I've decided to tackle the replacement of my input shaft bearing myself, partly because I can't afford to send it to Rick Pembro, and partly to get over my incomprehension of how gearboxes work. I should have done this years ago, but not being able to find any decent guides or threads online detailing the job put me off. The Haynes section is apparently pretty accurate, but it was always a section I just skipped past with fear.

Not naming names, but certain members of this forum have also contributed to that fear in the past by advising against trying to do gearbox work yourself as soon as the subject is mentioned. Not having much mechanical knowledge when I joined this forum, this just added to my fear of tackling them until now.

I'm going to document my progress with as many pictures as I can and hopefully this will help others in the future. I'm also going to go back after I'm finished and take more pictures to edit in, as oil-covered hands weren't very good at holding a phone.

Expect many questions!

Go for it...

Behold, a gearbox:



As we all know, these are full of spinning things, bits that fire out and hide in the corners of the workshop, smelly sludge that used to be oil a few decades ago, fairy dust and, in my case, a dodgy input shaft bearing. I'm mostly using a haynes manual to do this, with some advice from Sean and any others who wish to chip in.

First step is to remove the output shafts - 6x m9 nuts then use a bit of wood behind the <insert right name here, bit the driveshaft bolts to> and a few taps with a hammer to get it loose, then withdraw. There will be some shims behind, remove these and keep with the hub you removed. Also remember which side is which as it matters.

This is where I hit a problem - one of my shims had disintegrated, which I'm sure will make re-assembly interesting.





After this is done, remove the top and back covers. When removing the top cover, hold it firmly down as you unbolt it, as there is a spring underneath it which likes to try and escape. If it does, you'll spend a week looking for it.

We shall follow this post with interest. To unscrew the 2 rear nuts. Secure the bearing with a thick washer and a 7 mm short bolt. The shaft will shut out backwards if not secured. Lock the gear box engaging 2 gears. 1st gear (right side rod) and 4th gear (left side rod) Unscrew the speedo nut (top shaft) and lower nut (left hand thread) WITHOUT opening the peening.

The order the haynes manual tells you to do things confused me somewhat - removing the output hubs before the top/rear covers for example, but as this is the first time I'm doing this I'm not going to argue. If I find at the end that things could go in a different order then i will point it out, as the Haynes order does seem overly confusing.

Anyways, once the top and rear covers are removed, I would recommend using a magnetic screwdriver tip to remove the ball underneath the spring you found under the top cover - it will try and escape while you are faffing about with the selector rods.



These are the selector rods:



Removing them requires undoing the clamps at the top of the selector forks. I started at the 4th gear rod, which is on the left in this picture and before removing the rods used a small sharp screwdriver to score either side of the clamp, to make lining up for reassembly easier. It isn't a bolt as such on the clamp, but a small shifter was able to grab the flats and turn it all the same - my smallest spanner was an 8 which was too big. A 6 maybe?

Once the clamps are undone, the rods can be pulled out through the rear of the casing. I just made it sound easy - in reality they were covered in oil, had some corrosion which got them stuck as they passed through the clamps and my hands were freezing so it was a bit of a faff. Eventually they were out and the 1/R and 2/3 selector forks can be lifted out. Haynes recommends putting the rods and forks back together so you don't forget which is which. I forgot to get pictures of the above, but it is easy enough to figure out. Have a picture of lots of pinions and oily bits instead. You can see the 4th gear selector fork still in place.



As you remove the rods, the detent balls and springs will try and make their escape. Be careful not to lose any! I dropped one into the gearbox itself, which i hope is attached to the sump plug.

After this, Haynes tells you to remove the clutch bellhousing and differential. I'm not sure why it tells you to remove the hubs right at the start, then do other stuff, then come back to the diff end again. I suspect that you could do all of it right at the start.

Anyways, inside the clutch housing you will find this:



If you are doing this yourself, you will probably also have the clutch release bearing over the input shaft. Mine got swapped to my other box when i took this out of the van a while back.

Undo the four nuts and four bolts that are in the bellhousing and then give it a clonk with a mallet to loosen things up. Stand the box on end to stop the diff falling out and remove the bellhousing. Be careful of the nuts on the back of the gearbox - I was using a bench with a gap in the middle so they were safe.



Remove the differential, taking care not to lose the outer bearing cones or to get them mixed up. Don't ask me why - just what the book said. I assume its something to do with why the shims need to be kept together too. I used some spare wire and threaded it through everything.



Time for the rear nuts. Photos are a bit thin on the ground here as my hands were minging and my phone is new. The top nut is also the speedo drive and the bottom nut is just a nut, albeit with a left-hand thread.



Use the 4th gear selector fork to engage the gear and use your fingers to shove another slider into a position that it blocks the shafts from turning. I poked a screwdriver in there to hold it all in place while i undid the two nuts.



Once the nuts are undone, remove the top rear bearing. I used a taped screwdriver to carefully lever it away from the casing so as not to damage anything.

This is where things got more complicated, as it turns out that what looks like two solid shafts covered in pinions (gears, cogs whatever you want to call them) are full of bits sliding over and inside each other (ooh er...). Not to be deterred, I carried on...|

Poke your fingers into the box, and you'll feel a pinion at the top, rear of the box that you can poke out backwards where the bearing was and off the shaft. remove it, along with the spacer beside it (next thing on the shaft towards the front).





At this point, I got stuck. Haynes does one of its famous tricks and tells you to remove the mainshaft, without any explanation of HOW. I tried twisting, turning and swearing, all to no avail. i couldn't see how to remove something that is bigger than the hole behind it and long enough that it cant disengage from the bit in front of it.



At this point the light was going, my hands were numb and the dog had been crossing her legs in the house for half the afternoon so I packed up and called it a day. I'm going back tomorrow to have another try... any comments, suggestions or requests for photos just let me know.

Does this help?


Take R, 1, 2 and 3 "packet" without dismantling it yet.

Sorry, very hard to explain with foreign language, in Finnish it would be easier to me to explain...

Some photos more about gearbox rebuilding

Martin,
you may also notice that Jasu has removed the collar holding the input shaft bearing in place (2 x M7 setscrews) so that the input shaft can be moved forwards...

Also, as already advised, I hope you've taken note of the shims between the output housings and the differential/crownwheel bearings.
They're more important than the outer races, tbh.

Thanks for the replies folks - glad to know some of you are watching over me for when i cock it up Have some replies of your own!

Viking, I'm not really sure what you mean by 'secure the bearing...' but the nuts both came off fine without any real hassle. Where would this bolt and washer go? Also, what is the reason for removing the nuts without relieving the peening? (I like to understand why I'm doing something, not just how )

Jasu, i saw that picture just as i let this morning to go to the garage, and it was a big help - thank you!

Ken, thanks also for the pointers. As mentioned above, though, when i removed one of the hubs, one of the two shims was in bits (not all of which i could find, worryingly). I assume that this shim will have to be replaced - is it a massive pain in the ass to figure out what size i need?