Changing out gear ratios in transmission

[toad]

Ok...
I have an 06 N/A Sol, and as those of us with stock N/A's know, the motor turns a lot of RPM's at 60 and 70, basically killing our gas mileage.
Well, I was watching my tach the other day, and noticed that the drop in RPM's is not constant between all he gears.
It basically drops 1200 between 1st and 2nd, and between 2nd and 3rd, but it only drops about 850 between 3rd and 4th, and only 800 between 4th and 5th. (This is when shifting at 3000 rpm's, at 6500 rpm's, it drops 2600, 2600, 1750, 1700)
So here in my idea.
I have done the math and so forth.
The original gear ratios are:
1st 3.75
2nd 2.26
3rd 1.37
4th 1.0
5th .73
Final Drive 3.91
My question / idea was about switching out 4th and 5th as follows;
1st 3.75
2nd 2.26
3rd 1.37
4th .83
5th .50
Final Drive 3.91
This would have the drop even across the entire board, and would have the motor only turning 1500 rpm's at 60mph, and 1725 at 70mph.

What do y'all think?
Can it be done?
Can the 2.4L handle a .50 5th gear stock?
How much would it cost to change out gears in a transmission?

[SolNut]

No, not enough motor!!

Trade out your NA Trans with a GXP and hang an GXP 3.73 Diff in it.

Good luck.

Steve

[Mac]

I have not seen the inside of these trans but i dont think they have a modular design like the Richmond ROD 5's and 6's do. If my guess is correct then changing any ratios would be next to impossible without custom made parts. Even in an ROD these parts are $$. a .5 over drive would bog this motor down like it was driving through MUD. You would never be able to use it at speed and would be in 4th at top speed. at cruz you might be able to keep it in 5th but you would find your foot pressing down on it for to keep it going so in the end you might even get worse MPG. up hills you would be looking at 3rd gear as well. Since your 4th is now what was 5th. Gear ration and rear end ratio pluss tire height is all tricky stuff when you start to change one area it affects the rest.

The better choice might be to change out the rear end gearing to a lower ratio, i do not think they make any yet, but would be far less $ ? But this will casue a lose of bottom end power out of the hole. longer shift points.

an other option might be an after market OverDrive unit, but these are not cheep too, i think in the end the money you spend will not pay off any time soon.


The LOWEST cost to lower RPM is get a taller tire. Say if the N/A has the same size as the GXP a a 245/45/18 if a 50 or a 55 fits it would lower the final drive ratio on the cheep. At least if DO NOT like the out come you can put the stock size tires back on. YOu change the trans or DIf and you do not like the result you are out BIG$$ money and stuck with what you have,
__________
I check the pontiac site and the N/a and the GXP have the same gear splits, so getting a GXP trans will do nothing. Its the rear dif that are not the same. But again going up in the tire will be far less $$. I did this in my z28 even though i have a ROD6 and a 3.08 rear, for freeway Flying i use a 265/55 now instead of the 50 why? i used to run a 2.73 rear and i like this set up for that car. In a sol you would burn out the clutch to get going or have to be pushed it into first.

The motor is the issue here and not HP but here is where torque is the beast of choice, and it takes alot of that to move a heavy big car with 2.73-3.08 and still be able to turn high 12's. and be able to run down the high way at speeds we wont talk about here but i can do over 60 in 1st in that car. i think our sols are in what 3rd? at 60? the z28 still leaves my sol in the dust 0-60 0 to what ever where ever you may want to drive, but the sol has a small fuel tank. at least until i find a way to stuff a 40+ gal tank in that.

[silversolstice]

Toad what are you used to driving?

The cruising RPM in the NA is lower than many 4 cylinders cars already.

I agree with MAC and 209.

EDIT: I forget key words in my sentence.

[bigblau]

Toad: if anything, you need to keep the rpms up to get anything out of the N/A. My advice would be to keep the trans and rear stock. Save the money you would spend on those components and get a DDM supercharger kit. I promise that will solve any issues you may currently have with gearing. Should also get better milage if you can resist keeping your foot off the accelerator.

P.S.: Consider trading the Solstice in for a Jetta TDI if it's milage at low rpm that you're looking for. It'll also pull like a beast.

[shabby]

The cts/sts has a 3.23 and 3.42 diff that apparently bolts up to ours, this would be the easiest option.

[JRinKY]

Taller tires are not an option due to limited clearance in the wheel well.

Mac is correct, the transmission would require custom-made layshafts and gear clusters to change the ratios.

