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

[Ivan141]

Guys,

I would like to get a little discussion going on this subject. 3rd member (the "pumpkin" that contains the diff) problems have been tormenting many of us over here in europe, and since we dont have a chance of finding ae86's at the junkyards, we usually need to fix stuff with new parts.
Prices are astronomical for almost everything in&around the differential so it would be a good idea to list the best solutions to problems.

So if we can collect experiences/know-how in this thread we might be able to put a good how-to for the aeu86 website together.

I'll start off with my own experiences:

My diff went bad after I practiced a bit of drifting (about 10 minutes worth) on dry asfalt 1,5 years ago. I noticed the LSD wasnt doing much of anything anymore (probably worn or overheated) and stopped playing around. I let the car sit for a few minutes for things to cool down, then when I drove off, a horrible racket came from the rearend. Only when I press the throttle though, so it's most likely the ring gear.
I have been driving around with mux's old 3rd member ever since, which also whines like crazy, but it was better than mine.

Upon inspection of the ring and pinion gears of my old diff they actually dont look too worn.
From what little information there is out there, the most likely cause of failure in these 3rd members is that the collapsible spacer (crush collar) gets crushed too far when you abuse the car, which causes the piniongear to come out off alignment. Some racing series in the US (dwarfcars) use the same toyota rearends, and some have switched to solid pinion spacers with shims to adjust the pinion. This is common practice among offroad 4x4 drivers as well.
I know for a fact that TRD made these spacers for racing ae86's, so they might be available still.. maybe SYM or some of the other parts guys can help us find these.
One of the dwarfcar parts shops also makes these themselves, available for around 75 dollars with shims in the US.

As far as the availability of the other parts (r&p sets/bearings/diff rebuild parts) is concerned, that info is largely available in older threads so we could compile that into the how-to/this thread sometime too.

At the moment I'm most interested in the whole adjustment procedure though, I have 2, maybe even 3 differentials lying around at home that I can rebuild, having them all done professionally is out of the question cost-wise.

I know this is a bit off a rant, but please those of you with usefull experiences or good questions feel free to chip in.

[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.

[Kas]

From my own expirience, my LSD wasn't working at all, I purchased new stock parts from Toyota, and remove LSD from husing.
Took LSD to Toyota specialist for rebuilding LSD and after rebuilding, he told to me, that my LSD wasn't worned, but someone used wrong oil, or didn't change it at all.
Clutch lose their friction, and LSD wasn't working.

[SutteR]

Mine is a "regular" one... It is working quite well but with my GF in the car I'm not supposed to drive faster than 80-90km/h since it's so loud.

After the renewal process it was a bit more silent but after a few turns it gets louder and louder. The ring and pinion come out of alignment very quickly, as Ivan wrote it too.

[Ivan141]

Just ranting on a bit, we can sort through all the stuff people posted (thanks firehawk) later.

So far I have gathered the following stuff:

4x 3rd member housing:

4 sets of ring&pinions:
-one 4.3 off my own car, made lots of noise, doesnt look too badly worn.
-two 4.1 ratio sets, one good, the other has been outside for years and was rusted, dont know if it can be fixed.
-one brand spanking new 4.5 ratio set from toyota (about 450 euro's)

3 OEM zenki LSD's:
-old one off my car, state of insides unknown, probably OK.
-one out of the rusted axle, looks OK
-one with broken clutchmembers/planetary gears...useless unless I find some clutchmembers.

I have a few complete sets of new bearings.

My plan is to get all the necessary tools and start rebuilding some diffs myself. The only things I cant get my hands on are a press and maybe some special tools. AFAIK, the press can be found at many shops, I'm lucky to have some connections at a volvo dealership that probably have one. I have seen plenty of 4x4 guys with toyota diffs do all the work without any special tools, those diffs share the same design, just a bit bigger.

Here's a list of tools
I'm sure are necessary:

-Bearing puller/separator: needed to remove bearings from carrier/pinion.
-a press to remove the bearings with.
-Dial indicator (micrometer) with magnetic base, necessary to measure backlash/runout of the ringgear
-Small torquewrench, Inch-Lbs model with beam or dial indicator to measure rotational torque (to check pinion bearing preload).
-Big torquewrench, up to 240Nm, needed to squash the crush collar down and put the correct amount of torque into the pinion bearings. Also to tighten the various bolts around and on the differential.
-Gear marking compound, so you can check the contact pattern of the gears.
-some general tools, including brass/softmetal drifts to remove outer bearing shells from the 3rd member.

The parts needed depend on what your installing (used/new gear).
The new toyota gearset comes with most of the mounting hardware included. If you install a used set you'll need:

-Crush collar (buy this from toyota, aftermarket types are usually inferior welded tube's).
-Pinion seal
-new pinion stake nut
-locking tabs for the ringgear bolts
-adjusting shims to set the pinion depth with.


