Oil feeding the layshaft
Turbo Mini Forums

Hello folks,

I have been looking at the possibility of pressure feeding the layshaft bearings with filtered oil.

It looks like it should be fairly simple to do, but is it worth it?

I have pulled an old A+ layshaft out of a box and drilled and tapped the oil ways 1/4"unf (the only tap to hand) it was pretty easy I was expecting the surface to be much harder than it was.

What do you reckon yay or nay?

Worse thing you can do is to over-feed it. I'd say nothing larger than a 1mm hole will do it

Really,

Whys that?

I was anticipating needing a restriction so it didn't pinch all the oil from the engine.

Obviously the bearings don't need much oil as the oil level is only just up to the hole when fully filled at stand still as stated by Hoggy, and as soon as the cogs turn and the engine pinches some the level will drop.

One other thought, We have all seen knackered layshafts (admitedly many are due to poor quality replacements) but I've not heard mention of the bearing surface in the layshaft getting chewed up.

well from what i have seen they do jack shit to to improve reliabilty in the layshaft and bearings, im not saying it isnt worth the etxtra hassel but to be honest you need to do both ends if you was going to do it. also any bit of crude which bypasses the filter can get led straight to the layshaft through gallery 8 ( i think) and will soon knacker the bearings any way.

best bet is to use old standard layshafts and replace bearings every 2 years on medium output motors or every year on high output motors eg 200 bannas plus.

always looking for them bigger bunches of bannanas

Gallery 8?

I presume thats the filter bypass valve?

I think miles are more important than years:)

All indications are that this should significantly improve the reliability - but the worse thing that can happen is to 'fill' the void between shaft and laygear cluster, with more flow than can escape - ie if you have 'pressure' in this cavity, then the bearings are over-oiled - basically they start to slide rather than roll.

In short - don't go overboard. a little oil is a 'better' scenario than too much oil, but I suspect most attempts at oil-feeding layshafts have been incorrectly done.

Thanks Dave,

That makes sense now, I get what you mean about the bearings, essentally they can start to "aquaplane" if thre's to much oil.

Part of the reason for thinking of doing this is the fact that I am on the old Pre A+ remote change box with the smaller bearing at the diff end, and was thinking of trying to give it a "helping hand"

I've done away with the oil filter bypass a feed from after the filter should give a nice clean feed to the bearings.

I'll see what pipe work i can arrange with 0.5-1mm restrictors.

mini13, any pics on you project would WELL be appreciated

Once I sort some fittings out I will mock it up on an old box and get some pickies.

The main issue is the fittings for the layshaft, 1/4" unf is really the biggest that you can make the thread due to the slot for the retaining plate.

Been busy the last couple of weeks so havent been able to give this much attention, I have some fittings now though, and a spare weekend as the missus is away (which tbh i should be spending wiring up my mk1)

I have had a couple of thoughts on on this though,

I could feed each end of the shaft, but in an effort to simplify the instalation there are two other alternatives,

feeding one end of the layshaft and blanking the other end, or feeding one end and leaving the other open or partially restricted, more to stop oil entering than stop it escaping.

Personally I think feeding the diff end (smallest bearing and more load as its at the 1st gear end?) and partially restricting the oposite end with a restrictor twice the size of the inlet restrictor is a good starting point.

One other thing I have notice while looking around at various gearbox instals is the switune/quaife dog kit has a/some hole drilled in the laygear to either let oil in or out

Drilling the laygear is a good idea - or if your name is matt woods, merely weakening the laygear further!

I have heard the swifty/quaife kits only have two bearings in the laygear though. Thought more was better on this matter?

Not neccesarilly. If thy dynamic capacity of the bearings is within the required duty, then that will be sufficient.
There is actuallly another issue - that of deflection of the layshaft or laygear which will reduce the life of the bearings significantly - maybe they have stiffer shaft assemblies which have less angular deflection and can take the higher load.
More is not neccesarilly better - a better design is better.

good point, I guess the laygear may be quite a bit stiffer than the standard item! But I think it uses standard layshafts.

swiftune also sell there own layshafts, I got one with my gear kit

Team Racing

yes, but they are of the same design as the standard items right?

i've started the same process on my box a couple of years back. I had intended to feed both ends of the layshaft with a restricted feed, i was thinking of about a .5mm hole in the middle of a plug in the pipe, but would certainly take note of mr gearbox's suggestions!

I've seen the future and tbh its Pie

Apologies or not having got pics up yet, I have been wiring in the ECU and stuff where ever possible, its getting there now honest!

However,

I have now finally got a pair of 0.5mm jets aranged in -3 fittings on the ends of the layshaft....

but whilst looking at looking at my gearkit and thinking it would be nice to also feed the mainshaft nose needle roller I realised that I can by putting another fitting and jet into the first motion shaft bearing on the transfer case.

I shall knock up this other jet at some point and get it fitted along with the others.