dr_jekyll Posted September 3, 2010 Share Posted September 3, 2010 evning all . i have read many threads on many sites about diffs , what will fit what and what wont and the answers i find are varying greatly. im looking to build a definative thread on diffs . whats interchangable and whats not. my own current situation reads like this: I am fitting a torsen diff from a jspec auto inplace of an open diff on a jpsec 5 speed. both have the smaller casings . some say it will be a straight drop in swap and others say the pcd on the prop flange will be different .....(all we know is , hes called the stig) i have just been under my car with the open diff and i mesured the pcd to be 3x89 . i have them been under my 5 speed car that has the torsen diff and i also mesured the pcd to be 3x89. the diff casings are identical so as far as i can see it will be a straight drop in. however mesuring pcds under a car while the prop is attached id difficult so i will be removing the diffs over the weekend to take proper mesurements and make sure. in the event of the pcd actually being slightly different i can see noi reason why the prop bolting flanged on the front of the diff cant be removed and swaped. if anybody knows for sertain if this is , or is not possible please post at the risc of sounding like a tw4t please only post if you are 100% sure through experience of what you are posting as i want to keep this thread as to the point and accurate as possible to avoid the futer confusion for peple wishing to find answers . as i have found all the different guesses and hear say confusing while trying to find out what would fit and what wouldn't more to come Quote Link to comment Share on other sites More sharing options...
dr_jekyll Posted September 5, 2010 Author Share Posted September 5, 2010 UPDATE i have removed the diffs and i can confirm that the na open and the tt auto diffs DO NOT have the same stud pattern. the na diff pcd is 3x92mm and the tt auto diff is 3x99. in order to fit the tt auto lsd in place of the na open diff you will need to : a. use the rear prop section from a tt auto or b. swap the fronts of the diff as i am going to do tomorrow wen i have a deep enough sockett to remove the bol that holds them on. apart from that the casing is the same and will bolt up in place on the car and fit straigh to the drive shafts. Quote Link to comment Share on other sites More sharing options...
Dr_Doom Posted September 5, 2010 Share Posted September 5, 2010 I have been told that it is possible to swap just the front of the diff so that it fits the NA propshaft. I'm pretty sure your option 'a' wont work as TT and NA prop shafts don't split in the same place. Quote Link to comment Share on other sites More sharing options...
JamieP Posted September 5, 2010 Share Posted September 5, 2010 UPDATE. So, i was right then;) Quote Link to comment Share on other sites More sharing options...
dr_jekyll Posted September 5, 2010 Author Share Posted September 5, 2010 it would appear so but i have heard so many variants i had to dig in myself Quote Link to comment Share on other sites More sharing options...
dr_jekyll Posted September 5, 2010 Author Share Posted September 5, 2010 I have been told that it is possible to swap just the front of the diff so that it fits the NA propshaft. I'm pretty sure your option 'a' wont work as TT and NA prop shafts don't split in the same place. i thaught the front sections differd but the rear section were all the same lenth . dont they all join behind the baring that bolts to the chassis Quote Link to comment Share on other sites More sharing options...
Dr_Doom Posted September 5, 2010 Share Posted September 5, 2010 i thaught the front sections differd but the rear section were all the same lenth . dont they all join behind the baring that bolts to the chassis The TT prop seperates on a spline before the bracket where it bolts to the car. The NA prop seperates on a 4-bolt flange after the braket where it bolts to the car. Quote Link to comment Share on other sites More sharing options...
dr_jekyll Posted September 5, 2010 Author Share Posted September 5, 2010 The TT prop seperates on a spline before the bracket where it bolts to the car. The NA prop seperates on a 4-bolt flange after the braket where it bolts to the car. thats exactly the point of this thread now i know Quote Link to comment Share on other sites More sharing options...
hodge Posted September 5, 2010 Share Posted September 5, 2010 So what's the difference between an torsion diff, an open diff and a LSD diff. Quote Link to comment Share on other sites More sharing options...
dr_jekyll Posted September 5, 2010 Author Share Posted September 5, 2010 open diff allows both wheels to spin independantly . lsd allows limmited rotation differance between the 2 wheels when cornering torsen allows both wheels to spin independantly at low speeds and easy driving but locks both wheels together when under high load Quote Link to comment Share on other sites More sharing options...
