CitroJim wrote:
MA 'boxes are a bit trickier than a BE3 'box and a LOT trickier than a 4HP20 auto....
Many a true word spoken in jest...
My advice if you are tempted to dismantle an MA is don't. That is unless you enjoy Krypton Factor puzzles... They are not for the faint hearted.
To be honest, I have spent two very enjoyable evenings and most of today doing battle with the MA.
I fell at the first hurdle really, when taking off the 5th gear synchro hub. One false move and it exploded in a barrage of springs and balls in my hand

I'd not appreciated these 'boxes have baulk ring synchromesh...
The rest of the 'box is held together with copious quantities of Loctite that makes it fun undoing things. It's seriously worrying when you have to use a 3 foot breaker bar on T30 Torx bolts... As if that is bad enough, the gear selector arm is pinned to the selector shaft with a tapered cotter pin and to get it out required a pin punch on the end of a 4 lb club hammer and wellying the living daylights out of it.
Luckily I managed to find all the errant springs and balls from the fifth gear synchro and managed to do the same thing with the 1st/2nd synchro later on

Lucky again, I managed to recover the bits after their freedom flight.
Anyway, the 'box ended up as a pile of bits and the reason for the lack of drive became apparent. The crownwheel is heat-shrunk onto the diff assembly and the crownwheel was found to be spinning quite merrily on the diff housing with absolutely no resistance whatever. Apart from that glaring design weakness, the MA box is a sturdy little thing and brilliantly designed and executed. The diff generally was clearly a Friday afternoon job in the design department as in addition to the crownwheel weakness, the diff sun and planet gears showed considerable wear. Elseware, there was not a spot of wear anywhere, even all the synchros looked in fine order and are a vast improvement on the old-fashioned cone synchros in the BE3.
Now for the Krypton factor bit. Those exploding synchro hubs and their springs and balls needed reassembling. Basically, it is necessary to get three balls on the end of three strong springs in a 120 degree arc around a circle back in place simultaneously whilst all the time said springs and balls are trying desperately to make a bid for freedom. I liken it to fitting a wriggling baby into a babygro only a bit easier.
I had a few abortive goes in the garage and got fed up of scrabbling around retrieving lost balls and springs again and thanking my luck that they did not end up in some inaccessible crevice. In my workshop there are plenty of those.
So, thinking I needed to do the job where flying springs and balls had nowhere to hide, I retreated to the kitchen. I tried again... Ping, plink! Where did that ball go? Sounded like it ricocheted off the washing machine. No sign of it. Under the washing machine? No, not quite. It bounced under the washing machine and ended up resting on a ledge up inside the casing of the washing machine...
I retired to bed then and slept on it. I dreamed up a fitting jig and got up early this morning and made a jig. It nearly worked but still the balls and springs flew.
Finally, after THREE hours of trying, I finally cracked it just using hands and fingers. There is a definite knack to it and it takes a lot of practice to get it but then it's easy. The second one I did in three minutes.
One good thing about the MA is that there are no shims and nothing to adjust. Both main and layshafts float on roller bearings.
So, the conclusion is this. If you have an MA that's lost drive, the diff is duff but I reckon the crownwheel could be carefully welded to the diff housing and all would be well again. It would need a skilled welder. The downside is that to get to the diff, the gearbox needs to be totally stripped.
Compare with a 4HP20 crownwheel bolted to the diff assembly with about 15 M12 bolts... That makes more sense.
This problem is, I'm told, a common failing, mainly in Saxos owned by youngsters. Lots of drag-racing starts in McDonalds car parks seems to be the killer for the diff...
There was a reason for all of this. Robyn's 206 has a bit of a baulky first gear. When hot it's a bit reluctant to engage. It does not grind or anything, just baulk. In light of going through an MA, I'm fairly sure the first gear synchro is worn and I'm now happy to fix it if/when it gets worse. Baulk ring synchros, when worn, will not so much grind like a worn synchro in a BE3 but rather make gear engagement difficult.
All in all, an interesting exercise.
I rounded off the day by visiting New V6 and running her up prior to retaxing her in early December. I also gave Old V6 her usual checkover and found all to be sweet.
The weather here has been excellent today. A bit on the brisk side, damp at times, sunny at others but no snow. The BBC got it wrong again... We were due plenty according to the forecast...