3rd member talk (ring&pinion setup etc.)

[firehawk]

As I'm writing this, I have almost three LSDs worth of parts on my desk as I'm trying to figure out which of them I should use to put together one for my car. I'll try to write a bit of something that may be useful to those who have trouble with their original LSDs.

First of all, when the differential is removed from the carrier, if may also be a good idea to change the differential case bearings if they haven't been recently changed;

BEARING (FOR DIFFERENTIAL CASE): 90368-41050 (2 needed)

However, before you rush to order this from your Toyota parts desk, stop by at a bearing shop and ask for a price on the very same bearing by its Koyo part number LM501349/10.

Fixing an LSD which doesn't lock up properly is fairly easy - in most cases the clutch plates/washers or the springs which compress them are worn out and need to be replaced. These parts are still available as new spares from Toyota, as well as a complete kit from Techno Toy Tuning. The parts are as follows;

SPRING, COMPRESSION (FOR CLUTCH MEMBER): 90501-23474 (4 needed)
WASHER, REAR DIFFERENTIAL SIDE GEAR THRUST NO.2: 41361-14051 (2 needed)
PLATE, CLUTCH: 41385-14010 (2 needed)
WASHER, REAR DIFFERENTIAL SIDE GEAR THRUST NO.1, T=1.85 (#6): 41361-14070 (2 needed)
WASHER, CLUTCH MEMBER THRUST: 41383-14010 (2 needed)

Depending on which country you're in and whether you're able to barter some discounts, the above parts should cost something in the ballpark of 100-200eur.

However, with cars that have seen lots of kilometers or hard driving, there may be other parts that need to be replaced as well and these are not quite as easy to get. The LSD casing itself is pretty solid, but there may be hairline fractures at the bottom corners of the side openings, near the ring gear flange. Small ones should not cause problems, but if pieces of metal have chipped off near the fracture, the casing may need replacing. I haven't asked whether the casing sub-assy is available as a spare, but I doubt it.

Besides the clutch plates and washers, the diff contains the usual differential components; two side gears which connect to the drive shafts, two pinion gears (aka. planetary gears) and the clutch members, one of which also acts as the pinion shaft. All these parts are known to break, so they need to be inspected for damage and replaced if necessary. Herein comes the problem, though.

Of the parts listed above, only the pinion gears (41341-14020, about 40-50eur a piece) are still available as spare parts - the rest of them are discontinued and if broken, need to be replaced with good used parts. Finding such parts is pretty much a game of luck. By buying a used LSD, you may or may not get the parts that you need. Buying several used LSDs will eventually get expensive, so at one point it must be decided which of the parts are good enough to use and which are junk.

This is problem I'm currently facing. I have a some new parts, some good used parts and some that are a bit suspicious. The pinion gears are not fractured, but the teeth are fairly rounded. The side gears, however, have some nasty-looking cracks and hairline fractures on the bases of some teeth. My other set of side gears looks even worse, with whole pieces of the teeth missing (they're for zenki, so they're useless for me anyway). Now I have the dilemma whether to just use the side and pinion gears I have, or try my luck and buy one more LSD in the hope of finding better gears. I'd hate to ruin a whole lot of brand new parts when a side gear breaks into pieces and damages everything inside the differental carrier.

Well, this ended up being pretty much a rant as well, I hope there's some informative content as well. I'll include a few photos of the damaged side gears (the better ones) to this post. Photos of broken clutch members can be found in my project thread.