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MG MGA - Oil fill plug, size

Hello All,
I thought I could use my 3/8 inch rachet to unscrew the filler plug on the 5 speed Sierra tranny,so I could fill with tranny oil, now that it is in place and level. Turns out though the square hole is just too small for a 3/8 driver to insert into. The 1/8 inch driver is not large enough.
Does anyone know of a simple alternative to do this? Or will need to grind down a cheap 3/8 inch rachet to fit and if so what is the size I need to reduce it down to?

Ray Ammeter

Ray. I have done this type of thing for a number of applications. What I do is to find out the required size by measuring the hole using a set of dial calipers. Then, I take a short, hex head bolt of about the diameter of the cross ways measurement and mill/file/grind flats on it, test fitting until it can be inserted to the full depth. Chamfering the front of the bolt (just run a file across it to break the sharp edges) will allow it to be inserted more fully.

Then, use the proper sized socket for the bolt head, insert the bolt into the hole and turn it out/turn it in as necessary.

Les Bengtson

Ray, I'm pretty sure the oil filler plug on my gearbox had a hex hole. I remember using a metic allen key to loosen and tighten it. 10mm seems to ring a bell.
Andy Bounsall

Thanks Les and Andy,
Andy you were right. Once I got a better a pair of eyeglasses and more light to measure the hole I saw I needed a big allen wrench to fit the hole. I got it out, filled the tranny with oil making it one step closer to getting it back on the road.
I got to admit, I'd been looking at that 5 speed tranny for months sitting in my spare bedroom and never gave it much thought to what I needed to unscrew the filler plug.

Ray Ammeter

This thread was discussed between 21/07/2008 and 22/07/2008

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