Car has 178,000 miles, has always had regular ATF. Considering switching to synthetic. I don't care about smoother shifting (though I might like it if it was a result); main goal would be extending life of transmission.

Would this likely be the case?

And, as long as torque converter is drained too, is there any downside? My last tech strongly advised against switching, saying it could create problems. I have no desire to invite unnecessary problems, but I want to take the best possible care of the original transmission.

(I know there are some scattered posts on this...I've read them...but would like some more extensive input.)

Thanks!

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 157k miles
06 E320 CDI "Rutherford", Black on Tan, 175k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 144k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 70k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

If you are only concernd about your trans life then just stick with the cheap ATF. Don't spend the extra money for the synthetic.

Mobil 1 is $6 a quart vs $1.50 for the Autozone special.

Clean trans fluid is the key.

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2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Downside: more expensive
Upside: smoother shifts when the transmission is cold, better wear protection.

Though, conventional ATF is just fine. Just change the fluid at 15,000 mi, then 15,000 mi later, change the fluid again, and the filter too. You'll get a long life out of your transmission if you take care of it.

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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.

Why every 15K when manual says every 30K?

__________________
14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 157k miles
06 E320 CDI "Rutherford", Black on Tan, 175k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 144k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 70k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

Every 15K because we are trying to keep these old boxes working nice.

Use the Regular fluid

I go by what the manual says, I think 15k is overkill. An old trans is an old trans if you keep your car long enough chances are you will have to rebuild it at some point. 200k-250k seems to be when a large number fail. Mine is at 254k and is still shifting nice, knock on wood.

I run Mobil 1 ATF becuase it shifts better with it.

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2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200

I switched to Mobil 1 last october and it made a large difference in how it shifts when its cold out (much quicker/better response) and overall it runs smoother and shifts nicer. For some reason it also "looses" a lot less....I use less than a quart a year now to keep it topped off, where on dex III I'd use almost that much every 3 months....tranny has all new seals inside as of 3 years ago, so I have no clue why it did that. I just know I like the synthetic, and I want to keep it alive as long as possible....237k and counting.....still shifts great....

I just ordered a new pan (old one is damaged and leaking) and filter/seal kit from fastlane a couple days ago for my dad's '83SD, it will be switched to synthetic as well this week when I get around to it.

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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

I was planning on going with Royal Purple this coming week when I do my tranny, but it is $10 bucks a quart!
My buddy used Royal Purple in his Nissan pickup in the tranny and rear end, and his rpms dropped by 350 at 60mph. (save your posts stating that that couldn't happen, because it did) That is why I'm considering it. Although I won't be able to judge rpm drop as my tach doesn't work....

BTW, what weight rear end fluid should we use? 85-90, or 85-140, or other.....

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Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John

Hijack alert...

What should I use in my 76 300D (115 chassis)?

Tks alot
~Nate

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95 Honda Shadow ACE 1100.
1999 Plymouth Neon Expresso. 2.4 swap, 10.5 to 1 comp, big cams. Autocross time attack vehicle!
2012 Escape, 'hunter" (5 sp 4cyl)

I switched to synthetic at at 210000 miles and my transmission went out at 224000. But it wasn't related to the fluid the tech said. After the rebuild, I use only the synthetic and have around 310000 miles on it now. All on synthetic changed at 30000 mile intervals. I use the Mobil 1 synthetic because it is the best and I only want what is the best in my automobiles. I could tell no difference in the shifting, but it is a better oil and the transmission should have less wear running it.

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1995 S-350
370K + SOLD
1952 220B Cabriolet
39K kilometers + SOLD
1998 E300D
310K +
2012 E350 BlueTec
120K

A Dexron/MerconIII approved transmission fluid will do the job.

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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.

To be more specific, is there a danger that, after switching to synthetic, debris will be loosened and leaks will emerge that would not occur if I stick with regular ATF? I should add that the fluid and filter have been changed every 30,000 miles (it now has 178,000) and, the last time it was changed, the tech commented on how good/clean things looked.

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 157k miles
06 E320 CDI "Rutherford", Black on Tan, 175k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 144k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 70k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

I've heard of the "Engine Rebuild in a Can"; is this the "Extra Transmission Gear in a Bottle"?

I have been using amsoil atf for the last 90k miles. have changed it 3x and no problems, oil always come out cherry as if it where new. I have original trans and have 261k on the clock and it shifts fine except for and occasional flare, I will drive it to it quits.



1984 300d 261,000 miles

Maybe the switch to synthetic loosened up something finally allowing the tranny into it's final gear after all these years.

John

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John Hughes, was in Landstuhl, Germany but currently in San Antonio, TX


1978 280CE Astral Silver now 59,xxx miles and counting "Silber-Kugel"
1986 300E Black Pearl Metallic 143,xxx miles 5-spd daily driver w/ blk leather "Schwarz-Schönheit"
1989 190E 2.6 (euro) 5-spd Desert Taupe 112,xxx kms Had to leave behind in Germany!!! "Helga"
1983 300D Pastel Beige now 312,xxx + miles SOLD

OBK#24