Well like the title say's I need the 2.73:1 gear to toss into my rear end. Any idea's on where I can get this gear, or is this going to be a custom setup?????

 

Custom as far as I know. Never seen a gear that tall for our cars.

 

those gears aren't made for the mazda diff.

you can put an 8.8 ford diff in and some mustangs come with 2.73 or 3.08 or 3.27

you will have to have it narrowed and have the brackets welded on and then adapt the brake lines

 

Well the plan for the car is to road race it, and the speed group Id like to run in is 130+ group. Then what is the tallest gear I can toss in there, and not have to worry about being at 6K at 130 mph. Id like to be sitting around 3.5K ideally at those speeds since this will be for long distnaces at a time.

 

130MPH for long distances on the road? **** man, that doesn't sound safe at all. I don't know exactly what that is in km/h but it sounds forkin' fast.

As a matter of fact, at more than double the posted speed limit, that sounds like "pound-me-in-the-*** federal prision" kinda fast!

(quote courteousy of Office Space )

Jon

 

 

130mph is like 240kmp correct me if I am wrong. Not that fast really. And are you talking about the topspeed road races they have like out in California. But damn I didnt think you would need rockey gears to go that speed.

 

Tallest gear I know of for an RX-7 is actually the stock 3.909. I've never heard of anything higher than that. You can go with a ford 8.8 from a mustang, use FWD offset wheels so you don't have to narrow it (as far as I know), and slap the 3.08 from a 89-95 thunderbird or cougar. The t-birds and cougars come with IRS, but the ring and pinion are the same as any other 8.8 and most likely easier to come across as there are tons of them in the junkyards.

 

130 mph equals about 210 kph, you'll have no pull at low speed though, I would aim at about 3.5 rer ratio, I know of a 3.77 available, you're going to spend too much time getting up to speed which will affect your average from point a to point b

 

The plan is to put in the T-II. This is the link to the kind of racing Im planning on doing.
http://www.silverstateclassic.com/ And since this will be for long distances I want to keep the RPM's down so I can keep the heat and fuel consumption down. And doing 130 MPH will hopefulyy be nothing. Id like to target a top speed of around 150 mph if not more.

 

If you go too tall of a rear gear ratio, you may not have enough power to pull that kind of speed.
Another option that you can look into, is an aux overdrive unit. This would give you the gearing needed to get up to speed quicker, and the ability to lower the RPM once you have attained the speed.

 

One website says that you can use the 3.308:1 out of an 82-84 diesel B2000/Ford Courier, that'll put you at about 4600rpm@130mph with a gear limited top speed of 200mph, and that could save you money. But, the more important question is how much power do you have? If you're going to be making over 300 the stock drivetrain shouldn't be utilized.

 

there is a 3.6 somthing that you can get out of old 626's

 

doing stuff like this on public roads is just asking for trouble, but if you must do it, make sure you have pleanty of downforce

 

Dude, Did you even read his post? You've posted twice already and still don't comprehend what's going on, Sheesh.

 

well enlighten me on your definition of road racing....

 

I would use another car altogether. The 1st Gen RX-7 is NOT aerodynamic at all for high speed.

If I were you, I would look into a third gen.

 

Here, I'll help you.

 

http://www.silverstateclassic.com/

Read the thread, it was mentioned once or twice before.

I also agree with Directfreak, the first gen isn't that aerodynamic of a car. The FC with the aero package is decent, I remember its CD being something like .31 which isn't too bad. I imagine a third gen would be your best bet for aero though.

 

Not "street racing" as in ricer revving up at lights and drag racing through traffic. "Road Racing" is done on "road" courses but this doesn't necessarily mean public roads. It means not on ovals, not drag tracks, and not city streets in traffic. It is a track with corners, both right and left. They can be anything from fairly short courses such as autocross tracks to larger tracks like Laguna Seca, Road America, etc, to large closed of courses through closed public roads that are used in sanctioned events with security and safety measures taken. The 24 hours of LeMans race course known as Sarthe is actually a track that is nothing more than several public roads in the country that are blocked off to form the course. They just have grandstands next to some of ther roads in areas. Road racing has been around for as long as there has been auto racing. It is not a new term.

 

okay, I digress. I apologize for my first post.

 

just a ? since were on the topic couldnt u go wit the big gears and supercharge it to even the ratio out

 

haha even 'road racing' where would you run a FB without it going air-born at those speeds?

i think we need a little more info from the poster about what he plans to do. that gearing i can only think being helpful would be on salt-flats, it would take one helluva track for those to be useful.

i would look into the older mazda rear-ends, or totally hack-job the one you have. the auto with a torque convertor is a really good idea, too. however the auto's for these cars are very weak. maybe look into fabbing up a adapter plate and using a diffnerent transmission/rear end entirely if you are that serious.

g'luck

 

.31 CD means nothing when it comes to downforce, CD is coefficient of drag, the amount of resistence the car causes when moving through the air, down force is directing the airflow to push the ends of the car down increasing traction.

An FB can easily be made to have decent downforce with testing and proper airdams, skirts and a good efficient rear wing.

You need to aim at 3.77 or similar for your diff or you wont be able to get up to speed within a decent time frame, you have to have an average speed from a standing start in these events.

For those who dont know many of these events are held, they are legal, regulated and held on very fast, stretches of good tarmac, the event is dial in your average speed and then the car closest to that actual speed over the course wins, usually from 50 miles to 150 miles in length.

130 mph is actually considered a beginners class, groupings up to 200 mph and over exist.

 

no 1 answered my ? but wat u guyz think is the best gear ratio to go wit for street racing and the track