I have considered the 3.43:1 cts/sts drive axle that shabby mentioned. It would certainly hurt 0-anything acceleration, but most of what it would do above 20 MPH is change the optimum gear selection. It would also change the engine speed at various road speeds, but in many cases it would be a beneficial change as it would put cruising speed for most of the speeds at which I cruise, at 2500 RPM instead of either 2000 (too low) or 3000 (too high).

The cts/sts drive axle is the same model series from Getrag, so it would be a direct bolt-in. The question would be whether the new ration can be programmed into the BCM.

[sahein]

Originally Posted by toad Ok... I have an 06 N/A Sol, and as those of us with stock N/A's know, the motor turns a lot of RPM's at 60 and 70, basically killing our gas mileage. Well, I was watching my tach the other day, and noticed that the drop in RPM's is not constant between all he gears. It basically drops 1200 between 1st and 2nd, and between 2nd and 3rd, but it only drops about 850 between 3rd and 4th, and only 800 between 4th and 5th. (This is when shifting at 3000 rpm's, at 6500 rpm's, it drops 2600, 2600, 1750, 1700) So here in my idea. I have done the math and so forth. The original gear ratios are: 1st 3.75 2nd 2.26 3rd 1.37 4th 1.0 5th .73 Final Drive 3.91 My question / idea was about switching out 4th and 5th as follows; 1st 3.75 2nd 2.26 3rd 1.37 4th .83 5th .50 Final Drive 3.91 This would have the drop even across the entire board, and would have the motor only turning 1500 rpm's at 60mph, and 1725 at 70mph. What do y'all think? Can it be done? Can the 2.4L handle a .50 5th gear stock? How much would it cost to change out gears in a transmission?

Maybe you can try doing a 6 speed custom installation.

[JRinKY]

sahein : Maybe you can try doing a 6 speed custom installation.

The 6-speed would close the shift gaps, but the overall ratio range of the currently available 6-speed transmissions is the same as or smaller than the 5-speed we already have.

[shabby]

Originally Posted by JRinKY The cts/sts drive axle is the same model series from Getrag, so it would be a direct bolt-in. The question would be whether the new ration can be programmed into the BCM.

It just hit me, do these cts/sts diff's have that torque bar attachment? If not then you'd have to swap the internal gears.

[sahein]

Originally Posted by JRinKY The 6-speed would close the shift gaps, but the overall ratio range of the currently available 6-speed transmissions is the same as or smaller than the 5-speed we already have.

Tremec TR-6060 six-speed manual transmission

The gear ratios on the 2007 Ford Mustang Shelby GT500:
1st: 2.97
2nd: 1.78
3rd: 1.30
4th: 1.00
5th: 0.80
6th: 0.63


The gear ratios on the 2009 Pontiac G8 GXP and the Chevrolet Camaro SS:
1st: 3.01
2nd: 2.07
3rd: 1.43
4th: 1.00
5th: 0.84
6th: 0.57

[Mac]

ROD 6speed
First Gear Ratio: 2.77:1
Second Gear Ratio: 1.87:1
Third Gear Ratio: 1.46:1
Fourth Gear Ratio: 1.18:1
Fifth Gear Ratio: 1.00:1
Sixth Gear Ratio: 0.62:1

Though mine is geared
3.27
2.22
1.87
1.56
1.00
.76

whats nice about these guys is both the upper and lower shafts are modular so changing ratios is rather easy. But I have no idea how well they or if they would fit or what custom work would need to be done. The LOng Shifter for these are slick though way above a Hurst in smooth tight shifting.

[SolNut]

Originally Posted by Mac I check the pontiac site and the N/a and the GXP have the same gear splits, so getting a GXP trans will do nothing.

NOT TRUE for a '06!!!!!

Steve

[JRinKY]

sahein : Tremec TR-6060 six-speed manual transmission .... The gear ratios on the 2007 Ford Mustang Shelby GT500: .... The gear ratios on the 2009 Pontiac G8 GXP and the Chevrolet Camaro SS: ....

The ratio range of the AR5 is 5.14:1.

The Mustang box has a smaller range, at 4.71:1

The G8/Camaro box does give a slightly wider range at 5.28:1

Mac : ROD 6speed .....

Both of the RODs have narrower ratio ranges, at 4.47 and 4.30:1

So any of the six-speeds would give you closer ratios, but none would give much advantage as far as lowering engine speed at cruise.

shabby : It just hit me, do these cts/sts diff's have that torque bar attachment? If not then you'd have to swap the internal gears.

For me it wouldn't matter, I don't have a torque bar now.

[bradyb]

Buy a 6 speed Camaro/Challenger, that would help.