mi6_

Hi. New to the forum. Got a 2007 Impala SS a few months back.

I am confused about what the axle/final drive ratio on the 2007 Impala SS model is???

I know that the GXP has always been the 2.93 ratio. The 2006 Impala SS was a shorter 3.29 ratio. My 2007 Impala SS listed a 2.93 axle ratio for the 2007 model year. Has GM changed the 2007 Impala SS to the 2.93 final drive ratio?

The GM Canada site says the 3.9L and 5.3L cars have a 3.29 Axle ratio for 2007 (contrary to the Canadian brochure that says it is a 2.93 ratio).

The US Chevy site also says it has a 2.93 axle ratio.

Car & Driver had this for data:

2005 Grand Prix GXP

DRIVETRAIN
Transmission: 4-speed automatic with manumatic shifting
Final-drive ratio: 2.93:1
Gear - Ratio - Mph/1000 rpm - Max test speed
I - 2.92 - 9.1 - 54 mph [87 kph] (6000 rpm)
II - 1.56 - 16.9 - 101 mph [163 kph] (6000 rpm)
III - 1.00 - 26.5 - 143 mph [230 kph] (5400 rpm)
IV - 0.70 - 37.3 - 137 mph [221 kph] (3650 rpm)


2006 Impala SS

DRIVETRAIN
Transmission: 4-speed automatic
Final-drive ratio: 3.29:1
Gear, Ratio, Mph/1000 rpm, Max test speed
I, 2.92, 8.2, 49 mph [79 kph] (6000 rpm)
II, 1.56, 15.3, 92 mph [150 kph] (6000 rpm)
III, 1.00, 23.8, 143 mph [230 kph] (6000 rpm)
IV, 0.70, 34.0, 154 mph [248 kph] (4500 rpm)


So have they changed the 2007 Impala SS to a 2.93 final drive ratio, or does it still have the shorter 3.29 ratio???? I have tried to run mine and see what it does. Seems like it shifted into second at about 80 kph, and into third at about 150-160 kph. I noticed that if you run hard with the gear selector in 1st, that it would exceed redline (6,000RPM) by about 300RPM, so I am not sure if I was over-revving in each gear and reading a higher speed. It is too risky to go a 100 MPH to find out when it shifts, so i don't want to try it again and cause an accident.

Personally, I think the 2.93 ratio is a joke. You would never use fourth gear with that low of a final drive ratio. At least with the 3.29 you still have decent economy, while using all four gears to reach top speed.

eddiemoney

iTrader: (2)

My 2007 Impala shifts 1-2 around 50mph

SDfbody

My 2006 shifts at 6100 at 55mph, and 6000 is about 100mph in second gear on my car. So I'd say I have 2.93's.

eddiemoney

iTrader: (2)

I think I have the 3.29s then. . . maybe it is an improvement for gas mileage reasons. . .as I am seeming to get better mileage in my 07 than a lot of the 06 guys. I get about 24-25 on the HWY at 80mph, 15-17 in the city (under 35mph usually, with a lot of stop and go).

SDfbody

I thought I read somewhere that all the LS4 cars had 3.29 gears, but a 1.12:1 drive ratio on the drivechain that makes it 2.93 really.

pgbSS

You probably saw it on this site. Here is the thread where this was discussed (gear ratio info towards the bottom of the page).

https://ls1tech.com/forums/ls4-performance/515647-impala-ss-vs-pontiac-gxp.html

live2ride

My 06 Impala seems to fit the 2.93 rate. A log of the computer showed 49+ mph at just over 5400 rpm.

mi6_

We'll there is a difference between the GXP and at least the 2006 Impala SS. Car & Driver got different speeds in each gear, so the '06 Impala had to have a 3.29 final to produce the slightly quicker times and lower maxx speed in each gear. The car clearly accelerated quicker, so I'd have to say the they certainly did test cars with different final drive ratios.

Funny thing is that if GM did indeed change the ratio for 2007, it certainly didn't make any difference in fuel economy. Car & Driver got better numbers out of the 3.29 ratio on the Impala SS compared to the 2.93 on the GXP!

