Doctor Derek Doctors
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| posted on 1/4/16 at 11:03 AM |
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MX5 Diff/Driveshaft Knowlede
Part of the plans for development of the Single Seater Locost is to offer an option of using an MX5 diff and driveshafts instead of the Sierra
versions the design currently calls for.
I'm thinking of using the Talon Diff cover here:
http://www.talonmotorfabrication.co.uk/shop/4581381144/fabricated-diff-cover/9582956
As it will allow much easier fitment to the chassis and I have read up on the problems with the broken rear arms/wings on RRR cars.
What I'm asking of the LCB collective is which MX5 diff to actually use? I don't really know MX5's so need some help.
My priority list is
1) Readily available (no point specifying something rare that people cant buy)
2) LSD option
3) Low Cost
4) Robust
I'm also looking for a ratio somewhere in the region of 3.62-3.92
Also are all of the driveshafts the same?
Really I need to buy a diff/driveshaft/Upright set-up so if anybody has anything suitable or can point me in the direction of a good one on ebay it
would be appreciated.
Designer and Supplier of the T89 Designs - Single Seater Locost. Build you own Single Seater Racecar for ~£5k.
Plans and Drawings available, U2U or e-mail for details.
Available Now: The Sports Racer Add-On pack, Build a full bodied Sports Racer for Trackdays, Sprints and Racing.
www.t89.co.uk
www.racecarwings.co.uk
callan@t89.co.uk
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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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adithorp
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| posted on 1/4/16 at 11:24 AM |
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This DIFF GUIDE should help.
I'd guess the later torsen/ATB would be the one to go for.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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Slimy38
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| posted on 1/4/16 at 11:51 AM |
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Make sure you buy the right diff cover, the one that I got first didn't line up at all. In general the 'small/short' diff cover is
1.6 and the 'large/long' cover is 1.8. They're very well made though, with nice machined surfaces in the required areas.
Oh, and don't throw the old casing away too quickly!! You need the drain plug, filler plug and vent plug to mount on the new cover. I also
reused the driveshaft oil seals although he doesn't recommend doing that.
Here's mine being fitted;
http://slimyroadster.blogspot.co.uk/2014/07/more-diff.html
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Doctor Derek Doctors
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| posted on 1/4/16 at 01:03 PM |
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Cheers, reading through the info I think the one to go for is the 1.8L MK2 version, as open and LSD cases are all the same so people have the option
without changing the chassis.
Designer and Supplier of the T89 Designs - Single Seater Locost. Build you own Single Seater Racecar for ~£5k.
Plans and Drawings available, U2U or e-mail for details.
Available Now: The Sports Racer Add-On pack, Build a full bodied Sports Racer for Trackdays, Sprints and Racing.
www.t89.co.uk
www.racecarwings.co.uk
callan@t89.co.uk
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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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theconrodkid
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| posted on 1/4/16 at 02:48 PM |
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even when you have removed all the hardware dont throw the rear cover away,the ears can break off and MX5 owners will be wanting such items.
who cares who wins
pass the pork pies
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Slimy38
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| posted on 1/4/16 at 04:52 PM |
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quote:
Originally posted by theconrodkid
even when you have removed all the hardware dont throw the rear cover away,the ears can break off and MX5 owners will be wanting such items.
B**ger, I just put mine on the kerbside... didn't even consider retaining it!
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sdh2903
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| posted on 1/4/16 at 04:59 PM |
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Only seems to be certain kit manufacturers who manage to break them due to how they mount them. I've not heard of many failures from mx5's
or the westfield or mnrs that utilise the mx5 donor.
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big_wasa
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| posted on 1/4/16 at 05:55 PM |
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Why not think a little more forward. The mx5 is just about the donor of choice these days. Why not have a look at the rx8.
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daniel mason
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| posted on 1/4/16 at 06:31 PM |
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If the rear chassis is wide enough,I'd look into the options of turning the engine 90deg and looking at a chain diff. It makes gearing so much
easier to alter!
