Technical already broken replacement gearbox whoops!

[DexterDog313]

hey

I wonder if anyone could advise me on a issue i currently have, recently i managed to get hold of a second hand gearbox for my evo, so far I've fitted it to the car and hooked up the linkage, starter motor, reverse light switch and other bits, however what i did (and i regret doing this) is starting the engine without the driveshafts attached so see if the clutch was engaging/disengaging. anyway after doing this.... i cannot get the driveshafts back in as it seems I've disturbed the bearings in the diff. i cannot get them to line up and has appeared that some teeth have jumped so the spline bearings are no longer opposite if that makes sense. (also dropped a cv joint circlip in there too)

My only option to fix this is to remove the 8x bolts for the diff and remove the final drive gear and reset the bearings so they are lined up, if anyone knows an easier way to do this then please help me

Yes i wish i had put the driveshafts in first before starting but i was paranoid about the clutch not working and thinking I'd have to take the box back off, plus my first time doing a gearbox so was jumping the gun a little.

any advice would be appreciated cheers

 

[GrandePunto PL]

This is a classic "trap for young/new players". Lesson learned.
Differential gears are free to move, two biggest ones (forgot the names, not "satellites", the other ones, "output gears"?), you can even remove them by hand, that's how you start disassembly process. You just pop them, push, one finger (pictures below).

If you start the engine without axles...you can even blow the gearbox, rip the casing apart.
In theory, you should be able to position the gears by hand (plus screwdriver etc.), if they are not too far out of place (and still "clocked" properly, otherwise you'll never push both axles back, only one will fit).
If not possible, then yes, you must pop the differential cover and fix the position of the gears manually (plus "clocking", so 2 axles align - DSC01302.jpg).
That's why used gearboxes should be shipped like that - picture "Correct_Shipping" (with differential internals secured, so nothing can fall off/out).

Gearbox (C514 family) service manual:

 

[DexterDog313]

This is a classic "trap for young/new players". Lesson learned.
Differential gears are free to move, two biggest ones (forgot the names, not "satellites", the other ones, "output gears"?), you can even remove them by hand, that's how you start disassembly process. You just pop them, push, one finger (pictures below).

If you start the engine without axles...you can even blow the gearbox, rip the casing apart.
In theory, you should be able to position the gears by hand (plus screwdriver etc.), if they are not too far out of place (and still "clocked" properly, otherwise you'll never push both axles back, only one will fit).
If not possible, then yes, you must pop the differential cover and fix the position of the gears manually (plus "clocking", so 2 axles align - DSC01302.jpg).
That's why used gearboxes should be shipped like that - picture "Correct_Shipping" (with differential internals secured, so nothing can fall off/out).

Gearbox (C514 family) service manual:

Thanks for the response, i guess my only answer now is stripping the diff casing is that can this be done with the gearbox still attached to the engine? the way i see it is i can get to the 8x bolts however as the diff is quite big, i'm wondering if i can support the box, undo the gearbox mount on the right hand side and then shift the engine towards the front.

i'm very reluctant to have to remove it as i somehow got it on with some sort of superpowers ( lifting it from above and wriggling it on)

probably just the diff seals i'm concerned about. and yes i will use some atv sealant after putting it all back together as don't fancy a trail of oil everywhere i go!

 

[GrandePunto PL]

Yes you can remove diff only, but it's a struggle.
Removing whole gearbox is not that hard (been there, done that). It weights only 30 kg.
Example (clutch swap): https://www.youtube.com/@WMCS/search?query=Fiat
You should remove the axles from the car (don't leave them like in those videos, will be easier to manipulate the box).

As for sealing, in theory it should be anaerobic stuff (Loctite 500-something, service manual mentions it), not RTV silicone (it will hold up, but not permanently I guess, maybe it's about stress, vibrations, temperature cycles - so it will kinda peel off, creep out).

 

[DexterDog313]

Hey. Just an update. Its not good tbh. So I've got the gearbox on. It drives but I've managed to get air in the slave cylinder. Probably cause it was hanging around for a while. So before removing the diff cover, I went to pick up some high temp sealant but apperently the guy at the shop said threadlocker works well. He was very wrong. Me being a sucker although I had my doubts used it as a sealer round the diff cover. Tightened the bolts up. Fitted gearbox to the car and apart from the clutch issue, it's dripping gearbox oil. Worse when it's hot as its thinner.

So in a nutshell I'm back to square 1. Will look at doing it on a weekend soon but for now I'll just keep topping it up. Got an mot booked tomorrow so least it's only an advisory.

So lesson learned. Threadlocker is not a rtv sealant. Oh and might aswell throw a new clutch kit on it as used the old one to save costs

It's been a bloody nightmare

 

[GrandePunto PL]

Loctite 573 flange sealant is not just "thread locker". Curing mechanism is the same (anaerobic), but they are different products.