11 replies to this topic

[new_van_man]

Gearbox finally stripped but what to replace.

I had planned to buy the rebuild kit and replace everything however, I was wondering people thoughts on this? How often does everything need replacing? Gearbox probably done some 80K miles maybe never stripped down no evidence to suggest it has.....

Main Double Roller Bearing - feel i should replace this but it is pricey, the old bearing looks to be intact and in good condition. Plan to reuse the circlip is this ok?





1st Motion Single Roller Bearing - Not sure about the condition of this, it seems ok but it has a gap in the middle of it, is this correct? sorry forgot picture?



The layshaft - showing signs of wear at the roller bearing ends. Bearing for first motion shaft although this seems ok, i.e no play or wear on shaft, so will replace layshaft and needle roller bearings. The steel needles feel quite loose?









New springs for sycro hubs - do these often loose tension? The balls seem ok (do they wear much)?

The synchro hubs - one has a layer of rust (only surface on the top of the outer ring) does this matter? The teeth look used but intact.
















Some of the gears have slight scoring on the top of the teeth is this normal? Will they be ok to use?








4 new baulk rings - now i\'m not sure if these need replacing or not, they are show some signs of wear on edges of nobbly bits (slight curvature), but still seem quite a tight fit to the gears....








Central oil pick up vs original? The gearbox is going on a standard rebuilt MG 1275 lump.

There was a collection of very small shards of metal at the bottom of old oil pick up strainer. Prob about size of two two penny pieces on base of strainer. Is this normal?



Bearings in casing and clutch case assembly (idler gear bearings i think). Firstly, should the cog which sits in the top of the casing be able to move when housed in the bearing, i.e movement of about 1mm, feels like you can wobble it in the bearing? How best to remove these? Take it i can drift it ourt of case but how to get it out of clutch case assmebly?


Will leave the diff for another day......

Guys thanks again, certainly couldnt do this without all your help! Learning very fast, but is fun if a bit frustrating at times!

Edited by new_van_man, 03 November 2010 - 11:07 PM.

[new_van_man]

Oh sorry forgot to mention the gear selctors - how can i check for wear? Are there any points where tehy wear specifically. There are some shinny bits on bottom edges, hard to see in pictures tho is this normal or wear?










cheers muchly

[Guess-Works.com]

2nd gear's mullered, the dog teeth are what you want to be looking at, compare it with the other gears, there may be similar wear on the synchro ring. Check the selectors by putting the corresponding synchro ring into the selector and move side to side, there will be a little movement but anything approaching a mm of movement I would consider changing.

Baulkrings you'll need to try on the gears, I run a rule of, anything less than a 35 thou' (0.9mm) gap they go in the bin.

Replace any broken bearings, which your single roller is one.

[new_van_man]

Ok I know this was a thread from a long time ago but what with one ting and another i havcnt got round to putting this back together as yet. But I'm looking to make a start again!

Just a couple of quick questions if thats ok?

Firstly with selector shafts, The third and fouth selector seems ok, a very small gap but definatley less than 1 mm. The first and second selctor has more wear, but is max 0.6mm (i wedged a feeler gauge in the gap) is this the best way? I am i best off replacing this selctor fork? Or is still ok to use? Sorry for poor quality picture below:









2nd gear the dog teeth (small teeth, is this correct name?) have a few teeth which are chipped. the picture again is not great, however the helical teeth look ok see picture below: I take it i need to replace this? The dog teeth are not all chipped, just a few. The syncro hub and slide part look ok, with no chips etc and it appears it is the dog teeth on second gear which have taken a beating. Also the oil strainer had some swarf lodged firmly in its grill (assume this is second gear dog teeth remains...)





and finally third gear, the dog teeth look good with no chips but the helical teeth look chipped on the inside edges of the gear. There is also some scoring along the top of the teeth. Is this knackered too or ok to use? What would cause wear like this? The laygear didnt show signs of wear, could it suggest wear in bearings of either layshaft or main bearings causing motion shaft to drop or twist and thus give undeven pressure on thrid gear, causing the wear?





and finally, i take it this baulk rimg is knackered? The other three have a gap of at least 1mm between edge of ring and gear cone, well bigger than my largest feeler gauge at least!



I intend to replace layshaft, layshaft bearings, 1 (maybe all 4) baulk rings, main bearings, 1st motion shaft needle bearing as well as diff pin, planet wheels and diff bearings. Should i replace the bearings which sit under the gears? (i.e the plastic caged needle roller bearings?, there is no sign of wear on 3rd motion shaft or in internal surfaces of gears, but is it a false economy not to replace these.

Any help much appreciated,

Edited by new_van_man, 25 January 2011 - 09:18 AM.

[new_van_man]

The other thing was my final drive ratio. I currently have 62 and 18 on crown wheel and smaller gear respectively. I take this give a final drive of 3.44 as per post 84 metro? Would i gain much by changing to 3.1, I will be using the car on the motorway quite abit and would like to be able to do 80mph without feeling like i'm about to takeoff (i.e engine screaming as well as fuel economy issues).

I take it taht its just a case of changing teh crownwheel and gear?

Cheers all help very much appreciated.

[new_van_man]

A slightly better coupleof pictures of second gear





Cheers

[icklemini]

that gear is mullered... paperweight!

[new_van_man]

that gear is mullered... paperweight!

Is the marking on the helical teeth of third gear also bad? What would cause that kind of wear?

[bmcecosse]

You need a new 2nd gear - and a new baulk ring to go with it, and layshaft and needle rollers, and the single row bearing. Otherwise -I would reuse the rest. Selectors etc look good enough for re-use and any markings on the gears are possibly there from new, or perhaps some dirt passed through -but they will be fine for re-use. You don't show pics of the laygear - is it ok ??

[new_van_man]

Cheers mate for the advice as you can tell this is my first time. The gearbox and engine for that matter hasnt been run for 7 years so is in need of a bit of TLC.

I thought the laygear looked ok, no chips or missing teeth, here are a couple of pictures before i took it out of the box and started fiddling. Hence my question about third gear?

One other thing if I may. The top hat upon which 1st gear sits was very tight on third motion shaft and had to heat it up to get it off. Will this still be ok to use? Are they normally that tight? And what is the best way to clean all the black gunk of the third motion shaft and sychro hubs? I tried gunk but it only got some of it off?

Thanks for looking, much appreciated.

[Guess-Works.com]

If you heated up the top hat then I would replace it, you could have warped it or altered the hardened properties of the journal surface, and yes sometimes they can be well stuck.... I would also be hesitant to re-use the main shaft for the same reason.

The carbon build up on the mainshaft and other parts is best removed with a de-carbonising solution, however, these chemicals are not available from your 'diy' store... something which may be worth a try as a 'one off' solution is oven cleaner and a tooth brush ( wear gloves and mask ).. try it on a scrap part first ( second gear then ) and don't use it on anything aluminium.

[Dusky]

A bit of topic, but how do you guys undo the big circlip from the main bearing?

Its the only thing I need to remove to get the gearbox apart