F20 gearbox help

[marc69]

I thought I had wrecked my xe gearbox yesterday at knockhill.

Today I took the selector off the top, realigned the forks and I can now get reverse, 1,2,4 and 5 with no problems.

I can't get 3rd (which was the gearchange I broke it on) and all it does is make a grinding sound.

Can I repair this box easily or will it need to be new one?

I have a F13 with a broken casing, if the f20 is repairable, will bits of the f13 be any good?

Any advice would be appreciated,

Thanks

[meritlover]

Have you checked the alignment procedure for the selector shaft in case the pinch bolt has slipped? Also check all the bushes and linkages before condemning the box.

[phunkynova]

It could as simple as the selector rods have moved a bit down where the two rods fit into each other and are pinched up by a 13mm bolt.

[marc69]

I have tried manually pushing the selector forks back and forth with a long screwdriver (selector removed of course) and all drive except 3rd where it just makes a grinding noise. reverse works but there is a little grinding noise too.

[meritlover]

Did you try it with the selector housing back on? Sounds like its rooted

[Stuart]

You will 95% have smashed the synchro ring where the strutt keys (or dog keys, or any other names for it) grip before the slider engages the gear. These are weak on all F10-F20 gearboxes as they are single ring where 1st/2nd are double and much much stronger. You can fix it by stripping the gearbox and taking the output shaft apart to replace the rings from an F16 or F20, sorry, the F13 parts wont fit.
I am sloly in the process of working out if we can do away with the metal that breaks in the ring as its not 'needed', OR to simply have new rings made up that are stronger since 3rd and 4th get a beating these days.

[marc69]

Thanks, I am convinced it is not the selector forks etc as when I am selecting the gears by hand in the box, all the selector bits are moving inside smoothly, including third gear, there just doesn't seem to be a third gear which sounds like what Stuart says.

If this is the case then are there more modern cars that can be found in the scrap yard with F16/F20 gearboxes?

If so...here is the lazy bit....can I just remove the end of the box with all the gearing, and put it into my gear box complete?


If this is all going well...would I need to remove the bottom (diff plate I think) and make sure there are no broken bits of teeth etc in the box, then put a new gasket set on etc?

Thanks

[meritlover]

If so...here is the lazy bit....can I just remove the end of the box with all the gearing, and put it into my gear box complete?


If this is all going well...would I need to remove the bottom (diff plate I think) and make sure there are no broken bits of teeth etc in the box, then put a new gasket set on etc?

Thanks

yes,
if you're careful you will be able to reuse the gasket.
refill with fresh oil

[marc69]

Thanks, seems an easier way to do it and there are no gearboxes for sale in the area so with the added cost of a courier....expensive.


Next thing is, does anyone know which cars about 10 years old (scrapyard finds) that would use the F20. Or will the F16 end and gearing also just slot straight in?

[Stuart]

Something about bearing sizes means the bell housings aren't swappable.

daewooooo use d16 and d20's which are the same boxes

[Stuart]

Oh, you have to ensure the final drive is the same otherwise the diff won't work

[marc69]

Ok, I sort of understand that...I think.

So the safest route would be to remove a f16/20 and replace the broken cogs and put it back together?

Do corsa b and cs and astras of the same age use either the f16/20 box?

Thanks

[Stuart]

B would be f13 or f15 c would be f15 maybe f17 and some f23 Maybe.

you need Astra/vectra/cav/calibra stuff.
replacing the goosed syncro rings isn't an easy job, well ok it is easy but it takes time and patience lol I'm part way through a guide to do some of the job, I just need to add pics

[marc69]

B would be f13 or f15 c would be f15 maybe f17 and some f23 Maybe.

you need Astra/vectra/cav/calibra stuff.
replacing the goosed syncro rings isn't an easy job, well ok it is easy but it takes time and patience lol I'm part way through a guide to do some of the job, I just need to add pics

Would it be easier/quicker just to replace the gearbox then?

[Stuart]

Aside from knowing that you are putting a set of synchros back in that arent cracked, then its far simpler to swap the whole box.

If you have the time and the long reach pullers and the desire to have an in depth fiddle with a gearbox then I'd strip the clusters to be sure its a broken ring and then replace.

[marc69]

I have bought a gearbox and it should be here by the weekend.

Are there codes etc or anyway of telling if the final drive is the same, I would rather just remove and replace the gearing than the whole box.

Thanks