Switch to full style
Lets talk clutches and everything drivetrain related
Post a reply

Final Drive upgrades

Thu Dec 18, 2008 9:01 pm

I wanted to start a topic on final drive upgrades. Final drives have been an inexpensive performance mod for many cars.

While it is not the easiest of mods to do to our cars, it might be a good solution for those who already plan on dropping their gearboxes for a clutch and it might be much more affordable in the long run vs having to get a huge turbo kit. Alltracs might get much more out of their ct26, ct20 or ct27 with a lower final drive. For those of us with taller than stock tires this helps bring our FD closer to stock.

Alltrac ratios
Final Drive: 4.285
1st (3.384); 2nd (1.913); 3rd (1.333); 4th (0.972) 5th (0.731)
Rev: (3.545)

RC Ratios
Final Drive: 3.933
1st (3.583); 2nd (2.045); 3rd (1.333); 4th (0.972) 5th (0.731)
Rev: (3.545)

Rally ratios
St185 Rally (1989.9/6):
Final Drive: 4.285
1st (3.230); 2nd (2.142); 3rd (1.518); 4th (1.258) 5th (0.731)
Rev: (3.545)

Here is a link to a calculator to see how the FD can effect your gears.
http://www.housemanautosport.com./ratio ... ulator.htm

Rav4 Gearbox
We have already discussed that a Rav4 gearbox is an option for a lower final drive and closer ratios. The only concern being the strength of the gearbox.
Links to threads:
http://www.alltrac.net/phpBB2/viewtopic ... light=rav4
http://www.alltrac.net/phpBB2/viewtopic ... light=rav4
http://www.alltrac.net/phpBB2/viewtopic ... light=rav4

Fensport 4.4 Final drive
I found this link that at one point the fensport y2k gt4 had a 4.4 fd.
http://www.motoraddicts.com/experts/blo ... elica99414
Spensport offers this final drive as an option in one of their gearset kits. I emailed them about getting the FD separate for the standard box.

Info from their page.
3.933 Final drive (25mph per 1000rpm, ie 200mph at 8000rpm), also available with 4.4 Final drive(22.5mph per 1000rpm, ie 180mph at 8000rpm).
http://www.fensport.co.uk/partsfiles/st205tuning.htm

However it seems like most cars that make too much power they can be better with a higher final drive.
http://www.modifiedcars.com/cars/Toyota/19345.htm

Anyhow, a lower final drive may be a good option for some of us with moderate power goals.

EDIT: Added final drive mod link for reference.
http://gtfour.supras.org.nz/428ratio.htm
Members don't see the above ad. Register now
Last edited by CMS-GT4 on Mon Jan 12, 2009 5:26 am, edited 2 times in total.

Fri Dec 19, 2008 6:14 pm

Fensports say their Fd will only work with their gear set.

Sat Dec 20, 2008 2:58 pm

*stickied* and still open

Mon Jan 12, 2009 5:15 am

So it looks like the MR2 guys had this idea as well. A 4.5 final drive was made for the mr2 by Phoenix Power. I am not sure if there are any left though. The final drives of the mr2 and alltrac share the same part number so this should work for us.

It equates to 5% more usable torque but a lower top speed.

You can use the calculator to see how it might affect your power band.
http://mr2oc.com/showthread.php?t=28712 ... inal+drive

This would be an alternative to using the rav 4 gearbox and keeping the stronger internals of the alltrac box.

I ran my number through the calculator and even running my over-sized tires my final drive would still be slightly lower than stock with stock tire size.

Mon Jan 12, 2009 7:15 pm

For those who want a taller final drive the solara final drive is an option used by the MR2 oc guys.

http://mr2oc.com/showthread.php?t=12392 ... inal+drive

Fri Jan 16, 2009 12:08 am

There is a gt4dc member from Russia who is opening up shop for fabricating parts. He can do custom final drives for our boxes in the $500 usd range. This is likely the path I will be going when it comes time for my gearbox project.
If there is interest we can get a group buy of 5 or so down the road.

He is also possibly offering a close ratio dog box for much less than the c-one unit.

Tue Jan 20, 2009 6:05 pm

Just for comparison I wanted to post the EVO 9 5 speed specs to compare to the gtfour boxes.

Curb Weight: 3,263 lbs (EV0) 3,219 lbs (EVO RS)

1st: 2.785:1
2nd: 1.950:1
3rd: 1.444:1
4th: 1.096:1
5th: 0.761:1
Final drive: 4.529:1

Tires: 235/45ZR-17

Tue Jan 20, 2009 9:58 pm

Very interested in these "Russian" final drives / gear kits indeed ! However, as my car is a pure street car, I am not interested in a straight cut dog engagement kit, but rather a closer ratio helical cut syncromesh kit that will work with the stock bearings, syncro cones, etc.

That's one of my main attractions to the C-One kit - however repulsed I may be by the price ! :-)

Basically, I am trying to achieve a top speed of 130 to 140 mph max at 7,500 RPM in 5th gear on 225/45/17 rubber, and reduce the gaps between 1st and 2nd gear especially, without raising 1st gear to a level that getting the car off the line in a "spirited manner" is difficult.

Tue Jan 20, 2009 10:00 pm

Any sort of timeline on when the kits / fd will be available ?

Tue Jan 20, 2009 10:56 pm

We have to have at least 5 definite buyers then he will make them. I am working on the funds right now for it.

Wed Jan 21, 2009 1:06 am

Will it be a FD, a gearkit or both ?

Will it be a syncromesh gearkit or dog box ?

What ratios for the gearkit and FD ?

Cheers !

Wed Jan 21, 2009 3:05 am

The Russian company is just the final drive set.

Wed Jan 21, 2009 3:47 am

He is offering a gearset too, when there is enough interest.

Prochorus familiaris wrote:The 1st question:

Now we are on decision - to make or not to make?

The talk is about close ratio gears, for our cars (GT4) it's produced only by C-One in Japan, look it here:

http://www.c-one.co.jp/C-ONEPARTS/close_mission.html

Their price is 2800$ ExWorks, with airdelivery it will be up to 3500$ because of "nice" weight of the parcel.

We can do make the stuff like this, even upgraded, i.e. little bit more nicely selected ratios, more stronger steel, more tough treatment of the material, etc.
We have some tech claims to C-One stuff, because we have in our team (consists of 1 ST185 & 4 ST205 for rally + 3 ST205 for writing the verbatim before the rally) in competition with dog-gang gearboxes, and C-One sometimes give us the problems of damage & in some sense we aren't pleased with ratios selected, so there is a space for improvement & upgrade.

Our project price will be 1800$, i.e. minus 1K$ at least. May be even more cheaper, it's hard to say before production start.
Also our delivery will be much cheaper, because it based on lower tariffs.

Now we are on the decision point - to make or not to make?
We don't want to make it & then to put it on the shelf as in museum.

SO - Do you think it could be interesting for you?
Please input your IMHO. For us to estimate the demand.

Any questions are welcome.

Wed Jan 21, 2009 12:17 pm

Consider me heavily interested with cash waiting. As long as it is not a dogbox and the ratios suit my purpose.

I'm THIS close to buying a C-One kit, but the price is turning me off. If there was another (as good or better) alternative at a reduced price, I will be all over it.

Mon Mar 23, 2009 11:52 pm

Any further developments in this area guys ?[/quote]
Post a reply