The Triumph Dolomite Club - Discussion Forum

After having placed this topic on the Facebook sit and not having any specific responses I thought I'd post it here to see if anyone is able to give me some info.

I want to know what the third hole in the Sprint rear hub is for. There are three - two are threaded for the brake drum retaining screws but the third - which is sited just on the ridge in the pic - anyone know if this is a drain hole for when the oil seeps out of the hub or is it for another purpose?

Cheers peeps.

As I'm in the middle of refurbing an axle I've just had a look. Unfortunately I have no idea why it's there.

Looks like the sort of hole oil would leak out of.

Thanks Mart.

Thanks Steve. My thoughts too. Looking through the 'third' hole the hidden face of the hub flange can be seen when the half shaft is rotated which, to me, suggests that if it is blocked up then any oil seeping through the bearing from a leaking axle oil seal will only seep out vua the brake plate - not into the brake drum.

Would need to see a cross section but it could be to allow atmospheric pressure behind the hub possibly to help the oil seal? Just a guess though.

I was wondering about that. I would have thought there would have been oil seals at the diff end of the axle tubes - to prevent any diff oil from running into the tubes (if the diff has been overfilled for example) which would then slop about in the tubes. Also, isn't there a sort of threaded vent plug fitted to the top right side of the diff casing for releasing pressure? Not sure otherwise what this little plug is for. But it's the question of whether to block up the 'third' hole in the hub flange that is troubling me.

You put a padlock through it to stop people driving off with your car!

The factory had to many in stock, so got rid of a few.

Tony.

Since what is in that part of the hub should be GREASE not oil, my hypothesis is that it's a breather hole so that more grease can be added to the hub bearing without pressurizing the GREASE seal on the inside face of the bearing.

To get axle oil here (and I did, once) the oil must defeat both the oil seal in the axle tube and the grease seal on the hub bearing, then somehow outwit gravity to get out through that level hole rather than down past the brake shoes. It CAN happen but it's quite rare and needs (I think) the axle tube oil seal to have been leaking quite badly for quite a while. In my own case, one of the drum retaining screws was missing and the oil came out through that too! But a new axle tube seal fixed it permanently.

As a subsidiary, I should think this hole would also protect against excessive greasing of the hub bearing, any excess grease would just get pushed out through the hole.

Steve

I am thinking it may be a jig location hole, to hold the flange while all the other holes are drilled and tapped.