Busted flywheel ring gear

[printjunky]

Snapped the ring gear on my SIII. Luckily I was sitting in my driveway. It's taken me three, 3-hour shifts, well layered, on my back in the snow after work to get everything pulled that needed pulled, but I finally have the tranny pushed back and the clutch out. Problem is, how am I going to jam the flywheel/motor to keep it from spinning? An opposing wrench, maybe?

And anyone know offhand what size the flywheel bolts are? Pretty sure I took it off 2 summers ago when I had the motor out for timing and cam (and various other) work. So I must own something that works. Seems like maybe 19/32 would work, but I don't think I own that size. Maybe 15mm would work?

[ignotus]

I think you can use the hand crank. Put it on the dog and brace it with a jack stand so it won't turn. Or maybe you do this for tightening......I guess a big cresent wrench would work there too braced against the frame.

gene

[I Leak Oil]

Use an impact if you can get it in there and you won't need to worry about the engine. Not sure how far back you've moved the tranny.
Short of that I use a large adjustable wrench on the crank pulley dog and brace it against the frame rail.

[printjunky]

Good call guys. Ignotus, you're correct, the starter handle is for tightening, but I can probably get a pipe wrench on the flats. (I think that's what I used to R/R the dog last time I needed to.) Definitely no room for an impact unfortunately, ILO. Hopefully a breaker bar, those suckahs are tight!

[busboy]

Order that ring gear NOW. I couldn't find one on this side of the pond for a gas engine and the diesel is different. I had to get one from the UK and it took just over two weeks.
Here is one part number ERC5293. and here is the updated number 506799. It's not that hard to remove the whole transmission through the passenger door side then use an impact on the flywheel bolts. While it's apart I would machine the flywheel and install a new clutch and release bearing for the small amount of money in parts.

[printjunky]

That'd be great, Busboy. I also need to replace my 1st gear synchro, rebuild my handbrake, and fix a few other minor things. But, I'm doing this in the yard, in the snow, with no hoist, and the Rover is my (only) daily driver. So time (and temperature) are of the essence. As is money, though, I may in fact do a clutch if I can get quick delivery. Then again, I might wait til better shadetree weather. Ring gear should be waiting when I get home. Trevor at Rovahfarm had it in stock.

[busboy]

I hear you on working outside in the snow, I twisted wrenches in plus 35 and minus 35 and below my whole life the aircraft were too big to get inside. Glad to hear you have a starter ring gear, good luck. I think the flywheel bolts were 11/16 but maybe 5/8. Definitely not 19/32, metric, BSW or BSF.

[printjunky]

Yesterday, it was at the end of a 4 hour stint and 11:30pm. My jacket was freezing to the ground and my feet could no longer take it. So my assessment might have been off, but I could have sworn a 5/8 was too big - started to roll on the points, and a 9/16 was too small. I'll double-check once I get layered up and back out there.

[printjunky]

Well, that was a bust. Literally. Baked the flywheel for a little over an hour at 465. Should be heated through by then. Low mass, etc. Aligned it with the flywheel. It seemed pretty tight, but I have no idea how tight it's supposed to be, so I continue on, tapping, tapping, tapping. Then about 90% on, and SNAP! Busted. $85 (and MUCH MUCH MORE IMPORTANTLY, 8 day without a vehicle, down the drain. For good measure, I smashed the absolute F@#k out of my thumb.

[printjunky]

Some further consideration ...

I've done a little more reading, and something was definitely amiss. The flywheel was outside (around 30f) and the ring gear was in the oven for 70 minutes at 465. Given those factors it was still a very, VERY tight fit. Had I read a little more beforehand, I might have better known what to expect - that it should be closer to an interference, or transition fit. Some even recommend turning the ring a bit to seat it before it cools. There was no way that ring was even close to loose enough to do any turning. Even heated (and placed on a cool flywheel) it was a tight press fit at best (well, obviously not even that, or it would not have broken). ((FYI, I had read two instances of ring replacement on MGs, both of which involved hammers.))

One of the functional problems, is that once I got it started and saw (and was very surprised by) how tight it was gong to be, I felt I couldn't stop or back up, because once the ring shrunk it was never going to move again, and I'd never be able to heat it discretely again (though, theoretically, maybe with the mass differential, I could torch it and get it off). So I had to forge ahead and hope I could get it seated on the flange.

[busboy]

I have done them before and you don't have very long to work time wise. It is possible to shrink the flywheel with liquid nitrogen to give a little more time but even then you must work quickly. The last one I did I decided to let the clutch and brake machine shop do it as they were machining the flywheel surface anyway. They had the whole thing for 2 1/2 hours start to finish, cost $30.

[I Leak Oil]

I'm sure someone here can get you a used assembly at a decent price. Probably easier to have the flywheel resurfaced than it is to go through all that.

[printjunky]

Busboy, I am the king of woulda coulda shoulda. And desperately suffer from "Jeeze, I can do that!"

I hope next time I think "What was it that Canadian guy said on the RN forum about letting the pros have at it?"

(Also, have since talked to a couple of heavy diesel mechanics who had the exact same things to say (use liguid N, and move fast).)



ILO, See my new post for the saga that is my purchase of a used flywheel assembly. You'll laugh, you'll cry, you'll overimbibe, you'll throw tools. Well, that what I did anyway.