DIY Noisy Gearbox repair

EXTRACTED FROM FACEBOOK GROUP "MICRA SPORTS CLUB AUSTRALIA" - ALL TAKEN VERBATIM FROM Mickel Tantucz - DIY IS AT OWN RISK, not mine, nor his :D



So do you have a noisy gearbox? Is it noisy and sounds like it's going to fall out of the car? If you answered yes to both questions, high chance is you have a worn out Input Shaft Bearing. As photoed (and highlighted in the 5th photo) you will see that it is just an $18 bearing (Part Number 6305CM, can be picked up from most bearing shops.

This process is possibly a 4out of 5 star rating for "difficulty". If you have removed your Micra gearbox before this will be an easy task for you.

I DO ADVISE YOU TO PUT YOUR VEHICLE ON 4 AXLE STANDS FOR THIS JOB AND ON FLAT GROUND!

Step 1: remove the follow - battery, battery tray (3x12mm bolts), air intake tube (or take the intake box off also, there is an 10mm box on the right hand wheel arch), starter motor (2x14mm bolts, best to use an 6inch extension for the bottom bolt), earth strap from battery. You will find there will be a few connections that bolt to the gearbox in some places, best to disconnect these for there is no hassle removing the gearbox.

Step 2: This is where the gearbox starts to be removed. You will find there are 2 x 14mm bolt that sit under the thermostat housing, remove these.

Step 3: Remove both front wheels off vehicle (if you have done so already), get someone in the vehicle to jump on the brake and hold it down while you use a 32mm (maybe 30mm can't remember) and crack the drive shaft bolts then once that is done, disconnect the brake line to the strut. After this has been done remove the brake caliper (if you can/or have place the caliper on the spring by using a coat hanger bent into an S or zip ties) then remove the brake disc/rotor. Next stage is to remove the steering rack off the hub (17mm socket) you may find there is a split pin in place remove this and then the nut. If this doesn't come away easy use a hammer and hit the section where the tie rod end sits in the hub (this should pop out once loose. Once you have done both sides you can continue on to disconnecting the strut from the hub. After that is done you may want to drain the oil in your gearbox before you continue you on to removing the shafts from the gearbox to avoid a big mess

Step 4: Remove both drive shafts and put out the way. You will now has to venture under the vehicle and undo the selecting rod and stabilizer from the rear engine mount (12mm nut and bolt). Once that is completed you next disconnect the rear engine mount (12mm or 14mm can't remember) once disconnected, remove the cross brace that sit directly under the car (front to rear, you will need to disconnect the front engine mount from it also (14mm also) plus 17mm rear bolts, 14mm front bolts). Pull this out from under the vehicle and place aside (inspect the engine mount for tears/sagged, mine needed replacing due to busted)

Step 5: Remove the bracket the engine mount sat in (3x12mm bolts, will need deep socket or short extension). You will see 2 engine supports that bolt into the bottom of the gearbox to the engine undo the 4 (12mm) bolts and pull the supports off (I removed the bottom 2 and lightly undid the top 2 allowing them to dangle). You will find there is 1 (14mm) bolt on the front side of the gearbox/engine that is in place, remove it.

Step 6: Place something under the engine that will allow the engine to be supported (I used 4 bricked haha) once done (you have 2 ways of doing this step) you can undo the main bolt for the gearbox mount (2x14mm nut/bolt) or you can undo the 3 (14mm) bolts that bolt into the gearbox (take in mind they are different lengths) one the mount is removed your gearbox is ready to come out.

Step 7: Jiggle/Pry (if you can) the gear box from above; NOTE: there is 2 small dowels holding the box together. Jiggling from above will allow the gearbox to drop without crushing you once it is out and on the floor drag it out from underneath the vehicle now you on to step 8.

Step 8: Lay your gear box face down (as you can see pictured) and remove the top plate (6x10mm bolts, mark on the gearbox were the tabs go) then pull off the cap and spacers (mine had 2). Once removed now onto the next part of pulling the gearbox apart, you will find (12x12mm bolts, make where the first bolt you remove and lay out bolts in a clock wise direction: due to one bolt being bigger then the rest), once these are all removed find a place where you can pry the casing open (you may need 2 or 3screwdrivers for this). Once the casing is loose carefully remove the casing and place aside (NOTE: EXTREMELY LIGHT). Once the casing is off you'll see what it's like internally (photo 1).

Step 9: PULLING THE GEARS APART. This is a careful process also (MAKE SURE YOU TAKE PHOTOS FOR REFERENCE, THIS IS THE "TRICKY" PART) as pictured in Photo 1 there is 3 selectors, carefully remove the rod holding the selectors in place and then remove the selectors from the gears and be aware there is a locator for each one. Once removed, you will find 3 x10mm the require removal, remove these and the selector bracket that was being bolted down next you want to remove the REVERSE GEAR slowly remove the rod from the gear with the spacer. You will find a triangle bracket that is holding the Main Shaft in, remove the secondary shaft and the differential. Undo the 2 (12mm) bolts from the triangle bracket, then you are stuck with 1 star/security screw this is a T40 socket remove it and the bracket and the shaft is ready to come out. You may need to lightly tap the main shaft out I the bell housing. You will find in photo 5 the bearing that is circled, this is the one that is the cause to all the noisy, if you rock it side to side and it moves a lot it requires replacement.

Step 10: REMOVING THE BEARING. The Input Shaft Bearing is held in place with a snap ring remove this and place in an important area! Next you will need to either use a press or punch and hammer (best bet is go to your local mechanic with the new bearing PN: 6305CM and also new nismo mounts if you had been looking to replace them also (Rear, and Gearbox mounts). Once the new bearing has be put on and snap ring placed back on you are ready to put it all back together.

Pretty much putting it all back together is reversal of pulling it apart.

I hope this helps someone out and then don't end up needing to spend stupid money on a new box I also recommend using new oil when the gearbox is back together and reseat it with Grey Max and replace the shaft seals while it's out.

NOTE: check your clutch or replace your clutch at the same, if your rear main seal is leaking best replace that at the same time enjoy...

ADDITIONAL INFORMATION: When 5th Gear fork (top of input shaft) is removed the sleeve can come off (Blue arrow below) easily and the little shift plates fall out (recesses,red arrow below) - be careful not to lose them.

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