staticlag

FEED 4.77 final drive review:

Getting the parts required for this has taken me around 3-4 months.

I bought the FEED gear used from Murix, great guy. He said it took him 3 months to get from Japan new.

$600

Can be bought new from www.mazdaparts.com for $677 plus probably $50 in shipping

http://www.mazdaparts.com/ProductDet...000-1156400947

or www.japanparts.com for $726

Then I had to get the Mazda bearing Kit, which are the two bearings for the main pinion, the two bearings for the axles, the three oil seals, and the crush washer.

Diff bearings- 011827350A (2ea) MSRP-56.80ea Website-45.44ea
Axle seals- P04327238A (2ea) MSRP-8.25ea Website-6.60ea
Pinion seal- RA0327165A MSRP-21.50 Website-17.20
Pinion Crush spacer- R00427171A MSRP-10.00 Website-8.00
Pinion bearing #1- 060427220 MSRP-35.45 Website-28.36
Pinion bearing #2- R00127210 MSRP-61.20 Website-48.96

$202

I got mine from www.onlinemazdaparts.com a forum vendor. They also have great prices on coils

Then The install is going to cost $500 (note, this is just for the gear install, if you cant remove the diff yourself then it will probably cost around $800 bucks for the whole thing)

So this is a bare minimum $1300 install. But realistically this will probably cost you around $1700.

The shop in town specializes in transmissions. They said that the fittment was perfect and the backlash, meshing and preload set itself on the first try.

Maybe a lot of you haven't heard of this before, but the 4.77 gear shortens the gear ratios for all the gears (shorten meaning that any given gear will seem to last shorter in comparison to driving speed). So driving around in third gear at 3000 rpm, you will no longer be at 30 mph but rather at some lower speed. Its a ratio difference so its not like this just raises every rpm by 1000 for any given speed but rather it will vary with what gear it is in.

4.77 means that the drive shaft coming from the transmission has to turn this gear 4.77 times in order to turn the wheels once. This is raised from the stock 4.44 gearing. This functions the same way that the low gear functions on your car or on a bike. Its very easy to turn the pedals because torque is amplified by the gears but you need to turn them very quickly to go fast. Luckily the RX8's rotary engine has revs to spare and rather meek low end grunt. So this seems like the perfect mod to trade some revs for raw acceleration, this will let the rx8 zip through the gears right into the power band and be able to put more power to the ground in general.

Top speed is limited to about 163 mph now as opposed to the 185 ish limit of 6th gear now. So at about 9K in sixth gear you will be at 163 mph.

This drive promises a noticeable increase in torque in every gear.

chattering in video is only from the camera bouncing up and down, there was no background noise in the cabin other than the exhaust

http://videos.streetfire.net/video/1...ad014d0acc.htm

Review:

This is easily the best mod out there for the N/A rx8. I honestly couldn't feel my flywheel upgrade that much, but this is like 4x the difference that the flywheel felt like!

Even though it is pricey it really gives a lot of grunt to the rx8, Pulls feel stronger in every gear.

At 70 mph in sixth revs were at 3900

at 80 revs are 4400

at 85 revs are 4750

It is harder to drive though, engine braking is MUCH more pronounced. So I don't really recommend this for someone who isn't already well acquainted with rev-matching and smooth shifts.

Engine feels a lot more responsive and I can definitely notice MUCH more pull.

The gear is very silent, there are no abnormal noises from the differential. The gear is well made.

this easily tops my list for the best power mod to do for the RX8, really gives the car back some pull, makes it more fun to drive because it feels even more revvy than it already is.

Ground was wet outside so I couldnt really do any serious starts because I wasn't getting any traction in 1st gear.

It feels good, I'm very pleased with how this mod turned out and I will post some RX8 vs RX8 comparision vids when my buddy gets his out of the shop.

Overall, this makes my mod recommendation list:

1. Lightweight wheels
2. FINAL DRIVE
3. RP short shifter
4. AP pulley
5. coilovers & swaybars
6. flywheel
7. REVi + duct
8. test pipe + exhaust
9. mazmart water pump, gauges, koyo radiator, battery relocation, grounding kit, strut tower bars.

It Really is the best mod out there aside from some wheels <17 lbs (cause those help you not only in acceleration but also steering and braking)

Sidus

nice job!!! great info!!

looking forward to see the pics and video!!!

nmarz77

Sweet!!! I've been waiting for a review on this for a while now! I finally bought my 8 last thursday and this will be the first mod done.

lazi

murix bought that from me some time ago =)

cooldriver88

how badly does this affect your gas mileage??? at like 70 mph in 6th where does your RPM's sit?

tiltmode43

iTrader: (15)

Excited to hear what you think!

staticlag

first post updated with review

nmarz77

Sweet! I'm glad someone with a 6MT finally got this done and posted a review! Thanks for being our test mule! J/k Seriously though I am happy for ya and I hope you enjoy this mod. Can't wait to see some vids and/or hear some stories.

