Okay I’ve read quite a few threads about these diffs now and other shortcomings with the Mk 2.5
everyone seems to agree that the LSD are fragile, now I’ve got a Mk2.5, 1.8 sport, 2005. As such it is probably in the bracket of cars with this super fragile LSD. the cars got 22k on it but would have been serviced/MOTd quite a few times. Now if it’s already broken then I’m sure I’ll find out (When changing Diff oil, or something going bump while I’m out, but not happened yet) but if it is broken whats the next action needed? Replacing like for like doesn’t seem to make sense as they were fragile to start with. Does one replace it with a diff from a Mk3, Mk3.5 or even an RX8 or are all of these LSD as bad as each other. They say ignorance is bliss, I’m starting to beleive it as so far found out on my model.
LSD are prone to breaking. Engines prone to leaking oil, Clutches prone to juddering, Oil guage is just a light really, Temperature gauge just shows you it’s hot when it is already very very hot. I’m sure there will be more revelations to come, Could need a thread by a techy on when you buy a Mk2.5 this is what you have to change to be able to trust and enjoy your car!!
Love driving the car but why oh why must there be so many potential problems
Yes, three letter acronyms are tricky things for other languages to understand. Although the first people to go mass market usually win - like with ABS. Whatever the identifier would be, it would be easy to cast it in to new LSD only castings, not that it would be any help with MX5s.
Is it worth it so cars can be more easily identified for an optional part of a randomly changing technical inspection in one market? Not so far it isn’t.
Is that car MOT’d? Do you use it on the road? Does your insurer know?
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Yay! Full house of the usual questions.
Yes, it is MOT’d. Hence my interest in road testing instead of putting it on rollers, and my careful selection of MOT centres who aren’t run by idiots (and no, I don’t use a “friendly” MOT centre, I use a selection of normal MOTs centres).
Road use: I use it for social, domestic, commuting and pleasure (it says something like that on the insurance certificate). As I did the previous cars I’ve had with welded diffs. It also means I can drive it to and from tracks.
Yes, my insurer knows (I’d rather tell them than commit fraud, surprisingly), in fact the reason my insurer got my business was that they knew what it was when I phoned for a quote. Also they were cheap - £300 fully comp with all mods declared, diff, cage, turbo, even stickers. It’s not something you can get an on-line quote for though.
If I can have a go at guessing the next questions:
The effect it has on driving is exactly the same as a spool diff that was mentioned in AT’s post up there somewhere. Some low speed understeer on tight corners, tending towards neutrality as corner radius increases. Some wheel hop when parking. Excellent traction and very predictable when made to oversteer. It’s basically like a 2-way clutch diff (as fitted by some OEMs), but it remains locked on neutral throttle. It fact it’s exactly like the diffs fitted to karts - the cliche handling benchmark.
No, I wouldn’t recommend it for everyone else - wet mini-roundabouts can be understeery hell unless taken slowly or sideways, and only one of those options is legal or socially responsible. Also the wheel hop when parking gets a bit annoying at times.
I have a welded diff so I can do things like finish 6th in national level drifting competitions at high speeds against significantly more powerful cars. Also it was £500 cheaper than retrofitting a 2-way clutch diff, with the added advantage of predictably staying sideways during gear changes and clutch kicks.
Some owners in the US are swapping these diffs with the 4.100 “Bosch” Torsen used on the 2005 Mazdaspeed turbo MX5 (I think “Bosch” just signified a change in ownership of Torsen); this is effectively the same as the Torsen T2 fitted to 10AEs, Icons etc, but it has a slightly higher torque bias ratio (2.6:1). Otherwise, contact somewhere like Autolinkuk, and see if they are breaking 1998-2001 6-speed cars (which will have Torsen II). I can’t get my head around what final gear ratios are on 03-05 cars, since Mazda used a number of different ones in these cars, according to the market (I don’t know if Mk2 Roadsters 6-speeders were the same as Mk2.5 MX5 Sports. In the US, the equivalent models are not the same). Not sure if other parts will be required; probably.
