Hi guys! Does anyone know what is the horsepower limit of the sierra(sapphire) cosworth 4x4 rear differential?

 

It's not the horsepower that kills the diff, its the torque, other than that, no idea

 

dunno but 3rd gear goes first, I know that first hand!!

steve

 

Well I have 400bhp & 500nm of torque and I am planing to install stronger gear kit because I am repairing my gearbox quite (often and not only the third gear but also 2nd, 5th and input shaft gear!) thats why I am asking...

 

If I was in your position I'd try to get hold of a 7.5 inch diff, all you have to do to make it fit is chop 1 ear off of the beam and re-weld it back in (30 minute job).

Other alternative would be a complete 2wd saphire rear beam, just swap the 4x4 brakes and escos rollbar over to the saph rear beam and you're sorted. The ratios are 0.02 out so 100% safe to use in 4x4

Cheers
Dan

 

has anyone broken one and at what stage?

 

it depends how the power comes in tbh, i broke 3 front diffs, 1 rear diff, and 3 gearboxes on a t34.48, at 370bhp 420lbft.

but bigger turbos are kinder to your drivetrain if you dont launch it,

 

They cost nothing to buy (well, £50-£100..?) and don't break as often as the gearboxes and drive shafts, so drive on driver!

 

I broke the one in my Westfield last year running somewhere between 400 and 450 horses. It had a lot of abuse over 4 years both on track and saw at least 50 full on Launch control starts. Ive no idea of its origins but assume it was just out of a normal 4x4 so would be about 15 years old too.

It broke on a launch with new sticky tyres.

 

Im looking at buying a limited slip one which is about 175 quid and then running 400bhp ish thru it in a locost. Stus experience leaves me with some hope tho!

 

not much weight in a locost
and if its only running 2wd it actualy takes less strain than 4wd cause it'll just spin the wheels
it should take that power for a while
if you can go for the 7.5" diff out a 2wd instead
they're stronger and you'll be able to pick 1 up no prob for the 175 you mentioned

 

Thank's a lot guys! It seems that the diff will hold since I don't do drag starts but again the weak link in my drivetrain is the gearbox because if I just plan the throttle down in any gear (except 4th and 1st) on full boost( 1.4bar) the gears will brake allways at 5000-6000rpm. So after installing stronger gears will see about rear diff.

 

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They're LSD as standard aren't they?
You're welcome to pay me £175 for the one I have kicking around at my workshop if you want?!

 

yeah, 3.62 lsd as std. They seem to go for about that on ebay

Of yourse if you fancy giving me a bargain

 

i broke 4,including 2 plated ones.
then i changed to a 7 1/2,plated diff.
i used a granada diff,available from ebay 30 to 50 quid.

 

what turbo you running mate?

 

Could your car's appetite for rear diffs have more to do with the strength of your Skyline gearbox, the amount of drive you're running to the rear wheels, or your launch technique than strength/weakness or otherwise of 4WD Cossie rear diffs?

 

you will allways break the weakest link,lol.
how long a 4wd diff lasts,has more to do with its condition,than the power you are running.ie 100k milage without any fresh oil and adjustment will break a lot sooner than a new diff,with fresh oil,and correct free play adjustment.
as a general guide,the planet gears normally fail around 450bhp,and the cwp at 500 bhp.
the 2wd is a lot bigger unit,so planet gears at 500 bhp, cwp at 550 bhp.
2 of my diffs broke under acceleration,one in 2nd gear and the other in 3rd gear.
as i said,just use a granada rear diff,same as the cos 7 1/2,just uses a different back plate. there are loads on ebay 50 quid ish .

 

Good to know what to expect from them.

 

does it have to be 24v cosworth diff?

just dont think other granadas will have lsd?

 

I am running stock turbine housing with a compressor from GT 38.

 

a lot of the 2.8' and 2.9's had slippers in them
dont know if its standard or option etc but seen plenty with them mate

 

check the link mate, full list of diffs and ratios.

http://www.locostbuilders.co.uk/view....php?tid=19116

 

i know the 4x4 will of had 7in like xr4x4 but never knew the2wd did,good to know that

 

how good will a 4x4 diff be in a 3dr, fully stripped ect with around 400bhp max id guess?

the cunt off here who sold me genuine 3dr stuff, clearly neglected to mention that the rear beam and diff were 4x4...

my only spare is off the 1.6gl 4 speeder lol. taller geared tho, so may do 200mph in about 10 miles lol

but you need the push in shafts not bolt on jobbys.

lloyd, how do adjust them etc?

 

Isn't the 2WD a 7.5?

 

Your engine will never make over 400, so you should be fine with a 4WD diff

 

yeah 2wd is 7.1/2 i was talking about 4x4s

 

if you remove the back cover from the diff,the stub shafts are held in by c clips,
you can interchange the larger 2wd stubs and the smaller 4x4 stubs.
ie 7 1/2 inch diff with the smaller 4x4 shafts.

 

thats good to know then

is there anyway you can tighten the lsd up?

ie make it have as little slip as poss?

as most people you see in a 2wd cos trying to do a burnout just light up the 1 wheel usually lol

renton - coont