My tranny has developed a leak which is coming from a (valve,modulator) on the rear passenger side. Can someone give me some help to identify what this part on the tranny is. Someone has suggested this area of the tranny is related to the overdrive. ???? Just want ot learn a little before I take the car to my mechanic. The vehical is a '88 300E. Thanks

Marks88

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'88 300 sold
'83 300cd

You should check out lino's recent B2 piston thread - it has some good pictures, and tips on how to access the passenger side of the transmission. The first step is to really clean it up, get a flashlight and mirror, and figure out where it's leaking.

The black plastic part which has a wire pluged into it on the rear of the transmission is the kickdown solenoid. Just forward of that solenoid on the side of the trans is the rear pump. It is not difficult to replace the seals, just watch for falling parts when you remove it.
Next toward the front is the B2 piston (I think). I haven't had that part off yet, so I can't help with it, but I'm sure that resealing it wouldn't be hard.
Back to the rear pump. It usually leaks at the round cover that is held in with a snap ring. Inside there is a spring and a piston. It can be very difficult to get the cover back in as the spring is very strong. Put the o-ring in the housing first, followed by the spring, the the little spring seat and then the cover. Press in the cover and hold while putting in the snap ring. It helps greatly to have a helper as it takes atleast 3 hands. There are an oil cooler line on that side of the trans which could also leak. Also check the dipstick tube seal.

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84 500 SEL (307,xxx miles)

pmckechnie,

Thanks for the info. I found use of a car lift and was able to run the motor and watch a very steady drip coming from "this kick down solenid". There wasn't any black plastic part or wire. It kinda looks like something has hit up against the transmission. I found what looks like epoxy on the solenoid area. I have had this vehicle for 4 years and never any trouble from the tranny. I'll have to take the car to my mechanic for a closer look.

Marks88

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'88 300 sold
'83 300cd