Limited Slip Diff

[trickyricky308]

Hi there, I recently bought a Mk1 1.6 (1992) and am looking at getting a limited slip diff for it. I am planning on using the car for track use once I have a roll bar fitted and really want the LSD for that (and the odd smiley moment off a roundabout). I understand the 1.6s sometimes came with a viscous LSD, are these any good, or is it better to try to source a torsen from a 1.8? I have heard the VLSDs can wear out and essentially revert to being an open diff, if I was buying a second hand diff is there any way I can check to see how worn it is? Or if I bought a worn one how much does a rebuild cost?
Thanks a lot and sorry for all the questions!

Also hi, I'm new!

[binnerboy]

IMHO a torsen all the way. The VLSD uses the viscosity of the oil to lock, this reduces over time eventually becoming an open diff. Not sure how long this takes though.

Torsen is a mechanical LSD so it will also wear out over time but will take more of a beating.

I am not a mechanic the above is just from reading around. Take someone knowledgeable with you if you are buying a second hand LSD.

[binnerboy]

here you go more info than you could ever possibly need about LSDs and MX5s

http://www.miata.net/garage/diffguide/index.html

[trickyricky308]

Thanks for the responses There is a lot of info in that link! There is so much conflicting info about these things it's hard to know what's what, if the wear in a VLSD is from the viscosity of the oil reducing, then a change of diff oil should fix that right? Looks like to get a Torsen into a 1.6 you need the driveshafts and propshafts from that too, which seems a bit excessive (especially as I'm on a bit of a budget). It looks like a used VLSD can be had for about £100 whereas a torsen (with the drive and propshafts) will be at least £300. I guess those prices say a lot about what's best really! I'm not sure that I'm any closer to a decision but it's good to know more on the subject!

[VladD]

I don't think the fluid can be replaced. As far as I know viscous LSDs are usually sealed.

[binnerboy]

in that link I posted it says teh VLSD is not a servicable item so I do not think it can be refreshed.

Reading more of it I think torsen is the way forward as a VLSD may just be wasted money, but it is your cash not mine.

there are other options (Kazz , quaife) , all of which are more expensive

[Richyvrlimited]

binnerboy said:

Torsen is a mechanical LSD so it will also wear out over time but will take more of a beating.

A Torsen can't wear out, it uses helical gears for the LSD action.

If it wears out, you've broken it - and will really know about it - and will need a new differential.

[Richyvrlimited]

trickyricky308 said:

Thanks for the responses There is a lot of info in that link! There is so much conflicting info about these things it's hard to know what's what, if the wear in a VLSD is from the viscosity of the oil reducing, then a change of diff oil should fix that right? Looks like to get a Torsen into a 1.6 you need the driveshafts and propshafts from that too, which seems a bit excessive (especially as I'm on a bit of a budget). It looks like a used VLSD can be had for about £100 whereas a torsen (with the drive and propshafts) will be at least £300. I guess those prices say a lot about what's best really! I'm not sure that I'm any closer to a decision but it's good to know more on the subject!

The viscous section of the LSD is sealed, an oil change won't help. Also it's not just the oil breaking down, the plates do too as I understand it.

Also note that the VLSD has the much weaker 6" ring gear, they're known to give up with stock power. With track work you'll be on borrowed time.

The Torsen (or any 1.8 differential) uses a much stronger 7" ring gear and on anotherwise stock car is pretty much indestructible. With FI they start breaking above 350hp.

None of the differentials like wheelhop though, if you encounter it back off the throttle immediately.

[binnerboy]

Richyvrlimited said:

binnerboy said:

Torsen is a mechanical LSD so it will also wear out over time but will take more of a beating.

A Torsen can't wear out, it uses helical gears for the LSD action.

If it wears out, you've broken it - and will really know about it - and will need a new differential.

believe him not me ^^

[trickyricky308]

Thanks for all the responses guys, I think I'm gonna save the money up and go for a Torsen diff when I can (with all the driveshafts etc). I've not ruled out adding power down the line and I'm hoping to do a decent amount of track work so it sounds like the best choice!

[upsidedownmark]

.. and just in case you weren't convinced, the locking potential of the VLSD is very low anyways, something like 15% I think.

[towelie]

a functioning vlsd is just about good enough for the job on 1.6 na

Speaking to rich at blink motorsport he reckoned they had a way of servicing the vlsd's but I'm not sure he does it for the general public.. may be worth phoning him.

Also 1.8 torsens are usually 4.1 final drive, whereas a 1.6 vlsd is 4.3!

A stock mx5(no turbo) will be dog slow with a 4.1 and not worth it IMO. If you went FI then yes change it as the 1.6 diff goes bang quite quickly with some FI abuse.

[skinny]

you can get torsens with 3.9, 4.1 and 4.3 ratio although the latter is rarer. you can also get a pre-loaded torsen diff with 3.6 ratio but these seem to eat themselves.

3.9 is one of the main reasons i decided to go torsen, wanted my gearing a bit longer.

[GC8]

Don't be tempted by the Togichi Fuji Super diff from the NB2. It sounds better as it has clutch cones, but Mazda used them because they were cheaper and they have a reputation for eating themselves (to qualify this, if you drain the oil pieces will almost certainly come out).