Changing the final drive at last

[johnny27]

At last I got me self a f13 box with a 4.18 fd. I heard the fd can be changed with my orginal box still in the car, by opening the access plate? Where are the two gears located, i presume its in between the driveshafts? And where is this access plate? Thanks for your help.

[johnny27]

Anyone please, i was hoping to get it done this weekend.

[mikeyredtop]

ive never done it but am going to do it, the final drive isnt just the diff as some ppl may think, u have to take the other fd cog out on the lay shaft and change that...

[johnny27]

Where abouts is the diff located? is there a plate to screw off to get to it? cheers

[MechaT]

Its held in by a huge castlated nut it easy enough but the problem is the diff bearings have to be preloaded correctly when you do it back up. You need a special torque meter thingy to do it.

[rysmee]

yeah.. its a total nightmare trying to change anything that involves the diff, especially to change the bearings, but you wont have to do that.
now i thought the final drive gear is the large cog that is with the diff, but as said above you may have other things to change.. you'll have fun getting it off and back on though(and trying to get the bolts to the torque).. i did the haynes manual way and boiled the gear for half an hour to epand it..makes for nice cooking sauce too!

i couldnt find the tool to do the diff bearing adjuster back up to the req torque so left that to novatech.

[mowgli]

well, when I last stripped a box, I simply put it on the bench, undid the endplate & pulled the main & lay shafts out as a lump. the last gear on the layshaft is the output gear, and would need swapping. For the diff, I undid the locktab, found a suitable piece of metal bar and unwound the big nut, having marked its position and counted how many turns it took. if you swap the pinion gear onto your original diff, it will go straight on & fitting is easy.

[Stuart]

the job is acctually very straight forward and easy. it just takes a little time and patience.

first off undo the gear selector at the top of the box (should be 4 10 or 11mm bolts) and remove the unit.

oh drain the gearbox fluid by taking the diff access plate off (its the big trapezium shapped plate to the rear of the engine, in lineish with the clutch.

take both wheels off and pop the lower ball joint bolt in each. this will enable you to pop the driveshafts.

place a jack under the gearbox and undo the front left engine mount, then lower the box

undo the bolts around the end of the box, most will be 14/15mm and. the cluster will eom out with a touch of carefull tapping with a hammer. i do mean CAREFULL dont welly the bastid.

with the casette out of the car you will see two shafts pointing upwards. the longer one is the imput shaft and the one with all the larger gears and other crap on is the output shaft.

on the top end of the output shaft there is a small gear not meshing with anything, thats the pinon gear of the FD, just pop the circlip off and the gear will come off. some will just come off by hand, others ive done needed a puller on them. bear that in mind.

replace the gear you removed with your new one, get it the rightway round as its got a spacer whim pre machined into it.


for the diff gear. undo the locking tab on the casing. place a mark on the casing and nut to give you a clue as to how tight to get it again.

its very fiddly but you need to get a steel bar that fits in the castles and undo the thing.

the diff will come out. (remember whatway it was! lol) undo the bolts and replace the crown wheel.

refitting IS reverse of removal. use plenty of RTV silicone on all the seal faces to be sure it doesent leak once rebuilt.

hope that helps

[mikeyredtop]

ive never done this but some diagrams ive seen the fd on the lay shaft (output) it part of the shaft...

[Stuart]

thats the big block gearboxes F16 F20 F28


the small ones F10-F15 are seperate.

[MechaT]

thats the big block gearboxes F16 F20 F28 the small ones F10-F15 are seperate.

Nice one. Good to hear from someone who's actually done it. I've heard contradicting comments from people who 'heard that' or 'think this'.

[mikeoxford]

tools you will need.

circlip pliers.
2 leg (or three!) gear puller. to pull the pinion of the gear casette (one part of the FD)
and a BIG vice - to grip the crownwheel in to remove from the diff if your not replacing the diff altogether.