Makita cordless drill - slider switch problem

[shd1970]

I have a Makita cordless drill (8391D) which has a slider switch on the top (position 1 for screws and position 2 for drilling)
When its in position 2 and drilling a hole down, it has a really annoying habit of the slider switch slips forward a fraction and the drill disengages

Anyone else had a similar problem and is this slider switch (or whatever the slider is engaging) replaceable please ?

TIA

 

[rsgaz]

That sounds like the teeth in the gearbox are fuggered.

It will be an expensive part to replace, so if your batteries, charger and case are still in good nick, then just buy a new naked/bare drill...

https://www.ebay.co.uk/itm/142911431379

 

[shd1970]

That sounds like the teeth in the gearbox are fuggered.

Thanks for the reply
Any way that i can check that by taking it apart ?

As i say, the slider literally only shifts 5mm forwards but whatever happens inside, is enough to stop it spinning
Move it back fully into the number 2 position and its perfectly fine

Other than that, its perfect and its not had a particularly hard life, only DIY

 

[rsgaz]

Any way that i can check that by taking it apart ?

Yeah, just watch some videos on drill dismantling first if you've never done it... (particularly chuck removal)

Under the speed selector, you should find two springs like in Marius' video. Maybe a stronger spring in one of the directions could fudge it together and make it stay, if you didn't want to fork out for a new drill. But ultimately, the gears are almost definitely the root of the problem.

 

[rsgaz]

Oh, and if you've never dealt with circlips before...

...enjoy the part where it pings off at 100mph and hits you in the eyeball or ends up in the neighbour's garden!!
(i.e. buy some circlip pliers!! )

 

[shd1970]

thanks again rsgaz

10:40 of that video seem to show the springs on the underside of the switch which i am guessing are what hold it in place and may have weakened...perhaps ?

 

[SammyInnit]

If you're not the sort of person who's into re-building drill gear boxes, I wouldn't reccomend it at all. As I remeber it was a common problem after a while with this model drill. Used to tape up the gear selector on one setting or the other.

A problem I've noticed on other makita drills I've taken apart, the case screws for the gear housing can come loose, which causes play within the planetary gearing, in-turn causing slop when selecting the outer ring, checking those are done up tight would be something worth while.

I'd also try engaging one of the two settings while the drill is running at a low RPM, it might be a case of slop causing the outer rings and inner gearing to be out of alignment.

As rsgaz said though, it could just be easier to buy a new body - that said being the old makita Nicads, they don't last forever either.

 

[mattylad]

We have several Makita drills where the chuck wobbles because we also use them with carbide bits in to grind/smooth 20mm drilled hole edges, so this is quite interesting to me.
Where would be the best place to obtain replacement parts from?