Sam's gearbox thread

[samc88]

As some of you will know from other threads, I do have a spare series 3 gearbox which I've been toying with the idea of a strip down with to see whats inside ( as I've never done a gearbox before )and either rebuild it or see what good spares I can use. This isnt complete, lacking a bellhousing, top cover and gear behind the mainshaft (I presume it used to have an overdrive fitted). Anyway, here is the tale of how I stripped it down, hopefully it will be of interest to some.

Here it is on the bench





First thing I did was to remove the transfer plate bottom cover using a 7/16ths spanner to undo the 10 nuts holding it on





Most of the nuts except 3 came out with the studs. So I decided to take all the studs out and when it comes to reassembly I'll put them all in with locktite.

The transfer plate was then removed by knocking a thin scraper all around to try and break the seal made by the gasket. Do this gently so as to avoid damaging the plate or casting.



Revealing some gears:



There is quite a lot of debris in there (I think this is from when it had a period of being stored outside though)




The nut and spring washer securing the intermediate shaft was removed using a 15mm spanner



To get better access I tipped the gearbox over (i.e. so the transfer box plate would be underneath) and a nut fell out:



Then of course I tipped it back up revealing



Yes all this had been dropped in the transfer box! I wouldnt imagine it would last very long if it was run with all this in there

Land Rover state to use a special tool to grip into the grooves on the intermediate shaft end but I imagine this to be jolly expensive so I managed with a pry bar and a hammer to knock it out



Anyone with a bit more common sense than me will probably see the next problem a mile off, yes of course I realised there isnt enough clearance to get the shaft out so had to remove the hand brake back plate.

First the split pin and castle nut were removed with a 1" socket on a breaker bar. The box has to be locked up for this. On a complete box its easy, you can just put it in gear (which is what I did on my other box when doing the rear oil seal), on one like this its a bit more awkward.





this could then be removed allowing access to remove the backing plate. Note there is a felt washer behind it



The nut, washer, felt washer and main part were cabledtied up to keep them together



The 4 nuts and spring washers holding the back plate on were removed with a 15mm spanner





As you can see, the shaft now has plenty of clearance to come out





Then the intermediate gear can be rolled out of the casing



Inside this is a long roller bearing



Next the thrust washers either side of the gears in the casing were removed





Judging by the colour difference either side of each one, I'd say they are worn? Do you agree?





Next, the last job of tonight was to loosen off the external (there should be 5 on a complete box, I had 3) and internal (3 of them) fasteners using a 15mm spanner and socket.

External example:



Where 2 of the internal ones are, the third is behind the mainshaft in this pic



So there we have it Tomorrow I'll hopefully get the boxes split

Do any of the parts so far look a bit life expired to you?

(Also regarding the books, I have nothing against them they were just handily nearby and of the right size the help stop the gearbox toppling over when doing the castle nut If I had some wood I would have used that )

 

[jamesmartin]

thrust washer for intermediate gear look ok ,they are only bronze coated on gear side,without top cover main case is scrap

 

[aaronmorris]

You're a braver man than me, I'd love to be able to rebuild a gearbox. But I'd be scared of fecking it up, Mind you if its already fecked I don't suppose it matters

 

[samc88]

You're a braver man than me, I'd love to be able to rebuild a gearbox. But I'd be scared of fecking it up, Mind you if its already fecked I don't suppose it matters

Well I didnt actually pay for it so that helps a bit As I see it I've got nothing to lose in seeing what its like inside If I can source the missing bbits then it might get rebuilt at some point but if not I'll keep it as good spares for if the running gearbox ever goes wrong

 

[samc88]

Right then, got the boxes separated this afternoon:







I decided to strip the transfer box out first so put the gearbox back on the trolley.