Kirk Posted September 5, 2010 Share Posted September 5, 2010 Bare in mind there are a few types of LSD and torsen is one of them. Alot of them you will find are helical geared diffs but the best are definatly the clutch type ones. Quote Link to comment Share on other sites More sharing options...
dr_jekyll Posted September 7, 2010 Author Share Posted September 7, 2010 new update. after a long hard search i found a 34m deep socket and have removed the 2 diff bolt flanges. the splines on both diffs are identical so the open diff flange fitted straight on no problems. i then bolteerd evrything up nice and straight forward, drop in fit. So conformation that with the original bolt flange from your existing open diff the j-spec tt auto diff is a direct replacment for the lame open diff that most of the the w58 5 speed na cars come with . i have taken the car for a short run and the gearing difference is minimal and tbh hardly niticeable so that wont be an issue for you. happy Quote Link to comment Share on other sites More sharing options...
mwilkinson Posted September 7, 2010 Share Posted September 7, 2010 Good to hear you got this fitted Craig. I take it it's working fine? Quote Link to comment Share on other sites More sharing options...
dude Posted September 7, 2010 Share Posted September 7, 2010 new update. after a long hard search i found a 34m deep socket and have removed the 2 diff bolt flanges. the splines on both diffs are identical so the open diff flange fitted straight on no problems. i then bolteerd evrything up nice and straight forward, drop in fit. So conformation that with the original bolt flange from your existing open diff the j-spec tt auto diff is a direct replacment for the lame open diff that most of the the w58 5 speed na cars come with . i have taken the car for a short run and the gearing difference is minimal and tbh hardly niticeable so that wont be an issue for you. happy You cannot just swap the front part of the diff, well you can but it prob will not last very long, the problem is the crush washer you should have changed, it is not just torqued up you need to either check the back lash in the diff using a dial guage or cover the crown wheel and pinion in enginners blue and make sure you have the correct mesh pattern, you did change the crush washer didnt you????? Quote Link to comment Share on other sites More sharing options...
dr_jekyll Posted September 7, 2010 Author Share Posted September 7, 2010 You cannot just swap the front part of the diff, well you can but it prob will not last very long, the problem is the crush washer you should have changed, it is not just torqued up you need to either check the back lash in the diff using a dial guage or cover the crown wheel and pinion in enginners blue and make sure you have the correct mesh pattern, you did change the crush washer didnt you????? what do you mean? ithe front part of the diff with the 3 holes sloted straight on , lined up perfectly . there was no washer behind the bolt just a multi spline? can i have more info ion this. the bolt holding the face on has a in dented part that goes into a keyway so i just put it back on the same plece it came off . the only side affect iv seen after giving the car a good testing is that the speedo is wayy off,. the gps was reading 100 and the speed was saying 75. Quote Link to comment Share on other sites More sharing options...
dude Posted September 7, 2010 Share Posted September 7, 2010 what do you mean? ithe front part of the diff with the 3 holes sloted straight on , lined up perfectly . there was no washer behind the bolt just a multi spline? can i have more info ion this. the bolt holding the face on has a in dented part that goes into a keyway so i just put it back on the same plece it came off . the only side affect iv seen after giving the car a good testing is that the speedo is wayy off,. the gps was reading 100 and the speed was saying 75. It is the amount of torque on the 34mm nut that determines the backlash on the gears. Quote Link to comment Share on other sites More sharing options...
dr_jekyll Posted September 7, 2010 Author Share Posted September 7, 2010 oh i see. well as said the nut is in the same position on the same turn as i removed it so fingers crossed lol Quote Link to comment Share on other sites More sharing options...
dude Posted September 7, 2010 Share Posted September 7, 2010 oh i see. well as said the nut is in the same position on the same turn as i removed it so fingers crossed lol You may be lucky dude, fingers crossed Quote Link to comment Share on other sites More sharing options...
dr_jekyll Posted September 7, 2010 Author Share Posted September 7, 2010 cheers mate . Quote Link to comment Share on other sites More sharing options...
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