Author Topic: Changing final drive ratio (Read 26031 times)

kennysabarese · « **Reply #25 on:** August 24, 2011, 03:54:21 PM »

Smaller means less revs while cruising and better MPG

For drag racing AFAIK there are two ways to think about it. If you go with a smaller number you will be in gear longer and won't have to shift as much, but you will put less power to the ground. So if you could do a 1/4 and not shift into 4th that could help.

The second option is to go higher, and you have to shift into 4th, but 4th won't be such a dog.

Arabas · « **Reply #26 on:** August 24, 2011, 04:03:28 PM »

and for real life drive use, I believe (I isin capital, like saying MY opinion) the higher, something like 4:1 ratio would be ideal, coz accelerations would be much faster..

just my 2 euro-cents

kennysabarese · « **Reply #27 on:** August 24, 2011, 04:04:49 PM »

Since our first gear is a granny gear, I was thinking that a 4 or 4.11 would make first useless and you might be able to start from 2nd gear.

I do know that GM drag racing FWD cars use a 3 speed automatic, but I don't know what the final drive ratio is off the top of my head.

Critterman · « **Reply #28 on:** August 24, 2011, 04:04:58 PM »

2.73's would give you the best gas milage, but no grunt at low end, you would probably still be in 3rd for any driving below 55. Car might not be able to pull 5th gear at highway speed.

3:93's are the tightest gears (n/a) standard. So they probably would be best for drags unless you could get some custom 4.11's

kennysabarese · « **Reply #29 on:** August 24, 2011, 04:06:28 PM »

Quote from: Arabas on August 24, 2011, 04:03:28 PM

and for real life drive use, I believe (I isin capital, like saying MY opinion) the higher, something like 4:1 ratio would be ideal, coz accelerations would be much faster..

just my 2 euro-cents

That's the reviews I've seen in the Camaro forums. It really wakes up the car and it gets going.

Arabas · « **Reply #30 on:** August 24, 2011, 04:07:58 PM »

if anyone is coming to Greece, pls put in your baggage a used 3.91 diff with torque arm on it from the NA kappa and i will do the swap to show the results... i will even pay for the carrier

kennysabarese · « **Reply #31 on:** August 24, 2011, 04:09:41 PM »

DDM has tons of Kappas laying around. They should do the swap and dyno and go to the drag strip!

Arabas · « **Reply #32 on:** August 24, 2011, 04:15:59 PM »

no need for dyno, just before and after accelerations (from stop, and 40-80km/h, 60-120km/h and 60-160km/h in various gears) sorry for the km/h.
it is like 750-1000$ to ship a carrier to where i live and honestly it is not worth the trouble...
if someone actually does this mod, i would love to know about it!

LatinVenom · « **Reply #33 on:** August 24, 2011, 05:53:38 PM »

When you come to the USA in one of your possible trips, pick one up and take it with you.

snaponbob · « **Reply #34 on:** August 24, 2011, 06:48:07 PM »

What is in the cars (LE5 and LNF) is most likely the best compromise for mileage and performance, especially given the miserable set of ratios we have in a light truck box. And, there is zero relationship to slush box 3 speeds in front wheel drive drag cars. Those can use high stall speed converters to get going with a "long" gear set, and that does not compare to rear wheel drive manuals. As it is, we have a very short first gear with a shortish second, and they get "long" after that. Using a slightly lower numerical final drive would help to 70 (which is why I may switch to a 3.42 if I change classes as that would help a LOT in Solo) but kill things above 70 (in drag racing) with a stock or near stock power output. Going to a 3.91 would be a mess because first would multiply the available torque even more creating a bigger launch traction problem followed by a very quick shift to second - time consuming. Ideally the LNFs would have longer 1st and 2nd with the existing final drive, but that won't be happening.

As for fuel mileage, a 3.42 MIGHT help, but at speeds where aero matter (highway speeds) the engine may have to work harder at lower rpms, and that would translate to more load, and THAT means more throttle, and THAT means more fuel.

If I DO switch turbos for the 2012 race season, I will get a base line fuel consumption figure around town and on the highway, then switch the final drive to 3.42 and after resetting the BCM for the change, will go do it again. Assuming this all happens, I will post it. But that will be LATE winter/ early spring.

kennysabarese · « **Reply #35 on:** August 24, 2011, 06:54:51 PM »

Quote from: snaponbob on August 24, 2011, 06:48:07 PM

miserable set of ratios we have in a light truck box.

