Sunday, April 11, 2010

A week of buying!

This week I have bought a few items required both for the reassembly of the gearbox, and to fit missing parts. Most were sourced as MGA spare parts.

From Moss Motors USA, a new clutch plate, a clutch alignment tool, a rubber clutch lever boot, a rear gearbox extension oil seal, and a rubber boot and fixing ring for the gear shift lever.

From eBay USA, a rebuilt clutch plate and pressure plate to keep as a spare set

From eBay UK, a NOS 9-tooth starter pinion to suit the M35G starter motor. This will put a new pinion on the starter to match the new ring gear on the flywheel that was fitted last week

From Bull Motif Spares UK, a dust cap to fit the clutch inspection hole in the gearbox casing. This is a bit of a punt as it is a Morris Minor part, but the cover in the picture looks to be the same shape as my hole, and perhaps it is the same

From LRSeries shop (Land Rover Spares UK), 4 engine mounts type NRC2054. One of mine requires replacement (the difficult one of course, under the manifold) so this will give me 3 spares. I'll fit the engine mount while the gearbox is off the motor, it might make it a bit more manouverable

From eBay Oz, 6 rubber boots to suit Morris/Austin brake and clutch master cylinders

This weekend was spent cleaning up parts, and wire-brushing and painting with Wattyl Killrust epoxy enamel (I love Killrust, it's a great paint system!) The gearbox received a coat of Killrust etch primer, and then a coat of Killrust epoxy enamel in mid-Brunswick Green to match the engine.

I inspected the driveshaft, and all looks good. There is no apparent wear in the universal joints, and both ends were cleaned and greased, followed by a coat of Killrust in black.

Monday, April 5, 2010

Ring gear and flywheel on

Had a win today. Used the oxy-acetylene to heat the incorrectly positioned ring gear, but being a tight fit as I heated the ring, so too the flywheel was heated. Stalemate situation.

I flipped the flywheel over, and drove the ring gear off with a punch, working slowly around the perimeter, and gaining a fraction at a time. Once the ring gear dropped off, we preheated the kitchen gas oven (the one I should have used yesterday) to 260 degrees centigrade, placed the ring about mid-oven, and turned on the fan. The ring gear was placed the right way up in the oven to fit straight on to the flywheel, which was sitting on the kitchen bench.

After 10 minutes I donned a pair of welding gloves, took the ring from the oven and placed it on the flywheel, where it sat down perfectly on the rebated seat exactly where it was supposed to sit! Sooo easy! Within about 5-10 seconds of sitting on the colder flywheel, the ring gear cooled and contracted sufficiently to grab tight.

Once it all cooled again, I mounted it back on the rear of the engine, and torqued the flywheel bolts to 4.8kg/m like the good book said. The lock tabs were then set against the flywheel nuts.


Compare todays photo with yesterdays photo and see what a great difference there is!

I checked the propellor shaft in the end of the gearbox extension for wear in the rear bush, and there was no detectable movement in the joint. So it looks like I just need the oil seal to make this task complete!

Sunday, April 4, 2010

Gearbox out, flywheel off

Bugly arrived in Darwin with the advice that if the starter wouldn't engage but just sat there spinning, then a partial rotation with the crank handle would fix it ... no problem! Does this sound like a worn ring gear to you? About 12 months ago I bought a ring gear off eBay suitable for an MGA 1500 engine, so decided to fit it over Easter.

The workshop manual said "Support the power unit (engine), which can be done with a small portable crane through the cab door ..." The reason for this is that the gearbox mounts have to be lifted off the rear cross member before the transmission can be withdrawn rearwards from the engine. So ... coming up, one dodgy overhead crane ...


I had already taken the front quarter windows out, so a wooden packer under the 50x50 RHS worked wonders! The chain ran through the back door and hitched around the left rear chassis member. Not much strain on the chassis, as most of the direct weight was on the window sills. I have great faith in Mr Morris's welding!

Once the gearbox was removed, the wear on the ring gear where the starter motor sat was obvious. I have heard that an engine will usually come to rest on the cylinder with the highest compression, which is why one position of the ring gear gets most of the wear.


Once the flywheel was removed, the extent of the wear was evident, and little wonder that poor Bugly had starting problems! Even the pinion on the starter motor was worn, although not too badly.


The worn ring gear was removed by supporting the flywheel clear of the work bench by some wooden packers, and driving the gear off the flywheel with a punch, working gradually around the perimeter. Actually, I used a cold chisel as it had a wider contact area.

There are two ways to expand the ring gear to allow a "shrink-fit" to the prepared flywheel. Firstly, the ring gear can be placed over the flywheel, ensuring that it is right way up, and the flywheel is adequately supported. Heat via an oxy-acetylene torch is then applied evenly around the ring gear, until it expands sufficiently to drop into place on the flywheel. Once in position, it can be checked and adjusted to ensure that it is seated correctly before it cools and shrinks. But BEWARE it is HOT and will BURN IF TOUCHED!

The second method will ensure that a more even heat is applied to the ring gear ... simply cook it in the oven at around 250 degrees centigrade for twenty minutes or so. Take it out using a good set of welding gloves initially, then by means of multi-grips or vice-grips or similar tool, carefully place it right-way-up in position on the flywheel, and check to ensure that it seats correctly. The same warning regarding "HOT" also applies here.

I chose method 2. Silly me ... I used our hooded BBQ, which usually cooks a roast at 250 degrees no problems. But today, it struggled to make 220 degrees (it has a temperature gauge on the hood). I though I'd still try it, but as it was not sufficiently hot it cooled quicker, and didn't quite seat properly on the flywheel before it cooled and shrank seated higher than it should be up the flywheel.

Therefore tomorrow, I need to find an oxy welding set and finish fitting the ring gear using the first method!

While the gearbox was out, I checked and cleaned all components. The rear oil seal in the gearbox extension at the output shaft is well worn, and requires replacement. This was the reason for a substantial pool of oil under Bugly when parked. The seal presses into the cast aluminium housing, and seals against the tailshaft, or propellor shaft. The tailshaft bears in a long bush forward of the oil seal, which may also be worn ... I will check that tomorrow.


On the other end, the clutch drive plate is still serviceable but worn, and it would be a little silly not to replace it now while the gearbox is out. The clutch pressure plate has been replaced at some stage (it still has the "Coventry's, Perth" sticker on it) and appears to be in good condition. The carbon thrust bearing also appears to have been replaced at some stage, as it is a "Repco" part. It too is in good condition.

So the bits I am chasing are:

New starter pinion assembly (9-tooth)
New clutch drive plate
Rear gearbox extension oil seal
Rear gearbox extension tailshaft bush (possibly)
Clutch withdrawal lever rubber boot
Gearbox casing upper dust cover