2001 Mercedes C-Class Gearbox Oil Change

2001 Mercedes C-Class Gearbox Oil Change

By Lawnmower | Bootstrap Automotive | 27 Sep 2021

Some more work undertaken today, the Mercedes received a gearbox oil change, probably for the first time in its history.

Getting the car up in the air was a piece of cake with my new lift from CJ Autos. This is a tilting lift with worm drive gearboxes and is apparently capable of lifting 2 tonnes. Its a brilliant bit of kit for a home/DIY mechanic as it folds almost flat for easy storage, is relatively portable at about 40kg and gives great access. At full lift it will raise a car nearly 90cm at the pivot point, but if you are only lifting one end with the lift in the middle, the nose or tail can be much higher up. The only small fly in the ointment was that while the lift pads easily clear the sills when its fully 'down' it is still about 2cm too high to clear the catalytic converter on my Mercedes, so you have to slide the lift in halfway, jack the front of the car up a bit then slide it all the way across. however once in and lifted access is really good.

I undid both undertrays to get at the gearbox which feels like its a long way back - it must be about level with the front seats at a guess? Anyway, I had to have a furkle about to find the fill plug. With gearboxes I was always told that you MUST undo the fill plug first, because if you undo the drain plug then discover the fill plug isn't coming out you're stuffed with a gearbox empty of oil and no means to refill it. The fill plug came undone with a 18" bar with a 14mm hex drive on the end with minimal fuss, the drain plug on the other hand was no at all keen to release its death-grip. it takes a 17mm hex drive bit and with as much heaving and grunting as I could muster with the 18" bar it wasn't letting go. Luckily I had my Clarke mains impact gun to hand which rattled it out with ease, I think it had just seized itself into place over the last 20 years as the threads were quite clean once it came out.

The contents of the gearbox were stinky and very black, suggesting it was old, if not original.


The drain plug has a magnet in it to catch swarf and metal filings and things, and the outlook wasn't that great


Lots of shiny bits is rarely a good sign, but they were all small slivers so maybe sort of ok? A seeing to with my trusty inspection magnet and some carb cleaner and a rag had it looking better


Next job was to work out how much gearbox oil had been removed. The received wisdom is that these were filled with 1.8 litres from the factory, subsequently it was discovered that the gearshift was a bit poor and Mercedes best solution was that on refill, just add 300ml less oil. So, step one, assemble some professionally calibrated measuring devices


The cream soda bottle is 1 litre, the fizzy water bottle and sprite bottle are 500ml each. I used an old funnel to direct the contents of the washing up bowl into the bottles


I make that about 1750ml. The cream soda and sprite bottles are full, and the fizzy water bottle is about half full. there will have been some left in the gearbox and my measurements will be slightly off but thats all I needed to know. I had bought 2 bottles of Redline MTL gear oil from ebay, because its American it came in 946ml (1 quart) bottles


I used a bit of clean hose with the funnel from earlier, slid down the side of the cylinderhead and into the fill hole. I had replaced the drain plug by this point, making sure to use a dab of gear oil on the threads and not tighten it up too much. This worked pretty well


I poured all of one bottle in slowly, checking to make sure the hose hadn't fallen out of the fill hole and it wasn't dribbling expensive oil all over my garage floor. Mercifully it was fine. The next step was to use a syringe and some thin hose to remove 550ml from the other (full) bottle of MTL


I have some big 60ml syringes so just drew off 11 lots of 50ml and put it into the empty bottle that I'd used first, then added this slowly to the funnel arrangement. Accounting for oil left stuck to the inside of the bottle I make this about 1500ml, probably more like 1550ml including the remaining contents of the gearbox.

I did the fill plug back up, having whipped the hose and funnel out the top, wiped it all down with a rag as best I could, refitted the undertrays, lowered the car back down, jacked it back up so I could side the lift out under the cat, withdrew the lift, lowered it back off the jack, shut the bonnet and then started it up. No horrible noises, no puddle of gear oil.

I took it out for a run around. 2nd has always been a bit iffy, crunching if you try and rush it from cold. With the new gear oil it was better, but still not to be rushed. Since the car is by no means a ball of fire, this isn't too much of a problem - its certainly better, especially once the gearbox oil has warmed up, but its not transformed the car. Still, its one more life-extending job on the old girl. If this oil lasts another 112k miles and 20 years I'll be happy. The Redline MTL seems to be recommended by a lot of MB forum bods - who all seem to be in the USA - along with Royal Purple which was quite a bit more expensive. I think the total cost of this was under £20 which isn't bad.

The job was actually quite a bit harder on a RWD car than when I have done the same on a FWD one as the gearbox is so far back, but once I'd banished mental images of the lift collapsing and crushing me to death under 1500kg of Mercedes it was actually fine.

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Bootstrap Automotive
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