graearea Posted May 27 Share Posted May 27 (edited) since I'm tracking my R400, I've replaced the Quaife with a tracsport. although it's totally fine on a roadcar, and will happily slide the tail about on the road and make nice straight 11s, for the track you really need a plated diff. This would make a great improvement over an open diff. be aware it came out of a 6-speed R400 so it is the short ratio. in mine it tops out at 130mph. the car was at 60,000 miles when I took it out and I hadn't noticed any problems. the ATB has a lifetime warranty on it. 800 quid, but I'll take offers. 'd Edited May 29 by graearea changed photos as I'd uploaded the wrong ones. Link to comment Share on other sites More sharing options...
Wrightpayne Posted May 27 Share Posted May 27 6 speed is usually paired with a 3.6 ratio diff and 5sp with 3.9. 1 Link to comment Share on other sites More sharing options...
graearea Posted May 27 Author Share Posted May 27 oh crikey. well.... it's the same as what I had before. and the one I bought of Simon Rogers said 3.92. it is the close ratio, as mentioned. Link to comment Share on other sites More sharing options...
John Vine Posted May 27 Share Posted May 27 If the diff is the original one, it's a 3.62. About five years ago, I exchanged emails on this very subject with both the previous owner of your car and CC themselves. JV 1 Link to comment Share on other sites More sharing options...
Roadsport06 Posted May 27 Share Posted May 27 If it is a 3.9 diff the engine revs will be around 7600 rpm to hit 130 mph 1 Link to comment Share on other sites More sharing options...
graearea Posted May 27 Author Share Posted May 27 2 hours ago, Roadsport06 said: If it is a 3.9 diff the engine revs will be around 7600 rpm to hit 130 mph 130mph at the top of 6th downhill at the nurburgring. I've managed 125ish in the uk at Bedford JV, I'm not sure what the score is then. it must have been changed at some point or Simon has made a mistake as well, as the gearing definitely hasnt changed since swapping diff. Original owner seems to back this up @john aston Link to comment Share on other sites More sharing options...
ScottR400D Posted May 29 Share Posted May 29 (edited) Is this K series? The R400D with 6sp has a 3.64, at least in the BMW housing it does. Must be a bit buzzy, the 3.64 is bad enough! Edited May 29 by ScottR400D Link to comment Share on other sites More sharing options...
ScottR400D Posted May 29 Share Posted May 29 On 27/05/2024 at 21:23, graearea said: 130mph at the top of 6th downhill at the nurburgring. I've managed 125ish in the uk at Bedford JV, I'm not sure what the score is then. it must have been changed at some point or Simon has made a mistake as well, as the gearing definitely hasnt changed since swapping diff. Original owner seems to back this up @john aston The top speed is irrelevant unless compared with RPM. Link to comment Share on other sites More sharing options...
John Vine Posted May 29 Share Posted May 29 37 minutes ago, ScottR400D said: Is this K series? The R400D with 6sp has a 3.64, at least in the BMW housing it does. Must be a bit buzzy, the 3.64 is bad enough! Looking at my correspondence from five years ago with the previous owner, it's a 2007 R400D with 6-speed box and (originally) a Ford 3.62 diff plus Quaife ATB (as confirmed by CC at the time). JV Link to comment Share on other sites More sharing options...
graearea Posted May 29 Author Share Posted May 29 OK. well. R400D with a ford housing. 130mph off the limiter last year at the nurburgring. not sure exactly what that is. I've not topped it out since I put what Simon sold me as a 3.92 anyway. I'll pull the back off it. anyone want to tell me how many teeth the crown will have? Link to comment Share on other sites More sharing options...
7 wonders of the world Posted May 29 Share Posted May 29 no need to pull the back off it simple pop a dab of paint on one of the outputs and another reference on the case same on the pinion flange and tuen the falbe for one complete revolution of the output, easy to differenciate between 3.92 and 3.62 Link to comment Share on other sites More sharing options...
ScottR400D Posted May 29 Share Posted May 29 You’d really need to count both the CW and pinion. So the Ford CWP 3.62 and the BMW is 3.64. 3.92/3.62? A typo perhaps when you bought it? Link to comment Share on other sites More sharing options...
ScottR400D Posted May 29 Share Posted May 29 3 minutes ago, 7 wonders of the world said: no need to pull the back off it simple pop a dab of paint on one of the outputs and another reference on the case same on the pinion flange and tuen the falbe for one complete revolution of the output, easy to differenciate between 3.92 and 3.62 I was going to suggest similar but didn’t think the difference would be that great! I guess if one’s close to 4 and one to 3.5 it’s not too hard! 0.3 of a turn after all. Link to comment Share on other sites More sharing options...
7 wonders of the world Posted May 29 Share Posted May 29 (edited) assuming your running ZZS 215/55/13 rears 130mph equates to 7800 rpm with a 6 speed and 3.92 final drive Edited May 29 by 7 wonders of the world Link to comment Share on other sites More sharing options...
7 wonders of the world Posted May 29 Share Posted May 29 with a 3.62 same top speed equates to 7200rpm Link to comment Share on other sites More sharing options...
graearea Posted May 29 Author Share Posted May 29 (edited) It's a 3.6! Advert edited Edited May 29 by graearea Link to comment Share on other sites More sharing options...
7 wonders of the world Posted May 29 Share Posted May 29 .....so with your new 3.92 @ 7200 you will only see 120mph Link to comment Share on other sites More sharing options...
graearea Posted May 29 Author Share Posted May 29 (edited) Oh no! Ha ha. Well that will make almost zero difference Thanks all! Edited May 29 by graearea Link to comment Share on other sites More sharing options...
ScottR400D Posted May 30 Share Posted May 30 12 hours ago, graearea said: Oh no! Ha ha. Well that will make almost zero difference Thanks all! If it is a 3.92 the revs will be higher at all times and fuel consumption will be worse. It’s about 7% difference in gearing. I wouldn’t want it, the 3.64 is bad enough when used on the road in terms of the revs for any given speed. Link to comment Share on other sites More sharing options...
John Vine Posted May 30 Share Posted May 30 14 hours ago, graearea said: It's a 3.6! Advert edited Thanks for the confirmation. To be strictly accurate, it's a 3.62. JV Link to comment Share on other sites More sharing options...
Wrightpayne Posted May 30 Share Posted May 30 As ford sierra diffs are getting quite rare, good ones more so, I’d probably pause while you consider whether the 3.9 is right for your usage? It used to be circa £300 to rebuild a diff just in case you need to swap the slipper into your 3.6(2). The ATB will have value whether its in a full assembly or just on its own. Link to comment Share on other sites More sharing options...
graearea Posted May 30 Author Share Posted May 30 I don't need to go over 120 to rinse porsches on track. The car is pretty aggro at 70mph with or without the diff Link to comment Share on other sites More sharing options...
ScottR400D Posted May 31 Share Posted May 31 9 hours ago, graearea said: The car is pretty aggro at 70mph with or without the diff ? ? 1 Link to comment Share on other sites More sharing options...
graearea Posted May 31 Author Share Posted May 31 (edited) It's at about 4000rpm at 70mph so very noisy Edited May 31 by graearea Link to comment Share on other sites More sharing options...
ScottR400D Posted May 31 Share Posted May 31 4 hours ago, graearea said: It's at about 4000rpm at 70mph so very noisy On 30/05/2024 at 16:57, graearea said: The car is pretty aggro at 70mph with or without the diff Worse with a 3.9. Don’t forget to adjust the speedo. 1 Link to comment Share on other sites More sharing options...
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