Gearbox rebuild

[gammakeith]

Dear all,

I think I have now pretty much decided the gearbox is the source of my severe 1st gear judder as everything else has been ruled out now (as best as I can anyhow).  I think the crown wheel and pinion are skipping under load either due to wear in gears or the output shaft bearing allowing the pinion to move..

Thus, I have pulled apart my spare gearbox, cleaned it up and been pleasantly surprised at how good it is.  All bearings are pretty much perfect and the layshaft even looks OK to reinstall.  The first and reverse gears are a little mangled so I will replace those along with the slightly scored 1st gear selector.  All other gears and differential look perfect and the synchro hubs all look good. The input shaft is worn where it runs in the bronze bush so thats going to need changing as well.  126Fan is going to get an order pretty soon so I would welcome comments based on the attached photos (assuming they appear OK).  I would also welcome any tips from anyone who has done one of these boxes.  I've done a few motorbike boxes but not a car one before!

Thanks,

Keith

[Rusty's Uncle]

Hi Keith
I have stripped down quite a few 126 gearboxes and put a few back together. Apart from the usual 1st /reverse problems I have seen a whole range of problems from broken selector forks, detent springs, a stripped diff, gears welded to shafts through heat etc , etc. if your car is off the road then it might be worth stripping that gearbox as well. Apart from using new parts I have also put together some successful "best bits" gearboxes 

[gammakeith]

Thanks!  I've seen from posts in the past that there are numerous "failure" modes.  Unfortunately, the missus is still using the car so I need to keep it on the road for as much as possible.  However, when I had the box off the car a couple of weeks back to sort clutch etc, I whipped the top cover off the gearbox and the layshaft didn't look too bad but was certainly notably more worn than in my "spare".  Thus, I suspect there would not be much I could use 

Latest feed back from the missus is that its not juddering as much.  The last thing I tried was to tighten up the driver side preload adjuster for the diff a little ie to mesh pinion and crown wheel a little tighter.  I know its not correct to do it on the car but I thought I had little to lose. Whilst that seems to have improved things at least for the moment, I could feel a clear "bump" at one point when spinning the driveshaft on that side so something does seem to be amiss......

Keith

[Rusty's Uncle]

I think that it would be impossible for the pinion to jump on the crown wheel as that would require massive wear or re-alignment. Could be a bearing breaking up or the crown wheel is bolted to the diff housing by six bolts and if they came loose then it would cause problems for the diff. Either way it will be interesting to hear what you find in that box of tricks  when you replace it. I do have a big box of gearbox parts from various rebuilds but of course no good spare 1st / reverse parts 

[Scarlettkitten]

Good luck with the gearbox, I wonder if there are any uprated 126 gearbox parts, 1st especially available.  As I'm fitting a 1242 FIRE engine to my bis gearbox I may need to pay attention to what you're doing LOL 

[Gadge]

Performance gear kits are available  usually with shorter ratios. You can also fit a 5th gear too which may be a real benifit if your fitting a FIRE engine.

[Piotross]

I have part of 1st gear to gearbox of 126