changing gear ratios?

how do you change gear ratios on a manual transmition?

Move the shifter??? (Is this a trick question?):rolleyes: :rolleyes:

hahaha. i think he means changing gear ratios from 3.27:1 to 3.45:1 or something like that. gearing your car taller for higher speed, etc...

But seriously....

Gears are always changed in sets of two in order to change the ratio. Usually the easiest ratio to change is the final drive ratio, since OEMs usually have options for different transmission/engine combinations -- ring gear/pinion gear set. If you actually need to change a ratio inside the transmission, things get more difficult. Chances are the OEM will not have this available unless it is a very common tansmission used in a lot of cars. If they do, you may not be able to get exactly what you want because things may be so tight in the transmission that you may need to change two gearsets -- a higher numerical gear ratio requires a smaller pinion and a larger gear. In order to fit on the shaft centers, the sum of the teeth for the pinion and gear must always be equal. For example: If you have a 25T pinion and an 80T gear (Ratio = 3.20), the sum of your new gearset teeth must be 105T. That means that if you want a ratio of= 2.89, you need a 27T pinion and a 78T gear(assuming you have the space for the larger 27T pinion). Even if the OEM doesn't have this combination, you could always have it made custom-- not cheap.

ah ha! thanks for the info:)

As Craig stated, sometimes the manufacturer puts out two transmissions for the same car, based on the motor. Most of the time they have different gear sets in them. That is the best, cheapest, most assured option if you are after transmission only.

If you car is a rear driver, the better option, and less expensive is to change the 3rd member. You will be surprized what you accomplish. Huge gear variations are generally available for rear ends.

Front drivers are a different story, and can be painful (both in expense and reliability) trying to find something that fits.

I've got to ask. Why change the transmission gear ratios? Is your shift points too wide apart or too close?
For more acceleration, why not change the finals in the axle/transaxle? As Craigfl pointed out, most manufacturers produce more than one gear ratio. If fact, check out the different years for your vehicle. Sometimes after a year or more they change the gear ratios.
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There are a few reasons to change tranny gear ratios. For instance one would be having a lack of first gear. Seriously. Alot of drag racers in the old Foxs would run really really steep gears (not like they don't now or anything) and they it would make their first gear so short it was worthless. DSM's do this too...not due to gearing but just do to having an already short first gear when they start running some serious power you spin thru most of first gear.
Another reason would be if you run certain types of races you want to shift at certain times in certain places. You can get Jerricho (sp) trannies with custom gearing (I belive NASCAR uses them too).
Why someone who doesn't race would want different gears...I don't know.

Seabass

Exactly!
Most of the stuff I see posted is about someone wanting to get their vehicle to do 0-60 MPH in 3 seconds or runnin the 1/4-mile in 10.0 secs @ 125 MPH.
It seems the kids are willing to spend tens of thousands of dollars on turbo's, roots-blowers, NOS and whatever to make lots of power. But what worries me on these "wannabe" street warriors is do they really know how to build a fast car?
I've seen more posts about gear-changing in the tranny's and wonder, WHY? For most driving the stock gears are fine...unless you are planning to go to Sears Point or run Baja.
What about brakes, drivetrain or even any safety features? It's easy to go fast...it's alot tougher making it stop quickly and safely.

I can't believe that just happened...tons of typing and lost it all. Dammit.

I'll make it brief this time...

I agree about what you said with the whole "street warrior" thing. The said part is...90% of these people don't know how to work on their car. It's mainly the young folks on the road. I'm always having some punk in his Honda Civic or Mustang that mom and dad bought them zip thru traffic. I'm not old...I'm 22...but I have learned alot and have always paid for my cars, tickets and insurance. It's called responsibility and parents (not ALL...but most) aren't teaching their kids that anymore. Junior wrecks the Mustang...ohwell...grounded for a week...and then a new car aslong as you promise to go to church with mom and drive her to PTA meetings.

I have learned a simply theory of "If you don't know how to work on your own car...you should have nothing but a stock car". But then speed shops would be out of buisness and it would hurt the competitoin between speed shops and prices would be more for me. Everyone wants to be fast...it's human nature. It's all in how fast your wallet will take you. If you can't work on your own car then it'll cost you more. I'm not made of money...so I have no choice but to work on your own car.

I do have to say that there is nothing wrong with changing rear end gears. I don't want that impression from my post. Both my cars came with 3.08's stock. Both have 3.73's now and one maybe going with 4.10's if first gear doesn't become too worthless with the blower and 4000rpm stall converter.

I hear ya!!!
I'm an old man by most standards (41) but i've done some racing with motorcycles and cars. Used to run a Yamaha RDZ350 for awhile back in 1989 for fun. Laid it down onw too many times...it starts to hurt!
I ran 1/4-mile (too boring) and still run my Porsche 924, but it's sold I think to someone.
After almost 2 decades of being the "I wannabe a racer car driver", I'm donw. Too much money, no where to really drive fast. But I learned alot of lessons. How to calculate gears, RPM's, tire diameter vs MPH...
Question for you...what cars have the 3.73:1 and the other that you might go to a 4.10:1 rear axle?
I used to run a everyday driven 68 Charger w/B-block, 750 CFM 4-bbl, stock auto-trans w/4.10 or 4.11:1 locker axle. But I also had large 16X9" wheels on the back, almost stock 14X7" on the front with ladder traction bars on axle to frame. Ran consistant 12.6's to 12.8's at 108-116 MPH thru the traps, which seems slow now, but with Mickey Thompsons and partial free-flow exhaust it was quick. Top speed with the oversize rear tires was 131 MPH at 5600 RPM. I had a lower speed stall converter at 2600-2800 RPM.

I'm not saying that I want to go and change the ratios, or that I would if I was building a street racing car, but I was just wondering.:smoker2:

Anybody know Jericho's website? I am looking for a 7spd sequential shifter for my Supra,it's very rare and I am quite sure it'll cost as much as the car itself,just thought I'd ask.

Google turns up nothing.

Regards,
Knight

I hear you guys on the "Street Warrior" thing but take it ez on the Mustang guys!!! I agree many of them can be annoying but you gotta admit it's the Import driving kids who are the usual culprits. Also a lot of it just comes from age. I but I have spent more wrenching turning hours than most people on this website. My first car was an 83' Mustang GT that i bought for $500. Before I blew then engine I had made the car into the New England Pure Street Champion best 1/4 time 12.02 with a 5.0L motor. I'm only 20 and have my share of speedind tickets. I used to drive that 83' on the street all the time. Now I won't even give a guy a second look at a light. What scares me isn't the kid who knows nothing bout cars and talks shit. It's the guy who knows nothing and can afford the 125hp of NOS running around town.


V-8's All Throttle no Bottle!!!!!!!!!!