lsdweb
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| posted on 15/10/08 at 08:25 PM |
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BEC diff ratios
Hi All
I've done a search but can't seem to find a definitive answer!
I'm sorting out the bits for my build (a sort of morph from my single seater into my Westfield chassis).
I've got a Subaru diff (previous post) which looks good, is 22kg in weight
and a lot longer than the Sierra / Freelander. It was also £60 complete with shafts / cvs etc.!
The chassis is an SEi (independent) so I Won't have the problems with the rear diff mounts fouling the de dion which I was originally
planning.
It's a LSD and has a ratio of 3.55:1 which is in between the two ratios I was using on the single seater (54/16 and 54/15)
I was just wondering what others are using. This is a non road going sprint / hillclimb car by the way.
Regards
Wyn
[Edited on 15/10/08 by lsdweb]
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Wadders
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| posted on 15/10/08 at 08:37 PM |
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I don't think there is a definitive answer Wyn, It also depends which engine and wheels you use.
I switched from a 3.62 to a 3.14 and although there is a difference, i wouldn't say either was better than the other, just different.
For that money i would give it a go, can't imagine it will be any problem, especially for the hills.
Al.
Originally posted by lsdweb
Hi All
I've done a search but can't seem to find a definitive answer!
I'm sorting out the bits for my build (a sort of morph from my single seater into my Westfield chassis).
I've got a Subaru diff (previous post) which looks good, is 22kg in weight
and a lot longer than the Sierra / Freelander. It was also £60 complete with shafts / cvs etc.!
The chassis is an SEi (independent) so I Won't have the problems with the rear diff mounts fouling the de dion which I was originally
planning.
It's a LSD and has a ratio of 3.55:1 which is in between the two ratios I was using on the single seater (54/16 and 54/15)
I was just wondering what others are using. This is a non road going sprint / hillclimb car by the way.
Regards
Wyn
[Edited on 15/10/08 by lsdweb]
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lsdweb
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| posted on 15/10/08 at 08:44 PM |
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Thanks Al
I guess you're right.
The 3.37 (54/16 tooth combination) was OK for the hills although I was only getting bursts of 2nd at Llys y Fran which is very twisty. Some of the
guys were trying 54/14 (3.86) ratios but you can waste time changing up and down all the time!
I will try it although if I get it wrong it'll be costly to fit a Freelander unit afterwards!
Wyn
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motorcycle_mayhem
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| posted on 16/10/08 at 11:51 AM |
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It's a Locost LSD, pretty difficult to ignore, in fact I'll....
OK, I've tried both the 3.2 Freeloader and 3.36 Sierra on my Westfield, using 205/60/13. Various Hairdrier units (R1's, Blades,
GSXR's and a TL1000R). Basically, anything around this ratio is acceptable, I've got around 8-12mph/1K revs depending on engine. Some have
the torque to pull right the way up, some not.
Simply adjust with wheel/tyre diameter
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rj
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| posted on 16/10/08 at 01:10 PM |
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Are you sure the diff ratio is 3.55 ? , reason I ask is that Subaru quote final drive ratios in the handbooks ,a combination of diff ratio and final
reduction in the gearbox , that is 1.1 : 1, so the diff could be 3.9 (3.55 x 1.1 = 3.9), suggest you count the teeth. Could you let us know the answer
? it would be nice find an alternative to the rare long ratio Sierra diffs !
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lsdweb
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| posted on 16/10/08 at 04:50 PM |
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RJ
I counted the teeth (I'm not at home so can't access the figures) - it's definitely 3.5454. I think it was 39/11 teeth (that works
out right)
Unless there's some other method of altering the gearing in the nose of the diff I'd say this was just right!
Regards
Wyn
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rj
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| posted on 18/10/08 at 06:11 PM |
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Brilliant, what car is the diff from , Impeza Turbo ?
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lsdweb
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| posted on 19/10/08 at 05:48 PM |
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quote:
Brilliant, what car is the diff from , Impeza Turbo ?
Not quite sure!
Here's a photo of it in (it's not sitting square and probably too far forward)
[Edited on 19/10/08 by lsdweb]
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lsdweb
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| posted on 19/10/08 at 05:49 PM |
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Photo
 
Rescued attachment diff1.jpg
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lsdweb
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| posted on 19/10/08 at 05:50 PM |
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And another
 
Rescued attachment diff2.jpg
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Echidna
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| posted on 19/10/08 at 06:08 PM |
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Does anyone know the weight of a standard Sierra diff?
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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lsdweb
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| posted on 19/10/08 at 06:33 PM |
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Have a look here.
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Echidna
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| posted on 19/10/08 at 06:38 PM |
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Oh thanks!
So your new diff has about the same weight with the Sierra one, but yours is an LSD. Good find! 
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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lsdweb
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| posted on 19/10/08 at 07:15 PM |
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A touch heavier than the Sierra but it's a lot longer so I'll have a shorter propshaft. Plus it's a Subaru diff so should be
unbreakable. And it cost me only £60, and I got the shafts in that price too!
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