If you are having difficulty in getting the car into reverse gear it is probably due to the spring ring fitted to the reverse gear synchronising cone, this becomes distorted if the reverse gear sleeve has a chipped tooth. I have just stripped a gear box to replace this, not a job I would recommend unless you have the facilities. The good news is I think you can fix the problem without removing the gearbox. It took 5 weeks to get parts from Japan the delay was due to the spring ring not being listed in the parts catalogue. It seems that Mitsubishi no longer fit this ring on reverse gear (they must have had too many problems). I have re-built the gearbox without the ring and can confirm that it has no effect on getting reverse (it may crunch if you don’t fully disengage the clutch). The good news is all you have to do is take the ring off the synchronising cone. I think this can be done with the gearbox on the car, it’s worth a try but if it goes wrong you may have to take the gearbox off. I suggest the following:
Jack up the car on the nearside using the cars own jack and take the front N/S wheel off. Take the jack to its maximum height; this will also lift the rear wheel (put a block under the rear wheel and lower the car so the wheel is taking some of the weight – this is for safety). Put some axel stands under the sill next to the jack and under the front towing hitch (centre of the engine)
Drain the gearbox oil – you need a container of at least 2.5Ltr. Drain plug is under the N/S drive shaft – it’s the big nut (24mm socket).
Remove the plate on the bottom of the gearbox (put a tray or some paper under this to the catch the drips)
Remove the reverse idler gear; this is the small gear that goes between the input shaft and output shaft and is held by a single bolt to the right of the OIL filler plug (Oil filler plug is marked OIL on the bolt) on the front casing of the gearbox. Support the gear while taking the bolt out to stop it dropping (you don’t want to chip the teeth).
Put car into 5 th gear.
You will now see the reverse gear synchronising cone and the offending steel ring; the synchronising ring is brass ring next to reverse gear on the end of the output shaft.
You will now have to split the steel ring to remove it. This may not be that simple as it is made of hardened steel. Using a screw driver it should be possible to remove the ring from the synchronising cone to give you a bit more space, but it won’t move far. If you have to use a hack saw blade to cut the ring make sure there are no metal fillings in the gearbox casing before you close it up.
Once the ring is removed re-fit the reverse idler gear (tighten the bolt to 48Nm) and check that you can engage reverse gear. The locking devices stops you going from 5 th to reverse so make sure you start from neutral.
Clean the plate and the bottom of the gear box with a degreasing solvent (petrol?) and apply some liquid gasket sealer to the bottom plate only. Make sure you apply this as a continuous bead. You need a good quality liquid gasket I have used Locktite Black Tite – it’s not cheap but it is good.
Fit the bottom plate and refill with clean oil (you need 2.2Ltr – don’t overfill the box) – Job done.
Total cost excluding labour should be under £50. (Locktite is £17) and depending how hard it is to remove the steel ring should take under 2 hours.