There has been a lot of discussion about different final drives that are available for DOHC B-series trannies. I want this post to pertain to only hands on/real world experience. This will help to summarize and dispell all of the falacies about a higher FD.

If you have any factual information or gear ratios that are derived when using the OEM JDM ITR, or any other manufacturer's, FD please share it.


Here are some topics that I am sure a lot of people will like to have answered:

1. How severely is interstate/freeway driving affected?

2. What gear combinations are you using and what are your observations about your particular setup?

If you can think of any other topics that need to be addressed please share them with the rest of us.

Please try to keep this post as 'on-topic' as possible.

-kenji


[Modified by kenji, 1:09 PM 11/2/2001]

 

OK I have a JDM 4.785fd in my USDM ITR tranny. 1st-5th gear are all USDM ITR. I did not change the 5th gear to GSR. The RPMS are 400-500 higher at freeway speeds. It takes a little getting used to but I still cruise between 80-85 comfortably.
My car makes 180 to the wheel on a MD dyno and has run 13.6 in the quarter.

Mattj


[Modified by Dropspeed, 1:22 PM 11/2/2001]

 

We are running a Spoon JDM ITR 98 Spec tranny in Daniel's (SPOONDEG) B16A powered EG and here is some feedback direct from him (he is standing right behind me)

Speedo reads fast - shows 90 and really is about 80
Pulls very nice from a stop and while rolling
When shifting, rpms do not drop, even with Spoon FW
Highway driving at indicated 80, tach shows roughly 4500

Note: His car is stock other than JDM ITR pistons, VAFC, ECU from Locash, and the above mentioned FW.

 

HUH? Why?

 

kenji: I'll let you know tonight about the freeway driving! hehe

 

Don't take that literally. Of course they drop, but what Daniel meant is that the tranny is so nicely geared that you can keep the revs up - assuming you can shift properly. (Of course, this is really not a factor of the FD)
He tested on another EG with a B16A this past weekend and pulled quite convincingly on him.

 

Does this seem to be a problem with all final drives or just spoon? Is it that your speedo is already off?

 

This would be a problem whenever changing FD. You would experience the same thing if you changed your rim/tire size and did not keep the proper ratio.

 

Just changing the FD on a ITR tranny does not change the Speedo, pick up on an ITS trans must be different than the Spoon tranny?. Speedo still reads accurate on my car.

 

the speedo is based on rotations of the differential. Changing the FD will *not* affect speedometer calibration, since the diff will still be turning at a 1:1 rate compared to the wheels/tires. The diameter of the VSS ring gear does *NOT* change when doing a FD or LSD.



Only the ring gear is affected (on the diff), which in turn speeds up the rotation of the diff (and wheels since they are locked in a 1 to 1 relationship during normal driving)




[Modified by jeff652, 2:55 PM 11/2/2001]


[Modified by jeff652, 2:56 PM 11/2/2001]

 

Matt - Remember, this was dropped into an EG, so that could explain the difference. It is about 10% off at 80mph.

 

fwiw: rodney on this board has changed just the fd to ats 4.93 on his itr motored eg...

I have talked to him extensively on this subject. Basically, your rpm's will be 500rpm higher for the speed than they used to be.

example: used to be at 4500rpm for 80mph? now you're at 5000rpm for 80 mph.

I can drive at 75 instead of 80mph for the pull this gear gives. And for autox?

My mind is made up and I'm ordering this coming monday for sure!

 

Dropspeed, you must have other mods to be getting those 1/4 mile times besides a JDM final drive, right?

 

around 70 i'm at about 4000 rpm. You don't really notice the higher rpm change unless you really think about it, and you get used to it.


just JDM final drive

The only thing that I can think of is that i didn't know that it was so expensive to install the final drive ~$300 plus the cost of labor to drop your tranny. Overall it's a great mode makes the R alot more enjoyable to drive

 

wow I do it for a hundered if the trans is out of the car . . .

That's expensive

 

Yes. Check out the website on my sig and you'll find them in there.

Mattj

 

what i would like to know is at what whp does the jdm fd become a performance liability?
say your laying down 200-240 would one be better off w/ a stock tranny or does the jdm fd yeild a better et w/ that hp level?

also how difficult or involved is the install for a shadetree mechanic and what tools and other items are needed to complete the install?

i'm pretty good w/ the airs tool but ive never disected a tranny, would i be better off dropping the tranny and taking it to a transmission shop for a bench job?

 

The performance liability issue is that your engine revs more which in turn speeds up the process of wear and tear. Whether your making 160 or 240 to the wheel you are gonna get the same result.

How difficult ? I would not recommend it for a novice.. D is in the process of changing his and even with the Helms manual its quite difficult and if you don't know what you're doing and never done it before don't experiment on your car for the first time. You'll need a gear puller for sure and a press to put the gears on when you change the mainshaft. It is recommmended to change bearings and seals.

I'd pull the tranny and watch someone do it, this way you can learn how its done.

 

there's those damn left-handed threads again...

D

 

as far as wear and tear thats a given w/ a igher reving motor,what i mean by performance liability is at which point or whp do the shorter gear affect your et? say for example someone w/ a 200 whp teg has a itr tranny w/ the jdm fd and someone w/ the same has 240 whp or more who will have a better 1/4 mile time? im assuming the jdm fd will have better 60 fts but at what whp point does the jdm fd actually hurt your times?

 

I almost bought his JDM/FD and then he just said lets take my car for a spin "with the ATS 4.93."

We did and I can attest that although his car is a highly NA hybrid ITR/EG, that the even higher 4.93 FD is not at all unbearable. I'm seriously considering it next for a good springtime mod. But, then ya know I'll want to do alot more by then like clutch and light flywheel so maybe I'll just save up a bunch of those mods before taking it to the shop.

and YES the FD is one of those things that I'd love to change for Auto-X, thats exactly why he built his car. GOTO:
http://www.b18c5.com to see the car and what he's done to it.

The fun part is actually riding or driving his car and feeling just what these different mods feel like and do Before I shell out $ and actually find out for myself. One of My next mods for the X is a Mugen rear sway A La Rodney's experience.

Thanks Rodney, Learning from your experiences...

A.

 

not a problem 1grey. i wish i could just take everyone who doubted the ATS worth for a ride in my car. then i'm sure they would change their tune. i don't think i will respond anymore to the jdm final or ATS final post anymore. i just post the same thing over and over. i had a kid in the civic forum tell me ATS gears were made by a company in canada! all well.

 

can someone take a look at my ?'s i posted above?

 

The only reason it would hurt the quarter mile times is if you can not put the power to the ground. If your car is spinning the tires and not hooking-up. Otherwise there should not be a problem.

Mattj

 

Wear and tear is pretty much the same. The only negatives that you come across with a higher HP and torque application is being able to breaking contact much easier. As for what horsepower it becomes a liability, that's hard to say. It really depends on your driving skill and the rest of your setup. There is no magic number.