Lets talk gearing...

KZGUNS · Sep 8, 2023

So on my car i currently have 3:73 I believe I need to confirm as the PO had them installed and i haven't verified but i do believe that is correct. I'm running a TKO600. I really feel like I would benefit from 3:31 or 3:55 as I really don't have much of a first gear and i can easily spin through 3rd I also think with taller gears i would give the supercharger some time in first and second to build boost. I'm pretty sure I'd still have traction issues but probably more controllable.
For those that don't know I have a 347 running at about 10psi
What are your experiences

General karthief · Sep 8, 2023

I bet 3.31 would be near perfect.

LILCBRA · Sep 8, 2023

I don't think you'd notice a huge difference stepping down to 3.55, so my vote would be 3.31 as well.

KZGUNS · Sep 8, 2023

LILCBRA said:
I don't think you'd notice a huge difference stepping down to 3.55, so my vote would be 3.31 as well.

that's my thought as well. My bro sets up differentials so its just the cost of the gears and stuff (beer) lol

AeroCoupe · Sep 8, 2023

3.31's get my vote. I have 3.73's and 1st is completely worthless with the 331 and second is just about as bad. At some point the gears will get swapped in mine.

FastDriver · Sep 8, 2023

What's your power & weight, and do you care about optimizing the 1/4 mile?

KZGUNS · Sep 8, 2023

FastDriver said:
What's your power & weight, and do you care about optimizing the 1/4 mile?

power, not sure 100% but its a well built 347 all forged with a FPP Boss block 10.3:1 with a supercharger. Not terribly concerned about 1/4 mile it really struggles to hook up drag radials. I feel it has enough power to still pull hard with 3:31 gears. its a pretty much option less lx i'd guess around 2800lbs ish

FastDriver · Sep 8, 2023

Which heads/intake/cam? Rev limit is 6k? Also, are they standard ~26" tires? I know I've seen your posts here, but memory sucks...

2000xp8 · Sep 8, 2023

My car makes 480/500tq through 3.73's, a tko600 and drag radials.
It was always a little hot to handle making so much down low.

I don't think the gear swap is going to solve your issue.
I do think a better suspension will.
Since i swapped in the torque arm and tq springs i feel like this car is much more controllable, especially when you desire to keep it straight.
My suspension is pretty much the maximum Grip package, less the rear sway bar and with rear springs in the back.

KZGUNS · Sep 8, 2023

FastDriver said:
Which heads/intake/cam? Rev limit is 6k? Also, are they standard ~26" tires? I know I've seen your posts here, but memory sucks...

Promaxx heads. B&M intake but it’s custom adapted to an Eaton M112 yes ~26” rev limit is 6400 but it can take more. Cam card attached it’s a custom Brian Freezy spec

FastDriver · Sep 8, 2023

Healthy cam. I'd guess you're seeing upwards of 500rwhp or slightly more when pushed to the limit and your practical RPM limit is going to be dependent on the efficiency of the blower, which will be putting heat into the intake air.

Anyways, at those power levels and ypur estimated weight, you'd trap in the mid-high 120s, or maybe right at 130. So, while I don't have my computer and the tools I built, a quick estimation says ~3.48 would be optimal to run through the traps at 130. You said that's not really the goal, but the point is, of course it'll still pull like hell with taller gears. Based on your stated goals of taming the early gears, I also support the drop to a 3.27 or 3.31. Just realize that if you were spinning 3rd, this won't do much for 1st and 2nd. Some other benefits would be lower RPM at cruise, and maybe 1 or 2 more mpg.

@2000xp8 also has my vote in that traction should not be achieved by gearing, but by tire & suspension. Still, you won't be making a mistake if you choose to adjust your rear gears.

I've tried quite a few drag radials and none impress me quite so much as ET Street SS's.

Chris

KZGUNS · Sep 8, 2023

FastDriver said:
Healthy cam. I'd guess you're seeing upwards of 500rwhp or slightly more when pushed to the limit and your practical RPM limit is going to be dependent on the efficiency of the blower, which will be putting heat into the intake air.

Anyways, at those power levels and ypur estimated weight, you'd trap in the mid-high 120s, or maybe right at 130. So, while I don't have my computer and the tools I built, a quick estimation says ~3.48 would be optimal to run through the traps at 130. You said that's not really the goal, but the point is, of course it'll still pull like hell with taller gears. Based on your stated goals of taming the early gears, I also support the drop to a 3.27 or 3.31. Just realize that if you were spinning 3rd, this won't do much for 1st and 2nd. Some other benefits would be lower RPM at cruise, and maybe 1 or 2 more mpg.

@2000xp8 also has my vote in that traction should not be achieved by gearing, but by tire & suspension. Still, you won't be making a mistake if you choose to adjust your rear gears.

I've tried quite a few drag radials and none impress me quite so much as ET Street SS's.