The procedure for setting a differential up can be found in many places, the guide in the toyota manual is pretty comprehensive and contains all the torque settings etc. you'll be needing. If you go to http://www.ringpinion.com there is some usefull guides in the tech.section there, especially the Yukon gear setup manual has some usefull picture guides on proper gear contact patterns.

Some interesting things I have picked up:

-when using used gearset it is better to concentrate on a good contact pattern on the coast side of the gear flanks than on the drive side

-the best starting place for pinion depth is to use the washer of your original pinion gear.

-for quick pinion depth setting you could sacrifice a new bearing, if you widen the inside mating surface a little so it doesnt need pressing on anymore you can just slip it on and off while your fiddling with the contact pattern. As long as you dont damage the bearings too much by pressing them on and off this isnt necessary though.


I'm currently on the lookout for the tools I'm still missing, after that it will be a case of starting with some used gearsets and learning by practice untill I get things right.
As Tsuchiya said: it is easy to make plans, to carry them out is more difficult. Nothing is more true when your busy with these old cars.

[gon]

Hi there.
I have all those tools ( the hardest to find is a Small torquewrench, Inch-Lbs model with beam or dial indicator to measure rotational torque (to check pinion bearing preload) I have managed to get a second hand Tohnichi Rotary Torque Screwdriver Model 26RTD (http://www.tohnichi.com/products/pro_RTD.asp)).
I have installed my dif 4 or 5 times, last time it was with a brand new 4.7 ring and pinion.
I did everything according to the manual, and the dif made no noise at all.
After an our on track with slicks and grip driving style the differential still makes no noise, but in the last half hour I practiced a little drifting, and the dif started to whine like crazy.
I am suspecting that the problem is the oil temperature (I’m installing and oil sensor and an oil temp gauge in the differential) or another possible problem is when you are drifting for a long period, the oil goes to the side axle (due to G forces) and stops lubing the ring and pinion.

I don't think that the problem is the crush sleeve (I have suspected that, but after my new 4.77 started winning I did take it out again, and it doesn't seem that the pinion is lose or something.) I did notice that after drifting the differential is incredibly hot (I Have a KAZZ 2way)

[Ivan141]

Yes, heat is probably the biggest problem, but then the question is: what gets damaged/out of spec and causes the whining?
I have been looking around a bit at different solutions to differential overheating, here's what I've seen so far:

-Increasing oil capacity. Richmond gear recommends people to cut out the oil filler plug on the axle, and reweld it a bit higher. This makes sure there is enough oil in the diff, even during prolonged high-G exposure.

-Increasing capacitiy the other way, there is this build-up thread of an N2 spec ae86 coupe where the rear axle housing is modified to allow more oil in it. A sort of protrusion is welded on the rear of the axle for that purpose. I have also heard a similar story from a guy that used to race a KP60 starlet

-Differential oil cooler.. like for instance TE71corolla here on the forum has. This is a very nice solution, but a bit difficult to do, expensive and increased risc of failure due to the extra complexity/exposed bits...not what I would want on my daily driver.

I might just do that oil filler relocation trick, if it cant do any harm I can afford the extra oil.

[Mux213]

Ivan, wouldn't the extra oil be a problem? Better lube yes, but more fluid for the gears to run around it, that also causes more heat, I'm no expert in these, I have no idea how bad this is. I guess it works both way, a little more heat generated, but alot more oil to soak up the heat.

I don't think you should rule out the oil cooler idea though, aslong as the system stays leak free it's as safe as stock, worse thing that can happen is that the pump shuts down, and then you are basically back to stock.
then again, wouldn't mounting an oil cooler mean the whole diff gets filled with oil to the top? that might actualy be a good thing?

I like the oil temp sensor idea

[NoHachi]

The best solution depends completely on which factor is the problem:

If it oil starvation, only more oil or baffling will do the trick. The best way to do it would be to add to the bellhousing with some extra storagespace.

If heats the problem, then your best bet is the cooler. The cooler does nothing to prevent starvation though.

I think the only way to find out is the temperature pickup.

[gon]

I forget to mention that when I installed the new 4.77 differential, the backlash was 0.17, after the track it was 0.25 (1000km after)!!!
0,25 is of spec, and with this backlash it’s normal for the dif to whine.
Like I said before, when I installed it the dif was silent but after the track it started to whine
So, the backlash did increase, and that has nothing to do with the crush sleeve.
It makes me believe that for some time metal to metal contact existed. That lead me to conclude that there was no oil for some time or the oil did get to a temperature that it could not lube anymore.