Change the trans and the rear to get what is best

Dave@DDMworks · « **Reply #36 on:** August 24, 2011, 07:00:34 PM »

If you can swap the transmission, switch it over to a T56? You would lose the torque arm and it would require a new transmission mount, but it is an option also. I know where to get a bell housing adapter for the swap if interested.

kennysabarese · « **Reply #37 on:** August 24, 2011, 07:02:15 PM »

The 6060 trans is even better

snaponbob · « **Reply #38 on:** August 24, 2011, 07:12:46 PM »

Quote from: Dave@DDMworks on August 24, 2011, 07:00:34 PM

If you can swap the transmission, switch it over to a T56? You would lose the torque arm and it would require a new transmission mount, but it is an option also. I know where to get a bell housing adapter for the swap if interested.

THAT is interesting.

cdnite · « **Reply #39 on:** August 24, 2011, 08:15:38 PM »

Quote from: Dave@DDMworks on August 24, 2011, 07:00:34 PM

If you can swap the transmission, switch it over to a T56? You would lose the torque arm and it would require a new transmission mount, but it is an option also. I know where to get a bell housing adapter for the swap if interested.

Im interested in a trans swap, a 6 speed would be perfect, I'll PM you.

Also, for those looking at final drive ratio changes the Lexus IS250 has the same bolt up transmission Asin AR-5 but without the ridiculous 1st gear ratio.

--Christian

snaponbob · « **Reply #40 on:** August 24, 2011, 09:24:42 PM »

SECOND gear in the GXP is a joke as well. Fifty seven mph in stock form? Really? What was GM thinking? At least the Cobalt guys git a set of gear ratios and final drive that made some sense.

As for the Lexus - same bolt pattern? DIRECT drop in? Where is that data on that?

SKY888 · « **Reply #41 on:** August 24, 2011, 09:30:38 PM »

how hard is it to get a new transmission mount?

NormSky · « **Reply #42 on:** August 24, 2011, 10:02:49 PM »

Bob, not sure you'll like the extra 20-30 lbs extra of the dry transmission, without fluids. Weights used to found GM Powertrain website.

Uranium-238 · « **Reply #43 on:** August 24, 2011, 10:06:02 PM »

20-30 lbs shouldn't do a whole lot. Actually how much does the torque arm weigh? I'm betting it's not light, and since you'd lose it in a swap...

snaponbob · « **Reply #44 on:** August 24, 2011, 10:48:02 PM »

For a street application, a trans swap might be worth the work. For Solo, all that is needed is a longer second gear. With a 3.42, 61-62 mph becomes about 68-69 MPH. With a turbo mod or swap and its associated tune, that 7-8 mph becomes an issue, and shifting is a) time consuming up and down, and b) unless one is REALLY smooth, shifting unsettles the car. With 105-108 octane gas (I think that is Alex's brew of choice) and corn (my choice) power is available subject to traction available, and time spent on the limiter or shifting gears is precious. He and I may go different directions (me SSM and him F/Prep). By the rule set, he'll be inlet limited but can go lighter, while in SSM I could dump a 7 liter in my car, but will opt for a turbo upgrade. He'll accelerate quicker and maintain higher cornering speed due to lighter weight and I'll (theoretically

) haul ass due to more power . In either case, a 62 mph second gear sucks.

Or, one or both of us will stay in B/SP after pissing off a bunch of Evos, and this will all have been mental masturbation !!!!!!!!!! I doubt any changes in class will be done 100% independent of the other.

DrJones · « **Reply #45 on:** August 25, 2011, 06:32:53 AM »

Quote from: snaponbob on August 24, 2011, 10:48:02 PM

Or, one or both of us will stay in B/SP after pissing off a bunch of Evos, and this will all have been mental masturbation !!!!!!!!!!

I do this so much I should be blind.

kennysabarese · « **Reply #46 on:** August 25, 2011, 06:48:22 AM »

Quote from: DrJones on August 25, 2011, 06:32:53 AM

I do this so much I should be blind.

TMI

snaponbob · « **Reply #47 on:** August 25, 2011, 07:54:03 AM »

Quote from: DrJones on August 25, 2011, 06:32:53 AM

I do this so much I should be blind.

MENTAL, not the other. Focus, Alex, focus.

1LILNDN · « **Reply #48 on:** August 28, 2011, 08:25:51 PM »

If you want to save gas and not try to win races go with the 2.73's . I think the 3.42 is your best Long 2nd gear.

DrJones · « **Reply #49 on:** January 17, 2013, 04:33:05 PM »

Bump to the future!

I just picked up a 3.23 caddy diff from schrams (it's nice having my parents live within 5 minutes of the place).
Verified the ring and pinion should swap over, just need to shim for back lash.

Should get me to around 72.5 mph in second gear with the new tire size.

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Author Topic: Changing final drive ratio (Read 26031 times)