Open vs LSD diffs

[evinX]

So im looking for a 3.7 ratio diff of a TT auto for a manual conversion.

My NA auto i believe has a open diff and to be fair i like the way the car drives, never had a LSD before so dont know what its like.

What id like to know for sure is...what diff is more likely to make the car loose its rear end and spin off easier?

A 3.7 ratio LSD can be had of a TT Auto,

But what car can i get a 3.7 open diff off and will bolt up to my na auto prop and driveshafts? With possibly having to change the flange over

Cheers all

[Swampy442]

No diff is likely to make the car spin off, thats entirely the drivers doing. A limited slip diff will give more traction to the spinning inside wheel, a locking diff will lock both wheels together.

A Supra diff will fit

 

[evinX]

38 minutes ago, Swampy442 said:

No diff is likely to make the car spin off, thats entirely the drivers doing. A limited slip diff will give more traction to the spinning inside wheel, a locking diff will lock both wheels together.

A Supra diff will fit

 

Cheers, Lol at the last bit. But what other 3.7 diffs can i get that will bolt to a NA auto?

[Swampy442]

I thought that had been covered?  Aristo, Supra, Soarer etc

[evinX]

24 minutes ago, Swampy442 said:

I thought that had been covered?  Aristo, Supra, Soarer etc

Would be nice to know exactly which one..its all still vague according to the interwebs 

[Frank Bullitt]

https://www.supraforums.com/threads/jza80-differential-info.608545/

[Scooter]

12 hours ago, evinX said:

 

What id like to know for sure is...what diff is more likely to make the car loose its rear end and spin off easier?

 

Swampy is right but if you aren't used to it a LSD might cause you more problems ie be more sideways than an open diff

[evinX]

8 hours ago, Scooter said:

Swampy is right but if you aren't used to it a LSD might cause you more problems ie be more sideways than an open diff

Thats what im thinking. Open might be better as its a all round daily.

Another thing im wondering is a 3.7 diff with a non turbo engine, will that be a bad idea as its supposed to be for a tt engine?

 

[Scooter]

If you are going for the manual conversion I'd personally try and get an NA ratio'd LSD 

Manual and no lsd is not ideal for making the most of being manual really.

 

[Noz]

I went from an open to an LSD. I didn't notice a huge difference in driving, if I'm honest I've never noticed any difference.

If you had a choice of either, I'd go LSD.

I've had wheel spins at 80mph on full boost and the car controls well (no traction control) and doesn't feel erratic, though obviously not as straight as you'd like. I do remember an open diff snatching a bit when I lost traction though granted at 420hp this was at much slower speeds.

If its just to get you started, I'd use whatever diff you can get your hands on. But LSD is the preferred choice in my honest opinion.

[Scooter]

A basic difference you should feel at some point is, T-junction/Roundabout wet and an enthusiastic throttle and with the open diff you light up the inside wheel (quite easily), generally it'll just keep turning the same and compared to the LSD you'll lack forward thrust until you ease off (relatively more) to stop the wheel spin. 

With the LSD and aggressive throttle you'll get both wheels spinning and that'll bring the back round and a (ease off/balance of throttle) the old 'dab of oppo' might be required or a nice powerful 'dig in' exit to the curve will happen ie controlled wheel spin......you just get more drive. In essence the closer you get to driving 10/10ths the more a open diff can frustrate and the LSD excite.

 

Edited October 18, 2021 by Scooter (see edit history)

[Noz]

These are all good pointers Scooter.

However thinking back to the op's post and considering what the end goal is, I think respectfully the NA is unlikely to notice much if any difference. Therefore focusing on ratio's is probably better advice than swapping to a more expensive LSD. So I change my opinion rather than LSD vs Open, to whatever ratio would give the best drive; especially if you've already defined it.

When mine was 370hp, I used to drive the open diff seriously hard and never noticed an issue. So I suppose from that viewpoint, the open isn't that bad at all.

LCD is just a preference with higher power or seriously hard driving.

[evinX]

So far im thinking an Aristo TT auto diff open or LSD with the 3.7 ratio

Just need to know exactly what year and model/ spec aristo i need to look for and will it use the same ear bushes as the Supra

[Frank Bullitt]

All info you require is contained in the link I provided. Years, part numbers, the lot. Including a full rebuild. Just click and read.

