Any tips for 915 gearbox end cover swap

[deano]

Hello (again),

Todays job was supposed to be swapping my 915 gearbox end cover, but I noticed that one of the four mounting studs was missing (thread is OK).

In any case, I thought it better to pause and ask for advice before cracking her open..... Haynes manual is not very useful for this job.

Any advice from those with experience would be appreciated. Engine gearbox are sitting on the floor on a dolly.

As you can see, the speedo bits are already installed inside the replacement cover (in good condition, but sounds like it has dirt in it when turned).

Where is the best place to drain the gearbox oil from - the main drain plug or the reverse light hole?

I am thinking, the first thing to do is to remove the reverse light switch and catch the oil.
Then, unbolt and release the cover, and slide it off the shift rod - will anything pop out, does anyone know?
How about when putting on the replacement cover, will it be obvious how everything engages?
I have a new shift rod seal - should that go on after the end cover is installed or before?

Thank in advice for any advice you can share

[deano]

This is my current gearbox end, with broken speedo cable housing (bottom left). Not sure what the top right plug is for.... any function, or just a plug?

[911hillclimber]

Ask Gary71
He did his box not so long ago.

[Gary71]

As you can see, the speedo bits are already installed inside the replacement cover (in good condition, but sounds like it has dirt in it when turned).

I’d take it all apart and clean it if it sounds gritty, as a minimum blast it with brake cleaner then put some oil on it until it feels ok.

Where is the best place to drain the gearbox oil from - the main drain plug or the reverse light hole?

I am thinking, the first thing to do is to remove the reverse light switch and catch the oil.

Main drain plug, but unless you need to change the oil just jack up the engine/box on some wooden blocks so it’s sitting at an angle. Oil will then (mainly!) stay inside the box.

Then, unbolt and release the cover, and slide it off the shift rod - will anything pop out, does anyone know?

Should just slide off, but may need a little (careful) tap to loosen the gasket. Keep an eye out for a little chromed rod that actuates the reverse light switch, this can fall out easily.

How about when putting on the replacement cover, will it be obvious how everything engages?

Should just slide back on. Watch that little rod though.

I have a new shift rod seal - should that go on after the end cover is installed or before?

Before

Good luck!

[deano]

Brilliant, thanks Gary! I don't see any obvious circlips or anything holding the speedo gear, so will blast with brake cleaner as you suggested. I have a feeling that it will be quite audible otherwise...

[Gary71]

It does come out, but I honestly can’t remember how!

[deano]

Sorry, more stoopid novice questions.

The old front gearbox end cover is now is removed and the old gasket is removed from the face (grrrr!).

Only about 1 litre of oil came out, even after tilting it about 5 deg. The book states 3 litres, so there might be 2 litres left in there - is this possible if the end cover is off?

What am I missing - there only appears to be a fill plug, about half way up on the side, but no drain plug? How is the gearbox oil normally drained on the 915?

The gear oil is quite expensive - it would be a shame to buy 3 litres and then to find that it only needs one litre

Any suggestions please from those with experience?

Thank you!!!!

[Gary71]

Here’s a pic:

[911hillclimber]

Both side and bottom plugs are tapered threads and can be VERY tight and are cast iron originally.

Make sure you can free the side fill first and if ok then the bottom plug which should be magnetic to catch any ferros 'debris'.

[deano]

How embarrassing, I only looked as far as the gear housing . That would be fun - its on a dolly, close to the floor.

Perhaps best to just top it up to the fill plug for now, and swap it at a later date....

Thanks guys, you can let go of my hand now

The 51 year old gears look like new!

[deano]

The replacement end cover doesn't seem to want to go on, at least not willingly

[Gary71]

Gentle wiggle and make sure the speedo gear, end of the 5th/reverse shift rod and reverse switch rod are all lined up.

It’s a fiddle but shouldn’t fight too hard, when nearly on there are also the little dowels top and bottom for the last 10mm or so.

Best of luck

[deano]

I had to remove the cover and rotate the shift rod a little bit, as it was holding the cover down a bit too low.

The cover slipped on easily once the rod was in a good position.

All back together now, thanks for the excellent help!