The Gearbox
More correctly, reversing box. Can cause much grief in a quad. The uppermost bearings are splash lubricated from the puddle of oil in the bottom. Sometimes not too well, especially if the oil has escaped via the older type filler cap. Wrong oil or neglect risks premature failure. A collapsed bearing is very bad news, and the ball bearings once spat out of the race can jam in the gears, the whole wobbling mess then breaks the alloy casing. Much expense follows. Aixam raised the recommended refill volume for their boxes from 0.7L to 1.0L but this means the fill level plug is no longer any use on the older cars, and also more oil is going to spray out of the top of the filler cap. I checked after 3000 miles last service. Out of the 1L, there was 0.7L left! It's supposed to go to 6000 miles!
Anyway, with mine having done 40 000 miles, and almost expecting expensive noises any minute, I decided to pull the box out and fit new bearings. A lot cheaper than a new box. I had to do something with the rear mounting anyway, it had gone frayed and squashy probably from the aforementioned escaping gearbox oil. I have a cure for the Houdini oil, by the way. See here I drained the oil after 2000 miles and none had gone missing. Fit a later type filler cap with a fitting for a vent pipe. Connect this to a breather pipe led upwards for a bit to let oil run back in, then down to stop muck falling in.
Down to the dirty bits - First I raised the car at the front. NOT ON WHEEL RAMPS as you need the drive shafts popped off the gearbox. This will entail splitting the ball joints or removing the wishbones so you can't leave the weight on the wheels! I used a pair of substantial axle stands under the corner/sill jacking areas. The crossmember there will take a trolley jack slightly further in so I could get the stand in. NOTE THE REAR WHEEL MAY LIFT ALSO so don't rely on wheel chocks this side. On your head (literally) be it if you do.
Undertray off . I left the drive belt on. Drained gearbox oil. Unhooked the gearchange cable from the operating arm on the gearbox then unwound the nut from the cable end so the cable would come off. Tucked it out of the way somewhere. Unscrewed the speedo cable (mechanical speedo). It's a knurled end and required finger force only. There were no other wires (neutral light?) to undo. The drive shafts need to be able to move outwards, so either the wishbones need taking off the inner bolts (2 each side) or the suspension balljoints undoing. If the balljoints, then the suspension needs compressing slightly to lift the joints out. The drive shafts can be hammered off the gearbox, they have spring clips inside which will let go given enough force. I confess to levering them off against the gearbox casing.
With the gearbox mount removed the engine is held by the front mounts only, so needed supporting to prevent it sagging and straining backwards. I used a wooden prop next to the sump, cut to length and wedged in until the weight came off the rear mount. The exhaust bolt had to come off the gearbox, and the two big bolts holding the box to the engine. With hindsight I would have done better to remove the exhaust front section, I took it off later anyway for better access. I couldn't get the through bolt out of the rear mount, so as the mount was dead anyway I got a padsaw and junior hacksaw onto it and cut it apart. The mount is likely to have a hex screw (6mm key) underneath and a nut on top and hard to get to because of the roll bar. The other 2 hex screws in the mount can be extracted instead.
The gearbox and pulley weren't too bad to lift out, leaving the drive belt in place, it weighed 24 lbs.
I cleaned the box, it was filthy black from belt dust and leaked oil, removed the plastic speedo drive and vented filler plug to protect them then had to get the pulley off. Locking the pulley was easy with a rope, and the nut came off. Could I get the pulley off? Could I heck! Heat, levering, improvised puller, hammer; it wouldn't budge. Not having an extractor I took it over to Rossefields in Bradford, where I bought the bearings and went for lunch across the street while they removed the pulley for a (small ) fee:
As you can see they also had some difficulty persuading it off ! The extractor tool AND a big hammer were required. I suspect a little rust was to blame, maybe the shaft key was wedged to the end as well? Before splitting the case I cleaned the drive shaft splines and wrapped some masking tape on them to protect the oil seals, also a smear of grease. The case had M6 screws around the centre join and mine parted easily, I left all the shafts in the gear selector half. Note the gear selector detent ball simply rolled off the selector and fell out. The bolt and spring could be removed first, it needs to come out before reassembling the box anyway.
The gears can now be seen. All the forward gears in this box are helical cut, and all the reverse gears are straight cut. There is one selector which slides along the second shaft, engaging either large dogs for forwards or smaller splines and teeth for reverse. Having seen that smaller gears and PLAIN bearings are used for reverse, I shall be more careful not to abuse that transmission direction...
I unhooked the spring which let the little reversing shaft come out with a "plop" from its socket complete with gear. The other shafts will then come out, unhooking the selector as they come.
I had to get creative (abusive) with the bearings as I didn't have a proper clamp type bearing extractor, just a simple gear puller. However, I wasn't worried about damaging the old races so felt Ok to pull at the outers, and occasionally wedge or lever them until I could get the puller on:
This was the end of the mystery tour, I chilled the shafts in the freezer a while, warmed the new ones (gently) with a hot air gun and had little difficulty refitting them, nor reversing the above steps to put the box back together. It was a little fiddly putting all the shafts back in the case but not too bad. I reused the paper gasket as it was undamaged, but would have made or bought a new one had it nicked or torn. Used a screwlock compound on the speedo screws, they are small and holding onto plastic. I don't have a torque figure for the M6 centre bolts, so used discretion and screwlock on them instead.
The pulley assembly is the subject of a separate page, but I did clean and de-rust the pulley shaft and centre bore before refitting it. The shaft key was tacked into the shaft groove with a bearing retainer compound to prevent it sliding inward and wedging, and a smear of copper grease applied to the shaft. New nylock nut and washer as the original washer was chewed up somewhat. I used the rope trick again to lock the pulley. As soon as I get a torque figure for the nut I'll post it here - I did the nut up to "tight" ft-lbs.
Aixam