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Sierra 4x4 rear diff

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Old 18-01-2009 | 11:21 AM
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Default Sierra 4x4 rear diff

Hi guys! Does anyone know what is the horsepower limit of the sierra(sapphire) cosworth 4x4 rear differential?
Old 18-01-2009 | 11:38 AM
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It's not the horsepower that kills the diff, its the torque, other than that, no idea
Old 18-01-2009 | 11:40 AM
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dunno but 3rd gear goes first, I know that first hand!!

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Old 18-01-2009 | 11:47 AM
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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...
Old 18-01-2009 | 01:07 PM
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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
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Old 18-01-2009 | 05:54 PM
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has anyone broken one and at what stage?
Old 18-01-2009 | 05:58 PM
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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,
Old 18-01-2009 | 06:43 PM
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They cost nothing to buy (well, £50-£100..?) and don't break as often as the gearboxes and drive shafts, so drive on driver!
Old 18-01-2009 | 07:42 PM
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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.
Old 18-01-2009 | 07:51 PM
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Originally Posted by Renton
They cost nothing to buy (well, £50-£100..?) and don't break as often as the gearboxes and drive shafts, so drive on driver!
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!
Old 18-01-2009 | 08:00 PM
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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
Old 19-01-2009 | 10:00 AM
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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.
Old 19-01-2009 | 10:09 AM
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Originally Posted by alistairolsen
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!
\

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?!
Old 19-01-2009 | 12:22 PM
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yeah, 3.62 lsd as std. They seem to go for about that on ebay

Of yourse if you fancy giving me a bargain
Old 19-01-2009 | 12:40 PM
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Originally Posted by alistairolsen
has anyone broken one and at what stage?
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.
Old 19-01-2009 | 04:06 PM
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Originally Posted by ybturbo
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.

what turbo you running mate?
Old 19-01-2009 | 04:11 PM
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Originally Posted by Lloyd
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.
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?
Old 19-01-2009 | 04:28 PM
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Originally Posted by Renton
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 .
Old 19-01-2009 | 04:59 PM
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Good to know what to expect from them.
Old 19-01-2009 | 07:14 PM
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Originally Posted by Lloyd
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 .

does it have to be 24v cosworth diff?

just dont think other granadas will have lsd?
Old 19-01-2009 | 09:21 PM
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Originally Posted by dom123
what turbo you running mate?
I am running stock turbine housing with a compressor from GT 38.
Old 19-01-2009 | 09:37 PM
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Originally Posted by col cos1
does it have to be 24v cosworth diff?

just dont think other granadas will have lsd?
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
Old 19-01-2009 | 09:59 PM
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Originally Posted by col cos1
does it have to be 24v cosworth diff?

just dont think other granadas will have lsd?
check the link mate, full list of diffs and ratios.

http://www.locostbuilders.co.uk/view....php?tid=19116
Old 20-01-2009 | 09:24 PM
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i know the 4x4 will of had 7in like xr4x4 but never knew the2wd did,good to know that
Old 20-01-2009 | 10:14 PM
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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?
Old 21-01-2009 | 08:38 AM
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Originally Posted by col cos1
i know the 4x4 will of had 7in like xr4x4 but never knew the2wd did,good to know that
Isn't the 2WD a 7.5?
Old 21-01-2009 | 08:39 AM
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Originally Posted by Fudgey
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?
Your engine will never make over 400, so you should be fine with a 4WD diff
Old 21-01-2009 | 08:02 PM
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yeah 2wd is 7.1/2 i was talking about 4x4s
Old 21-01-2009 | 08:15 PM
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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.
Old 21-01-2009 | 08:42 PM
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Originally Posted by Lloyd
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
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