Yay indeed! Excellent and informative post Captain Muppet I salute you and would love a go in your car sometime I’ve driven karts but never a car without a diff!
I also agree about going to the trouble of casting LSD (or whatever) into the diff case for what could be a changing test, but if they put “Preserve life always wear a helmet” stickers on the tanks of Jap motorcycles in the 70’s I’m sure it’s not beyond their wit to put a “Limited Slip Differential fitted to this vehicle!” sticker under the bonnet of a modern car in several languages too if they felt like it
Maybe that is the answer, for folk who are concerned to sticker their own cars. I know you say tell the tester but often you never get to see him. There are 3 at my local garage and you drop the car at reception. Considering all the junk we can buy for cars a sticker like this would be worth paying a couple of quid for if the club could have them made.
I’ve had a year off doing any track stuff in it (apart from winning an autotest) but next year I’ll be doing at least one day on the “handling” circuit at Barkston Heath in Lincs and hopefully a few days at Norfol Arena’s drift track - you’re welcome to as many passenger rides as your stomach can handle [:D]
Hi, no MX5s have a live axle. It was a term more often heard 40 years ago when discussing if a car had a live axle, usually with cart springs like a Ford or MGB, or independant suspension with coils such as Triumph TR6. The MX5 is a refinement of the latter.
I’m not sure of a specific term for an axle without a diff. A live axle might not have a diff at all, or may have a regular diff, or an LSD, but it refers to it being a beam between the 2 wheels which is part of the suspension locating the wheels rather than just supplying drive torque to them. Uh, that sounds complicated but compare an MGB rear suspension (live axle) with TR6 or MX5 (independant suspension) and you’ll see what I mean
MGB live axle with aftermarket anti roll bar (blue) and telescopic shockers (yellow) instead of lever arms fitted,
TR6 independant susp with coils and lever arm shockers
The handling you noticed at the Caterham day must have been fun. You can definitely get a similar feel with an LSD car on the road and it is very nice to feel both wheels bite pulling out of a corner
Ha ha, OK but a proper one would be good Regarding MOT testers I specifically asked one and he was not aware ANY MX5s have LSD… let’s be honest many people view them as hairdressers cars which is a shame when you drive one then look around and see how sophisticated it really is…
Woah, the Lincs one is close, an hour at most, I’d have to drop the good lady off at Belton and get my pass stamped but that would be good thanks please drop me a PM if it happens!
Got it,well explained- thats what a live axle means. I wrongly thought a non diff axle was the same…-I loved the caterham experience-brilliant little cars, The driver/owner also has an MX5 and said they were almost as much fun and a tad more usuable every day. He got me into them…
Hi, It’s a shame when it gets to you like that. I felt similar about mine which is why I persued the LSD saga so much.
I tried to get it in perspective. There are thousands of these cars out there but we only get to hear about the ones with problems so assume they must all be bad.
My own thoughts about it are that the roller brake testing doesn’t cause it. I think the design may be inherently a little weak and there may have been some quality control issues but even that is doubtful. We must really dismiss any car without a full known history as it could have suffered any sort of abuse.
Most likely in my mind is the known number of that model and years of cars with a badly juddering clutch. I’m thinking kangaroo starts here, so bad the dealer had to swap them under warranty. They would have hammered an LSD. If yours has not had such a problem, it was probably fixed by then, and I can recall no-one mention any of those latter Mk2.5 cars with a diff problem, then I would relax and enjoy. If the worst does happen the Mk3 diff won’t fit as the axles are a different diameter so you’d go for a Quaife or a standard open diff I think.
The rest are minor niggles that are present on most cars and cause almost no-one sleepless nights. Many cars don’t have temp and oil gauges and most are prone to a weep of oil somewhere
Just to add, if you want to tackle your demons now, have a word with a local garage with a ramp and explain your concerns to him. Find one who will let you watch as he changes the oil for you, it is literally a few minutes job and all the oil can be easily caught in a 1 litre jug or bowl. Yours is on 22K so is very unlikely to have ben done already and it will set your mind at rest.