Chris

I agree with all that. I inject methanol to cool my intake charge. I’d love better traction and really want a more usable 1/2 I do need to improve my rear suspension that’s for sure and also on my list. Thanks for everyone’s input. I’ll order up 3:31 gears and see how it drives and report back!!

2000xp8 · Sep 8, 2023

Here's the thing.
If you are doing the rear suspension anyway, do the suspension first. There's always the chance it's good enough.
If it's not, no harm done, do the gears.

Bullitt347 · Sep 8, 2023

It is amazing what setting the Center of Gravity and Instant Center properly will do for traction. Add good suspension components and it gets even better. Add good tires and it can be eye opening.

revhead347 · Sep 8, 2023

What tire height are you running?

Kurt

FastDriver · Sep 8, 2023

That's kinda what I was thinkin about too. He's running 26" tires. If he switched to 28s, he might make progress towards or solve both problems. Switching to 28"s means more sidewall, which means more traction. At the same time, it effectively makes 3.73s into 3.46s.

90sickfox · Sep 8, 2023

Hanlon Motorsports built my tko600 for my turbo 331 car. My rear gears are stock 04 cobra 3.55 and IRS. The gearing feels perfect. You may want to call Modern Driveline or Janlon to figure out what gear set is in your tko600. It would make it a lot easier to do the math for the rear gear that will put you where you want to be. Another option is tuning. A friend has his car set up so the recirculation valve stays open until he hits a button on his shifter to allow more boost.

Monkeybutt2000 · Sep 9, 2023

I just had 3.31s swapped from 3.73s. HUGE difference. Before the car would just blow through the rpm after the boost came on at 3k, 1st gear was totally useless,and 2nd wasn't much better. Now with the 3.31s,1st still isn't great,but 2nd hooks perfect. I have the 2.87 1st in my TKO600 , and run a 275-40-17 MT ET SS. Hope that helps.

2000xp8 · Sep 9, 2023

FastDriver said:
That's kinda what I was thinkin about too. He's running 26" tires. If he switched to 28s, he might make progress towards or solve both problems. Switching to 28"s means more sidewall, which means more traction. At the same time, it effectively makes 3.73s into 3.46s.

While that is a possible solution, 28's are a giant tire unless it's a drag car.
If it came down to it, i'd change the gears long before the tires on a street car.

Unless someone has 1st gear replaced, i'm pretty sure all tko600's are a 2.87, which is already pretty forgiving. The only option was for a different 5th gear.
There are quite a few variables that go with traction.
Tires, suspension, outside temperature, surface, power band and most importantly driving.

If you guys think gearing is going to fix a 3200lb street car that makes triple it's factory hp that came with no driving aids, i guess go for it but the problem is never truly going away.
For me, if the car stays straight and i'm confident in where it's going to go, i'll live with it.

Jarhead67 · Sep 9, 2023

KZGUNS said:
So on my car i currently have 3:73 I believe I need to confirm as the PO had them installed and i haven't verified but i do believe that is correct. I'm running a TKO600. I really feel like I would benefit from 3:31 or 3:55 as I really don't have much of a first gear and i can easily spin through 3rd I also think with taller gears i would give the supercharger some time in first and second to build boost. I'm pretty sure I'd still have traction issues but probably more controllable.
For those that don't know I have a 347 running at about 10psi
What are your experiences

I currently have 3:55 gears in my 86 GT with a 331 stroker which makes 350 bhp. It's a good ratio for the power I make, any taller and I'd have to install street slicks.

Lets talk gearing...

KZGUNS

I can swing up to 11”

General karthief

wonder how much it would cost to ship you a pair

LILCBRA

I wish I didn't have all of these balls in the air

KZGUNS

I can swing up to 11”

AeroCoupe

lube between the nut and the face. I know my lubes

FastDriver

I was uncomfortably high & wearing a helmet

KZGUNS

I can swing up to 11”

Attachments

FastDriver

I was uncomfortably high & wearing a helmet

2000xp8

KZGUNS

I can swing up to 11”

Attachments

FastDriver

I was uncomfortably high & wearing a helmet

KZGUNS

I can swing up to 11”

2000xp8

Bullitt347

I have been doing it wrong this whole time

revhead347

Apparently my ex-husband made that mistake.

FastDriver

I was uncomfortably high & wearing a helmet

90sickfox

Wasn't a pretty sight...and I've got big hands

Monkeybutt2000

Mustang Master

2000xp8

Jarhead67

Similar threads

Lets talk gearing...

I can swing up to 11”

wonder how much it would cost to ship you a pair

I wish I didn't have all of these balls in the air

I can swing up to 11”

lube between the nut and the face. I know my lubes

I was uncomfortably high & wearing a helmet

I can swing up to 11”

Attachments

I was uncomfortably high & wearing a helmet

I can swing up to 11”

Attachments

I was uncomfortably high & wearing a helmet

I can swing up to 11”

I have been doing it wrong this whole time

Apparently my ex-husband made that mistake.

I was uncomfortably high & wearing a helmet

Wasn't a pretty sight...and I've got big hands

Mustang Master

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