4.875 final drive review
 

Here's my review of the Autofactory 4.875 final drive.

Background
I've been thinking about getting a shorter final drive for some time now. I wanted to keep the car NA as I love the NA sound, throttle response and reliability. I've had much faster turbo and supercharged cars and I didn't need the 86 to be a fast car, just one that was fun and accessible. I don't care too much about acceleration times or laptimes in this car. I think the final drive is a great mod for the 86 these reasons:

• Car feels faster everywhere
• Stealth mod. No one knows you have it :)
• Doesn't affect reliability
• More shifting = more fun!
• Improve throttle response and torque in all gears
• Can redline the car all the time without exceeding the speed limit

Research
The standard manual final drive is 4.1

Some of the options out there include:

• 4.56 from Cusco/Toyota = 11% reduction
• 4.67 from Mfactory = 14% reduction
• 4.875 from Autofactory (also a Toyota part) = 19% reduction

The % reduction directly corresponds to the % increase in torque in each gear.

Initially I was leaning towards the 4.67 as that seemed like an ideal ratio. But after speaking to some users who had the Mfactory installed, they said there was an increase in noise, so I ruled that out.

One of the guys I spoke to who had a 4.56 said he wished he went with a 5.1. In the end, I went with the 4.875 as I wanted something more noticeable than the 4.56. And 99% of my driving was around the city anyway, with the occasional freeway and track day.

This page here compares the difference between 4.875 and stock. 5th essentially becomes where 4th gear was originally.
http://www.teammfactory.com/gearcalc...ission+1+%26+2

Impressions
I've had it installed for 2 weeks now and have done a mixture of city, freeway and mountain road driving. I'll be taking it to the track soon and will post more feedback later.

In city driving, the new gear ratios work really well! Its not tiring at all and if you were driving slowly (not reving the car), it is not noticeable compared to stock. I had a friend in the car and he didn't know about it until I told him. There's better throttle response and noticeably increased torque everywhere. 3rd gear in particular feels much quicker as it is easier to get it into the power zone. The car feels much more fun in the city.

Drifting the car around roundabouts and 90 degree turns is also easier. 2nd gear has more torque and I find I can now modulate the angle of the rear end better especially when doing a couple of loops at roundabouts :)

On the freeway at 110k/h, the revs are now at 3600rpm instead of 3000rpm. Its not that much of a difference. But if you do higher speeds on the freeway then there will be more difference.

On the mountain roads, I don't think it was any better or worse than stock. It really depends on the road you are driving and the speed the corners are at. On my favourite road, I find that 3rd gear is now too short and I take most corners in 4th.

My fuel economy before the mod was 8.8L/100km. I've reset it after the mod and after 2 weeks, its at 8.8L/100km again. I would expect you will use more if you do a lot of freeway driving, but its negligible in city driving.

Conclusion
If you are looking for something that makes the car feel faster, this mod is great. It really does make the car feel at least 19% faster as the torque is increased by that much in each gear and it revs through the gears that much more quickly.

If you are looking to improve your laptimes, then this mod may or may not improve it. It is not the same as increasing the power by 19%. It really depends on the track and the shift points before and after the mod. You will be faster between some speeds but also slower between other speeds as you will now need to use a higher gear.

Good review. Still debating which one I'm going to get!

The thing I like about changing the final drive is it will keep me from doing 80mph on the interstate all the time. Also where/what did you pay for this kit?

who did the install? did u diy?

i bumped my civic's final drive from 4.76 to 5.062 and i never do 80 mph on the interstate anymore, i find myself doing the speed limit now :D Even with that small change it was super noticeable in every gear.

excellent review!

IMO a modified final drive is more for a weekend/track/not care much about economy car. It will definitely increase noise and decrease fuel economy.

I agree with your post about city driving and fuel economy. For someone like me that has a 90% highway commute I think a final drive mod would not really be ideal. 20% increase in cruising RPM and decrease in fuel economy when I'm not even driving "spiritedly". meh

It really depends on the type of driving that you do. Mines a daily driver and I don't go over 70-80k/h most days. We have very low speed limits here and they are vigorously enforced! I find myself less inclined to speed after this mod as the engine is able to pull cleanly in 6th gear from 60k/h

No. I bought the kit and installed it through a local shop in Sydney. Its not something you want to DIY unless you have experience with diffs.

I do mixed city and highway driving, about 40/60, with my 4.56 final drive and I went from an average of 27.9mpg to 27.4mpg. I personally wouldn't worry about losing 1/2 mile per gallon. No increase in noise that I noticed. At highway speeds in 6th gear I was only 500ish rpms higher than a stock 4.10 r&p.


I did it myself with never touching a rear end before. Already have a few thousand miles on it with no issues. Not really what I would consider "hard", just need to make sure you have the right tools.

This I did not know. I only knew about the 4.56 Toyota one.

Do you, or anyone, know the part number, and/or which car and trim, the Toyota 4.88 fd came from??

Thanks for sharing.

@drift86 is your car auto or manual?

I don't know the part number. But it comes in a box with all the parts required for the rebuild. Its not just a crown and pinion.

If you look in the parts section of the HyperRev magazine, almost all the Japanese final drive kits are made by Toyota (if you can read the Japanese :)). Whether its 4.56, 4.875 or 5.1. The kits for the 4.875 and 5.1 are more expensive and there's an extra part in the picture compared to the 4.56.


Manual.

Weir Performance also has a FD kit. The Supra FD will fit ours. http://weirperformance.com/finaldrivegears.html