Chevy Autotrac Question

[remist17]

I know this is a Truck site and I usually go in the old ones but I am buying a 05 Tahoe with Autotrac. Can anyone tell me about this option ? I have no clue. The dealer said it is a awd system that transfers the power of slipping to not slipping tire. I guess the front axel does not turn unless its required to?

Any help is greatly appreciated and if you can recomend a maintance schedule or tips I thank you !






So I am confused... Picked up the Tahoe this weekend. The spec page said I have stabiltrac and no mention of Autotrac. Can someone tell me what options I have? I attached some photos above

[DirtyLarry]

Right from the GM Service Manual Description and Operation. There is also an excerpt in the Owner’s Manual that explains the operation although not as much fun to read a book as it is to read online.

Autotrac, or Autocrap as I like to call it, is not the most reliable and durable of 4wd systems but it is standard equipment on GM SUV’s from 1999 to current and is a convenient system (when it actually works) for the wife to make her way to Kohl’s on a slick winter day in the family truckster.

Dodge also uses this exact same New Venture Gear system in their 1500 series trucks and SUV's although under a different marketing name. Ford has a Borg-Warner system that is basically the same as well.


AutoCrap Description and Operation

The New Venture Gear model NVG 246 RPO NP8 transfer case is a 2-speed automatic, active, transfer case. The NVG 246 EAU provides 5 modes, Auto 4WD, 4HI, 4LO, 2HI and NEUTRAL. The Auto 4WD position allows the capability of an active transfer case, which provides the benefits of on-demand torque biasing wet clutch and easy vehicle tuning through software calibrations. The software calibrations allow more features such as flexible adapt ready position and clutch preload torque levels. The technology allows for vehicle speed dependent clutch torque levels to enhance the performance of the system. For example, the system is calibrated to provide 0-6.78 N•m (0-5 lb ft) of clutch torque during low speed, low engine torque operation, and predetermined higher torque for 40 km/h (25 mph) and greater. This prevents crow-hop and binding at low speeds and provides higher torque biases at higher vehicle speeds, in order to enhance stability.

The NVG 246 EAU transfer case features a 4 button shift control switch located on the instrument panel. When the ignition key is in the RUN position, the transfer case shift control module monitors the transfer case shift control switch to determine if the driver desires a new mode/range position. At a single press of the transfer case shift control switch, the lamp of the new desired position will begin flashing to inform the driver that the transfer case shift control module has received the request for a new mode/range position. The lamp will continue to flash until all shifting criteria has been met and the new mode/range position has been reached, or has been engaged. Once the new mode/range position is fully active, the switch indicator lamp for the new position will remain ON constantly.

During normal driving situations, the transfer case can operate in the Auto 4WD mode. In the Auto 4WD mode, the transfer case shift control module monitors rear wheel slip speed, based on the inputs from both the front and rear propshaft speed sensors. When the vehicle experiences a rear wheel slip condition, the transfer case shift control module sends a pulse width modulated (PWM) signal to an electronic motor, which is the transfer case encoder motor. This motor rotates the transfer case control actuator lever shaft, applying a clutch pack. This clutch pack is designed to deliver a variable amount of torque, normally delivered to the rear wheels, and transfers it to the front wheels. Torque is ramped up to the front wheels until the front propshaft speed sensor matches that of the rear propshaft speed sensor. Torque is ramped down to the front wheels. The process would repeat if rear wheel slip is detected again.

The NVG 246 EAU transfer case has the added feature of also providing the driver with 3 manual mode/range positions:

• 4HI - 4 Wheel Drive high range
• 2HI - 2 Wheel Drive high range
• 4LO - 4 Wheel Drive low range

The driver may choose to select any of these mode/range positions while driving the vehicle. However, the transfer case will not allow a shift into or out of 4LO unless the following criteria has been met:

• The engine is running.
• The automatic transmission is in NEUTRAL.
• The vehicle speed is below 5 km/h (3 mph).

This transfer case also has a NEUTRAL position. A shift to the NEUTRAL position allows the vehicle to be towed without rotating the transmission output shaft. NEUTRAL position may be obtained only if the following criteria has been met:

• The engine is running.
• The automatic transmission is in NEUTRAL.
• The vehicle speed is below 5 km/h (3 mph).
• The transfer case is in 2HI mode.

Once these conditions have been met, press and hold both the 2HI and 4LO buttons for 10 seconds. When the system completes the shift to NEUTRAL, the red Neutral lamp will illuminate.

