Is200 Diff

[Asi]

hi there,

i was wondering if this diff would fit the is200

http://www.lexusownersclub.co.uk/forum/ind...showtopic=58028

thanks

[Dimitris Papamichail]

hi there,

i was wondering if this diff would fit the is200

http://www.lexusownersclub.co.uk/forum/ind...showtopic=58028

thanks

Did you buy it?

[Steviewevie]

I'm no expert on this but I would have thought the diff itself would fit. But if the final drive is designed for an RS200 (i.e. different engine to the IS200) then I don't know what this would mean for connecting it to the IS200, i.e. whether the gearing would be too high/too low/etc

[Asi]

not bought it yet so that means it would fit without the final drive

[Asi]

anyone?

[Steviewevie]

Try PM'ing Monster-Mat.

[Monster-Mat]

yup will fit the is200

[Asi]

yup will fit the is200

even witht the final drive

thanks

[Steviewevie]

I think the final drive is just the gearing inside the diff, isn't it ? I could be wrong. So it's probably a question of whether this final drive, designed for an Altezza with a different engine, will work with an IS200 ?

Again, probably a question for Mat.

[edeath]

If the Diff will fit it fits - whats inside doesn't really matter if it connects to the prop ok and to each axle fine. But doesn't that final drive not just shorten all the gear ratios which would up the general acceleration but lower the top speed of each gear? Would be fine on a high revving car like the RS200 but imagine it would annoy me on a supercharged IS200 if used everyday.

[Asi]

if it shorten the top speed then aint really post buying it.

[Steviewevie]

Yeah, that's what I meant, that I would imagine it would affect the top speed and acceleration - I don't know whether that's positively or negatively, but I'd be wary about buying a gearset that was designed for a different engine. Maybe that isn't much of an issue though ? As you say edeath, the RS200 does rev higher than the IS200.

[Asi]

well lets see what mat has to say to it? but if its shorten the top speed then its not really worth it.

[Steviewevie]

Final drives are always going to be a compromise though, aren't they ? e.g. you choose a final drive to give you better acceleration, but the downside is a slightly slower top speed. How often are you realistically going to need the top speed though ?

Conversely you could pick a higher top speed but worse acceleration (can't see too many people going for that).

[Asi]

Final drives are always going to be a compromise though, aren't they ? e.g. you choose a final drive to give you better acceleration, but the downside is a slightly slower top speed. How often are you realistically going to need the top speed though ?

Conversely you could pick a higher top speed but worse acceleration (can't see too many people going for that).

true but depends better the acceleration is and how bad would the top speed be.

[Steviewevie]

ok, poking around on ToyoDIY, it looks to me like a standard Altezza with 3S-GE engine has a final drive of 4.3. If the kit being advertised has a final drive of 4.5 then that's a slight change.

However, it looks like the IS200 with 1G-FE has a final drive ratio of 3.9. So going from 3.9 to 4.5 is going to be a pretty major change, I would have thought.

I could be interpreting the figures wrong though ?

[TigerFish]

Final drive would also effect your speedo reading if the speedo pick up is on the gearbox.

[Asi]

oh well. seems too complicated. will buy the is200 sport diff.

[Steviewevie]

Found more information and graphs on TRD's website here. Looks like the final gear ratio that I posted for the Tezza was correct, except for manual cars between Oct 98 and May 01 where it was 4.1).

[edeath]

hhmmm so is a higher ratio longer or shorter gearing?

[Dimitris Papamichail]

They are selling a Lexus sport diff on the eBay, pick up only.

[Asi]

seen them but its 300 miles away from me.

[Steviewevie]

hhmmm so is a higher ratio longer or shorter gearing?

I've been trying to get my head around this, and it's making my brain hurt !

I think that the ratio refers to the number of propshaft revolutions which are then converted to wheel revolutions - e.g. with a 4.5 final drive the propshaft is turned by the engine/gearbox 4.5 times to make the wheels revolve once.

So with a higher-numbered final drive you get a lower top speed, because obviously the engine can only do so many revs and the higher ratio means you turn the wheels less times, hence lower top speed.

It seems that conversely though you'd get better acceleration to trade off against that loss in top speed. I actually can't get my head around how you get better acceleration, though I'm sure there must be a very simple explanation ! :duh:

[TigerFish]

hhmmm so is a higher ratio longer or shorter gearing?

I've been trying to get my head around this, and it's making my brain hurt !

I think that the ratio refers to the number of propshaft revolutions which are then converted to wheel revolutions - e.g. with a 4.5 final drive the propshaft is turned by the engine/gearbox 4.5 times to make the wheels revolve once.

So with a higher-numbered final drive you get a lower top speed, because obviously the engine can only do so many revs and the higher ratio means you turn the wheels less times, hence lower top speed.

It seems that conversely though you'd get better acceleration to trade off against that loss in top speed. I actually can't get my head around how you get better acceleration, though I'm sure there must be a very simple explanation ! :duh:

Just to make you think about it even more, you could change your tyre aspect ratio to compensate

[Steviewevie]

ok, after some more Googling, I think I've found the answer. Through a higher-numbered final drive you are putting more torque through to the driving wheels, which will give you better acceleration. But as well as decreased top speed, you'll be doing more revs to do the same speed that you usually do (e.g. 70 mph on the motorway), meaning more wear on the engine, increased engine noise and worse fuel consumption.