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. I've done it this way and recommend it, though it was very fiddly trying to get the screws back in. Use a hex bit in a small spanner - I had a hex bit from an impact driver set, with a 5/16 ratchet ring spanner. I also filed a small amount of the thread off the bolt ends to give them a lead-in through the mount and spacer into the steering rack holes. A balldriver will reach from above behind the engine.
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 bearings (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.
Follow-up June 2010:
7500 miles later, on a long drive to a rally, I got a turbine-like whistle intermittently from the front left - ish of the car.Worse at higher road speeds and loads. Uh-oh.. I carried on, a little nervously, and got home with the noise slightly more frequent. Bearing again, I thought. Sure enough, revving in neutral with my head under the bonnet produced quite a bearing whistle at higher speeds. Box out again. The Taiwanese 6205 on the gearbox input had failed, visible marks on the track and very rough. Had I ignored the noise I am sure it would have broken up before long.
Here's an admission for you. Looking back through my records the previous gear oil change had been at 7000 miles instead of 6000. Not laziness - it seems I had forgotten how to add up.... Could this have been a contributory factor? I don't know. One thing was sure, the full litre was still in there.
I pondered fitting a roller bearing, as they are good at high speed loads, but since the input drives a helical gear and there must be some side load I stayed with a deep groove ballrace, hoping my replacement was of a higher quality.
Oh yes, and the rear pulley didn't want to come off again, heavier dose of copper grease this time I think!
New set of bearings about 50 quid's worth from a local bearing factor. You can easily get cheaper bearings. I didn't want cheaper bearings but if you can get GOOD bearings cheaper then by all means go for it.
The hard-used 6205 is a NSK, made in Poland as it happens.
October 2010
The saga rumbles on...
The rear pulley circlip escaped (see the pulley page) and rubbed on the gearbox casing, mounting and nut. I had to drop the gearbox a bit to remove the pulley and since it had rubbed the oil seal area, decided to take the thing out, put a new seal in at this position. It seemed silly not to replace all 3 seals, so while it was being stripped anyway, do the bearings again, this time all SKF from the internet supplier Simplybearings and a higher ETN9 spec for the input bearing. Taking some advice from the Aixam and Microcar Yahoo group I bought a higher clearance version for this and the 6204s, to allow for the pulley shaft heating the bearing inner before the box has warmed up. There were again no signs of abnormal wear in the box though I thought I could detect a slight roughness in the previous input bearing. At least the pulley came off easily this time.
Here are the new ballraces and seals.
The seals are twin lip style to keep muck out. There is no rim or step in the housing to locate them so I pressed them in (by hand!) flush with the outer surface. Grease was applied to the sealing edge and to the shaft before assembly. THIS IS ESSENTIAL for seal fitting if you want them to last.
I cleaned and de-burred the scuffed casting around the input shaft, this is what the pulley had done to it:
And inside. The alloy overhangs the hole quite a bit:
And just because I like pictures of shiny oily metal - click thumbnail because the picture is quite big. Or don't if you don't want to.
Aixam