Mythbusters - S and T series diff strength

[Hen]

There is much discussion in sprinter circles about the advantages of upgrading from the stock Oz S-series to either a T18 or JDM T-series diff. One thing which gets mentioned regularly is that you will be getting bigger, stronger axles.

This is total rubbish. I checked in the shed this evening and a (small diameter) T-series axles fits both a T18 T centre and an AE86 S centre perfectly. The splines are the same. And it is here at the end of the splines that every broken axle I have seen has broken (imagine trying to disassemble your diff if it had broken elsewhere)

In short same splines = same chance of breaking = same strength.

(The rare, late, larger axled JDM T series should be a little stronger, but as rare as my teeth)

You could argue that the T 6.7" crown wheel is stronger than the 6.38" S type, however I feel that the axles are far more likely to let go due to abuse than the crown/pinion.

There are several good reasons to upgrade to a T series rear end, but don't fool yourself that strength is one of them.

Hen

[oldcorollas]

breaking axles is usually associated with a locked centre (due to the reverse loading that occurs during cornering) or perhaps a very tight clutch pack LSD...???

i have a feeling that the abuse level and the type strongly affect where failure occurs...
ie, drag with hard launch, dorifto with locker or 2way LSD, circuit with more pregressive power application....

[slide86]

im sure that heaps of people think that upgrading to T series will allow 15000rpm clutch drops, with 10 inch wide tyres and expect it to hook up. not f**kn likely!

then complain that someone told em the T series was so much stronger than S series.

i think there is a massive myth associated with these diffs. sure they are good to upgrade the centres. But i think we can safely say that with a good LSD, or even a CIG, BOC locker the axles will be the first things to suffer. no matter T, S, P, Z, A or R housing. (i made up the last three, dont worry )

[Mos]

Hi Hen,

While not disagreeing with most of your post you can't ignore the simple empirically determined fact that people seem to break less T series diffs than S series... (and crown/wheel pinions than axles).

(Edit: actually, I take that back - I know of way more T series diffs being broken, given that they are by far the majority in small cars - so by that defn S series must be stronger, coz there's less broken ones around ;p)

Let me tell you a story about a certain white sprinter (not my white sprinter).
Once upon a time it got itself a 4age. Then it started having fun - blew the S series diff two weeks after the conversion (to be honest I don't know if it was the centre or axle but always assumed centre).

Then it got a JDM drum break T series. This diff, and centres were happy for a very long time.
Then came along big old mean GZE.... now more fun started.

This poor T series diff.. heh.. went through a total of 8 diff centres. The last (8th) time it let go, it was the axle (after which an S series diff housing was installed and the car promptly sold)[axle broke where the spline ends - weakest part].

(This sprinter also went through 3 T50 gearboxes, two of which are under my house - if anyone wants to play they're yours - they stripped off a third of the teeth of second gear).

Virtually every other time anyone has broken a diff it's something in the centre that lets go (brother destroyed the little differential gears, apparently by starting the car in gear, with the handbrake on ).

This does seem to suggest the axles are far stronger than the crown and pinion gears... I suppose it wouldn't be hard to work out the relative strain on the area of steel in question, and they may very well be similar, but (other peoples') experience speaks for itself...

JMO - Out of curiousity what bits have you (and others) broken in diffs?

Other than that the only (sane) reason to upgrade to a T-series is for the disc brakes ;p (well that was my reasoning anyway ).

Mos.

[Hen]

My reason for upgrading to T was so I could get an LSD centre, and then I have proceeded to run a locker for 2 years...

Mos, that is very interesting to hear. In two years I have broken (all behind a ZE which got thrashed hard regularly):
- 1 S centre (welds dropped out because I welded it poorly, so not really a hardware fault)
- 1 S axle (attempted half donut with hot, sticky rally tyres on bitumen)
- 2 T axles (running tall 215/60R15 or so tyres)
- 1 T crown/pinion
- Current T is getting very whiny and has LOTS of backlash
- Tore teeth off 2nd in 1 T50

All this has been while using a welded centre, so I suppose that minimises the number of moving parts, but loads things up more.

I'd be interested to hear more people's experience of S vs T and axle vs centre breakage.
Hen

[Classique71]

And when is it realised that a stronger diff like a hilux is needed ??

or is this seen as a disadvantage due to the obvious weight increase ?

[Mos]

In the case of this certain white sprinter, I remember the discussion clearly.
Him:Blew the diff.
Me:Ah cool, how much for centre?
Him:$50.
Me:Ah cool, you can get a hilux for $400, right?
Him:Yep, when I blow $400's worth of centres we can talk.
Me:Ok
.. the rest, as they say, is history

(I also remember installing that 9th diff vividly )

Hehe..
Mos.

[Mos]

All this has been while using a welded centre, so I suppose that minimises the number of moving parts, but loads things up more.

Wouldn't that be, as Stewie suggested, due to reverse loading of the axle?

I'm only guessing (and maybe vague memories of materials in high school) that twisting in one direction could stretch grains over time but not necessarily weaken them a lot. But when you're then taking those grains and stretching them the other way it causes a lot more fatigue than just the one direction. Stew?

FWIW that axle took the 8 or so centres without a problem (until it popped) - that sprinter was the most thrashed car I have ever been in, rollbacks were a norm, defn a drive it like you stole it scenario.

Have all the broken axles been the side that gets pushed against the road or random?

Mos.

[oldcorollas]

that sprinter was the most thrashed car I have ever been in, rollbacks were a norm, defn a drive it like you stole it scenario.

