[ToocoolZ28]

What should the 1st gear ratio be multiplying "1st gear x rear gear" ratio. Right now I have a 3.31 rear gear with 2.20 1st gear which gives me 7.28 which isn't optimum for driving in traffic. I'm going to be buying a new Tremec TKX and am trying to figure out which gear ratios to order. I don't want a super steep ratio in 1st, I had a trans with 3.27 1st gear with 3.73 rear gear and I didn't like it, too steep for me. So now I'm running 3.31s in the rear and am trying to decide which way to go with the new trans. What's the right thing here? The car isn't a race car but it does have 600hp and 640 lbft.
I'm thinking somewhere around 10:1 with 28" tall rear tires.

 

[TTurbo565]

10 or even 10.5 on that gear is perfect with the torque you have. It will be easy to drive even if you have an aluminum flywheel. I run a 2.66/3.5 on a 27 inch tire and aluminum flywheel. Nice set up with 520lb/ft @2300 rpm at the wheels.


Sent from my iPhone using Tapatalk

 

[O'Man]

What should the 1st gear ratio be multiplying "1st gear x rear gear" ratio. Right now I have a 3.31 rear gear with 2.20 1st gear which gives me 7.28 which isn't optimum for driving in traffic. I'm going to be buying a new Tremec TKX and am trying to figure out which gear ratios to order. I don't want a super steep ratio in 1st, I had a trans with 3.27 1st gear with 3.73 rear gear and I didn't like it, too steep for me. So now I'm running 3.31s in the rear and am trying to decide which way to go with the new trans. What's the right thing here? The car isn't a race car but it does have 600hp and 640 lbft.
I'm thinking somewhere around 10:1 with 28" tall rear tires.

Currently running a Richmond (non OD) 5 Speed with a 3.04 first. Rear is a 9 inch Ford with 3.25 gears. Calculates out to 9.88. Tire size is 235 / 70 -15. Works well for me.

 

[lucifershammer]

I agree keeping it around 10 is good. I’m running a 2.74 first gear, 3.73 rear gear so works out to 10.22 and 27” tall tires. Works good for me.

 

[69-CHVL]

11.19 for me and feels real good!

 

[69-CHVL]

Tell you what the 3.27/.72 unit looks interesting with a 3.31 rear gear. The 1st 3 gears are deeper and then you get a more "even" gear drop from 4th to 5th. Rear gear effectively becomes a 2.38. Right now mine is the equiv of 2.49 and I could use more OD honestly.

 

[O'Man]

I agree keeping it around 10 is good. I’m running a 2.74 first gear, 3.73 rear gear so works out to 10.22 and 27” tall tires. Works good for me.

10.2 / 9.88 more or less the same. Don't need to pull the stumps of 150 foot ok trees out with these cars. Dumped my 3.27 first gear for the 3.04 forst gear set in the Richmond for just that reason. Even with the 3.04 the 1 /2 shift is like shifting UP into 2.20 X 4.11.

 

[pannetron]

I run a 2.66 1st gear Magnum with a 3.60 rear and 26.7" tall tires. That works out to about 9.6:1 and works great for me.

 

[SRU1436]

Use this.

Wallace Racing - Starting Line Ratio Calculator

 

[427L88]

Ron, right now I'm at 9.75:1 , and wish for schooch more , and that's with short ( 26") 275/50/15 slicks at the strip. On the street, it's fine. As you say, 12;1 is clearly too much ( unless its a HP-built spinnin' machine like a old skool 7200 rpm shifin't 427.) Between 10 -10.5:1 ought be a sweet spot I should think. Particularly with a taller tire. a 29" tire might want near 11:1

 

[GoFast Beaumont]

11.07 here. 2.97 and 3.73 gear. Might switch up to a 4.10 next season. Higher SLR the better in my opinion

 

[Aml383]

What should the 1st gear ratio be multiplying "1st gear x rear gear" ratio. Right now I have a 3.31 rear gear with 2.20 1st gear which gives me 7.28 which isn't optimum for driving in traffic. I'm going to be buying a new Tremec TKX and am trying to figure out which gear ratios to order. I don't want a super steep ratio in 1st, I had a trans with 3.27 1st gear with 3.73 rear gear and I didn't like it, too steep for me. So now I'm running 3.31s in the rear and am trying to decide which way to go with the new trans. What's the right thing here? The car isn't a race car but it does have 600hp and 640 lbft.
I'm thinking somewhere around 10:1 with 28" tall rear tires.

