Technical what size allen key for the gearbox oil drain?

[smart51]

I have a gearbox oil leak, so I need to top it up. I know I need a 13mm square socket for the filler. What size allen key do I need for the drain? The biggest I have is 10mm which is way too small.

Edit to ask, what is a good thread sealant for the drain plug thread?

 

[fiat500]

I have a gearbox oil leak, so I need to top it up. I know I need a 13mm square socket for the filler. What size allen key do I need for the drain? The biggest I have is 10mm which is way too small.

Edit to ask, what is a good thread sealant for the drain plug thread?

I'm not home so can't check. But it is common to some later Fiats and I think it's 12mm.

 

[Goldnrust]

A nice little hack if you need a big Allen key for a one off job like that, is to find a bolt with the right head size to slide into the drain plug and lock two nuts off against each other on the bolt (Or even better weld the nut to the bolt) then you can just put a spanner on it.

That's how I got my gearbox drain plug out, sorry I can't remember the size off the top of my head though.

 

[smart51]

I have a 12mm hex socket now so can remove the gearbox drain. The filler plug is not moving though. I've tried a 13mm spanner with the other end on an axle stand and lowering the jack. The engine mount takes up all the movement. Does anyone know where I can get a 13mm square socket?

 

[smart51]

I can confirm that a 15mm 12 point socket will fit on a 13mm square pin. I can also confirm that my filler plug is not for turning. I'm very glad that I followed procedure and tried to remove the filler plug before draining the oil.

 

[the hobbler]

I can confirm that a 15mm 12 point socket will fit on a 13mm square pin. I can also confirm that my filler plug is not for turning. I'm very glad that I followed procedure and tried to remove the filler plug before draining the oil.

The method that I normally use to remove the gearbox filler/level plug is to use a short 1/2in drive extension THE WRONG WAY ROUND---you put the female end of the extension over the level/fillplug and then use a suitable socket on the male end. First time removal of these plugs is difficult as they are put in TIGHT! To the best of my knowledge, both drain and level/filler plug are "taper" plugs---you shouldn't need a sealant on them.
Due to the position of the filler/level plug, it is often very difficult to get any oil into it, so my dodge is to get a length of clear (so you can check the oil going down it) plastic tubing that will fit into the filler/level plug. Have this piping long enough that it can come up through the engine bay to a comfortable working height---fit a funnel to the end of the pipe in the engine bay. The gearbox is at its correct level when oil comes out of the filler hole.
If you have a '126' gearbox, you can use a good quality 20/50 engine oil---if you have a 500 gearbox, you use a SAE-90 oil

 

[smart51]

It is done! I used four 1/2" socket extenders to reach out beyond the brake drum, a set of mole grips and a length of steel pipe over the handle of the grips to get it out. 900ml of oil came out. I put a litre in and it just started to trickle out. Either the drip from the joint between the diff and gearbox is worse than it looks, or it wasn't full when I bought it. I'll keep an eye on it to check.

 

[smart51]

One test drive later and it shifts gears a lot better with the right amount of oil in it. I've left a clean oil pan underneath it to see how much drips out.

 

[Goldnrust]

Glad you’ve had some success

If you’ve not played with it, I also suggest checking the adjustment on the gear stick. There’s two 13mm head bolts on the right hand side of the transmission tunnel, you can loosen them and slide the base of the stick back and forth.

Even some small adjustments improved my shift quality. As far as I know, you should be aiming for a perfectly vertical gear stick when it’s in neautral.