5 Speed box: Replacing the seals

[JonB]

HI all

Quick report on today's fun & games with the 5 speed box, with the objective of replacing the front and rear oil seals. I followed the procedure in the workshop manual, which meant removing the output shaft and casing for the rear seal, but the front seal was easier - you just unbolt the cover and replace the seal. There's a load of guff in the manual about choosing the right spacer for a 10 thou gap as the cover bears down on it and it in turn holds the input shaft bearing down, but I thought I'd just go with what I have. Risky, I know.

Both covers need to be refitted with new gaskets smeared with Wellseal (an ancient and holy rite for Lotus owners, accompanied by a muttered prayer to the Lotus gods). Wellseal is odd stuff. Sold in toothpaste tubes yet runs like snot and sticks like snot. Fortunately I'd already made the rookie Wellseal mistakes while working on the differential pinion, so knew what to expect.

Every bolt needs to be smeared with RTV sealant ("instant gasket") or they'll leak oil. Which I am trying to solve with this effort.

Output shaft casing away. Look at all those scary geary things! Deffo do not want to muck about with any of those, no siree!

All the gubbins need to be protected from the old gasket, which had to be scraped off with a screwdriver. In this picture, the gasket's tenacious hold on the mating surface has been broken, and it is cleaned with acetone ready for the new gasket.

Using Special Tools JONB0001 (A.K.A. "rubber mallet") and JONB0004 (A.K.A. "the old seal") to seat the new seal in the casing

Which gives us this.. new seal in situ

Using Special Tool JONB0002 (A.K.A. "a big fat nail") to put the rolled pin back in the gear selector rail

Using Special Tool JONB0003 (A.K.A. "a bit of steel bar and two bolts") to hold the output shaft pinion while I torque up the big fat nut (to 120 LBS/FT)

Clutch actuating mechanism cleaned and regreased (the bearing, too, which seems to be in tip top condition)

Sorry I didn't take more pictures. Of note is the circlip behind the output shaft bearing, which must be removed in order to remove the pinion for access to the rear oil seal. It's deep in the casing and a bit of a bugger to reach with stubby circlip pliers. But I managed it after five or six frustrating attempts. The clutch actuating mechanism with its fiddly little springs is easy to pre-assemble on the bench, with reference to the manual which shows the correct orientation for the springs that go either side of the release bearing. It's been described as a lash up but I think it's quite clever and - on my car at least - in pretty good shape considering the age of the thing.

Now the box is back together waiting to be refitted. All the Wellseal is glistening at the joints and I think perhaps the Lotus gods verily do smile down upon me. Ahem! Maybe... But you all know what my luck is like!

[mbell]

Nice job. I probably should have read that bit of the manual when I had a spacer made up for the input bearing on my box (whoever rebuilt it forgot to fit one!). I'd think if you are re-using what was in there to start you be fine.

Have you added a breather for the box? My theory is that most of the leaks are caused by lack of a breather on the box rather than issue with the seals.

[JonB]

Not yet, it is on my to-do list. Thanks for reminding me! Shame I fitted the gear lever and bent the tabs down.. duh!

I need to score a suitable spigot to which I can attach some tube to drop any oil on the road. Or maybe I'll just drill a hole in the top of the casing next to the gearshift? Was thinking of tapping a thread in the cover so I don't have any nuts underneath that might come loose and drop into the box.

By the way, I didn't know anything about the spacer until VinceReynard told me about it. Still couldn't find it, then noticed the lip on the cover was a different metal. I thought it was machined into the aluminium.

[mbell]

I've bought:
https://www.mcmaster.com/9833k11

For a breather for mine. I don't know if such things are easily available in the UK.

Really not sure why I went for such a large one when I bought it, a smaller one would be fine. If I get to fitting it, I was planning on drilling and tapping the top cover by the gearstick.There very little oil in that part of the box, so with the above filter I think it is very unlikely to get oil coming out.

The spacer is important for holding the input bearing and therefore shaft in place, which is useful for selecting 4th gear. I think the sizing is mostly to keep a suitable load on the bearing while allowing the seal to crush enough to work.

[JonB]

I?m pretty sure I can drill an M10 bolt easily enough. It?d be like the diff vent.

[vincereynard]

Gearbox breather -
viewtopic.php?f=37&t=39417

Way back in May 2017! How time flies when you are having fun. Out of interest there is no sign of oil in the tube, so very little gets up there.

You will have to take the lever out to fit the gearbox! An advantage of the VinceBodge is it makes that much easier. Maybe you were just practicing?

[JonB]

I can take the lever off easy. Just unscrew at the anti sizzle joint.

I know about your breather design and it?s good. But I want to try and avoid yet another ?5 eBay transaction. They?ve been adding up scarily lately!

[RichardHawkins]

I am installing an MT75 Ford gearbox, which has a breather designed in from the start. The breather is a socket button head screw with a 2mm hole drilled through it (looking a bit like a carburettor jet). The breather is located near the top of the box, and is nearly horizontal. There is no pipe attached.

Hope this helps,

Richard Hawkins

[JonB]

OK, so a follow up on this thread - I tapped a thread in the top of the gearbox by the gear shift and wound a bolt into it. The bolt was drilled through its shaft, with a cross drilling on the head so it acts as a breather like the one on the diff (and MT75 gearbox from the sound of it).

Showing the location of the breather

Total cost: ?NIL. That's my kind of bargain.

[2cams70]

You could just use the breather from the Ford 4 speed box. Has a nice floating metal crimped on cap that prevents dirt/water from entering and also helps deflect splashed oil back into the box. It would screw straight into a suitably sized tapped hole.

[JonB]

Bit late for that!