im reading alot about the final drives in the rx8s and a few people have swapped over to the 4.777 final drive and they love it but is this a direct bolt on or do u have to have the differential modified to make it fit? will it be worth the cost? ive searched and have gotten back mixed results but i wasnt sure how old the thread was or if theres been any new changes on this.. any help is appreciated, i did use the search button but still am a bit confused on this

 

Going with 4.777 diff, you need to have a skilled transmission guy open up the back axel and replace it. In so doing it will fit just like it does on the 09's but will require some shimming to make sure it's perfectly secured and lined up.

It's a great mod, well worth the money.

 

thanks i appreciate the help and the non bashing for not beeing able to do a more thorough search

 

About to make a thread about it.. I just got mine. Great power increase I noticed, still getting used to the whole shifting much earlier..but when I let off the gas I notice a REALLY weird sound. I'll post about it now, but if anyone knows the answer that'll help..thanks.

 

i heard that after installation, you'd have to calibrate some stuff with the speedometer. and you'd need a kit to do so. what do you need to know about that? or was that BS? haha! thanks

 

Keep in mind that if you are planning on ever going FI you probably want to reconsider this mod. I'm no expert, but I'm pretty sure there are some FI guys out there looking for longer gears instead of shorter ones given by this final drive ratio.

Basically, while you may like the extra low-end power now, if you later have a significant increase in power, this mod may not be very good for you.

 

Speedo is NOT affected!

 

For RX8, I think the speed sensor is not taken off the engine revolution, so the FD has no impact on the speedometer. My rpm increased compared to the same speed before and after my FD mod.

Cheers
Alan

 

I am actually debating on going 4.10 or 3.90...the way it is now...its crazy.... :P

Chris

 

If you go FI, just sell 4.77.

 

As far as I know is there are 2 ways to do the 4.77 diff
one is as you said, that's changing the gears in the diff, 2 rings
you really need skills to do that, if you dont do it right, you will **** up the diff

the second way is replace the whole diff, that's easy, but costly tho, over $1000 for the whole diff where the rings for only $300 or so

 

^agreed

 

I got an expert to switch the internal gearing with new shims for $150. A general mechanic took out the diff unit and put back in for $100. The gear itself should cost you no more than $600

 

That's a good deal, only charge you for $150 labor for internal gear !!

 

I can't imagine your setup... Do you have a custom tranny yet? I believe that Fluid was saying he was going with a 3.9 for his sometime in the future.

 

http://www.ricks2k.com/products/yellowbox.php

speedo IS affected. not too much, though. if you want more accurate speeds, though, check this out. not bad.

 

^ Don't know what you are talking about. It is NOT affected on an RX8

 

I hope you know it's not affected....

edit: Woops had this page opened for 3 hours...

 

Speedometer isn't affected. Pretty sure that the speed reading is taken off the wheel axles. Means that only wheel or tire changes would affect the speed ometer.

 

^ Correct

 

"This 1-2 percent error can be magnified even further when you install aftermarket wheels and tires or change the rear GEAR SET." that's in the second paragraph of the link i sent.

http://www.ricks2k.com/products/yellowbox.php

also, check out this thread. they mention the yellow box constantly.

https://www.rx8club.com/series-i-aftermarket-performance-modifications-23/4-778-final-drive-%24296-77054/