Have all the broken axles been the side that gets pushed against the road or random?

Mos.

i never actually got to see it in action but i remember the almost weekly updates

more like.. "drive it like you've been paid to break it"

would be interesting to hear if it is right or left breaking more often...

the main issue with the reverse loading is that with cornering, one tyre travels further (the reason there is a differential.. to allow speed differential between the wheels )... with a locked diff... ONE TYRE MUST SLIP.... otherwise you are going in a straight line... no physical way around this (except tyre in the air )


with enough power, you can get one tyre to keep slipping, or both tyres keep slipping... but more usually (esp when the power transmitted is not larger enough to break traction on both), the tyres grip, then slip, grip slip..... so this loading and unloading results in reverse torsional loading of the axles, and is the perfect situation for promoting fatigue...

this also afects the pinion gears, but not as much as the splines on the diff.

fwiw, with a smaller B series and tiny axles, i broke a pinion gear (lost a few teeth), broke a spinder gear tooth, blew apart the cage of a pinion bearing.... but NEVER broke an axle... (and quite a few gearboxes )

whereas other people with less power (if you can say a K series has powah ) broke MANY axles with a locked diff,..... but never centres....

[Vios-GT_07]

i remember the old gze spoontah.. the diff broke when we were driving it home on the day we bought it... no whining or anything prior to it.. it just suddenly started rattling.. blew the center on it.. even with a severely out of tune gze which was overtaken by a stock 1.5 lancer.

as long as you don't lock the diff or kick the clutch it i reckon the S series is pretty tough. It can cop a fair bit of abuse if abused right...

A diff builder was saying 'diffs are not indestructable. You could spend 10,000 bucks on a diff and it'd break after a few runs. Even Detriot Lockers can break if abused. Diffs last if used properly even in the harshest of applications' coming from a guy that supplies diffs to the rallies and drags.

[Toycrash]

So do you ppl makr the axles for keeping it rotating on same direction, when you disassemby your rear?

This might be one of those reasons you blow an axle, I have never seen a T or S series axle being snapped on open diff or eith true working LSD.

Snapping axles with welded diff has nothing to do with how much torque the axle will take.
Spools are for drag, not for street nor track.

[The Witzl]

Good morning all

I am going to have to agree with Mos here, not because he is such a nice guy and all, but because his experience matches perfectly to my own experience with regards to diff centres breaking.

Let me tell you the story of a little black AE71.....

It started life as a humble, temporarily paddock bashed AE71 with a 4A-C, until said 4A-C siezed in a way that only Mr Rex Kellway himself was capable of describing. (yes, it was fucked). This is when it met your humble narrator.

It then received a replacement 4A-C donated by the friendly Mr Mos from his front yard (spiders in the ports and all). It was a happy car until it was found that the bog warmer diff had seen better days (and less metall content in its diff oil).

A month or two later the little black AE71 then received a burst of new life thanks to a 4A-GE conversion, and a simultaneous swap to a T18 T-series diff, g'box and tailshaft. It was a happy little car again.

Much fun was had, until an evening of perhaps too much fun following by loud whining complaints from the little T series centre ended the fun.
Then the centre got replaced
Then a visit to WSID and 8 runs ended the happiness, and a month later the screaming centre was removed.
The centre was again replaced.
Many months of happiness continued.

Then one day, the diff suddenly locked up. The little black car was kicked and bashed until it gave in and unlocked the diff, and it was driven around for another couple of weeks until a new centre was sourced. The unhappy locking diff was removed to find a wayward locking pin for the spider gears (refer: http://www.rollamods.com/witzl/ae71%...diff%20007.avi)

With the new centre, it was happy again....
Until a trip to brisbane progressively wore the poopoo out of it, and the diff gave some large backlash and whining.

Then came a big mean TURBO, and a new centre.
Then came another trip to WSID.
Then came the backlash, and more whining.


----------> In short - that's 5 replacement T-series centres, and not a single broken axle.
Even with a turbo 4age.

[RobertoX]

When I pulled the s series out from behind my 4ac, one it's axles had a nice little twist in it right next to the spline (I'll see if I can find some pics later), this car was bought off an old lady

Another T centre that I saw lying on the floor of an Adelaide 'drift workshop' had 2 stubs of axles stuck in it sheared off just after the splines, it was a clutchpack lsd of some sort.

[SIKTOY]

----------> In short - that's 5 replacement T-series centres, and not a single broken axle.
Even with a turbo 4age.

I have found in my cars the more hellies you do the more axels you need
and the more racing starts you do the more centeres you need

Thats my 2c

P.S I have a few spare axels if you need them

[mumblezzz]

Dont know how you guys break axles. My experience with both S and T diff are that the centers keep shitting themselves.

#1. Welded S diff. 2nd hand POS that the welds broke apart a week after installing and chewed the ring and pinion.

#2. Welded S diff #2. Lasted 8 months before getting removed because the whining was so loud. (Some hachi people from the 1st melbourne trip will remember this one.

#3 Open S diff . installed on a friday. Then proceeded to develop a death whine at the track day the very next day. Yanked on sunday

#4 Welded S diff. Lasted for about 3 months before one of the bolts in the center broke free and went for a ride around the diff a few times and had its way with my ring and pinion. Cracked the shits and put a T diff in.

#5 Welded T diff. Lasted 1 drift day. broke on the last lap of the day. Got the shits and bought a cusco 2 way.

Never had a problem after installing the LSD. Used it for about 4 months in the hachi and then was resurected in my KE70 which has since been sold and lives on in another KE70 shell.