1989 300 SEL TRANSMISSION REAR PUMP - PeachParts Mercedes-Benz Forum

benjira · #1 08-17-2009, 04:33 PM

Hello Group
Looking for a leak today, I thought was coming from the transmission pan.I noticed that the leak was coming from the pump right above the pan (on the right side looking towards the front of the engine)How hard of a fix is this?And can just replace the seals?Any assistance would be appreciated. I looked on the CDROM and can not find a transmission section.

Thanks
BB

pawoSD · #2 08-17-2009, 05:34 PM

The rear pump is inside the rear housing piece of the trans. It may be that the gasket on that rear piece is leaking....to replace it you'd have to disconnect the driveshaft/remove the flex disc, undo the nut holding on the output flange, then support the transmission from the pan, remove the cross beam and trans mount, unplug the kickdown solenoid and remove the speedometer sensor (one small bolt).....then undo the number of bolts holding on the rear cover (drain all fluid from pan plug first!!) Once the cover is removed, replace the gasket, make sure the surface is clean, install new gasket, place cover back on trans, tighten all bolts to 14-18nm or so....and then re-install everything else. A new flange nut is required and must be dented into the locking slot to prevent it from coming loose. Its a good opportunity to replace the rear output seal too before you install the flange.

benjira · #3 08-17-2009, 11:59 PM

I cant do this without taking off the flex disk?

pawoSD · #4 08-18-2009, 12:07 AM

Quote:

Originally Posted by benjira

I cant do this without taking off the flex disk?

If it is the rear cover gasket leaking, the flex disc, output flange, and other stuff I mentioned must all come off. Its really not that bad of a job, just time consuming.

A few pics from when I did it:

benjira · #5 08-18-2009, 12:41 AM

The leak is coming from here.

pawoSD · #6 08-18-2009, 02:08 AM

Quote:

Originally Posted by benjira

The leak is coming from here.

That is indeed the rear pump cover....it has a simple rubber o-ring in there....however, I am not sure if the cover can just be removed, o-ring replaced, and cover reinstalled.....I'm sure others will know....

I circled the item you are looking it in this pic of a schematic.... you can easily see the o-ring in question:

rs899 · #7 08-18-2009, 06:31 AM

Just take the 3 small nuts you can see off. The pump assembly should come off.

benjira · #8 08-18-2009, 01:28 PM

do I have to drain the fluid to do this?

rs899 · #9 08-18-2009, 01:33 PM

No- the fluid should be below the rear pump. But , I would jack that side of the car up just to be sure

benjira · #10 08-19-2009, 02:26 PM

Okay I am about to try and take the assembly off,are there any surprises that await me once I do this?Is there enough clearance to get the piece off?It is never as easy as it looks.Any idea what size hex head those are?

lbackusmb · #11 08-21-2009, 04:06 PM

Hey pawoSD - that's the first schematic I've ever seen that was clear. Do you have one for an 84 300SD you could post that includes the legend for the parts. thanks

pawoSD · #12 08-21-2009, 06:39 PM

Quote:

Originally Posted by lbackusmb

Hey pawoSD - that's the first schematic I've ever seen that was clear. Do you have one for an 84 300SD you could post that includes the legend for the parts. thanks

I have a much less detailed one with a legend, but I don't have one like the picture I posted with a parts legend....as you can see in the image, that was page 2 of 2 for that pdf.....the first page has similar details about the other gear sets/drums.....no parts legend aside from what it shows.