RS_91

Can someone please explain gear ratios and the final drive to me. I never really understood it. What does it mean and what is a good final drive.

any help is appreciated, thanks.

B18C5-EH2

I'll break it down as easy as I can:

The final drive determines what the max speed in each gear the tranny will go, and also how quickly you will rip through the gears.

Example?

I had a 4.929 final drive in my ITR tranny for a while. The stock unit is a 4.400. With the 4.929 FD the mph in each gear was lower, meaning I'd hit the redline quicker in each gear and also it lowered the max top speed in 5th gear as well.

When you reach the redline quicker in each gear basically the car accelerates quicker.

With the 4.929 FD I'd rip through the gears quicker, but the rpm were the same when upshifting...

That brings me to gear ratios.

Gear ratios basically effect how far the rpm drop between shifts.

Example?

If you have a tranny with closer gearing the rpm will stay higher when shifting into each successive gear. This means the engine stays in it's powerband more so than a taller geared tranny.

That's the simplest way I can explain it really.

RS_91

ok I think I get it, so the higher the final drive is, the lower your mph in each gear will go but it will go through the rpms much faster.

I got that, but what exactly does 4.929 mean?

B.

The FD in my tranny is 4.785 LSD built by cusco, 1st- 3.23 2nd-2.105 3rd-1.458 4th-1.103 and 5th-0.788 I find that this setup does work well for me on the track, but on the highway it seems like I rev so high due the the ratio in 5th gear. If Im crusing at 125km in 5th my revs are around 4000 rpm.....that's the only thing I don't enjoy. My little honda is not a fuel saver anymore

owen_the_soyboy

http://www.a-t-s-usa.com/ats-p...shtml

http://auto.howstuffworks.com/gear-ratio.htm

http://auto.howstuffworks.com/transmission.htm

nice info there B18C5-EH2 !
all I gotta say is the ats 4.9 fd is amazing in how it changes the feel of the motor thru the rev range. it makes the motor feel more powerful in lower rpms and in essence as if I had a larger displacement motor under the hood. so that is the good news. the bad news is that it changes the rpm for cruising at 80mph to about 5000 rpm in my car... kinda loud and not the most fuel efficient, but the acceleration possible without even downshifting is impressive.

HTH

1999all_motoR_teg

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by THE B &raquo;</TD></TR><TR><TD CLASS="quote">The FD in my tranny is 4.785 LSD built by cusco, 1st- 3.23 2nd-2.105 3rd-1.458 4th-1.103 and 5th-0.788 I find that this setup does work well for me on the track, but on the highway it seems like I rev so high due the the ratio in 5th gear. If Im crusing at 125km in 5th my revs are around 4000 rpm.....that's the only thing I don't enjoy. My little honda is not a fuel saver anymore </TD></TR></TABLE>


HMMMMM?? I'm not denying that you have a 4.785 final drive but I do have a few questions.

Well first question is that I thought the Cusco Final Drive was a 5.0 and ATS was a 4.9 and a 98+ ITR was a 4.785 but then again Cusco may make more than one.

Second question is if you have a 4.785 final drive and your engine and tranny are a B16 which is the same as a Type R tranny with a 4.4 final drive then how come your gear ratio's are the EXACT same as my 4.4 final drive Type R tranny?

Also third and last question with my Type R tranny I'm at 4200rpm at 120km/h so how are you at 4000rpm at 125km/h with a 4.785?? It was my understanding that with a 4.785 final drive you would be alot higher in the RPM range at a certain speed then you would be at that same speed with a 4.4 final drive.

Once again if I am wrong I apoligize and please someone correct me.

TIA

B.

it's funny that you say that because as I'm reading your post I just got of the phone with the guy I bought it from, his 5th gear ratio is the same as mine yet he is at a lower RPM at 120km, I have the JDM type r and he has the USDM, does this make the difference? I'm not exact on the rpm @ 120km but it's not to far from 4000-4300.

1999all_motoR_teg

Well mine is a 2000 USDM Type R tranny with a 4.4 though so thats why I asked.

B18C5-EH2

Okay let me try to clear the 4.78 ITR tranny vs. 4.400 ITR tranny stuff.

The 4.78 equipped Type Rs come with a USDM GS-R .787 5th gear and also the GS-R 4th gear.

The 4.400 equipped ITR tranny has a shorter 4th and shorter .848 5th gear.

This explains why the 5th gear cruising is identical on both trannies.

This is not up for debate - it is factual.



Also when trying to compare rpm vs. mph in any gear you must also understand that tires size and wheel size/overall diameter effect this as well.

Two cars with the same tranny will cruise at different rpm in 5th gear at 80mph if one has a 195-50-15 and the other runs a 195-55-15.

Tire size is the cheapest and easiest way to change your final drive aspect, but it's not as noticable as a 4.929 ATS unit or a Cusco 5.0 unless you get a 195-45-15 or smething crazy like that.

sohc_boy

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by B18C5-EH2 &raquo;</TD></TR><TR><TD CLASS="quote">
Also when trying to compare rpm vs. mph in any gear you must also understand that tires size and wheel size/overall diameter effect this as well.

Two cars with the same tranny will cruise at different rpm in 5th gear at 80mph if one has a 195-50-15 and the other runs a 195-55-15.

Tire size is the cheapest and easiest way to change your final drive aspect, but it's not as noticable as a 4.929 ATS unit or a Cusco 5.0 unless you get a 195-45-15 or smething crazy like that.</TD></TR></TABLE>
i was just going to mention this