i wanna get some better gears. most likely 3.29 ratio. anyone had some put on and what were the gains?

 

you already have 3.29 gears. You may want to do a little searching before you post these questions, like your camshaft queries and the like (this particular one is in the stickies). Makes you look a bit lazy and foolish to post stuff like this instead of doing a simple search. Your transmission has 3.29 final drive, however there is a chain drive that drops the effective ratio to a 2.93 at the wheels. Also, what possible reason do you have to put in a lower gear ratio? You are severely traction limited as it is and would likely be slower on the street.

 

worse mileage on the highway. but it might actually help in town but not hurt

 

and actually you need to do a little searching because we do only have 2.93 gear ratio

 

let me guess....your parents were related before they got married?

 

Pontiacs web site says 2.93's, and 3.05's in the base 4dr. In 3rd at 60 I do 2200RPM and doing the math confirms 2.93's. Also, ZZP sells 2.93, 3.29, and 3.69 gears. The Monte Carlos have 3.29 gears from what I have heard.

 

good one 06 ss. it takes guts to call someone out when you are doing it online

 

Look guys lets get this straight once and for all 05-08 GXPs,06-08 Monte SS's, 06-08 Impala SS's and 08 Lacross Super all have the SAME transmissions period regardless what the paper back gearheads claim.....All have 3.29 ratio with 2.93 final drive ratio thats why when cruizin freeway speed and then you give it gas to accelarate the RPMs feels loose and jump approx 1200RPMs before you feel any power 2.93s are economical for high end GM wouldn't go with all that technology(DOD)(AFM)to save GAS and then screw it all up with final drive of 3.29s.

 

well i guess i should get the 3.69 if im looking for an upgrade

 

B.S! We have 2.93 like Pontiac's web states! 3.29's in what? First? Why would ZZP and other sites sell 2.93's, 3.29's, and 3.69's then? My Camaro had 3.42's in first, second and third. What the hell is this split drive crap? GXPjay had 3.29's installed when he had his trans upgraded so maybe he can explain any difference to us.

 

- 258mm, RI 15 Torque Converter
- Enhanced Heavy Duty 3.29 Final Drive
- 2.93 Effective Final Drive
- Transmission case for transmission mounted starter
- Net-formed Input Sun Gear
- Ceramic bead Peened Final Drive Sun Gear
- Input/Reaction Carrier Assembly

- Contour Hardened ReactionInternal Gear

- Input Carrier & Gear Asm. with lube grooves

- Shot-peened, Black-oxided Input Carrier Pinions

- Shot-peened Reaction Carrier Pinions

- Shot-peened Final Drive Sun shaft
- Upgraded Drive sprocket Thrust washers (new for high speed capability)

This is in the sticky guys...

 

Sorry, haven't been on in a while....

What I do know is when we put in 3.29 gears in my tranny, before putting them in the tranny (I helped rebuild it...twice...) we compared the new 3.29's to the stockers and the stock gears are FOR SURE 2.93.

I would not do 3.69's, that's way too hardcore. I was in a heavily modded Supercharged Grand Prix with 3.69's and it was too quick to accelerate in the lower gears, we don't have that issue. I love my 3.29's!!

 

^youve been inside ur trany! Il go with whay u say!

 

Do we have to drop the cradle to do a gear swap/change? How hard is it to do the swap?

 

But I believe you changed the tranny sprocket gears and not the final drive gear. I have not seen anybody offer a different final drive gear. These tranny sprockets change the "effective" final drive ratio, but not the final drive gear. Stock, the drive sprocket is larger than the driven sprocket (in essence, overdriven). A 3.29 gear conversion will have the drive and driven sprockets the same size (1:1 ratio; allowing the effective and actual final drive ratio to be the same). For a 3.69 gear conversion, the drive sprocket is smaller than the driven sprocket.

GXPJay, I believe you know this, but it seems some of the other posters are confused by this since a RWD tranny does not use drive sprockets.

