL I've ever seen (3 weeks ago) is still on the Portland South Pick n' Pull yard. I was passing through, not much time, had to pick up riders going south. I got a couple of things, oh my God so much more would be worth a looksee. No idea if the tranny is still on it. They don't give you that info I don't think. I'm going to have to be ready to pop a tranny pan any time I find one.

https://www.picknpull.com/check-inventory/vehicle-details/WDBCB25D0GA252137

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Te futueo et caballum tuum

1986 300SDL, 362K
1984 300D, 138K