I have a 85 300D, 200K miles, and I am doing all of the major tune items. I want to change my transmission fluid tomorrow and I have heard use trans-x and I have heard its junk. Has anyone had any good or bad experiences with it? Will it effect my seals, or will it help clean it out? More important will it replace some fluid, I dont know how big the bottle is.

Don't use it unless your transmission is already conked out and you need something to get a few hundred more miles out of it. Just do a normal transmission fluid and filter change every 15-30k mi and be done.

__________________
'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.

Trans-x swells seals to reduce leaking. Obviously that isn't good for the transmission but, like H said, its good if you want to get a few more miles out of a worthless clunker.

Done use redneck product for the benz!!! Do it properly and skip all of the "TRANSMISSION HELPING FLUIDS" you save both money and time...

__________________
Current Garage
2008 Mercedes GL320 CDI 188k mi Repair/Work in progress
1994 S350 160k mi Garage Queen & prepping for repairs
2005 E320 CDI 203k mi Healthy & Daily Driver
1994 S350 357k mi Retried as parts car
1984 300TD 214k mi Blown OM617 Poss OM603 Swap??

Sold
1987 300SDL 200K+
1994 S320 181K mi
2008 E320 Bluetec 127k mi
1999 S420 130K mi
1980 240D 360k mi
15+ Others that has come, stay and gone

GONE, BUT NOT FORGOTTEN
1995 E320 SE 220k mi
1984 300SD 350k mi

My tranny wrench says that, although stuff like that will sometimes fix a leak by swelling seals, it also can attack the glue that attaches the friction materials to the metal disks in the clutch packs. He recommends against it.

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

I just change my fluid and filter once a year with a good quality fluid like Valvoline Dexron VI Synthetic....it runs great with it.

Generally those "fixit" fluids cause many more problems than they solve.

__________________
-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 think it can be helpful in the following circumstance:

When you're going to change the fluids thoroughly, add a can the day before. It CAN help reduce sludge and gum buildup on the inside of a transmission. Whether or not this is a good thing for an old transmission is open to interpretation. But if you've got one on its last legs, or you don't know the last time the fluids have been changed, I say go for it.

Leaving a can in there... I don't want that stuff acting long term on the seals.

Running a good synthetic fluid on a good cycle will clean out more than a quick shot of Trans-X.....as has been mentioned it can harm the glues in the friction materials....not a good thing. I'd not use it.

__________________
-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)