Gearbox Nut


Ive heard people talking about a nut that comes loose in fourtrak gearboxes? I would like to know how you tell if the nut is loose & where it is? I have got the gearbox out of my 1991 trak to replace the clutch and would like to check this out before it all goes back together. Thank you for any info. Kev

It's the big bugger on the rear of the mainshaft.

To check the nut you will have to split the transfer box from the gearbox. There are about 8 long bolts holding the two together.

The nut in question is inside the internal spline that drives the transfer box.
Torque setting for the nut is 180 +/-14 ftlb.

You will have to lock up the gear cluster by taking off the top of the box and manually engaging 3rd and 2nd gears simultaneously. Then comes the struggle of holding the box down while you tighten up the mainshaft nut (after having released the deformed part of the nut which is Daihatsu's locking method).

When you have done all this, you will have to lock up the nut again. When I did this on my gearbox, I opted for something a little more positive than just bashing the deformable part of the nut and put a little bead of weld on the nut and the mainshaft.

I used a Clarke 90EN gasless mig welder (the sort normally used for hobby body repair). Max current was used (about 90 Amp) and 0.8mm gasless welding wire. The trick to get weld penetration is to back off the wire feed rate (practice on the edge of a thick bit of iron first). When you have had a bit of practice, you will find that you can make a weld bead about 4mm in diameter which has penetrated the metal well. To keep the weld size small, it should not take you longer than 2 seconds to do it. IMPORTANT ... bearings don't like having welding current passed through them (it tends to wreck the case hardening where the balls touch the races), so you will have to connect the earth clamp to the outside of the internal spline. Now, bite the bullet and do the same to weld the edge of the nut to the shaft, melting both the nut and the shaft. If you need to remove the nut in the future, this should be possible after about 10 minutes' work with a triangular file to clean up the weld and thread.

I rebuilt my gearbox about 10000 miles ago and have had no problems with the nut. OK, this is peanuts as regards mileage, but, at least, there can't be anything major at fault.

Not to sure mainshaft nut

hi there im just about to do my mainshaft nut and have been reading your post and i dont know what you mean by using a 2 pence piece or manually engaging 3rd and 2nd gears simultaneously.if you could explain it to me dumbed down a little bit it would be much appreciated or if there is any else i kneed to know.i dont have a welder is that ok. cheers gerry

tighten main shaft nut.

To tighten the nut up you have to stop the gearbox shaft from turning. One way is to loosen the gear selectors and slide them so 2 gears are engaged at once , then the box jams and you can tighten the nut. Some people have noted that it's possble to jam the gears an easier way ..... by putting a soft copper coin between the gear teeth . the metal stops the gears from turning as the teeth cant rotate, the metal is in the way. The soft copper coin won't damage the hard steel gear teeth.

You don't need a welder , you just need to make sure that the nut , once tightened isn't going to come loose again.

Vehicle has now done another

Vehicle has now done another 100,000 miles with no more trouble from the gearbox, or anything else, for that matter.

Please, Mr Daihatsu, why don't you start building 'traks again? I'd buy a new one tomorrow providing you don't put a computer in it !

Gearbox Nut

Instead of engaging 2nd & 3rd gear put a 2 pence piece in the gears for the transfer box, saves a lot of time.

Thank you everybody. Clutch i

Thank you everybody. Clutch is in and working fine. I checked the nut but it wasnt loose. There was evidance that someone else had been there before me.