Every time I see a lengthy sig detailing all of the money spent on parts to make the author's car perform better, I always look for a rear gear upgrade. Most times I am disappointed. Why don't the 2nd gen. guys put more 4.30, 4.88 gears in their cars?

Rotaries are notorious for lack of torque. The best way to counter this is to get the motor up in the rev band as quickly as possible. The best way to do that is to change the gear. Heck, when I had my Mustang 5.0, that was the single best mod I did. It mad the most noticable improvement, and that was from a 2.73 to a 3.55.

What brought all this to light was I drove a friend's car the other night. It's a 91 GTU w/ a streetported motor, lowered with Konis and coilovers, Mazdaspeed header with ISC 3" single exhaust. The car is pretty quick, but it takes so long for the motor to reach its powerband, then when shifted it takes even longer for the next gear to pull. I don't get it.

All of the ITS race cars I know of have 4.88s or 5.12s. You can't build a competitve car without one. While the 5.12 is unheard of for the street, I know that a 4.88 would be liveable, seeing that most street cars don't see past 100 mph anyway. It just makes getting there quicker and more fun!

 

Because it will give you stupidly high revs at a relatively low speed. Turbo IIs get shitty milage as is. I dont need to be seeing boost while cruising @ 60mph.

 

I run 4.3's but I don't blatently advertise all my mods

 

Well that's great when you have boost, since the higher gear will allow you to stay in the boost longer, but my experience is with NAs. I just find it odd to see someone with a 40 line sig, who is posting yet another question about what his next mod should be, since he already has $5K in engine/drivetrain mods, and no where is there a gear mod mentioned.

If you're gonna spend $1000 on a lightweight clutch/flywheel combo that may make a difference acceleration, why not take the same $$ and put the gear in that will DEFINATELY work?

I guess the next time I see a guy ask why he got killed by a BMW 3-series or a Chevy Cavalier, I will just shake my head and move on.

Crunching a few numbers:

Stock 5th gear, 225/50/16 tire=

4.30 will run at 2680 rpm at 65 mph
4.88 will run at 3045 rpm at 65 mph

Not as bad as you might think, given the acceleration benefit.

 

A gear change will probably be the first of my few modifications after I fix things that are broken. I have seen the GTU 4.3 ring and pinion set for sale, but where can other gear ratios be purchased?

 

I don't know what your smoking, TII's do 3000rpms at 70mph....nowhere NEAR 2650@65, and thats with 4.10'
s

 

Yeah where I live the speed limit on the freeway is 70mph and my normal crusing speed is around 80mph. With 4.88s do you know what kind of shitty milage Id get? It sucks now!

 

i gree that its a good mod for an na, buy it wont work on a t2 cause 1st is too short and so is 5th

mike

 

For me, I'd rather drive for hours at 120, than 10 second 1/4 miles.

 

You know the Civic HF get 42 mpg in the city if you're worried about gas mileage. I thought these were sports cars.

 

Maybe with the .756 5th gear from the GTUs (2934 rpm), but the .719 stock gear with the 225/50/16 tire equates to about 2790 rpm at 70 mph. Maybe I'm smoking, maybe not, but I didn't pull this out of my a$$, I have a gear calculation program that figures all this out and will even plot the chart if I want.

Personal attacks aside, I'll stand by the math. The point is that the gear mod should be considered by the NA guys way before a lot of the useless "junk" I see in some sigs. If you have an extra grand, there probably isn't a better way to spend it, especially if the exhaust has already been done.

 

nevermind.............. no coment


-Shawn

 

where would one pick up parts to do the gear change if they are relatively unfamiliar with such things (like me). a 4.3 could be pulled off of an GTUs, but what about your 4.88 and such?

 

There is no way to "drop in" any gears other than 3.909, 4.10, and 4.30. There IS a way to put taller gears in though. But it's out of the question for a TII, and probably not worth it for an N/A...

 

Anything below 4.30's on a street car is dumb in my opinion. (unless you're so severely underpowered that it takes that much mechanical advantage to get you rolling)

My best friend's `77 280z came with some 4.88's as prepared for ITS and first gear was so short that you almost didn't use it. Drag racing with a short first gear will get the car moving, but you'll only be doing 15mph when you have to shift all of a sudden off the line.

Road racers use the lower gears to make up for taller trannies and put them in their power bands while in turns and such. Up here at Brainderd International most cars are at their max speed in the straight away because they have the low gearing. (usually ends up in the low 140's depending on the size of engine and the cars running)

For a drag car to be running a 4.88 or deeper rear end would require the tallest tranny known to man to get you out of the hole without spinning the whole time or hitting rev limit before you were ready to upshift.

All of this being said towards streetable cars runing stock OD tires. Track prepped cars are a bit different because of the additional loads placed on the driveline turning over a 15" wide slick.

Some of you guys probably need the 4.30's just to make up for the 25lb rims you got. I know when I got my first set of heavy honkin rims it took a gear swap to regain the 2 seconds I lost to the rotational mass added. Brought my top end down from 135 to 105 and a damn honduh could out run my *** on the freeway. (2.73's to 3.55's)

 

Short of finding a GTUs in the junkyard (har T har har), what other vehicles might have the 4.30 rears? I'll be making a gear change when my rear-end finally gives-up.

Cory
Shhhh! Don't tell anyone!

 

hehehe, never saw this thread. Get the gears; have fun. And I was one of those guys who spent a lot of money buying things that didn't do half as much as this one mod did. But, no one ever said I was smart....

 

Yeah I too would like to pick up the 4.3 gears at some point in time.....where to find them?

 

Lee I think your car has this gear set already...

 

http://www.rx7.com/cgi-local/2catalog.cgi?cat=2&part=6

The table on the above page shows how each gear will top out in speed with different rear ends.

I have a 90 GXL, and there aren't many vehicles that can go 36+ mph in first gear. I may change to the 4.3 rear gears, but I'd rather have a 4.56... 10% more mechanical advantage than 4.1... to heck with gas mileage.