The NVG 246 EAU case halves are high-pressure die-cast magnesium. Ball bearings support the input shaft, the front output shaft, and the rear output shaft. A thrust bearing is located inside of the input shaft gear to support the front of the rear output shaft. The transfer case requires Auto Trac® II Fluid GM P/N 12378508 (Canadian P/N 10953626) which is blue in color. The fluid is designed for smooth clutch application. An oil pump, driven by the rear output shaft, pumps the fluid through the rear output shaft oil gallery to the clutch and bearings.

There are two versions of the NVG 246 EAU, which depend on the transmission applications and vehicle applications. If the vehicle is equipped with a transmission RPO M30, the transmission splines in the input gear will have 27 teeth. With this application the planetary carrier assembly will have 3 pinion gears. If the vehicle is equipped with transmission RPO MT1 or MN8, the transmission splines in the input gear will have 32 teeth. The planetary carrier assembly on this application will have 6 pinion gears.

[remist17]

Thanks for the input. It didnt have a manual in the truck so thats why im asking.

The option buttons are different then whats explained. I thing the first button is a picture of 4 tires and drivesahft (stick drawing) with squiggle lines, then one the the dealer said is always on(maybe AWD) and then 4lo. Is this a different set up. I have seen the setuo as discribed above in silverados but not this setup. They told me its a all wheel drive when needed but runs 2wd when cruizing.

[fiddy9apache]

i have the auto 4wd on my tahoe, good for the twice a year ice storms we get in texas lol.

[remist17]

So I am confused... Picked up the Tahoe this weekend. The spec page said I have stabiltrac and no mention of Autotrac. Can someone tell me what options I have? I attached some photos above.

[DirtyLarry]

Originally Posted by remist17

So I am confused... Picked up the Tahoe this weekend. The spec page said I have stabiltrac and no mention of Autotrac. Can someone tell me what options I have? I attached some photos above.

Looks like you don’t have Autocrap. Interesting, as I have actually never seen the system you have on this Tahoe in real life. Looks like you got stuck with full-time 4x4.

