mark.anson Posted January 22, 2004 Share Posted January 22, 2004 Ok ive done a search and im still confused. I will be sourcing my LSD soon, but im confused as to which donor car was fitted with which ratio.I understand that the 4x4 sierras were fitted with 3.62 LSDs.and the 2 litres were 3.9. Is this right and is there anyway from identifying the ratio if it is already out of the car.My nearest breakers has a lot of Ford stuff but its all off the shelf stuff so I dont find myself with the wrong diff just cos I couldnt ID it properly. BTW I want a 3.9 if poss.What is a reasonable price for an LSD.Breakers are quoting me £80 - £100 for the diff alone but I will probably get the whole subframe as I need the lobros and rear brakes as well. Quote Link to comment Share on other sites More sharing options...
Mark Stanton Posted January 22, 2004 Share Posted January 22, 2004 Got whole back end from an XR4 thingie for £100 so price ain't too wide of the mark. The diff usually has a tag on it which gives ratio unless you're unlucky and its been removed if its on the shelf of a scrappie and they don't know what it was from and the tag has been removed - you're gonna have to turn it's workings and check rotation Quote Link to comment Share on other sites More sharing options...
scruffythefirst Posted January 22, 2004 Share Posted January 22, 2004 its written on the crown wheel in gold glitter pen so whip the back off (easier said than done) and have a look that way if you get the chance. HTH scruffy Quote Link to comment Share on other sites More sharing options...
steve_m Posted January 22, 2004 Share Posted January 22, 2004 The 2.0 XR4x4 didn't come with a lsd as standard, it was I believe an option. Virtually none of them had it fitted, so if you're after a 3.92 ratio and a slipper then best bet is to get a cheap 3.92 diff - should only be £10-£20 at most as there are 1000's about, and transfer the crown wheel and pinion into a 3.62 lsd diff from the 2.8/2.9 XR4x4, or the slipper into the 3.92, which ever diff is in better condition. You can get this done by a local transmission specialist, prices range from £120 to £170 for new bearings, oil seals and transferring the cwp depending on how you pay and some even repaint it for you. Alternatively you can buy a new unit from Classic Conversions ready built but you'll need to breath hard before you see the price. Quote Link to comment Share on other sites More sharing options...
pistonbroke Posted January 22, 2004 Share Posted January 22, 2004 If I can ask the question because I am also interested How do you know if its ls or standard diff? Is there a surefire method to tell which is which? For e.g. If I were to turn one driveshaft side and observe the direction of rotation of the opposite side , is it always counter rotation on the standard diff and both rotate the same direction for a LSD ? thanks Quote Link to comment Share on other sites More sharing options...
scruffythefirst Posted January 22, 2004 Share Posted January 22, 2004 Isn't the slipper bit in the crownwheel? Scruffy Quote Link to comment Share on other sites More sharing options...
Eccentric_Rich Posted January 22, 2004 Share Posted January 22, 2004 Mark, If you're buying the diff from a scrap yard I would take the back off the casing (take a breaker bar as the bolts will be tight) and check condition of the crown wheel and pinion (make sure there's no damage to the teeth etc). Whilst the back's off you'll be able to see if it's a LSD, if it is the only visible gears are the crown wheel and pinion. You can also check the ratio by turning the input flange and watching one of the output flanges. It'll need 3.62 turns of the input flange to turn the output one revolution if it's a 3.62 and of course 3.9 turns if it's a 3.9 diff. Richard. Quote Link to comment Share on other sites More sharing options...
conibear Posted January 22, 2004 Share Posted January 22, 2004 If I can ask the question because I am also interested How do you know if its ls or standard diff? Is there a surefire method to tell which is which? For e.g. If I were to turn one driveshaft side and observe the direction of rotation of the opposite side , is it always counter rotation on the standard diff and both rotate the same direction for a LSD ? thanks There very stiff to rotate compared to standard Quote Link to comment Share on other sites More sharing options...
pistonbroke Posted January 22, 2004 Share Posted January 22, 2004 There very stiff to rotate compared to standard Hmmmmm! When you say stiff to rotate, is that on or off the car ? ATM I have the the car on axle stands and both rear wheels removed . It doesn't take much effort to turn either drive shaft by hand ,so can I assume its not a sticky? Reason I ask is when I drive round a fastish corner there is a very marked difference from oversteer with power on , to understeer , if I lift off the gas peddle. I read somewhere that LSD makes the handling more nuetral. but I dont want to spend good dosh for nothing, if you see what I mean. Quote Link to comment Share on other sites More sharing options...
