Transmission just started leaking badly
 

I suspected a leak after noticing a tiny puddle under my 300SD in a parking garage last night. I placed cardboard under the car when I got home, and this morning there was a lot of ATF on the cardboard, the puddle was maybe 4" x 2". This transmission has over 250K on it and I know that it will need to be resealed and possibly overhauled because it takes a full second to engage into R or D . The transmission shifts flawlessly, so getting it rebuilt seems a little premature. I have another transmission sitting in my garage that used to work very well until I tried to change the front seal on it. Afterwards, the car wouldn't shift out of first. I definitely need to go to a pro this time around.

Is there an additive that someone could recommend that might buy me a little time. I serviced the transmission 20k miles ago and I know that the pan gasket is not the issue. The leak appears to be coming from underneath the bell housing, so I'm assuming that it the front seal.

Trans X.
Read instructions as to initial amount... my wagon took two cans...$16 total at the time...
run that a few hundred miles... then switch to half that amount forever...
check my name in archives for my experience with it....
Naturally you want to put in new fluid and new filters if you have any....

Thanks. I've used trans x in the past, wasn't sure if Lucus was any better.

How would one compare the two ?

Have you been able to ascertain the location of the transmission leak? I've never had any trouble with the AT transmissions on 6 MB diesels going back to 1969. One leak @ the sending-unit of my W210. But it never created a trans. performance problem.





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I would suspect the leak is likely from the transmission cooler lines. Check thoroughly the clamps that hold the hard line portion. If the rubber is thin or missing from the line clamp, you are likely to have metal-to-metal wearing to the point it seeps through the wall of the tubing.

Some folks have had luck clamping a split hose over the area. However, I wasn't so lucky when this happened to mine and had to change out the hard line. They were ~$25 when I did this a few years back.

I'll be replacing my pads and rotors tomorrow, so I'll have the car high enough to check the cooler lines and clean the area really well. I'll be very happy if it's just a cooler line.

One other thing; I just had my car parked for a couple of hours on an incline and there's no sign of the leak on the driveway. Last night it was parked with the nose towards the street on a decline and it leaked a lot. What does that tell you?

I recently had the same issue decribed by SDBlue with my W126 - one of the the clamps that holds a transmission cooler hard line had lost its rubber bushing so there was metal-to-metal contact that wore a hole through the hard line. I used a dremel cutoff to make a clean cut of the line and spliced in a small piece of hydraulic hose with clamps. So far it has not been leaking.

Nothing definitive, until you can get it on a rack to ascertain and source the ATF fluid leak.











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Could be a front pump seal; my '96 E300D (722.4) had such a leak at 250,000 miles. Not much you can do except replace the seal.

I've heard that "miracle" cures like Trans-X can damage clutches by attacking the glue that holds them together. In fairness, that was from a transmission rebuilding shop (although a good one) that obviously has a vested interest in folks not using Trans-X.

Jeremy

I agree with the other member that said locate the source of the leak.

As an example if it was leaking where the Dipstick gots into the Transmission Housing that would not be a cause for a rebuild. Same if the Leak is at the B2 Piston Plate Seal/O-ring.

Some of the Older Transmissions have an exterior Blot to adjust the Brake Band that is used during reverse. Some have the Blot but it was made so it would shear off and there is no Blot Head. Some have gotten that sheared off Bolt out and replaced it with a regular Bolt.

Stretch knows a lot about the older Transmissions.

I got a good look at the transmission when I had the car up for the brake job today. The cooler lines were dry and a couple of pan bolts had ATF on them, so the gasket might be starting to go. There was also fluid at the bell housing.

I dried everything off, took it for a short drive, then parked it for several hours. To my dismay, the only spot where there was ATF was right below the torque converter which leads me to believe that the front seal is going. I'll use some Trans X and hope that it swells that seal a little bit. I'll also make sure to park the car on an incline in the driveway since it doesn't seem to leak that much in that position.

Wrong and unfair post. Plenty of people here on the forum with experience with Trans=X and similar fluids. Not fair to put them into ' miracle ' snake oil category when the way they work is straight forward... it swells the seal.
I have posted my experience with it from as far back as forty years ago... I only used it because a trusted family friend and mechanic recommended it at that time...
There is no evidence of damage to anything inside....... and it is an inexpensive possibly helpful first thing which can be tried...like $20.

Search YouTube. There is a video from one of the normal sources showing typical leaks causes and what's required to repair.