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MG MGA - Broken First Gear
|Need some gearbox dissambely help |
I need to remove the first gear assembly (part 93 in Moss catalogue) to replace a broken first gear. As luck would have it I have a complete new (from the 80's) first gear assembly so prefer to replace the complete assembly rather than just the first gear.
Almost completed the disassembly except for removing the first gear hub. The rear thrust washer (part 77) seems to be stuck. Perhaps the bush (part 99) needs to be removed first....but this is also stuck.
Any suggestions appreciated.
|R J Goebel|
have you read this, excellent
|Are you removing first gear from the front end of the shaft, having removed third and second gears?|
I've only dismantled one MGA 'box, but I'm pretty sure I removed it from the other end of the shaft, after removing the speedo drive and rear bearing.
I'm not saying it can't be done that way, just the way I did it. It's also how I've dismantled Spridget gearboxes, but you can't remove second gear from the front end of the shaft on the later ones, anyway.
|Dave O'Neill 2|
Have read through Barney's gearbox articles. The disassembly does not seem to cover removal of the first gear hub....or maybe I missed something.
This is my first attempt at the gearbox. The workshop manual seems to suggest re-assembly of the first gear assembly from the back of the shaft. Followed by replacement of the bearing.
Disassembly just says to remove the bush followed by the thrust washer...both of which are stuck. There is plenty of oil on the parts so not rusted on...just tight.
I must be missing something.
|R J Goebel|
|Yes my manual also says to fit from the rear ( gear ) bush from the front.|
|It's been about a year since I had mine apart, but I think removal of the entire assembly does have to be from the rear of the shaft. I only replaced the first gear ring, but I also replaced the bearing so I wound up taking all that apart anyway.|
I don't recall for sure but the thrust washer may be what keeps the first gear hub from being removed from the front, so it may have to come off to the rear also. I do remember scouring Ebay along with sorting the thickest thrust washers from the two boxes I took apart, to get the end float down to something reasonable. And both of the big bearing retainers at the rear were damaged, so I wound up sourcing another one.
I see that a new reverse gear is still available fairly inexpensively... Since it engages the first gear ring, it's probably not a bad idea to replace it also while you are in there, given the low cost. Of course, that's also true of the laygear (I may not be remembering how the reverse, first, and laygear interact exactly right), which is NOT low cost, and opens another entire can of worms.
Luckily the laygear is ok, although it will need a new Layshaft and bearings. The reverse gear has some of the case harding worn through so already have an order in for one of these.
Decided to remove the large bearing, it was marginal and now trash after using a soft drift (aluminum) to remove it from the shaft. Then removed the first gear hub from the back.
Had another look at the 2nd gear bush and thrust washer, still no movement in either, there is no obvious reason why it won't move so......maybe a previous owner used some locktite on the bush.
So, if anyone has removed the 2nd gear bush without removing the bearing please chime in........it will solve the mystery.
|R J Goebel|
|Be sure you get one of the "good" layshafts and full complement bearing sets from Moss. When I started buying my gearbox parts, the good ones weren't available... I ended up converting to the later 4 bearing gear which required reaming my case for the slightly larger layshaft.|
Still didn't totally avoid layshaft woes... The supplied shaft from Moss was too long, and didn't have the oil holes located correctly. Moss eventually coughed up another one, but being impatient I had already ordered a replacement from John Esposito which I used. My gearbox was together by the time the second Moss shaft arrived, which wasn't much better than the first had been, but the one I actually used seemed to be good.
|There are some errors in the Workshop Manual. It says to remove the 1st/2nd gear sliding hub assembly from the front after removing the thrust washer (which I think is correct). For reassembly the book says the first step is to install the thrust washer (forgetting the fixed splined hub) followed by 2nd gear and bush. Later it says to install the 1st gear assembly from the back end. Surely they can't have it both ways. I'm pretty sure the 1st gear male splined fixed hub goes off/on from the front end of the shaft. There is a fixed shoulder on the shaft aft of 1st gear and just forward of the center main bearing. The thrust washer is between 1st and 2nd gears.|
You don't have to remove the center ball bearing from the main shaft to remove the 1st/2nd gear fixed hub from the front. However, if you remove the center main ball bearing, then I think you can slide the 1st gear sliding cogged ring off the back (careful not to lose the detent balls and springs). This would allow you to leave the 2nd gear bushing and the thrust washer in place (as long as you don't need to remove the 1st gear fixed hub).
This thread was discussed between 03/01/2016 and 04/01/2016
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