Your VIN details:
AG1 - SIX-WAY POWER DRIVER SEAT AG2 - 10-WAY POWER PASSENGER SEAT
AJ1 - DEEP TINTED GLASS AJ7 - SIDE IMPACT AIR BAGS
AL0 - SENSOR INDICATOR INFLATABLE RESTRAINT FRT PASS AL4 - 2ND ROW BUCKET SEATS
AN3 - FULL FEATURE BUCKET SEATS AP9 - CARGO CONVENIENCE NET
ARL - PLANT CODE-ARLINGTON, TX AS3 - THIRD ROW BENCH SEAT
AU0 - KEYLESS REMOTE DOOR LOCK AXP - MPV VIN IDENT POSITION
A31 - POWER WINDOWS BVE - ASSIST STEPS
B30 - CARPETING, COLOR-KEYED B58 - COLOR-KEYED FLOOR MATS, CARPETED
B71 - WHEEL FLARES B85 - BRIGHT BODY SIDE MOLDINGS
CF5 - ELECTRIC SLIDING SUNROOF CJ2 - AIR CONDITIONING AUTOMATIC DUAL ZONE
C25 - REAR WINDOW WIPER & WASHER C36 - REAR HEATER
C49 - ELECTRIC REAR WINDOW DEFOGGER C5H - GVW RATING - 6,900 LB
C69 - AIR CONDITIONING -FRONT & REAR DF5 - ISRV MIRROR W/COMPASS & TEMP
DH6 - LIGHTED VISOR/VANITY MIRRORS DK8 - DELUXE OVERHEAD CONSOLE
DL3 - OSRV MIRROR W/DRIVER SIDE AUTO DIMMING, PWR FOLD & ADJ, HEAT, TURN SIGNAL DT4 - ASHTRAY MUFFIN
D07 - CUSTOM FRONT FLOOR CONSOLE EVA - EVAP EMISSION REQUIREMENT
E52 - LIFTGATE/LIFTGLASS FE9 - 50-STATE EMISSIONS
FK2 - TORSION BAR SPRING ADJUSTMENT FK3 - TORSION BAR SPRING ADJUSTMENT
GT5 - REAR AXLE - 4.10 RATIO G69 - LEVEL CONTROL AUTO, AIR, HD
G80 - LOCKING REAR DIFFERENTIAL JF4 - POWER ADJUSTABLE PEDALS
JH2 - BRAKE HYD POWER, DISC/DISC JL4 - VEHICLE STABILITY ENHANCEMENT STABILITRAC
KNP - HD AUX TRANS. COOLING SYS KUP - THROTTLE CONTROL ELECTRONIC
KW1 - 160 AMP GENERATOR K34 - CRUISE CONTROL
LM7 - VORTEC 5300 V8 SFI GAS ENGINE M30 - 4-SPD AUTOMATIC TRANSMISSION
NP5 - LEATHER WRAPPED STEERING WHEEL NR4 - TRANSFER CASE 4 WHEEL DRIVE NT8 - EMISSION SYSTEM FEDERAL, TIER PCR - SUN SOUND ENTERTAINMENT PKG: * DVD REAR ENTERTAINMENT SYSTEM * POWER GLASS SUNROOF
PDC - CARGO PACKAGE INCLUDES: * CARGO NET * CARGO SHADE * CARGO AREA MAT PDY - SAFE AND SECURE PACKAGE: * AUTORIDE SUSPENSION * SIDE IMPACT AIR BAGS * STABILTRAC VEHICLE STABILITY ENHANCEMENT
P25 - 17" ALUMINUM WHEELS QAS - P265/70R17 ALS WOL TIRES
R5C - TIRE BRAND ALL BRIDGESTONE SAF - SPARE TIRE LOCK
SLM - STOCK ORDERS SLT - EQUIP CHEV 'LT' SALES PKG
T96 - FRONT FOG LAMPS UC6 - AM/FM RADIO,RDS,6 DISC CHANGER, AUTO TONE CONTROL, AND ETR (REPLACES STD/OPT RADIO)
UE1 - ONSTAR SYSTEM INCLUDES 1 YEAR SAFE & SOUND UG1 - HOMELINK
UJ6 - TIRE PRESSURE MONITOR UK3 - REDUNDANT RADIO CONTROLS
UK6 - REAR SEAT AUDIO CONTROLS UQ7 - BOSE SPEAKER SYSTEM
U2K - XM SATELLITE RADIO - OVER 130 CHNLS OF DIGITAL ENTERTAINMENT SERVICE FEE EXTRA.1ST 3MOS.INCL U42 - REAR SEAT ENTERTAINMENT SYSTEM
VB3 - CHROME REAR BUMPER VFF - VIDEO FORMAT REGION 1, NTSC
VG3 - CHROME FRONT BUMPER VR4 - WEIGHT DISTRIB. PLATFORM HITCH
VXS - COMPLETE VEHICLE LABEL V1K - BAR LUGGAGE CARRIER
V22 - DELUXE FRONT APPEARANCE PKG. V54 - BLACK ROOF LUGGAGE CARRIER
V73 - STATEMENT OF VEHICLE CERT.-U.S. /CANADA V76 - RECOVERY HOOKS
XAS - P265/70R17 113S WOL FRONT X88 - CHEVROLET CONVERSION
YAS - P265/70R17 WOL - REAR YD3 - BASE EQUIP FOR SCH GVW PL-FT AX
YD6 - BASE REAR SPRING YE9 - LS TRIM
ZMJ - SPARE TIRE P265/70R16-111S BW ZM9 - HOMELINK UNIVERSAL TRANSMITTER
ZY1 - SOLID PAINT Z55 - AUTORIDE SUSPENSION
Z82 - TRAILERING EQUIPMENT INCLUDES: * TRAILERING HITCH PLATFORM * 7-LEAD WIRING CONNECTOR * TRANSMISSION OIL COOLER * HIGH CAPACITY AIR CLEANER 1SM - TAHOE LT PREFERRED EQUIPMENT GROUP: * VORTEC 5300 V8 ENGINE * IN-DASH 6 CD PLAYER (REPLACES STD/OPT RADIO) * REAR SEAT AUDIO CONTROLS * BOSE PREMIUM SPEAKERS * 1ST ROW LEATHER SEATING SURFACES * 2ND ROW SEATS LEATHER APPOINTED * 3RD ROW SEAT * ONSTAR SYSTEM INCLUDES 1YR SAFE & SOUND * STEERING WHL MOUNTED CONTROLS * PWR FOLD AND ADJUST HEATED OUTSIDE MIRROR WITH TURN SIG AND DRIVER SIDE AUTO DIMMING * CARGO NET * LUGGAGE RACK CROSS RAILS * TRAILERING PACKAGE * 10 WAY POWER HEATED BUCKET SEATS WITH DRIVER MEMORY * POWER ADJUST PEDALS * XM SATELLITE RADIO - OVER 130 CHNLS OF DIGITAL ENTERTAINMENT SERVICE FEE EXTRA.1ST 3MOS.INC * ELECTRONIC CLIMATE CONTROL * UNIVERSAL TRANSMITTER * ELECTROCHROMIC ISRV MIRROR W/ TEMPERATURE & COMPASS * 17" ALUMINUM WHEELS
1SZ - PREFERRED EQUIPMENT SAVINGS 41U - BLACK
52I - TAN INTERIOR TRIM 522 - TAN/NEUTRAL
6XK - COMP FRT LH COMPUTER SEL SUSP 7XK - COMPONENT FRT RH COMP. SEL SUSP


