I installed a rebuilt transmission in my 81SD 18 months and 45k miles ago. Put Mobil 1 in there. Hasn't leaked a drop since and the fluid is clear and very clean.
The rebuilder notes the fluid should be changed every 35k.
Question is can I run this any longer without causing wear? Or should I be making plans to change the transmission fluid and filter now? Anybody have information on extending between changes with synthetic trans fluid?

Transmission fluid is killed by heat. The normal temp is about 175F. For every 10F over that, the life of the fluid is cut in half.

It depends TOTALLY on your driving conditions. If you mostly cruise on the highway with very little stop and go driving then you MIGHT be okay with 45k mile changes using synth. If on the other hand you drive a good bit of stop and go traffic in ambient of 80F or better then you should be changing it MUCH more often.

How much did that new transmission cost? How much does ATF cost? If it were mine, I would be changing fluid only, in both transmission AND torque converter, at about half the normal interval and then fluid AND filter at the regular interval. If I were driving stop and go, I would be changing it so often that I would worry about wearing out the threads on the drain plug.

I am NOT a fan of automatic transmissions. I am a manual transmission maniac, but I do know how to make them live and have done so for other members of the family. The key is adequate fluid changes. These cars are VERY easy to change fluid and filter compared to many other cars. The difference is that they have drain plugs on both pan and torque converter. This makes it VERY easy and quick to do.

With an a/t the change it hot part does not apply, but the often part DEFINITELY does.

Good luck,

We all know how Larry feels about Trans Flushes

I will be picking up a trans filter and a case of Mobil 1 shortly. Thank you for the thoughts Larry.

I use mobil one in our transmissions. I change every 30k. I have been changing filters, but I am not sure if this is completely necessary every time. The filters are cheap, but it makes the job a bit messy.

I would say you get 4-5 quarts out of the torque converter and 1-2 quarts out of the transmission.... then you spill a half quart on you when you take off the cover to get to the filter.

I think if you are going to take off the cover to do the filter....get a decent size box and line it with a plastic garbage bag...this will help catch the mess...

I think you will need close to 7 quarts of fluid to re-fill it... about 6.6 or 6.7 if I recall.

lots of piece of mind after doing this job... i have found very little clutch material in the pan...

also it's interesting to compare the colors of old fluid to new... New is bright shiny red, old is usually a duller red. At least I hope yours will be red.

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1989 300ce 129k
( facelifted front,updated tail lights, lowered suspension,bilstein sports, lorinser front spoiler, MOMO steering wheel, remus exhaust,stainless steel brake lines). (Gone)

1997 s320 154k (what a ride). Sold with 179k miles. Replaced with Hyundai Equus

1994 e320 Cabriolet 108k



1972 280se 4.5 153k Owned for 12 yrs, sorry I sold it


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Just a reminder, if you do a lot of city driving, change the fluid and filter every 15k miles to make that AT last. Even if it's a highway car, change the filter and fluid every 15k miles. City car, or highway car, changing it every 15k miles will give you a maximum AT life.
-Joe

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'81 MB 300SD, '82 MB 300D Turbo (sold/RIP), '04 Lincoln Town Car Ultimate

Sooner or later every car falls apart, ours does it later!
-German Narrator in a MB Promotion Film about the then brand new W123.

I've got a question for you guys - I haven't actually sen a ATF filter for one of these cars yet. Is it a screen in the filter, or is there an actual filtering element? If it's just a screen, has anybody thought about putting an add-on spin on filter inline with the cooler lines? Would make the fluid change process much, MUCH simpler. Thats something I loved about my Subaru's, spin-on ATF filters. Can't get much more maintenance-friendly.

Can't vouch for all models, but mine take a paper-element in steel filter in the pan.

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Gone to the dark side

- Jeff

The 722.3 and 722.4 filters I've seen have a pleated paper-looking element.

Can you drain the torque converter of a Subaru?

You can try a WIX 58964 in-line ATF filter if a remote spin-on is too much trouble to install.

Sixto
93 300SD 3.0

I wouldn't use that, and god only knows what filters fit that thing. I would only buy a spin-on filter kit designed for an automatic transmission.