First task was to remove the selector plunger using a 15mm spanner:





This is made of 3 parts, the cap, the spring and the plunger which locates in the shaft



Then the cover plate was removed using the 7/16ths spanner



Next the pinch bolt for the forkselector was removed (apologies for the blurry photo)





Then the nuts holding the output shaft housing to the transfer box could be removed allowing the housing to be split from the box









The selector fork was then removed



Next thing to be taken off was the speedometer housing, again removing the nuts with a 15mm spanner







Here is the worm gear





With the housing are some shims (2 in this case)





These bits were then cable tied together so as not to loose them. Next was to knock out the shaft rearwards using a mallet. The bearing (Timken) looks pretty good



Then the big circlip on the front end was removed so I can remove the bearing outer race tomorrow (was too late to start knocking things really). Will carry on tomorrow after work

 

[jamesmartin]

you need to prise the smaller of the 2 taper roller bearings away so you can remove a circlip to get gears off shaft, all bolts are actually whitworth but you seem to be managing

 

[samc88]

you need to prise the smaller of the 2 taper roller bearings away so you can remove a circlip to get gears off shaft, all bolts are actually whitworth but you seem to be managing

Yes I had seen that in the book. Do you recommend doing that before getting the front outer bearing race out or after (as it shows in the manual)?

 

[jamesmartin]

knock end of shaft to push other race out then circlip ,and if you look circlips have tapered holes and only fit on one way when it comes to rebuild ,if you get more bearings the smaller taper bearing often now comes with too much chamfer on inner side so it presses over circlip and jams gear when setting preload the proper bearings were very square sectioned and new ones need to be

 

[samc88]

Okay, cheers James The bearings seem quite good (run nice and no sign of wear) so will decide later on on whether to replace or not, thank you for the advice though, thats most useful

 

[Imortalrelic]

Well done Sam keep the pics coming.
I am also in the process of stripping a box and am at about the same point.
What are you going to use as a packing piece for removing the bearing outer as the manual indicates?
James are you indicating that the gears can be removed prior to removing the second outer race removing the need for a packing piece?

 

[jamesmartin]

to remove the gears you need only to remove larger taper bearing race at speedo side as that allows enough room to lever the smaller bearing to reach circlip

 

[samc88]

I didnt use a packing piece in the end. The manual says to use an old bearing outer race. In the end it was way too tight and so took the gears and shaft out first and pressed it out.

Pics and an update to come once photobucket finishes loading the pics

 

[samc88]

First thing I did was to drift the bearing off the shaft (well as far as I could). Sorry for the blurred photo of this one



Then I removed the circlip holding the gears on which allowed me to withdraw the shaft out the forward bearing bore





This allowed me better access to get at the bearing race which was a very tight fit. Knocking it didnt seem to do much so got the arbor press out again to do it. Here it is about halfway out



the completely removed race




Leaving me with a stripped transfer case



The order the bits are on the shaft





Bearing outer race, inner race, circlip holding gears on and thrust washer



High gear





Low gear





Shaft with bearing



The transfer box looks pretty good gear wise so I think I will rebuild this at least as a good spare, the main box on the other hand... well we shall see. (This is more an exercise in seeing how to do one so its pretty interesting for me having never stripped one before)

 

[jamesmartin]

high gear is the helical tooth one low the straight cut

 

[samc88]

high gear is the helical tooth one low the straight cut

So it is I misread the parts book I've got

Edited now so its correct

 

[samc88]

Next on the list is the front output shaft housing,

The first thing to come off is the bracket for the high/ low range lever (already off on mine) and the 4wd control lever.

To get the 4wd lever bracket off, you must first remove the split pin and then the bolt in the centre





There is a washer behind the split pin



Then the bolt was removed




Next to be removed was the dust cover for the selector shafts



Done using a 7/16ths spanner









The 2 selector shafts were then knocked out using a mallet









The 4 wheel drive locking dog





One of the selector shafts



Then I took the flange off the front, again removing the split pin before undoing the castle nut. As I couldnt lock it off, I held the flange in the vise to undo the nut.





There is a washer behind the nut



The flange can then be pulled off





Next to come off was the oil seal housing, the nuts on the outside were removed



And it was gently prised off







The shaft should then just drop out the back



The front bearing was then pressed out. You can use an appropriate sized socket on a long extension bar and hit that with a mallet to knock it out



This bearing will be replaced as it doesnt sound particularly healthy (its like its got grit or something in it and it feels a bit notchy)

This leaves me with an empty output shaft housing ready for rebuild





Next up cleaning time ready for its rebuild

 

[Correus]

Did you finish this project?