Read this about the proposed MOT manual wording which concerns me so I’ve sent this off to VOSA by email:
Sir
MOT Roller Brake Testing and
Limited Slip Differentials
I
am writing as an owner of a Mazda MX5 2003 fitted with a Limited Slip
Differential manufactured by Tochigi Fuji.
I
am a member of the MX5 Owners Club and it has long been suspected by many
knowledgeable members that using a Rolling Brake Test during the MOT on these
vehicles does irreparable damage to the differential. In particular members have reported internal components
sheared and pieces of metal found in the oil when being changed. Some members have even reported cracked
casings where the said pieces of metal have jammed the crown wheel.
Personally
I have not had these problems but I have always insisted that my car was not
RBT tested but was decelerometer tested as detailed in your testers manual.
The
issue now is that you are proposing to change the wording of the manual to omit
the specific inclusion of Limited Slip Differentials.
I
copy the wording of the current and proposed Section 3.7 manual wording below:
Current:
Certain
vehicles should not be tested on a roller brake tester, e.g. vehicles with
More than one driving axle permanently engaged
Limited-slip
differential
Belt-driven transmission
Brakes for which the servo operates only when the
vehicle is moving
These
vehicles should be tested using a properly calibrated and maintained decelerometer or a plate
brake tester designated
as acceptable for the statutory
tests, see Sub-Section 3.7B and C.
Proposed:
Certain vehicles may not be
suitable for testing using a roller brake tester. Testers should take account of the
vehicle’s drive configuration, transmission type and any Vehicle Specific
Information before deciding whether a full or partial roller brake test is
appropriate.
If additional information is available from the
vehicle manufacturer, then this should also be taken into account.
Unsuitable
vehicles should be tested using a properly calibrated and maintained
decelerometer or a plate brake tester designated as acceptable for the
statutory tests, see Sub-Section 3.7B and C.
As you may suspect this is rather worrying for owners of
these vehicles. I and other members of the club would be interested to know:
a. Why has this change been proposed
and will it be made?
b. Will MOT testers now
refuse to test these vehicles using the decelerometer?
c. Will the reference to
LSDs still be on the pre-MOT check sheet or will it be removed?
Up until now MOT testers have been happy to test with a
decelerometer. You should avoid any
confusion occurring due to this change and be specific about LSD equipped cars
such as the Mk2 MX5, or there could be more damaged differentials leading to
potentially unsafe cars on the road.
Yes, looks good to me. VOSA have unloaded responsibility from themselves onto the MOT tester. It may or may not be coincidence that this happened just weeks after 2 MX5OC members made pointed and specific enquiries regarding the test, their rules, and LSDs. They quoted the freedom of information act to Tone and me which suggested they needed time for a meeting they should have had 20 years ago.
VOSA are negligent in their lack of keeping up with modern vehicles. In my case my car has had 4 RBT tests when it should have had none.
There is no need for RBT at all. It is a diagnostic test and not an MOT one. Does the car stop properly? That can be answered from a decelerometer test with an experienced driver/tester. Do we need to know which wheel is faulty if it doesn’t? No, that is not part of the test.
It’s crazy that a road test is not part of the MOT!! I was selling to the motor trade when RBT’s were introduced in the late 70’s and it was a shame to see how many good and knowledgeable small garages were put out of doing MOT tests because they couldn’t invest in the expensive equipment.
You’ll see my position on this has been constant; I am not convinced RBT testing is a problem for my vehicle as I’ve checked it myself and the preload across the LSD seems to be very low. I am not an expert though and the pre-load or construction of earlier cars may have been different. I am also reserving judgment in that if my diff packs up in future I will most certainly consider sueing the garage who did the test and possibly VOSA as well. This is very easy in the small claims court.
I’ve driven karts but never a car without a diff!
