I have been chasing down a transmission leak for months now on my 85' 240DL. I spent a week in September replacing the tail shaft bushing, bearing and gasket. Spent most of my time chipping away at the Ol 'gasket. Thought that was the issue but discovered another leak coming from the speedometer housing, so...went to pick n pull and got a replacement. Still leaking...I have cleaned up under the car to try to trace the leak. It is losing quite a bit of fluid. The drips seem to be focused on the passenger side of the transmission and the speedometer cable is soaked, however cannot see and leaks around the speedometer housing. Would love any suggestions/

 

Here's a list of I would replace during a transmission reseal. Common leaks would come from the bell housing orings - oil collects and run down the pan gasket area and you think it's the pan leaking. The cooler line fittings have an oring on the end, inside the trans, and those leak as well as the selector shaft seals. Not on the list is the oring on the kickdown cable. You have to remove the trans to replace the front pump oring and the bellhousing orings.

 

Thank you for the advice. I truly hope it is not all those seals. I just was checking on her again, it seems to be leaking when just sitting, and the drips are under the passenger side. Would you advise using a UV fluorescent dye to track down the leak?

 

This worked for me, on a transmission leak and an engine oil leak. Worth trying a $10 fix before a very expensive transmission rebuild.

 

Still working on solving this leak. I believe that it was coming from the speedometer gear box located passenger side in the rear of the transmission. The leak is coming from there and seeping into the speedometer cable. The speedometer cable had cracks from which the oil was leaking from, hence me theory. However, everything I have read indicates that transmision fluid should not be seeping out of the gear box. I replaced the barrel of the gear box with one from the junk yard, has a new O-ring and well as the other tiny seal that is on the end. And have replaced the speedometer cable once again, but now the odometer is not working. I will check both ends to make sure the cable rotates and is not kinked somewhere. If anyone has replaced a speedometer drive before, is there another o-ring on the inside of the barrel sleeve, what advice does anyone have. I have attached a diagram of what the speedometer gearbox looks like.

 

If the speedometer works and the odometer does not - the cable is ok, it's spinning, Commonly a plastic gear cracks/breaks in the speedo preventing the odometer from moving.