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/ProductDetail.jsp?LISTID=5150000-1156400947

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/10a68352-4964-4a40-83ff-99ad014d0acc.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)

nice job!!! great info!!

looking forward to see the pics and video!!!

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. :)

murix bought that from me some time ago =)

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

Excited to hear what you think!

first post updated with review

FEED 4.77 final drive review:

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.

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)

Sweet! :SHOCKED: 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. :naughty: :aroused: :yumyum: :aroused: :yumyum:

first post updated with review

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.

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.

New Video

http://videos.streetfire.net/video/c6e9c11d-3541-4e26-a4c6-99af0013b832.htm

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?

Nice video, but wheres the sound ;)

I have to agree with staticlag's review.

See mine:
http://www.rx8club.com/showthread.php?t=114306&highlight=feed+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

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

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?

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.:icon_tup:

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

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!!!!!!!

Hm, I wonder how the dyno would differ?

Hm, I wonder how the dyno would differ?

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

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

I agree :)

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 *

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

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

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.

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.

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.

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

5.1 gearing would be insane.

You better have a quick wrist to deal with all that shifting :)

All this gear talk is making me feel like I'm on a Mustang forum ;)

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.

Only difference then will be the contact rubber, will have to run wider if you want same area of contact...

Thank you nmarz77, finally someone who understands why I'd like to see a dyno, I'm not thinking necessarily for increase but to see how it changes exactly. I'm sure given the fixed ratio vs stock this could be calculated but Im way too lazy for that :)

Only difference then will be the contact rubber, will have to run wider if you want same area of contact...

Thank you nmarz77, finally someone who understands why I'd like to see a dyno, I'm not thinking necessarily for increase but to see how it changes exactly. I'm sure given the fixed ratio vs stock this could be calculated but Im way too lazy for that :)

Yeah I think the only thing my brain wants to do right now is IMAGINE what it would look like on paper......it's screaming "NO MORE F*CKING MATH ON A FRIDAY!"

I'm gonna do some google searches to see if I can find a dyno comparison of a before and after gear change so we can get and idea of what it might look like.

Well, the dyno in horsepower only mode (which is the dyno mode normally used for "horsepower" pulls)

Will measure inertial change in the large roller.

Even with the gear amplification the engine itself will not be able to "change" the inertia of the roller fast enough to show a torque or horsepower increase.

This is shown in the fact that dyno pulls in 3rd, 4th or 5th gear most always result in the same graph, even though each of those gears has a different "drive"

A dyno will not show change from this gear.

hey staticlag, you have the RB flash also right? How come you weren't taking the RPMs into the "10000RPM" zone?

Nice vids.

Well, the dyno in horsepower only mode (which is the dyno mode normally used for "horsepower" pulls)

Will measure inertial change in the large roller.

Even with the gear amplification the engine itself will not be able to "change" the inertia of the roller fast enough to show a torque or horsepower increase.

This is shown in the fact that dyno pulls in 3rd, 4th or 5th gear most always result in the same graph, even though each of those gears has a different "drive"

A dyno will not show change from this gear.

Smarty pants tehe, I just assumed that because torque was coming in earlier it'd show on the torque curve. :rolleyes:

FEED 4.77 final drive review:

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.


Great review! I thought it was a straight swap, and that everything required for the install would come included with the FEED gear. Guessing an AT will need all these also?

Ok well after a quick search I found an explination for us and a graph that show how the torque and horspower differ with the installation of a different gear. Check it out!

http://www.wallaceracing.com/reargear.htm

Ok here is one more link for ya. This one is really good because it explains how different performance upgrades(including gears) shift torque around. The only one that would apply to our cars though is the gearing explination.

http://clubs.hemmings.com/clubsites/mtfctulsa/Tech/power_and_torque.htm

Great review! I thought it was a straight swap, and that everything required for the install would come included with the FEED gear. Guessing an AT will need all these also?

Just do what I did and have it sent to Mazmart. They will take care of everything else for you.

Ok here is one more link for ya. This one is really good because it explains how different performance upgrades(including gears) shift torque around. The only one that would apply to our cars though is the gearing explination.

http://clubs.hemmings.com/clubsites/mtfctulsa/Tech/power_and_torque.htm

Yes, but as I said in my post, in "horsepower only" mode the dyno will not change, that is, the engine will not produce any more torque or horsepower for any given rpm.

