For open road races, autocross and any real racing what is the general range that you would want your rear end gears to fall into (i ask because all of my info on this is drag race specific). The car that this applies to is a 1990 camaro. The plans for this car include a 383/396 motor, full internals not yet decided on, most likely a richmond 6 speed transmission ( any other reccomendations welcome i am still in planning stages as i am 16 and broke). It will be running with a tpis mini ram and the motor will be built so that should i choose to when the whole car is finished i could slap on twin turbos. (i dont even know if the mini-ram would work in conjunction with turbos but well see). The car will be making a rediculous amount of power although the cam selection wont be to agressive because i would like to be able to at least drive this car as a weekend driver. So all of this being said what generally should i look at in terms of rear end gears for racing. If you would reccomend two different gears depending on wether it was a dedicated race car or still a weekend warrior please give both inputs.

 

Not enough info. You need to start with the rpm range of the motor, the weight of the car, and the type of track you will be running on. Once you have that info it is relatively straightforward to select gears.

Rich Krause

 

well i would be surprised if the rpm range went over 6500. The weight im honestly not sure about. As for the type of track it would be a wide range (which i know really sucks) but assuming both ends of the scale (ie a wide open road race course and a tight pilon driving autocross course) What would you reccomend for each just so i can get a general idea

 

run a set of 3:73 gears

the car will weigh in at about 3400 lbs,

and the course won't really matter if you're road racing it, or 'seat time', as some like to think of it.

.. and don't forget about a brake upgrade.

 

More info would help, but I'll take a stab at it. What is the high gear ratio in the Richmond 6-speed? If memory serves there a bunch of choices. So if you are buying a new tranny, it may be more a matter of picking the tranny gears than the rear end. That said, something in the 3.90-4.10 range is probably in the correct range. I just checked Richmond's site, and they have a HD 6th gear set with a 0.84:1 ratio. With this gear, a 28" tire, and 4.10's you will be at ~155mph. 3.90's give you 165mph. So unless there are some very long straights, that should be enough gear. But that's where you start. Figure out the rear end ratio for your top gear to give the expected top speed at peak rpm and select the lower gears according to the track.

Rich Krause

 

thanx for the good info i have a better idea now....once i have everything put together i just have to calculate what i want my top speed to be and set up the rest of the car accordingly. I guess it makes sense that lower the gear i can get away with the better. Right now i have a set of 3.73's in my stock 10 bolt but im going to save my pennies all winter and try to do a tranny and rear end swap right at the end of the winter time so that ill be able to handle my engine mods when they come...When i do that ill just figure out the gears accordingly then..

awww i know once i have my new tranny and rear end im going to have to make a decision what to do first...eninge mods or brake mods....i know i have to do the brakes but thats just no fun!!!

 

On street tires it's unusual to get much past 65 mph, and you don't want to have to shift into 3rd unless the course has a really wide-open section. With 24.5" tall tires, 3.73's, a 1.98 second gear, and the rev limiter set at 6000 rpm, I've used 3rd on exactly one course over the last two years. So if auto-x has much priority, shoot for an overall reduction in 2nd of 8.0 - 8.2 (I'm assuming you'll be on 275/40-17's at ~25.6" tall and sticking to that 6500 as a limit) and you should be OK, rpm-wise, at least as long as you remain NA.

Norm

 

Interesting reading ....

On 3 road courses (Motorsports Ranch, Texas World Speedway and Hallett), I shift 4 to 8 times less with 3.42s than a comparably equipped Z28 with 3.73s.

Lap times are comparable ...

If the 3.73 equipped cars can keep from lighting up the tires on corner exit, they can drive me off the corners. But, I can usually hang with them on the straights when they have to shift and I don't.

Just another data point ....

 

Thats a good point....ill have to figure out my powerband (i have all winter to figure out exactly every component i want to be running in my car) and consider exactly what i want to do. This is really encouraging though because with a drag car to be super competitive you need to go over 4.??'s to get real good times and theres no way you could street the car but with 3.73's and a car thats top end falls somewhere between 6000-6500 rpms my car should be very streetable

 

I have 3.73 rear gears and they work pretty well for me. Most of the road courses I go to are in 3rd for 75% of the course or so, 4th for about 20% and if the course is fast, 5th for the remaining 5%. However, keep in mind I have an almost stock LT1 engine (275 RWHP). If you build the engine you're thinking about I'd keep rear gears in the 3.42 or 3.23 range. Your engine will make plenty of TQ to pull out of corners and you'll find yourself downshifting much less. I bet you run most road courses in 3rd and 4th with 3.23 gears and shifting less is always a good thing. Less chance to miss a shift, which will inevitably happen just when you don't want it to.