17 replies to this topic

[MRA]

To answer "can a 998 gearbox be used" yes but not the early type, they standardized the cases later on and that will be ok, however if you are unsure place in position and rotate the crank by hand if it clonks on the gearbox then don't use it.

[Lukie-J]

Thanks for all the help. Can't afford the 4 pin diff at the moment so I'll stick with replacing the gearbox and diff together as I'm not 100% sure which it is yet. Hoping to dismantle and reassemble in a day. I'll have to just be careful with it.

[Spider]

The thing I've seen that kills any diff, even the X-pin type is wheel spin. High Loads, High Speeds and the diff itself, working very hard. The higher speeds centrifugal the oil out of the diff hemisphere, and then the planet gears dry run on the pin(s), they then pick up on each other. Any surface hardening that was there get ripped off (literally!) and then the rest of the wear / breakage process happens quite quickly from there. In a straight line, these parts don't spin very much at all relative to each other. At any corning speed where traction is maintained, while they do spin on each other, the speed differences are low enough that life of them is satisfactory. Usually, when spinning the wheels, it will only be one wheel and at higher speeds. X-pin diffs suffer the same, only it will take a little longer to occur though many of these seem to suffer worse for lubrication as there's even less windows to get the oil in to them.

 

So, don't spin the wheels, that is the killer.

 

The later pin design pin (that has the flats on it) are the worst for doing this, poor material, poor heat treatment and lower surface area. Dumb all round really. The really early pins had a cross hatch pattern on them, which did get the oil in a little better and were made properly, though I think they disappeared in the early 70's.

 

 

or fit something better, like an ATB.

Edited by Moke Spider, 26 May 2016 - 06:29 AM.