Chip

 

Just for the heck of it, here's a couple of links to GM's website that has the specs for the transmission, including the differential ratios and final drive ratios offered for our transmissions.

http://media.gm.com/us/powertrain/en...GENIVV8ENGINES

http://media.gm.com/us/powertrain/en...8_4T65_MN7.xls

For those who don't have excel, the spreadsheet in the second link has the following information:

2008 Hydra-Matic 4T65 Transaxle (MN7) 111606
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: 303 lb-ft (410 Nm)
Maximum gearbox torque: 400 lb-ft (542 Nm)
Gear ratios:
First: 2.92
Second: 1.56
Third: 1.00
Fourth: 0.70
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: solenoid control
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
DEXRON® III - China & Mexico
Transmission weight: 97.2 kg (214 lb) (MN7) (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 description: MN7: 258mm torque converter and heavy-duty gearbox
Assembly sites: Warren, Mich. (M15, MN7)
Applications: Chevrolet Impala (M15,MN7)
Chevrolet Monte Carlo (M15,MN7)
Chevrolet Uplander (M15)
Buick LaCrosse (M15,MN7)
Buick Lucerne (M15)
Buick Terraza (M15)
Pontiac Grand Prix (M15, MN7)
Pontiac G6 (M15)
Pontiac Montana (M15)
Saturn Relay (M15)

There is a cell note in the Final Drive Ratio cell as follows:
"Terry Andrzejewski:
Overall Final Drive Ratio changes based on model and sprocket selection"


And another Word document from GM on the site (Bold added, a few bits edited out):

2008 Hydra-Matic 4T65 (M15/MN7)
2008 Model Year Summary
Hydra-Matic 4T65 four-speed electronically controlled automatic fwd Car and Truck transaxle

• There are no planned performance upgrades for the 2008 Model Year, activities will be centered on cost and quality


OVERVIEW
The Hydra-Matic 4T65 (M15/MN7) was introduced in 1997, and has applications from mid-sized to large front-drive sedans and minivans, using V-6 and V-8 engines. It is a two-axis automatic four-speed transaxle with electronic controls, and features a unique dual chain and sprocket configuration that runs quieter than a single chain design. A stronger version of the chain, with heat-treated pins, is used with V-8 applications. In addition, for V-8 applications the starter motor is moved from the engine side of the engine/transaxle coupling to the transmission side, and the input sun gears are made with a process that increases durability. The final drive sun gear is double shot-peen with ceramic shot for improved strength and durability. The final drive planetary differential gets a larger pinion gear carrier, and the park position gear gets a stronger bearing. In addition, all pinion gears are made with a process to increase their strength.

The M15 is available with two different size torque converters (245mm & 258mm), while the MN7 features a heavy-duty final drive gear set.

There are three final drive ratios and three sprocket ratios, allowing nine separate overall ratios.

The operation of the 4T65 is controlled by either an Engine Control Module/Transmission Control Module combination, or a Powertrain Control Module. These controllers compensate shift timing for normal wear of components, which offers consistent operation for the life of the transaxle. If a driver manually selects a low range, but then fails to upshift at higher speeds, the control systems protect the engine from over-revving by automatically shifting to a higher gear. The controllers also reduce engine spark during abusive shifts that occur during “rocking” maneuvers, such as trying to extract the vehicle from a snow bank by rapidly shifting between forward gears and reverse gear. The control systems protect from overheating by automatically applying the torque converter clutch to reduce heat build-up from fluid shear, and a “limp home” mode allows the driver to operate the vehicle at reduced speed in the event of a transaxle control failure.

Most applications utilize the Engine Control Module/Transmission Control Module configuration The latest module is the T42 Transmission Control Module (TCM), which was introduced in 2004 for the Rendezvous application of the 4T65. This module has more memory and faster processing speed than previous modules, and the new configuration increases the flexibility and capabilities of the vehicle electrical architecture. The T42 utilizes “C” language common software (C-series) which provides a modular structure with stand alone architecture.


All LS4's come with the MN7 version of the 4T65E HD.

So I read this to mean that the differential gear ratio for all LS4's is 3.29. The sprocket ratios were not defined in the GM documents I found, but per the transmission tables in HP tuners, it appears that the 05 GXP had the 3.29 differential gears and an overall final drive ratio of 2.93, which indicates that the sprocket ratio is : 0.891.

The interesting thing about this is that the sprocket's "overdrive" ratio effectively reduces the engine output torque to below the rated maximum input torque for the transmission (only 303 ft-lb).

 

Thanks TiredGXP!

 

I wonder if that function is different on all MN7 trannies? The tranny does not function that way when in Tapshift mode which is the only way to select a low range on the GXP.

 

I think that's a new fuction (07 or 08). The '05's will just bounce off the rev limiter until you either back off or shift manually.

 

ya my 05 doesn't upshift the power just cuts out like a rev limiter