Lessons Learned Changing Transmission FluidToolsRatchet wrench
Socket, 19mm
Socket, 10mm
Socket, 13mm
Open ended wrench, 19mm
Philips Head Screwdriver
Chamois / Leather cloth (I used paper but leather would be a better idea)
MaterialsHeavy duty plastic sheet
Shallow container for catching used ATF
Lint free towels
Funnel with a small tip
1 gallon of ATF (I used Valvoline Dex/Merc Max Life Fluid - came in a red bottle at AutoZone)
Meyle transmission service kit (I purchased mine from MercedesSource.com). It includes a new pan gasket, three washers, and a new transmission filter.
Preparation Work1. Place chocks on back wheels.
2. Put parking brake on the vehicle.
3. Jack the vehicle up via the chassis bit behind the oil pan - I wanted a good amount of space to work under the car.
4. Place jack stands under the vehicle to secure it.
5. Remove the jack.
6. Place a large sheet of heavy plastic under the car. This is a messy job and I didn’t want to ruin the driveway.
I used Diesel Giant’s write up on changing Mercedes transmission fluid as a resource and, although it was helpful, it wasn't a true apples to apple comparison for my 300SD.
http://www.dieselgiant.com/mercedestransmissionfluidchange.htmThe 1980 300SD only has four bolts holding on the pan and 2 screws holding in the filter (Diesel Giant’s pan had six bolts and 3 filter cover screws).
I placed the shallow container under the pan to catch the used ATF and then used the ratchet with a 19mm socket to remove the banjo bolt from the transmission pan. It was a mistake to use the ratchet because when the ATF came out, it spilled all the way into the socket and I had to spend a lot of time cleaning it before I could use it again. I would recommend using an open-ended wrench to loosen the banjo bolt.
After dropping the transmission pan and getting all the ATF into the container, I gave it a good cleaning using de-greaser, water and a soft brush. MAKE SURE THIS IS CLEAN! Diesel Giant had his pan dry in the sun for 30 minute prior to re-installation. I did the same thing but was worried about small microscopic particles getting in the pan that I couldn’t see. Next time I’d take a blow dryer and dry it out just prior to re-installation.
DON’T USE ANYTHING TO DRY THE PAN THAT MAY LEAVE LINT OR OTHER PARTICLES. It needs to be spotless!
After I cleaned the pan I cleaned the fasteners that secure the pan with some degreaser.
After letting as much ATF drip from the filter as possible, I loosened the two phillips head screws to drop the filter. Just when you think there isn’t any more ATF fluid…there is more so keep that shallow container handy for this step.
Don’t waste much time getting that new filter on there - the more time it’s off, the more time contaminates can get into your transmission.
After getting the new filter installed, I re-installed the pan. Be careful not to over-tighten at this stage. I took my time and tightened one faster on one side, then went to the other side to tighten that one, then back again. It’s best to tighten things like this in as much of a star pattern as you can.
Even though the Meyle kit contained three washers, I only ended up using two because I couldn’t find anywhere the third (slightly smaller) washer would go - hopefully I didn’t screw up anything there.
The two washers I did replace were on either side of the banjo bolt and the fitting. It was difficult to remove the old washer from the banjo bolt. (I tightened the banjo bolt using the open ended 19mm wrench but when I went to put ATF in, it was leaking a little and I had to use a ratchet wrench to get enough torque to tighten it properly.)
After tightening the pan and the banjo bolt, replace the jack under the car’s chassis, remove the wheel chocks and jack stands and gently lower the car to the ground.
Procedure for Re-Filling Transmission Fluid1. Locate your transmission fluid dip stick and remove. Place it somewhere where it won’t become contaminated with lint or anything else.
2. Using a funnel, pour about three quarts of transmission fluid down the dipstick opening.
3. Turn the car on and slowly pour a little more transmission fluid in the reservoir. Wait for the vehicle to get up to operating temperature (80-90 degrees celsius)
4. According to the Mercedes manual for the 300SD, the oil level is correct if, with the transmission at operating temperature, the oil level is at the max mark.
Tips on Re-Filling Transmission FluidGo slowly. It took a while for my engine to reach operating temperature. Even when it did finally reach operating temperature (which for me is close to 90 degrees celsius) and the oil level was finally sitting at the max line, I sat in the driveway and slowly moved through the gears with my foot on the brake pedal. I took about five to ten seconds before switching it to the next gear and made it back to park. The level seemed steady at max and I took her for a short drive around the neighborhood. When I got back, I checked the level again and now the level was sitting a little bit above the max level so I need to drain off some excess fluid before I drive her again. The whole process is kind of a pain but I’d rather do it right than deal with a damaged transmission.
Pictures Here: https://imgur.com/a/452NOIBPersonal ObservationsFluid was definitely on the darker side but it wasn’t burnt smelling and there weren’t any particles in the drop pan - comforting. Both before and after the transmission fluid change my car slips out of gear from a standstill unless I’m coming directly out of park. A shame and my search for a solution persists. Details found here and copied / pasted below:
https://forum.w116.org/mechanicals/question-about-shifting-problems-with-my-300sd/msg139940/#msg139940 I'm trying to diagnose an issue I'm having during shifting.
It doesn't seem like a serious issue and I've found a workaround but I'd like to get everything running well *without* applying my workaround.
The issue: If I start the car, put it in 'D', and drive she shifts fine. When I stop at a stop light or stop sign and put my foot on the brake long enough to come to a complete stop and then press the accelerator pedal it seems like the transmission slips. It feels like she's starting in 2nd gear but not really - there is a total lack of power. My workaround is that whenever I come to a complete stop I move the shifter from 'D' to neutral and then back again into 'D' and then proceed to drive with no issues.
Any ideas? Is it a vacuum issue? Throttle lingage issue? I just want to know what I should tackle first because it seems like adjusting the transmission shift points is a big deal. Also, I checked my transmission fluid and it seems like it's at the proper level although it looks a little dirty. I'll probably end up changing it and the filter soon but I don't know if this would actually have anything to do with the issue I'm experiencing.