Gearbox failure

[®usty]

Was going for a drive recently, coming around a corner when I heard a sudden horrible noise (instantly turned car off & out of gear)
after an inspection, wasn't the engine or wheel bearings. Got on the hoist at the local Toyota suspecting (hoping) a bolt or something had flowed off from the axles, but the sound is definitely coming from the gearbox.

Toyota did the install of the LSD & new bearings late last year, since then haven't had any issues. Transmission did make a whirring noise - but I think that's normal for a mechanical clutch plate LSD.

A head serviceman(?) at Toyota suspected it was bearing failure - (input, output or diff) The reason they suspected bearing failure was some soda blasting powder may have still been in the case even though it was thoroughly cleaned by Toyota when the LSD was installed. But to know for sure the box would need to come apart.



Details
96 ST202 Celica with S54-06TRD have done 2,000km's since the LSD was installed


Noise sounds like a clunking mechanical noise, coming from the transmission.

Noise happens when: off torque/accelerator, in or out of gear, coasting in neutral.

Happened suddenly going around a sweeping corner.

No issues changing gears or sounds any worse in any single gear including reverse.

2,000kms on new LSD, TRD FF gear oil and new diff bearings.


It was last week when I went in and put the car on the hoist (I've got the car at my place since) They were going to price up a quote & work out a list of parts they would suggest replacing. I've yet to hear anything from them a week later.

This is a reponse I got on another forum..

That's rotten Luck. Ask your installer how he set the preload on the differential bearings. It's a critical step for bearing longevity. A lot of people ignore it because 8 out of 10 times the original shim is more or less the right thickness. plus it's a royal pain to Assemble, check, take apart, switch shims, reassemble, recheck, take apart again...etc. Maybe you were one of the unlucky 2/10. also ask them how they pressed the differential bearings on. Your supposed to press on the inner race, NOT the outer.... I accidentally crushed a cage on one of mine while pressing it onto the helical and had to buy a replacement. funny thing is there is no obvious visual indication that damage was done, so it's easy to miss something like that.

Plus I highly doubt it's the input or output shaft bearings. Two of them are sealed deep groove and the other two are really beefy non-locating rollers. You would have to do something incredibly stupid to harm them. The diff bearings are the most frail by far.

Whats your thoughts? Toyota incorrectly pressed the bearing in, or didn't have the correct preload. I have a spare shim they took out. Wouldn't have thought there would be much difference between the toyta & trd diff housing requiring a shim be removed?

[Dell'Orto]

Have you driven it since? Just to see how drive is now affected. After 3 months/2000k's I wouldn't be all that keen to pay anything tbh!

[®usty]

Just to toyota and back home. Driving isn't affected, from what little driving I've done, as long as you're accelerating you don't hear the noise

Exactly, my thoughts. When I talked to a Toyota parts person. His opinion was if the bearings failed as they were faulty then I would get replacement bearings free of charge, though unsure of labour chargers.
Not too sure about going back to this particular toyota to get them to fix the problem. Might ask around other gearbox specialist to get their opinion

[Jdawg]

Had exactly same noise from one of my old Valiants during some "Loss of traction" exercises.
Bang, then Clunk, Clunk Clunk the whole drive home.
Had spat a couple of teeth on the Spider gears.
A quick look at a diagram of the S54 LSD shows Side gear and Pinion gear sets. It could be that these have been damaged as you say it happened suddenly.
Only 2 ways I can think of if this is the problem, Abuse or your LSD carrier was not set up right when assembled.

[duddley]

If they have supplied the parts and done all the work it should be on them to re do the job.

[Anth_555]

untell the box is opened up you wont know whats wrong with it.
if they have coursed the problem they should have the chance to fix it. you dont no why it has failed and it may not be a bad mechanic but a simple mistake or not there fault at all.

[Anth_555]

also, whos idea was it to soda blase the housing?

[FST4RD]

My old familia did this, ok when accelerating in a straight line, but coasting, decelerating, accelerating whilst cornering made some awful noises.
Turned out the bearings had collapsed and diff had lunched itself.

[®usty]

Jdawg, if you are referring to the internals of the lsd with the side gear etc. I probably should have been a bit clearer it is a TRD LSD - mechanical clutch plate.



I have located the shims that we're removed from the gearbox. They replaced the drivers side shim aswell(which is a preset shim for the ring gear & driven gear) The passengers shim is the adjusting one to correct the preload.

I'm not sure why they replaced the diver's side? Because they had a new shim or the TRD housing is slightly shorter or longer than the toyota diff. The Shim is the same bewteen S54-06A & S54-06D (open & Helical LSD)


I've been told by someone who's installed a Helical LSD into a S54 how easy it is to crush a cage on a differential bearing without realising it. And that this is the most likely cause.

You're right, you don't know what exactly the problem is until you open it, but can look at the logical causes, and what was chaged. Repair manual says gearbox noises are caused by, oil level & oil type & bearings. The only bearings that were touched were the diff ones. And you can see from the pic of an S54, if they were pressed in on the outercage that would cause damage.