I'll have to watch mine closer. Maybe I do still have the 3.29 ratio?

Compg

Well lets see I have two Grand Prix's one with 2.93 (06 GXP) and one with 3.29 (04 Comp G). The diffferance between the two gear ratios are night and day. Lets talk just shifting and how long you can hold a gear in terms of MPH.
Comp G GXP
1st: 44/46 MPH 1st: 52/52MPH
2nd: 82/86MPH 2nd: 86/102MPH
3rd: 14xMPH 3rd: 14xMPH

This is where each car will shift at if I leave both in drive/where they shift at using TAP Shift. Usually after the shift I will be about 1-3 more MPH faster then when I started the shift.
HTHs,
Tate

Area47

the final drive between the two cars is the same.
i know for a fact the gxp will hit 156 in third at 6100. i like my clutches so i don't advise hitting 4th at wot

BADDLS1SS

iTrader: (22)

High 40's for mph on WOT shifts @ 6100 on the 1-2 and mid 90's for 2-3

Turns about 2300 on the hwy @ 80 mph with the t/c locked.

In HP tuner's when i had to adjust my tire height for the speedo (snow tires)
It reads: Final drive is "1.00" ?? maybe its that chain drive ratio?

Found this on GMpowertrain.com:

All MN7's have 3.29's.... no questions.


2007 Hydra-Matic 4T65 Transaxle (M15/MD7/MN7) 41806
Type: four speed front-wheel-drive, electronically controlled, automatic overdrive transaxle with electronically controlled torque converter clutch.
Engine range: 2.5L - 5.3L
Maximum engine torque: 280 lb-ft (380 Nm)
Maximum gearbox torque: 400 lb-ft (542 Nm)
Gear ratios:
First: 2.92
Second: 1.56
Third: 1
Fourth: 0.7
Reverse: 2.38
Final Drive Ratio: ( M15 ) 2.86, 3.05, 3.29
Final Drive Ratio: ( MN7,MD7 ) 3.29
Maximum shift speed: 1-2 7000 rpm
2-3 6500 rpm
3-4 6000 rpm
Maximum validated gross vehicle weight: 2903 kg (6400 lb)
7-position quadrant: P, R, N, OD, 3, 2, 1
5-position quadrant: P, R, N, D & DSC +/-
Case material: die cast aluminum
Shift pattern: (2) two-way on/off solenoids
Shift quality: variable bleed solenoid
Torque converter clutch: pulse width modulated solenoid control
Converter size: 245mm and 258mm (reference) (diameter of torque converter turbine)
Fluid type: DEXRON® VI
BOT190M1 - all wheel drive fluid for power take off unit
Transmission weight: 93 kg (205 lb) (M15) (wet)
96.6 kg (212 lb) (MN3) (wet)
97.2 kg (214 lb) (MN7) (wet)
112.5 kg (248 lb) (M76 with power take off (PTO) Unit) (wet)
Fluid capacity (approximate): bottom pan removal: 7L (7.4 qt)
Pressure taps available: line pressure
Transfer design: two-axis design, link chain assembly
RPO differences: M15: 245/258mm torque converter
MD7 - 245mm China Applications
MN7: 258mm torque converter and heavy-duty gearbox
Assembly sites: "Warren, Mich. (M15, MN7)
Shanghai, China (MD7)"
Applications: Chevrolet Malibu (M15)
Chevrolet Malibu Maxx (M15)
Chevrolet Impala (M15,MN7)
Chevrolet Monte Carlo (M15,MN7)
Chevrolet Uplander (M15)
Buick LaCrosse (M15)
Buick Lucerne (M15)
Buick Terraza (M15)
Buick Rendezvous (M15)
Pontiac Grand Prix (M15, MN7)
Pontiac G6
Pontiac Montana (M15)
Saturn Relay (M15)

06 SS

The magazine did NOT go out and record speed at redline, they took the numbers from the gearing that GM provided and CALCULATED what it would be. Since you seem bound and determined to believe you have a final ratio of 3.29....I have some great news for you! You do!