WoodsOfGreenRx8

Speaking of car in the shop, we went by & saw it. Looks pretty damn good, but going to have to bring the car back up a bit due to the kit.

Anywho, back to topic.

Glad you like it man. Know you were "jonesing" for it for quiet some time. Hit me up this weekend.

SoFL_RX8

Great post and information. This is what everyone has been waiting for concerning the 4.77

Now, could you re-do the video with some WOT pulls? Id love to see how the revs climb up in 1st ad 2nd with the new final gear.

staticlag

New Video

http://videos.streetfire.net/video/c...af0013b832.htm

nmarz77

Nice. You said your buddy has an 8 also.......you guys gonna do a couple runs against each other to see if there is a noticable difference?

Willicuddy

Nice video, but wheres the sound

mazdaexe

I have to agree with staticlag's review.

See mine:
https://www.rx8club.com/showthread.p...eed+final+gear

And I totally agree that the best mod would be a lighter wheel/tire, then it would be the final gear.

Im still pretty concerned about that actual gains of this final gear. it defn "feels" great.. but from a track test I did, it seems to perform the same as before.

Im guessing, it really helps the torque-less cars we have and really boost up the low-mid range. but at high ends, the gain seems minimal?

Oh, and if anybody is interested and around the area, I dont mind doing a few safe runs for comparison purposes. :P

Rotary Rasp

iTrader: (2)

Would this be a bad mod if you planned on going turbo down the road?

WoodsOfGreenRx8

Yea, when my car gets out of the shop, we'll head down to the local eight mile & do some test. No reason to get crazy stupid on the streets testing it out.

staticlag

Hmm, this mod really does help with torque in general, I think that I can get away with feathering the clutch at about 3K now instead of the 4-5K that I usually do for a "fast start"

I have noticed that I need to shift a lot more now, it seems like I'm constantly shifting while on the street. Well, thats mostly I think because I get up to speed faster, its a lot easier to accelerate and in order to keep it civil on the streets I need to shift more to keep the revs down ( am catless and it gets noisy for when im just driving around).

I plan on going turbo in the next one or two years, and I think that this mod would make a great addition to a turbo setup.

While recommending this, realize that you get gobs of torque in first gear from this mod, and adding 100+ tq as with an add on turbo is going to be a lot for a driver to handle in first and second gear. So, you may be playing fast shift catchup at the start of the race, but with this mod and a turbo in third gear and above the rx8 would be a beast!

So thats what I think I think that the final drive and a turbo would make for the ultimate rx8 experience in 3rd gear and above!!!!!!!

tiltmode43

iTrader: (15)

Hm, I wonder how the dyno would differ?

Willicuddy

You are not adding any power by putting in different ratio gears, you are just getting the power sooner.

staticlag

I agree

Japanparts.com

Excellent posting!

Japanparts.com provide discounting from our Website pricing for all RX-( parts to this Forum and the part won't take anything like 3 months....

Just to reinforce: This Part requires the preload/backlash/meshing setting done; or at least checked, which is a specialized job not everyone can expect to DIY

Definitely a worthwhile modification.....

Graham Ware
Export Manager
Japanparts LLC
* Since 1996 *

tiltmode43

iTrader: (15)

Thats the idea, its changing the rpm/torque, shouldn't the torque curve differ?

nmarz77

Yeah the torque curve will differ. Going from a 4.44 to a 4.77 will only yield a 7% increase in the torque at the wheels though so although it might be noticable in the seat of the pants it's really not that drastic. Since the torque curve will show higher but peak at lower rpms, the horspower band will change also but peak h.p. should stay the same. I'm looking to see if I can get my hands on a 5.xx series gear. Going from a 4.44 to say a 5.11 should yeild about a 15% increase of torque to the wheels.

The only thing is that I'm not sure that a downward shift in torque would be good for our cars for racing since we like to spend most of the time in the higher rpm band.

staticlag

Yeah, i thought about the 5.1x ish gear but you can get the same ratio as that with the 4.77 and some 17 inch wheels. Plus you have the benefit of going back to 4.77 if 5.1 is too much.

nmarz77

Very good point! Never thought of that. What size wheels are you running right now?