Although I'm sure you'll find a nice ratio that will suit most places!
It would be great to get a few more small single seaters out at some sprint events and this looks a great way of doing it on a realistic budget!
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Doctor Derek Doctors
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| posted on 1/4/16 at 06:41 PM |
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Not sure about the RX8 Diff will do some research to see what it's like. Might be a good option.
Designer and Supplier of the T89 Designs - Single Seater Locost. Build you own Single Seater Racecar for ~£5k.
Plans and Drawings available, U2U or e-mail for details.
Available Now: The Sports Racer Add-On pack, Build a full bodied Sports Racer for Trackdays, Sprints and Racing.
www.t89.co.uk
www.racecarwings.co.uk
callan@t89.co.uk
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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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PorkChop
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| posted on 1/4/16 at 10:19 PM |
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IIRC, the RX8 diff is a fairly high ratio (4.77:1 springs to mind, but I could be wrong!). A mark 3 MX5 diff is a very similar if not identical shape
to the RX8 and came in 2 ratios depending on if a 5 speed or 6 speed gearbox was fitted. All the 2000cc mark 3s came with LSD as standard - I think
the RX8 did too, but not sure.
The late mark 1 (both 1600 and 1800cc), mark 2 and mark 2.5 diffs and halfshafts are, to all intents and purposes, identical. An open diff is rather
cheap now and Ashcroft Transmissions did do an ATB replacement diff centre relatively cheaply. The most common ratio is 4.1:1, followed by 3.6:1. The
3.6:1 diffs are Fuji LSDs and tend to be weaker than the Torsen. You can get 3.6:1 and 3.9:1 Torsen LSDs, but they are rather rare. The market price
for a 4.1:1 Torsen seems to be around the £250 mark. I paid around £50 for my halfshafts from one of the MX-5 breakers.
I was considering putting a bike engine in my MX5 based car and came to the conclusion the only realistic way of doing it was to get either a working
3.6:1 Fuji diff, or get a Fuji diff that had a decent CWP but was losing its plates and fit an Ashcroft ATB diff centre.
An early (<1993) diff has a smaller CWP, but only came in a 4.3:1 ratio.
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luke2152
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| posted on 2/4/16 at 03:25 PM |
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I can vouch for the ashcroft atb diff centre - awesome bit of kit
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sdh2903
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| posted on 2/4/16 at 03:44 PM |
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quote:
Originally posted by luke2152
I can vouch for the ashcroft atb diff centre - awesome bit of kit
Good to hear. Not many reviews out there and I have one tucked away fitted to a 1.8 diff waiting for a new home.
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Sam_68
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| posted on 2/4/16 at 04:29 PM |
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quote:
Originally posted by PorkChop
... A mark 3 MX5 diff is a very similar if not identical shape to the RX8 and came in 2 ratios...
The Mark 3 (NC) MX5 diff would be a good choice, as it lacks the big torque arms of the earlier MX5 diff, so you don't need £200's worth
of Talon fabricated diff. cover to make it work. 
It's not the same as the RX8 diff, though - it's significantly smaller and lighter:
RX8 vs. NC MX5 diff comparison
I can supply you with an accurate CAD model of the NC MX5 diff., if you wish.
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Jasheuk
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| posted on 9/4/16 at 06:53 PM |
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Talon Diff help needed. Newby 1st post
Hi
I purchased a nearly finished Haynes roadste with Mx5 running gear. Having sorted the last few bits it was at the rolling road yesterday for the
second time after the clutch failed on the first go.
All good this time, achieved 155 at the fly but had diff oil coming out from the breather on the diff case. I have just tried to remove it to see
what the problem is, but it will not wind out, just turns round.
I assume it is threaded in the case, but am now thinking it may have a nut on the inside and have to dismantle it.
Any help and advise would be great. Booked my first track day Wednesday so need to sort this asap.
Thanks James
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