That 3.27 first gear with the 331 rear end is plenty tall enough.
Its a night and day conversation compared to 327 with the 373 gear you had.
And you'll have 5 gears man.
Id get the 327 but the 287 would be fine too.
But I think you're giving up some fun not getting the 327 ..
That'll be REAL nice with a 331 rear

 

[BillyGman]

IMO all that SLR math doesn't mean a whole lot. What I mean by that is to say: if it's a street car, then what RPM your engine will be reving on the highway at about 70 MPH is more important, (since many people cruise at around 70 MPH, but if you like to [email protected] MPH then the RPM at that point would be of concern) and with a strip car, what RPM your engine power peak is at compared to what RPM you're crossing the stripe at is most important.

For the street driving/highway cruising RPM part, that's your preference. For my hi-perf cars, I like cruising at 2,500 to 3,000 RPM. It isn't too annoying, and the purr of the exhaust note with most V8 engines with 350 cubes or more is usually nice at that RPM range as long as the exhaust and muffler choice is right. So that's why, be it street, or strip, or a little of both, I pay more attention to this calculator here....

Street Performance Calculator (richmondgear.com)

 

[DZAUTO]

All of the above ideal ratios are good recommendations for many cars. Our 70 is WAY different and it does just fine.
The 70 has a healthy SB400, M22W(2.56 1st gear) and 2.73 12bolt posi. That puts the final 1st gear ratio at 6.9888. NOT ideal, but the 400 has more than adequate torque to get it rolling from a dead stop with virtually no clutch slippage. The 70 does not have a tach, but according to calculations, at 70mph, the rpm is under 2400, and with the torque output of the 400, it does just fine leaving from a dead stop. And one thing I particularly like about it is being able to wind to 50-60 mph before shifting to 2nd gear, which is great when getting on the Interstate and into the flow of traffic.

 

[modern malibu]

I run a 3.06/1 1 st (automatic) with a 3.73/1 rear gear and 27 inch tall tire which gives me a 11.41 ratio. Some may think this is too much, but the fun factor is certainly there. Overdrive ratio is .070/1 which calculates to 2400 rpm at 72 mph.

 

[japete92]

There is no one size fits all. And I would not use the 'multiplication' factor you are seeking when choosing

.What is the 'power range' of the engine? An engine who's power range is something like 1500-4000 rpm does not need a 'close' ratio 2.20 first gear w/4.11 rear ( 2.56 first gear w/3.31, or so, 'wide ratio' is better). But one with a power range around 2500-6000 rpm would very much respond better to such 'close' gear ratio's.

Said another way. If you want to 'get moving' at approx 1500 rpm (and you have the low end torque to accommodate that) the 'wide ratio' 2.56 first gear w/3.31 rear would be my choice. A very nice street combo, in my opinion.

I would 'save' the close ratio screamer combo for a high revving small block; a la the Corvette fuel injected 327. That engine does not produce the low end torque to 'pull' at 1500 rpm. To 'get moving' that engine needs more rpm.

It's possible to drive the car with almost any combo. My question would be which drive train compliments my driving style and engine capabilities.

Just my opinions.

Pete

 

[ToocoolZ28]

Thanks guys, lots of different opinions here. My engine runs out of rpm at 5500, so the close ratio may not be best for me. Now which 5th gear (overdrive) .68 or .81??

 

[O'Man]

Earlier I said: "Even with the 3.04 the 1 /2 shift is like shifting UP into 2.20 X 4.11". Gotta take my lumps on that....I screwed up the numbers. Forget that reference to 4.11, not sure what I was thinking, but I wasn't thinking correctly. The Richmond 2nd gear is 2.13, indeed close to the 2.20 Munice, where I came up with the 4.11......????????? Sorry for the bum info.

 

[mr 4 speed]

I used to own a 1969 GTO that had a 2.88 1st gear T10 and a 3.55 posi.
Great combo

 

[VinceS427bb]

Thanks guys, lots of different opinions here. My engine runs out of rpm at 5500, so the close ratio may not be best for me. Now which 5th gear (overdrive) .68 or .81??

the .81 od = 2.68 overall gear
the .68 od = 2.25 overall gear
if your engine is done by 5500rpm
it should have enough torque to pull either of these gears at highway speeds..
do you want low engine rpm at highway speeds or really low engine rpm at highway speed?