I have it on reasonably good authority that the "crown wheel gear" (I think that is the correct terminology) from a 380 5spd transmission will fit straight into a 3rd gen magna 5spd transmission. This will effectively change the "final drive" ratio from 3.73 to 4.11.

Since my gearbox is getting pulled out next week, and the diff center being removed / replaced - it's as good a chance as I'm going to get to change the final drive gear.

I'm wondering if it would be a worthwhile mod.

I don't know of anyone on the forums who has done this - but if I'm wrong I'd love to hear from them.

Also interested to know what sort of RPM a 380 with 5 spd manual is doing at 100km/h?

I have it on reasonably good authority that the "crown wheel gear" (I think that is the correct terminology) from a 380 5spd transmission will fit straight into a 3rd gen magna with 5spd transmission. This will effectively change the "final drive" ratio from 3.73 to 4.11.

Since my gearbox is getting pulled out next week, and the diff center being removed / replaced - it's as good a chance as I'm going to get to change the final drive gear.

I'm wondering if it would be a worthwhile mod.

I don't know of anyone on the forums who has done this - but if I'm wrong I'd love to hear from them.

Also interested to know what sort of RPM a 380 with 5 spd manual is doing at 100km/h?
Dont think anyone in all my time on here has done such a thing, or even thought of such a thing....So you will be a pioneer

']Dont think anyone in all my time on here has done such a thing, or even thought of such a thing....So you will be a pioneer

Don't know if I could claim to be a pioneer. I was told about this by someone who has apparently done it to a TL. AFAIK they aren't a member of the forums.

well i havent heard of it being done yet but my mate told me that it should be able to be done! i know this doesnt give u a definate answer to ur question but he was pretty damn sure that it will fit and would be well worth while doin.so as soon as my box goes again ill be gettin a new pinion too for mine :D

If you have the opportunity to do it i say go for it. The V8 boys have been doing it without any major dramas. Advantages would be better acceleration of the mark. Probably better quatermile times as well. Engine wont labour as much in higher gears.
Disadvantages
Lack of traction
Speedo will be out
May go through a bit more juice
Engine will rev higher at 100 kays
If its an auto the shifts may need to be recaliberated (eg it may change too soon)
Tyres due to lack of traction due to better get up and go off the mark.
Thats all i can think of at the moment.

Good luck with it..
Regards

Well I'd do it, but my 1st gear is usable and well 2nd gear to. You will rev harder on the highway, by 400rpm or so, so 3000 instead of 2600 but it would be quicker. Have you priced a 380 gearbox from mitsu??? Have a look at the price against rebuilding yours, it might be better to buy a new gearbox instead, unless ur getting an LSD put in as it seems like ur interested in doing so.

Speedo most likely wont be out cause I thought it was done by the ABS sensor and it's gonna read the speed that the wheel is doing regardless of RPM

i have to vote against the idea

with the amount of power you have on tap, you'll be smashing through gears sooner. The acceleration you have with a shorter final drive may be good in 1st or 2nd, but you'll be in 4th gear sooner as well at lower revs, rather than still being in 3rd at higher revs

i know its not the same, but i tried really small slick tyres on my car at the drags. i got a 2 second flat 60 foot time and a pretty good 660ft time, but my final trap and time speed was down as i spent far too long in 4th gear. best run i got was a 14.2. was also a pain in the **** getting off the line. went back to bigger tyres, got a 2.1 60 foot time and ran consistant 14.1's

this was all in N/A form in my ralliart

Yeah. My biggest concern is traction (lack of). As is is now with my car - I can only squeeze on about half throttle in 1st gear before it's time to change to 2nd, and it spins the wheels freely in 2nd at full throttle. I guess I'm kinda hoping the LSD will improve the traction issue abit, and with LSD + 4.11 final drive, hopefully I won't be much worse off than I am now in terms of getting traction.

The speedo one is an interesting point. Can anyone confirm where the 3rd gen magnas speed sensor is???

does this mean a 380 owner could make the opposite move and fit a magna one for better fuel econmony?

I would have to say go for it. Going from 3.83 to 4.11 in my 9in (1970 360 VG valiant ute) made a great differance over the 1/4 got me from 11.2 to 11.1 @ 119MPH. Never noticed much change on the freeway way either.

Traction may become a minor problem but that can easily be sorted by suspension changes and better rubber on the front. I don't mean bigger I mean better. The tire compound makes more difference to the traction than size does within reason. I am not sure what sort of gearing Mitsu offers for the ratio of each gear but you may want to look into this if you have your box pulled down to suit the new final ratio, maybe make first a bit taller but that would be up to you and your driving style.

This is a change I will definitely be doing when I blow my slush box. There is one thing you do have to remember at some stage you have to make the choice between straight line speed (traction) and handling but generally not till you are dipping into the 13's or lower

Cheers
Jyp

I wouldn't do it, simply because it would make 1st and 2nd even less practical, and magnas rev at 2600 rpm at 110 already, wouldn't want it spinning any faster. If anything you'd try and make it a taller ratio, like 3.3 or something. The torque you put out would be more than enough to see gains, although you might suffer a bit at higher speeds. It'd make it quicker off the line but might see a slower 1/4 mile speed.

Just found this nifty little tool:
http://www.cvsr.net/gearhead.swf

According to that - the difference between a standard final drive and a 4.11 final drive at 60mph is only about 240rpm.

Interesting thing is the difference it makes to top speed.

Assuming a 6100rpm rev limit - a std final drive should wind out to somewhere in the vicinity of 240km/h. Fit a 4.11 final drive however, and the most you can hope for is about 218km/h. (Bearing in mind that a full replacement ECU would be required to bypass the factory ECU's electronic speed limiter)

might work alright actually... you've said before that your boost doesnt come on until around 3000rpm... if you had a shorter drive ratio, then you would be faster before boost, which would mean that if you took off in 2nd (completely scrap the use of 1st) it wouldn't take so long before you hit boost, nad you'd have 1 less gear change and less struggle off the line

4.11 pfff get a custom 9.11 and leave everything for dead off the mark lol

You could also play around with wheel/tyre sizes if you need to 'fine tune' things...

4.11 pfff get a custom 9.11 and leave everything for dead off the mark lol

Untill your redlining at 60 in 5th :bowrofl:

Rang mitsubishi today and got a price on a crown wheel and pinion gear from a 380 5spd manual.

$780 for the pair of gears (not bad for genuine parts I guess).

Considering I'm going to have to sell my body just to afford the LSD I think I'll end up giving the diff gears a miss this time round.

Haven't given up on the idea of getting an alloy flywheel thrown in while the box is out though :cool:

The 380 may have taller gears to match the lower diff as well.
Just a thought.