Edited October 18, 2021 by Frank Bullitt (see edit history)

[Scooter]

40 minutes ago, Noz said:

These are all good pointers Scooter.

However thinking back to the op's post and considering what the end goal is, I think respectfully the NA is unlikely to notice much if any difference. Therefore focusing on ratio's is probably better advice than swapping to a more expensive LSD. So I change my opinion rather than LSD vs Open, to whatever ratio would give the best drive; especially if you've already defined it.

When mine was 370hp, I used to drive the open diff seriously hard and never noticed an issue. So I suppose from that viewpoint, the open isn't that bad at all.

LCD is just a preference with higher power or seriously hard driving.

Perhaps your tyres were always very grippy R888's etc?  This will make a big difference, the lower grip on the tyres the more an open diff will show itself up!

The sportier SZ-R, was spec'd with a LSD as standard when it was an option on the regular manual SZ so Toyota thought it was worth it, but then Lotus generally prefer open diffs in their cars.  

I'm just saying what I've felt/experienced over time, I have a open diff at present and it's fine, some strong diffs can even give you (undesirable) understeer characteristics but if it's your thing an NA in a car park will do a clutch dump donut with a LSD but not without. 

Biggest issue will be finding one and as it's likely to be an open one, just go with that, then you can always upgrade later?

 

 

[Mike2JZ]

NA with 3.7 is going to feel gutless. You need to have a turbo to make the most of that setup. Leave it on 4.1 whilst NA 

[Scooter]

37 minutes ago, Frank Bullitt said:

All info you require is contained in the link I provided. Years, part numbers and everything required. Just click and read.

also a little excel spreadsheet on the attached.......I think the 3.7 will make it a more 'relaxed' especially if, as is often the way, your tyres are a tad bigger, rolling radius wise, compared to stock sizes.

[Frank Bullitt]

1 hour ago, Noz said:

These are all good pointers Scooter.

However thinking back to the op's post and considering what the end goal is, I think respectfully the NA is unlikely to notice much if any difference. Therefore focusing on ratio's is probably better advice than swapping to a more expensive LSD. So I change my opinion rather than LSD vs Open, to whatever ratio would give the best drive; especially if you've already defined it.

When mine was 370hp, I used to drive the open diff seriously hard and never noticed an issue. So I suppose from that viewpoint, the open isn't that bad at all.

LCD is just a preference with higher power or seriously hard driving.

Catching a drain cover in the wet with an open isn’t fun, that’s when you miss a decent plate LSD. Even the OEM torsen has its limits. A diff is only part of the overall package but it’s all down to what you can justify spending.

As a basic no frills entry to go with it you would need good suspension (not hard or crashy, doesn’t need to be stupidly expensive either), reasonably sized wheels with correct offsets, good tyres with a decent sidewall (Mr Noz ),

Then you add engine mounts, gearbox mounts, diff mounts and rubber doughnut for the prop.

After that would be rebuilding the subframe with OEM parts.

Edited October 18, 2021 by Frank Bullitt (see edit history)

[Frank Bullitt]

5 minutes ago, Scooter said:

also a little excel spreadsheet on the attached.......I think the 3.7 will make it a more 'relaxed' especially if, as is often the way, your tyres are a tad bigger, rolling radius wise, compared to stock sizes.

Yep, that’s a polite way of putting it

[Noz]

1 hour ago, Frank Bullitt said:

Catching a drain cover in the wet with an open isn’t fun, that’s when you miss a decent plate LSD. Even the OEM torsen has its limits. A diff is only part of the overall package but it’s all down to what you can justify spending.

As a basic no frills entry to go with it you would need good suspension (not hard or crashy, doesn’t need to be stupidly expensive either), reasonably sized wheels with correct offsets, good tyres with a decent sidewall (Mr Noz ),

Then you add engine mounts, gearbox mounts, diff mounts and rubber doughnut for the prop.

After that would be rebuilding the subframe with OEM parts.

Naaa man my and tyre size werent great and cheap tyres when I used to run 400 lol cheeky bugger though.