OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Walk Behind Lawn Mower Frames Four Stroke Lawn Mower Frames Self Propelled Gearbox resealing

Got a self propelled mower i'm fixing up for myself (after temporarily stuffing my knee). Masport 19in alloy with IC briggs motor.

The thing I am stuck on (pun intended - read on) is the transmission. I have a spare trans which I pulled down. Its made by general transmission.
They are a sealed unit but being retentive I want to change the trans oil.

Have pulled the spare one open and have contacted General Transmission, who were very helpful and stated the transmission is filled with 50ml of 00 grease (easy) and is sealed with dowsil 732.

I can't for the life of me get this $%#^ing stuff off! Have soaked it in mineral spirits which vaguely helped but it is a nightmare. Compounded by the fact the gearbox is made of PA plastic (who knows what will melt it).


1 Does anyone know what will move dowsil 732 (dow recommend either Isopropyl alcohol, Mineral spirits, xylene or tolulene). By the time I buy the other 3 of those, I might as well go buy myself a $140 transmission.

2 I don't want to go through this again so I am going to drill and tap a drain and fill plug in a convenient location. Any recommendations for a tap size for PA plastic? Wall thickness is about 8mm.

G'day Tyler,

I mostly have just used WD40 and the really thick bristle nylon brush and sometimes a plastic scrapper or a wood ice cream stick.

A brass wire brush if you have the room to use the brush.

If you can find a thick bristle brush without the cleaning fluid connector it should be cheaper.

I see there is a WD 40 Degreaser ,it says recommended for plastics but I haven't tried it.

As far as I know some mower shops use Simple Green Pro HD and it's good for an Ultrasonic cleaner ,I think
Bunnings sell it but will cost a bit as you may have to buy 4 litres.

I'd just put 2 grease nipples into the plastic ,that way you can remove one when you use a grease gun on the other.

You could use a BSPT 1/8" - 28 grease nipple but you may not have a tap or a Metric M10 x 1.5mm Pitch.

Cheers
Max.

Thanks Max

I will give wd40 a go. have tried every scraper I have and it just won't touch it.

Have got taps so will give a 1.5 pitch a go

Thanks again

Ok, end result, the best thing I used was mineral spirits with a soft brass wire brush as Max suggested

Caution to anyone else doing these, the maximum you want to use is a M8x1.25 and even then you will need to grind the head down to clear the height adjuster bar.

1.25 max pitch as the wall thickness is closer to 5mm so 1.5 is too coarse to get a few threads tapped in properly

Mineral spirits sounds like a generic term rather than a specific chemical. Is It different to turps or the alcohol based methilated spirits?

White spirits or dry cleaning fluid are the other names I know it by. Close relative to paint thinner I believe

I think I've seen white spirits labelled on bottles in the paint section.