hey all, not too sure where to post this, i do searches for both but cant seem to find the answers im looking for...
ive got an EG sedan with a b18c, turbo'd with a full race stage 1 GT kit...
im looking at getting an MFactory LSD, just wondering if i should go that one, or just an OEM ITR item instead...
but the main question is in the Final Drive. Ive got a 4.4FD atm, and while the LSD is getting installed i want to look at the final drive and which one is better for me, i will be doing a bit of drag racing at the local track, and hopefully the occasional circuit day aswell but majority of driving is on the street... i would like to get a 4.7 or 4.9FD but i have been warned against it,saying that because my car is boosted, its better to just leave the 4.4... what are your experiences?
cheers
Christian

 

You will enjoy the 4.785 or 4.928 FD far more than the oem 4.4. If you get the 4.928 though, best to change to a 3.070 1st gear as well to help with your launch. Don't listen to people when they say "longer gears for boost", it's a load of nonsense.

 

cheers dude, the person i was speaking to was from MFactory in Australia, Leonardo? he was the one that warned me against 4.9 lol i was thinkn a 4.7 same as the ITR, but my gears will be a little longer wont they? so that will help a little being boosted?
i know already the redline comes up very fast :p

 

It really depends on your application and what top speed you are wanting. If the top speeds in each gear are acceptable to you with the 4.928 FD, then there is no reason not to go for it.

Longer gears helping boost is nonsense. It's like saying you'll be faster by just staying in 5th gear everywhere you go.

 

welll im aiming at doing 11s one day, so that would require a top speed of about 200km/h or so?
id really like to go in cars with both to try them and see which i liek more... im leaning toward the 4.7 as its standard in ITRs etc so it cant be too full on...

 

The '98 Spec ITR has longer 4th/5th gears as well though, so the end result is very similar. Your 4th/5th will be shorter with the 4.785 than the '98 Spec ITR is.

Have a play around with our gear calculator, you mind find it interesting: http://www.teammfactory.com/gearcalculator.php

 

cheers dude...lol so much to chose from haha

 

i just think that if its too short, and u have to change to 5th on the strip, thats an extra gear change that will slow u down?

 

Unless you are trapping around 110mph, you will not have to change into 5th on the strip with a 4.928 FD.

This has nothing to do with "longer gears for boost". This nonsense just spread down the internet grapevine as people think that being able to stay in gear longer (which technically allows them to stay in boost longer) will make them faster.

 

and 110mph is about a 12.5 or so isnt it?

 

Around high 11's

 

I just wanted to say that the gear calculator is an awesome tool! Made me think totally different about drivetrains.

 

lol i think i just dont entirely understand it then :p

 

In a car that can hook.

 

My all motor DD runs a 12.7@107...high 11's , with boost, is going to need a 120 trap.

Traction is an issue with boost and FF, thats why people like the longer ratios. If you have a light car making crazy power, why not have a longer gear- turbos need load, more traction, and less shifts.

I always say run the shortest gearing possible. Given traction, the shorter the gears, the quicker the acceleration.

 

One of our sponsored All Motor drivers (Randy Reginaldo) done a 11.71 secs @ 114 mph. He is running our close ratio gearing

 

All motor though. A boosted car needs more power and high trap to make the same ET...11.7@114 is about perfect

 

Yeah, traction starts becoming a problem

 

Is an ITR LSD a "clutch type" or helical? I picked up a GSR trans with LSD (sopposably ITR) and it doesnt look anything like the quiafe my builder runs. Sorry to thread jack, just curious and a quick answer is likely from you guys. thanks

 

The ITR LSD is Helical. The cast casings do look different from the machined casings of the Quaife.

 

i see, thanks for the input, so what kind of abuse can the ITR diff take? Im throwing at least 375-400 whp at it, built GSR, T4 setup.

 

If i were you i'd stick to the 4.4 FD... Why???, because:
1) You said your car is DD as well, with the other two FD you'll require more revs to maintain any particular cruising speed.

2) Boosted cars tends to be happier with load... With a 4.9, you'd have excess wheel spin, killing your ET on the 1/4 mile

3) As Evs-one said previously, less gears to shift

Save the money for something more beneficial

 

There is only a 300/400rpm difference between a 4.4 and 4.785/4.928 @ 70mph.

Provided you have a good chassis setup and tires, a 4.928 wouldn't cause excess wheel spin other than in 1st gear which, as I mentioned above, is fixed by installing a longer 1st gear

Unless you require trapping higher than 110mph, a 4.928 will give you a better ET, not worse.

The best gearing you can have is where you cross the line at/near the end of 4th gear. Any chassis/traction setup should then be fixed around this.

 

most guys in a boosted application are going to trap way higher than 110. **** i trapped 109 in a bone stock b16a and a baby t3. Id imagine most guys have a bigger setup than i did. 120+ trap seems more realistic especially giving them room to grow, more power, ect.

 

If you are trapping more than 120mph, then even the stock 4.4 isn't enough. In this case, I would recommend the 4.05