Jerryg

Well I've been driving the Beast for a couple of weeks now and it really a lot of fun. I've noticed though that I don't ever use 1st gear, just start out in 2nd, and when I'm out on the highway I have to get into 6th at around 50 MPH or the exhaust noise will blow you out of the car. I'm thinking of swapping out the gears to 3.27 but before I do I would be interested to hear from you guys who have already made the swap. My plans are to use the car for weekend cursing and doing 1 or 2 track days a year just for fun.

I remember reading a post about someone who started out with 3.55 then went to 3.27 then back again just curious why the change back to 3.55.

Thanks

charchri4

If you do that just sell me your 3.55 diff and start over!

For what it's worth I've got 20,000 miles on 3.55s with and LS swap and Camaro 6 speed and feel the combo is perfect with 225/45/15s. I always use 1st and love the set up. (full disclosure I am on 255/40/17s now and still love the 3.55s)

If by track you autocross go the other way 3.73s would be about right for most courses. Otherwise have you thought about putting a drone killer and a cut out in it? It's a heck of a lot cheaper than gears!

Scottgill

I built my car more as a daily driver, l may hit the track 1or 2 times a year right now I'm running 3.08s that puts me right at 1800rpms at 75mph. The 3.27s should put you around 2100rpms at 75mph. That works best for me for what I use the car for. Its been a great vacation car my wife has to pack light and we don't bring home a bunch of junk!

charchri4

RPMs for 3.55s with a 25" tall tire

Scottgill

I left that part out I am running to 225/45 15's the Hancook RS three's which is right at 23"

mazdaspeedmiata

pretty sure the biggest hankook RS-3 is 225 45 15

.boB

Personally, I prefer a low first gear. If you do the math, there really is very little difference between 3.55 and 3.27 in first gear. I think the perception of "first gear is useless" is because the car accelerates so quickly that you're in to second in no time at all. Going to a taller gear just slows the car down.

Look at the kind of driving you'll be doing most, and then gear for that. If you're regularly going to be cruising at 80-90mph, then the 3.27 or 3.08 might be better for you. But if you do a lot of back country and in town driving, a 3.55 or 3.73 might be better.

V8MiataMike

Hey! They have roads with 100MPH speed limits where you are at?

I'm headed that way!!!

fitz

I just don't get this at all.
a T56 close ratio box has the following ratios
1st Gear 2.66
2nd Gear 1.78
3rd Gear 1.30
4th Gear 1.00
5th Gear 0.74
6th Gear 0.50
With 225/45-15 tires and 3.27 gears speed vs RPM are in table 1. At 70 mph you are turning about 1600 RPM, so far out of the power band you'll need to downshift to pass.

Switching to 4.10 rear axle ratio gives about 2000 rpm at 70 mph which is the lower end of the power band and you can pass without shifting. Why use anything but 4.10's with a close ratio T56???

wcw5023

T56's have two overdrive gears. So I feel like your point is invalid.... Who said you have to cruise in top gear at 70mph? And even so, whats wrong with having to downshift?

Im not trying to start an arguement, my point is just, its all just a preference anyways. There is no "right" or "wrong" . Out of all of the things in my build, I probably gave the least amount of thought into what "gear" I was going to run. Just toss one in, and see how you like it IMHO.

acedeuce802

In a close ratio transmission, gear ratio is a very small factor in performance, other than trying to eliminate a shift on a particular track. Changing gear ratios just changes the shift points, but acceleration is not very much impacted. In a T56, 2nd through 5th are pretty close ratio, and are what I would consider the gears where the rear end gear is negligible, other than making sure your speed on track is not outside of these gears. This leaves rear end gear choice up to 1st and 6th gear.

Pro's of short gear (4.1) - 1st gear becomes a crawling gear so it may be smoother to operate in parking lots or with an aggressive clutch, 6th gear is more usable at 70 mph, may need the higher rpm when cruising in 6th with a lopey cam or light flywheel

Pro's of long gear (3.27) - 1st gear has more of a chance of putting torque down or at least more time to react to it breaking loose, 2nd is likely able to put down torque with proper tires, adequate for cruising at higher speeds (75+)

I put more time than I should've in selecting a rear end ratio, I made a drag race simulator in Excel to show any performance gains with different ratio's, and mapped out how a stop light launch, 55 mph highway, and 70 mph highway will feel with different ratios. I ended up choosing a 4.1, mostly due to my clutch that is very aggressive for the street, so I wanted to launch from stop lights at a higher RPM and lower speed, as well as keep RPM's up on the highway to prevent bucking from the feather light flywheel.

fitz

True, it is just a preference. When I bought my 8.8 diff I found a zero mile one out of a Cobra R (aluminum case) for about the same as the iron case units with 50 K miles, but it had 3.25 gears. I prefer to match transmission gears to the power band of the engine so 4:10's made sense. All six gears are useful and the 0.5:1 final drive in 6th gives a top speed of 200 mph at 6000 rpm. Just a choice, nothing more. The 3:55's are close and also lead to a useful first gear and, I suspect, that is the reason why some who went from 3:55's to 3:25's went back.