Light weight diffs
DIY Si - 21/1/14 at 10:46 PM
Evening all.
I've tried searching but either I'm using the wrong terms, or just doing it wrong as I can't be the first to ask something like
this.
Basically, I'm looking for something lighter than the Sierra diff. I've read that the Freelander unit is 16kgs, which is much more like it
but the ratio is wrong by miles. Is there anything else suitable out there? It's destined for my Sprite, so fittings aren't an issue as I
need custom shafts anyway.
The only thing I need is a ratio somewhere near 3.8-3.9, as I've got a high(ish) turning V6 planned and an MX-5 box. The current Sierra unit I
have gives me a theoretical top speed of 160 mph, but first still being good for 40 mph.
So basically, I'm looking for a diff with a 3.8-4.0ish ratio, that weighs nothing and can withstand a reasonable level of torque. Does such a
thing exist? Or am I best sticking to the Sierra? 
daniel mason - 22/1/14 at 12:16 AM
think bmw will do something around there but weight will again be high! honda s2000 has a 4.1 but heavy too.
what about the subaru impreza rear diff? unsure of ratios but possibly an option!
rdodger - 22/1/14 at 08:50 AM
MX5 Diff?
Available in 3.9, 4.1.
If you don't like the way it mounts Phil Talon has a alternative.
TimC - 22/1/14 at 09:27 AM
English with Westfield's original SEI aluminium housing?
Sam_68 - 22/1/14 at 10:06 AM
quote:
Originally posted by TimC
English with Westfield's original SEI aluminium housing?
Or (along the same lines but better availability) how about the English diff with Lotus aluminium housing, from the old Elan/+2?
You can also get magnesium versions of the Lotus housing and aluminium nose pieces for the English diff, at a price, to further reduce the weight:
http://shop.tonythompsonracing.co.uk/final-drive-16-c.asp
Thetom - 22/1/14 at 10:11 AM
Before Xmas I ordered a reversing LSD diff from elite racing transmissions for my spire, I ordered the ally version but they do a magnesium cased
variant which is apparently 5kg lighter...but horrendously more expensive than the already expensive ally variant! Guess you wouldn't want
reverse so they may have other options...
Slimy38 - 22/1/14 at 11:02 AM
quote:
Originally posted by rdodger
MX5 Diff?
Available in 3.9, 4.1.
If you don't like the way it mounts Phil Talon has a alternative.
I was going to suggest the MX5 diff, but it turns out they're surprisingly heavy. Even with Phil's diff cover the overall weight isn't
much different.
DIY Si - 22/1/14 at 12:13 PM
Thanks for the suggestions guys.
Is there anything that won't cost the earth? As much as I'd like to save weight and have shiny magnesium parts, most of the options so far
are way too much money for the possible weight saved!
iank - 22/1/14 at 12:38 PM
No idea what they weigh, or the torque they'd take, but the Suzuki Cappuccino diff might be worth a look.
DIY Si - 22/1/14 at 10:08 PM
quote:
Originally posted by iank
No idea what they weigh, or the torque they'd take, but the Suzuki Cappuccino diff might be worth a look.
Having had a look, they're 5.1:1!
TimC - 22/1/14 at 10:14 PM
quote:
Originally posted by Sam_68
Or (along the same lines but better availability) how about the English diff with Lotus aluminium housing, from the old Elan/+2?
You can also get magnesium versions of the Lotus housing and aluminium nose pieces for the English diff, at a price, to further reduce the weight:
http://shop.tonythompsonracing.co.uk/final-drive-16-c.asp
Oof - nice thinking Martin. Must play the lottery.
CNHSS1 - 23/1/14 at 11:01 AM
quaife did a diff hosuing to take English diffs and convert to elan style IRS setup, saw it at autosports show a few years ago
Sam_68 - 29/1/14 at 07:45 PM
quote:
Originally posted by CNHSS1
quaife did a diff housing to take English diffs and convert to elan style IRS setup...
FWIIW, the Elan diff. uses Ford 'English' internals and cast iron nose-piece as standard.
The Quaife (and Tony Thompson) diff housings are not intended to 'convert', as such, the Lotus diff. to Ford internals (since it
already uses them), but rather are an aftermarket fix to the problem that the top mounting 'ears' on the original Lotus casting tend to be a
bit weak and have a habit of breaking off after 40-odd years of abuse and sticky modern tyres... which means, admittedly, that they may not live with
the torque of a tuned V6 for long.
The standard Lotus diff. is pretty light even before you start throwing money at magnesium castings, and you can sometimes get lucky and pick them up
for quite sensible money on E-bay, though.