conibear Posted January 22, 2004 Share Posted January 22, 2004 When you say stiff to rotate, is that on or off the car ? ATM I have the the car on axle stands and both rear wheels removed . It doesn't take much effort to turn either drive shaft by hand ,so can I assume its not a sticky? Both. Although my LSD is new I find it difficult to rotate the hub by hand with the wheel off. It's obviously easier with a wheel on but still much resistance. It sounds like you have not got LSD to me What happens to the rear end when you accelarate very hard from standing Quote Link to comment Share on other sites More sharing options...
scruffythefirst Posted January 22, 2004 Share Posted January 22, 2004 Whilst the back's off you'll be able to see if it's a LSD, if it is the only visible gears are the crown wheel and pinion. Is this right? I've got blatters old sierra's diff (XR4x4 2.9 - see my avtar) and i can see the 4 little cogs (are these the pinion - i don't think so but ) in the middle. The crownwheel has some bolts on the back of it that suggests it can be split into two? As i'm not at home and can't take a pic if i was, so I've nicked this off tims dax build site, this is supposedly an XR4x4 LSD. Mine looks just like this, and you can just about see the 2 part crownwheel. Scruffy Quote Link to comment Share on other sites More sharing options...
pistonbroke Posted January 22, 2004 Share Posted January 22, 2004 I only just got the car so not had much practise yet due to poor road conditions, I did give it a blast from a "rolling" start and the rear end "wagged" about, that was under hard acceleration and in 3rd ( I think ) at the time. What I have not tried yet is a standing start with revs on. I had a ride with the previous owner when viewing initially and he managed to get into a real tank slapper while demo-ing, also in 3rd I think.At the time the roads were damp and it was very cold. Since then on a dry road I have used full power in 3rd with no probs. Quote Link to comment Share on other sites More sharing options...
Blatman Posted January 22, 2004 Share Posted January 22, 2004 There very stiff to rotate compared to standard They shouldn't be. An LSD only starts to limit slip once the preload weight has been reached. Even on a viscous or ATB, it's *much* more load than you can generate by hand. A quick flick through the manual for the viscous LSD says that turning torque should be anywhere between 22 and 52ft/lbs...... If I were to turn one driveshaft side and observe the direction of rotation of the opposite side , is it always counter rotation on the standard diff and both rotate the same direction for a LSD ? No, not always. An ATB acts like a normal open diff when spinning the wheels by hand. A plate type will have both wheels rotating in the same direction. Not sure about a viscous diff, but I think the same is true. Reason I ask is when I drive round a fastish corner there is a very marked difference from oversteer with power on , to understeer , if I lift off the gas peddle. That's physics. That'll happen no matter what diff you have if you provoke it enough. A tank slapper is what happens when you lift off mid corner when you're going a bit too fast. Biggest problem there is it's *very* difficult to "get ahead" of the car once the tank slapper has started. You were crashing on your test drive. You were just lucky you didn't hit anything...... As for the rear end wagging about in third under acceleration, again, that'll happen anyway if you break traction. The difference is (and it's why Conibear asked, I reckon) is that if both wheels spin, it's an LSD. If only one wheel spins, it's not. A standing start will prove this. Two black lines = LSD. One black line, it isn't. Scruff. Is this right? I've got blatters old sierra's diff (XR4x4 2.9 - see my avtar) and i can see the 4 little cogs (are these the pinion - i don't think so but ) in the middle. The crownwheel has some bolts on the back of it that suggests it can be split into two? The 4 little cogs are called planet gears. They allow the car to turn corners by letting the inside wheel travel less distance than the outside wheel. The crown wheel is bolted to a carrier. This means you can swap crown wheels. IIRC, the "LSD pack" is somewhere in the middle of the crown wheel and planet gears...... The pinion is not visible in the pic. The pinion is connected directly to the diff flange, and is a bevel gear, like the crown wheel, only a lot smaller. You can calculate the ratio of a diff by counting the teeth on the crown wheel, and dividing that number by the amount of teeth on the pinion. *All* XR4x4's had LSD's. Quote Link to comment Share on other sites More sharing options...
pistonbroke Posted January 23, 2004 Share Posted January 23, 2004 If only one wheel spins, it's not. A standing start will prove this. Two black lines = LSD. One black line, it isn't Thanks m8y Can,t wait for a nice dry day to test the theory !!! Could be 3 lines on the road though , two black one brown As for the handling characteristics , I must be so used to front wheel drive I forgot how to peddle a proper car , I seem to remember when fwd first came out how a different technique was needed to get the line right. Now in my old anglia it was easy to tell , when cornering ,the inside wheel would pick up and spin like mad ! Quote Link to comment Share on other sites More sharing options...
scruffythefirst Posted January 23, 2004 Share Posted January 23, 2004 Cheers, mr B, all is well and as i thought. Just got myself confused for a bit there! Guess i've still got a lot to learn.... Scruffy Quote Link to comment Share on other sites More sharing options...
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