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Old 04-02-2012, 11:08 PM
Registered User
Join Date: Mar 2011
Posts: 3
wierd transmsission leak

i have a 1987 mercedes 300d with about 330k on it. i have been having problems with transmission leaking fluid. i first found the fluid leaking from the rear extended housing, so i changed the gasket and solved the problem. shortly after it started pouring fluid out again and found it to be leaking around the output shaft seal. i changed the rear seal(output shaft) filled the fluid let the vehicle idle with fluid fill and it did not leak. took it for a drive came back home and checked the fluid it wasnt reading on the dipstick. i added a quart and looked underneath the car and it was just pouring out. the rear extended housing should not have alot of pressure to force large amounts of fluid out of that rear seal. could the breather be clogged causing too much pressure internally which in turn would force fluid to find the easist way out which would be that rear seal on the output shaft. i dont know what could cause the fluid to pour out like that. i really need some help with this. any help would be greatly appreciated.
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Old 04-03-2012, 02:53 AM
Stretch's Avatar
Gettin' outa chokey
Join Date: Sep 2009
Location: Between a rock and a hard place (Back in Holland at the moment)
Posts: 13,986
Welcome to the forum coldbillie - you'd have done better by posting this in the diesel discussion. PM a moderator and I'm sure they'll move the thread for you to where others can help you better. (Send a PM to vstech for example)

As for your problem =>

There's a lot of "high pressure" (compared with the pressure at other parts in the transmission) things going on at the back of the transmission.

Close to the rear end of the transmission there is a governor which controls when the transmission shifts. On the opposite side of the governor there's a secondary pump This one works when the output shaft is turning. It sounds like this is the part that is leaking 'cos it didn't leak when you checked the car at a standstill but it did leak when you drove it.

Check the secondary pump housing - you'll find it on the right hand side of the transmission. (This forum generally uses the convention of right hand side meaning the side when you are sitting in the car in a normal position looking out the front windscreen)

There's a break down of the parts for a 722.3 / 722.4 transmission here,%20722.4.pdf
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!

Don't leave that there - I'll take it to bits!
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Old 04-04-2012, 04:15 PM
davidlee's Avatar
Join Date: Mar 2012
Location: Portland OR
Posts: 548
Hows it going, I have a 87 300D and had the same leak you speak of (didnt see leaking in park, but slowly leaked in gear and moving ), Its most likely the secondary pump seal on the rear pass. side of the trans, its a round cover, I had it replaced and my leak stopped
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Old 04-08-2012, 09:30 PM
Registered User
Join Date: Mar 2011
Posts: 3
thank you very much for your answer. i thought i had posted it in the diesel discussion. newby mistake. i found a used transmission for $500 and put it in, it works great. when i get some time i will pull that secondary pump and inspect it to see if it was the culprit of my leaking problem. once again thanks for your response, it helped me tremendously.
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Old 04-08-2012, 09:33 PM
Registered User
Join Date: Mar 2011
Posts: 3
hey thanks for your response. i will check the pump and the pump seal when i get a chance. it is great information for the future if i should have these problems again or if i want to put the old transmission back in if the one i have fails. once again thanks for your assistance.
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