Gearbox Fluid Change
Although smart say this is a non servicable item, it would be foolish to use the same oil year in, year out. I recommended you change it every 3rd service. People have found the gearchange is much improved after doing this.
This page now covers the following:
Roadster (452) fortwo 451) Important Although the drain plugs are hard to get to, do not jack your smart up to access it. This will raise the fill hole and increase the capacity. If you really must jack it up, level the car by jacking the front up level with the back. Drive the car until it is at full operational temperature, this allows the fluid to warm up and therefore flow better from the casing. Undo the top drain plug first, there is 2 reasons for this:
It allows the fluid to flow out easily from the lower drain
If you take out the lower plug first and can't undo the top one because it is
seized or the head becomes damaged, you have no way to refill the transmission.
If you do the top plug first and you cannot open it, you have no problems,
you can sort it out in your own time.
Official Service Schedule For Gearbox Fluid
Smart's stance on this has always been the same. In their view, the transmission
fluid is a non service item and does not need changing for the entire life of the car.
It's not an oversight, this is what they have said in all of their cars since 1998.
They clearly don't have a clue and they should be ignored.
Evil's Recommended Service Schedule
Anything between 40 and 60 thousand miles will be fine.
Fortwo 450 and Roadster 452
Looking from the left side of the engine you will see the below image.
The red circle shows the drain and the green circle shows the fill up point.
Using an 8mm hexagon (allen) key, undo the fill up point.
Get a container and place it under the drain plug you are about to remove.
With an 8mm hexagon (allen) key, unscrew the plug anticlockwise.
Don't forget to catch a lot of it up your sleeve and let the
plug fall in the container so you have to fish it out later.
Because the drain point is the the lowest part, the fluid doesn't have to be pre-warmed although it helps. When all of the fluid has dripped out, replace the plug and tighten it up.
Smart's recommended torque for this fluid drain plug is 43.0Nm.
You have two options or a bit of both when refilling, if you have bought 2x
1 litre bottles you may have room to squirt it straight in.
If you have a single 2 litre bottle or bigger you probably won't have room.
Get a length of tube that will fit into the hole, open the engine lid and thread the pipe down
through the engine and place the end of the pipe into the hole in the transmission casing.
Attach a funnel to the other end of the pipe that emerges from the engine bay, you may
want to get creative with duct tape as the funnel tip probably won't fit in the tube.
I constructed a makeshift funnel from a lemonade bottle and duct tape.
Using an oil listed below, slowly fill the funnel. The fluid will run down the tube into
the transmission casing. Stop filling when it begines to overflow from the inlet hole.
When it overflows, the level is correct. Withdraw the tube, clean the area and fit the plug.
The transmission casing will take about 1.4 litres of fluid and it is sold in 2 litre bottles.
Smart's recommended torque for this fluid fill plug is 43.0Nm.
The transmission fluid change is similar to that of the older smart fortwo and Roadster.
The main difference is the position of the draining hole.
It is now on the right bottom side of the transmission housing.
The upper filling hole is on the left of the transmission housing about halfway up.
Remove the top plug, remove the bottom plug and allow the fluid to drain into a ming vase.
Ghengis Khan emailed me to say that any waterproof container would be suitable,
not just expensive treasures from the ming dynasty. I'll take his word for it.
Refit the lower plug and torque to 43Nm.
Refill as shown above until it begins to overflow. The capacity is 2.3 litres. Refit the upper plug.
The Fortwo and Roadster use the same gearbox casing so the fluid capacity is the same.
It is worth noting that the new smart fortwo (451) gearbox is much larger so takes more fluid.
The oil rating for gear oil is different to that of normal engine oil.
75W90 gear oil has the exact same viscosity of a 10W40 motor oil.
This doesn't mean you should use 10W40 motor oil but you could in an emergency.
Engine oil is a lubricant and transmission fluid is a hydraulic fluid with some lubricational properties.
Drain Or Fill Plug Is Seized
If the top filler plug is seized then I it's probably best just to leave it. If you absolutely have to
top up fluid that is leaking then try spraying it in penetrating lubricant like PlusGas, leave it for
a few hours and try again. Heating around the plug can aid in the removal. As a last resort you
can grind a slot into the plug and attempt to remove it with a hammer and an impact driver.
If you can remove the top plug but not the bottom plug then don't worry.
Instead of messing about attempting to remove the seized plug, simply leave it in.
Take the oil removing pump you use for servicing (Pela 6000 for example), push the flexible hose into the top hole and pump as much of the fluid out as you can.
You will be able to remove a large majority this way.
If you jack the front of the car up you will get more out as it pools nearer the back.
Once you are happy you got most of it out (you will be able to see the removed fluid capacity
on the side of the tank on the Pela 6000), use the top hole to refil as you would normally.