Broke 2 front differential back to back...

[crashsvg]

So..... I have a s15 Silvia that we converted awd by chopping up a gts-4 shell.. 

Car makes about 500hp to the wheels... 

Cars fitted with a  twin disc spec clutch and the awd is controlled by a ets pro.. 

Awd works perfect... Launched the car couple of times while the awd controller was in auto mode and all was fine.. Launched the car manual mode full awd  front diff survived 2 launch.. Replaced the spider gears that were damaged launched the car again and still managed to strip the spider gears again.. 

 

At this point I'm looking at getting a os giken lsd....  I've never heard of these diff breaking this easily.. At the time of launch the car was down on boost only making around 380hp.... 

The diff front and back ratio are the same.... Can something else be causing the gears to break so easily or I'm I just having bad luck with 2 worn out differential 

Edited October 24, 2021 by crashsvg

[Duncan]

They don't survive abuse bwith big power and a lot of AWD, but 285kw should not be an issue.

I'd be looking for any sloppyiness between the driveshaft at the xfer case all the way to the front hubs, I think something is moving that is causing additional shock and the diff is the weak link

[BK]

As Duncan said there is something more likely fundamentally wrong with the setup, as the big power usually destroys the crown wheel and pinion not the centres. 

You have nowhere near enough power to break a centre so it definitely points to something else, like possibly never actually disengaging the front torque. If everything mechanically checks out, it's really the only thing as they are not designed for constant use.

Maybe you have just been unlucky

[crashsvg]

I'm getting the feeling something is wrong also.. With the initial set up of the car I've had a issue where the car doesn't roll freely as it should..  So for example I parked on a gently sloping hill and when I got back in the car to move it with the hand break down and foot off the breaks the car didn't move at all while in neutral.. I had to put it in 1st and give it a Lil gas for it to move.. I've had similar experience other places where the car is on an incline and refuse to move unless it's given a Lil throttle.... 

I've never driven a stock gtr so I'm not sure if this is something normal... 

Also a few times this happend I turned off the ets awd controller and the car would sometimes unlock itself and roll Foward .. I notice this but I assumed the awd controller was doing because it sense the car was on an incline through the g-sensor and sent powers to the front which somehow caused it to lock up... I'm confused to what's happening through because I know the ets controller also needs a tps signal to activate the awd pump and with my foot off the throttle that didn't make sense... 

Hope I'm making sense here. 

Some additional info.. 

The first gears that broke the car had stock ratios from the gts4 4.375.. 

We them fited the car with a 4.08 gearing  front and rear diff (I counted all the teeth on both diff several times to varify the markings) ... They were both 49:12.... 

Everthing was torqued to spec. 

 

I'll upload a pic to show where the spider gears are breaking... The second one broke in a pattern That suggests the gears are stripping because the passenger side axel isn't moving..  When i tried launching the car when it broke the second time  it was almost as if I was doing a fwd open diff burn out because I could see the tires smoking  front and rear on my driver side. 

[alexj]

It sounds like 4wd "wind up" you get when front and rear diff ratios are different. If the ratios are the same, then do the wheels have the same rolling radius front/rear? If they were a long way out you might get something like this.

Also, would be crazy, but... that front diff looks pretty dry, you are putting oil in there aren't you?

[crashsvg]

Same size tire all around, same diff ratio and ofc it had oil... Filled up until it over flowed... 

One correction also.. It's a full race awd controller installed.. 

Looking at both diffs and the fact they both broke the same place I'm thinking the awd controller may have been turned up too aggressive.. 

This only started happening since I started launching the car in manual mode.. The car had made over 25 launches previously in auto mode and never had a problem... But in manual mode it keeps striping the teeth. 

Maybe leaving the line we with  launch control and the twin clutch just is a bit too much for the teeth.... 

 

Have considering welding one of the broken diffs back together until I can get my hands on a osgiken.. Not sure how it would drive tho. 

 

[National Assessing]

Hey crashsvg, we're based out in Gold Coast AU and specialise in diagnosis and remanufacture/repair of differentials. Are you happy for someone to give you a call and see if we can find a long term fix and improvement for you?

We have decades of experience in this and would be happy to have a look for you.

Antonio

National Assessing & Engineering

https://nationalassessing.com/mechanical-services/mechanical-diagnostics-and-repair/