Now is is different than the "road simulation" mode that is discussed in these articles that graph horsepower and torque versus road speed on the x axis.

Maybe these graphs are what you are looking for in conceptualizing the change.

4.44 stock
http://img.photobucket.com/albums/v519/staticlag/4444.png

4.77 FEED
http://img.photobucket.com/albums/v519/staticlag/4778.png

Now, what is seen is a shrinking or shortening of the gearability of the car. By shortening the gear graphs the engines power is concentrated for any given speed. You spend more time in the sweet upper spot of the engines powerband rather than the boggy lower end.

Its just like any of the other gears in any car. Imagine the power difference between being in 3rd gear at 40mph versus being in 6th gear at 40 mph. You still have the same engine putting the same power out, but 6th gear is greatly lengthened versus 3rd gear.

This is the same thing, but only it shifts all the gears at once, making all of them stronger at any given roadspeed at given at the expense of top speed.

Just do what I did and have it sent to Mazmart. They will take care of everything else for you.

Did they replace your bearings? Or did they just switch them over?

Great review! I thought it was a straight swap, and that everything required for the install would come included with the FEED gear. Guessing an AT will need all these also?

You "can" re-use all the parts off the old piece, but they are all wear items, just like brake pads or oil or antifreeze. So while your in there its not a bad idea to give some preventative maintenance.

all the bullshit comments on the video forum are hillarious. Glad you're enjoying it man, seems very worth while.

Well I guess the confusing thing here is weather or not you are trying to measure the actual torque at the rear wheels or at the crankshaft. Dynos always correct the torque to try to get it to where it should be at the crank, so you're right, there should be no change in torque on the dyno sheet. If we measured the actual torque at the wheels though we would see HUGE numbers and big differences in torque output depending on what gears were selected. For easy example if we had a car putting out 160 lb/ft of torque at 5500rpm like mazda claims, and we were in 5th gear with a 1:1 ratio, with the stock 4.44 final drive the output torque at the wheels is actually 4.44 times 160 which makes it 710.4 lb/ft. now with your FEED 4.77 you should gain an additonal +/-7%. 160*4.77=763 lb/ft.

So you're putting down an additional 63 lb/ft of torque where the wheels touch the pavement. Sounds like a lot but when you consider you already had 710 to begin with, it's not a massive improvement. Now going through first gear would be 3.76x4.77x160=2,870 lb/ft with the FEED.

I know this has nothing to do with the dyno chart but it just looks cool on paper.

Well I guess the confusing thing here is weather or not you are trying to measure the actual torque at the rear wheels or at the crankshaft. Dynos always correct the torque to try to get it to where it should be at the crank, so you're right, there should be no change in torque on the dyno sheet. If we measured the actual torque at the wheels though we would see HUGE numbers and big differences in torque output depending on what gears were selected. For easy example if we had a car putting out 160 lb/ft of torque at 5500rpm like mazda claims, and we were in 5th gear with a 1:1 ratio, with the stock 4.44 final drive the output torque at the wheels is actually 4.44 times 160 which makes it 710.4 lb/ft. now with your FEED 4.77 you should gain an additonal +/-7%. 160*4.77=763 lb/ft.

So you're putting down an additional 63 lb/ft of torque where the wheels touch the pavement. Sounds like a lot but when you consider you already had 710 to begin with, it's not a massive improvement. Now going through first gear would be 3.76x4.77x160=2,870 lb/ft with the FEED.

I know this has nothing to do with the dyno chart but it just looks cool on paper.

I completely agree with you :)

all the bullshit comments on the video forum are hillarious. Glad you're enjoying it man, seems very worth while.

They are quite hilarious.

Did they replace your bearings? Or did they just switch them over?

I actually did a core-swap with Mazmart and got a whole "new" differential. It was actually built from a used diff from another AT, but considering Rick Engman built it I consider it better than new. Plus the diff that they used was actually a bit lower mileage than my original. I'm not sure which parts are new and which are used (other than the FEED gear being new and the diff housing being used), but Mazmart has such a good rep that I wasn't really worried about it. Their quality and customer service are top notch. I have since bought a water pump from them which is a top-notch piece.