Having said that, the effective ratio, what your wheels see, is 2.93 due to the chain drive system not being a 1:1 ratio.

They obviously used the effective ratio (which, in my opinion, is the proper way to do it) on the GXP calculations and then, a year later, just plugged in the gear set without accounting for the chain drive on the SS calculations.

Looking at the published ratio's for the transmission and my speed vs tach (even giving a wide margin for error on both) it is very clear that my 06 Impy SS has an effective gear ratio of 2.93.

So, in this case, everybody is correct.

BuffaloSS

iTrader: (3)

And on that note, C&D placed the Impala SS at 7th place in the "Quickest Cars of 2007 - $25,000-30,000" while the GXP placed 9th...stating that the difference in final drive ratio caused the difference. Don't read on though, Impala owners, there's nothing good to see there.

...not trying to start a flame war or anything...we all know C&D Testers cannot drive

mi6_

Humh, thanks for your thoughts. It certainly is possible that C&D just calculated the numbers based on the ratio. One thing I noted on the GM Powertrain site is that if you open the spread sheet on the 4T65 (MN7) transmission, it lists that final drive ratio is 3.29, however there is a note when you click on that saying that "overall final drive ratio changes based on model and sprocket selection". Maybe this is how we get the 2.93 actual final drive ratio. Maybe the selection is different on the Impala SS and Grand Prix GXP.

Anyhow, I ran my car hard today, and in 1st gear at 6,000 RPM, I was at 79 kph (49 MPH) which is consistant with the calculations by C&D (I was in "D" if it makes a difference). So their calculations on max speed seem to be correct from what I have seen. The thing that bugs me is that C&D's Impala SS with the "claimed" 3.29 final drive ratio was slightly quicker in acceleration. Now this of course could be down to simple production variances or different levels of mileage (or abuse). Still, for the Impala to be slightly quicker than the GXP (which is somewhat lighter) seems odd if they indeed have the same final drive ratios. They did claim that the Impala had a lower drag coefficient, so maybe that is part of the difference (if indeed there is an aerodynamic difference). I did the math on the the overall wheel diameter, and there is only a slight difference. The Impala actually has slightly tires in overall diameter. Also, C&D did indeed drive it to its top speed of 154 MPH. I am sure they would have noticed that it was in third at 6100 RPM versus 4th at 4500 RPM. So something still does not make sense to me. Are the GXP guys maybe getting the same shift points as in the Impala SS article. I am more confused now.

Interesting that my car lists the final drive ratio as a 2.93 on all the GM data on paper, but on their other sites, it is listed as 3.29.

Not trying to argue with anyone or start a war over who's car is faster (Impala or GP GXP). Just didn't understand myself, and was hoping someone could explain it to me.

I am wondering if the Impala SS used a 1:1 sprocket, and the GXP used the 1.12 or whatever it was. Just a thought.

BuffaloSS

iTrader: (3)

Between 2006 and 2007, the listing for the final drive ratio changed on the Chevy website, too...

Dr Octane

[QUOTE=BADDLS1SS]

Deleted

mi6_

Yeah, I am still confused. I certainly agree that GM would be using all the same hardware between all three LS4 cars. It would be pretty stupid of GM not to! I need to take mine to a track and give it some runs this summer. I think there I can see the shift speeds better. Too dangerous on public roads.

SILVER LS4

Forget what all the magazines say. Go to Chevrolet's official website and wind your way to specs. You will find the overall ratio on the Impala and MC is 2.93:1 on the 5.3.

SILVER LS4

It also said the same thing for the 2006 Chevys. In the 2006 specs the gear ratio was also listed in addition to the overall ratio. This may have been the source of a lot of confusion.

Area47

this guy would know more about it then a freakin magazine would


p.s. i have yet to see a stock mcss or impss get into the 13's

::stirs the pot some more::
boil boil toil n trouble