FYI - Mr. Engman did have to do some machining on the FEED gear to get it to within what he felt were good tolerances for a street car. But I can't complain - this diff is smoother than my OEM diff. And it is an LSD.

I bought the FEED gear, had it shipped to Mazmart, they built the new diff, had it shipped to me, my mechanic installed the new diff, and then i shipped the old diff to Mazmart.

Feel free to PM Paul at Mazmart about my diff build.

My car had this final drive, too. Recently I sent my ECU for knight sports swap for cancel of speed limiter, fan control and extend rev limit from 7500 to 8500rpm (sorry I had a AT one). Can I get my top speed back?

Recently I sent my ECU for knight sports swap for cancel of speed limiter, fan control and extend rev limit to 8500rpm (sorry I had a AT one). Can I get my top speed back?


Unless you are racing open road courses, do you actually need your top speed?

Unless you are racing open road courses, do you actually need your top speed?

you're right. but I just want to know the effect of another 1000rpm

what kind of rx8 do you drive that can hit 185?

im pretty sure rx8s top out at 148. so its not reducing it from 185 to 160ish. its putting it from 148 to about 135.

and this would also further kill gas mileage. highway speeds = higher rpm = lower mpg.

bout 160 stock

what kind of rx8 do you drive that can hit 185?

im pretty sure rx8s top out at 148. so its not reducing it from 185 to 160ish. its putting it from 148 to about 135.

and this would also further kill gas mileage. highway speeds = higher rpm = lower mpg.

This mod lowers possible top speed, not actual top speed.

By shortening the gears it puts the engine into its powerband when its 150-165 mph. So it actually will increase the cars ability to redline in 6th, in other words it makes 160mph+ easier for the car to do.

This mod lowers possible top speed, not actual top speed.

By shortening the gears it puts the engine into its powerband when its 150-165 mph. So it actually will increase the cars ability to redline in 6th, in other words it makes 160mph+ easier for the car to do.

I'm glad there's finally somebody on this forum that understands this.

Update: about 1000 miles have been put on the car since this change.

I have to say that the build quality is exceptional, the rear end is silent, feels great.

The extra torque really has made this a whole new car, and I can still feel the difference. Definitely up there on the list of recommended mods.

After a few full tanks I'm going to go ahead and say that this mod will reduce your mileage by about 1.25 mpg for 60% city and 40% highway driving. It does help around town as I find myself cruising in 5th and 6th gear on surface streets regularly. But highway mileage is down though, haven't gone on any long road trips so I really couldn't comment on a pure highway loss in mpg number.

How did she do on the track Dan?

with the diameter tires i run on the track it has been calculated that it is equivalent to a final drive of 4.78---so i can attest that it does really change the car. :)
olddragger

with the diameter tires i run on the track it has been calculated that it is equivalent to a final drive of 4.78---so i can attest that it does really change the car. :)
olddragger

what size is that OD ?

235/40 17"toyo ra 1. tire+rim+lugnuts =40lbs also!
OD

my avitar is a pictures with those rims/tires on the car
olddragger

235/40 17"toyo ra 1. tire+rim+lugnuts =40lbs also!
OD
I may go the same way for some track rims .
do you run those just on the track or street as well ?

Any 1/4 mile runs with times?

It felt good on the track. the shorter gearing Was really apparent in one turn where i kept hitting my limiter. in general the extra torque was a good way to get out of some turns. it felt very natural, it felt easier to heel toe. my in turn rotation felt tighter when i let off the gas. it felt very good. i can't wait to auto x it. it would probably eliminate some first gear action on some courses. less shifting = faster times

just for track. and you are exactly right--gearing is a big part of running anything
OD

Update 12/8/07:

Feels great! No noises or odd behavior from the diff.

Good to hear. Have you done a comparison run yet?

I'd like to see a comparison run too! Grab one of your local RX8 buddies and video a 20 roll, for academic purposes. :)

Good to hear. Have you done a comparison run yet?

Just some non-videoed, non formal runs.

As soon as the snow melts here we will get right on it!

Just some non-videoed, non formal runs.

As soon as the snow melts here we will get right on it!

So what was the outcome of these runs?

cant wait to see the #'s