NR4 Transfercase Description:

The Borg Warner (BW) model 4482 NR4 transfer case is a two-speed, full time 4WD, transfer case. The transfer case has an external planetary type differential, which has two different sets of pinion gears. The planetary differential provides a 40/60 torque split front/rear full time. This means the front and rear propeller shafts are constantly being driven for maximum traction in all conditions.
While in the 4HI mode, the transfer case external type planetary differential functions the same as a typical rear axle differential. The transfer case differential pinion gears function as the spider gears, and the sun gears function as the side gears.
The following actions occur because of the planetary differential:
• If the vehicle is on a hoist, and in the 4HI mode, the front propeller shaft can be rotated by hand.
• The vehicle cannot be driven in the 4HI mode if one propeller shaft is removed.
• Operating the vehicle on the hoist, in the 4HI mode, can damage the differential pinion gears, by over-spinning.
• Operating the vehicle with one propeller shaft removed, in the 4HI mode, causes over-spinning of the differential pinion gears.
The BW 4482 design of the planetary differential allows use with the Vehicle Stability Enhancement System (VSES) vehicles. The VSES takes use of the planetary differential, by applying braking to a tire that has less traction and dividing the engine torque to the other axle. A high/low planetary carrier assembly provides the high and low ranges, which is a 4-pinion gear, sun gear, and annulus gear arrangement, giving a 2.64 low range reduction ratio.
The BW 4482 case halves are high-pressure die-cast magnesium. Ball bearings support the input shaft, the front output shaft, and the rear output shaft. A needle roller bearing is located inside of the input shaft gear to support the front of the mainshaft. The rear of the mainshaft is supported by a bronze bearing inside the rear output shaft. The transfer case requires DEXRON®III ATF Fluid GM P/N 12378470 (Canadian P/N 10952622), which is red in color. An oil pump pumps the fluid through the mainshaft oil gallery to the gears and bearings.

[remist17]

Originally Posted by DirtyLarry

You didn't buy a 2wd Tahoe did you?

No its all wheel drive. Photos are in the first post

[DirtyLarry]

Originally Posted by remist17

No its all wheel drive. Photos are in the first post

Yeah, I see that now. I didn't notice you updated your original post with pictures....and a VIN.

[remist17]

DirtyLarry
From your specs you posted I think I have concluded I have the stabiltrac sysytem with NR4 Transfer case uses Dextron III Tranny Fluid .


So do you think this is a ok set up. I am not going to be off roading this my wife most likely will be driving the Tahoe.

[DirtyLarry]

Honestly, I don’t know anything about the NR4 system being Borg Warner is usually found in Fords. In fact, I never saw Borg tcase in a GMT800 before but looks like you got one. I have seen the NR4 RPO code in order guides but never an actual vehicle equipped with it. Let us know how it works for you. Congrats on the new family truckster!

[remist17]

Thanks... I guess if you guys havent seen this setup I might be a little concerned. But hopefully fingers crossed it will hold up.

Can any one tell me what the difference between Autotrac and Stabiltrac is. I am assuming these are both traction control setups. I think I have convinced myself with the help of dirtyLarry that I have a all wheel drive setup with stabiltrac and NR4 transfer case...

EDIT: Called local Chevy dealer to see if they could help me out! They told me they couldnt give the type of Transfer case but its a NR4 and takes Autotrac 2 Fluid, Could not tell me what Tranny was in it but confirmed the M30 option, Confirmed that it had stabitrac control.... No wonder GM is in the crapper ! They cant even or willing to help a GM owner out ! So I guess the question still stands:

1- The NR4 Transfer Case does it trully take Autotrac 2 fluid or Dextron III?
2- Can any one tell me what Tranny I have?

[Red84C10]

I have never seen a Tahoe with your set up before very strange but as far as what tranny it must be a 4L60E.

[DirtyLarry]

Originally Posted by remist17

Thanks... I guess if you guys havent seen this setup I might be a little concerned. But hopefully fingers crossed it will hold up.

Can any one tell me what the difference between Autotrac and Stabiltrac is. I am assuming these are both traction control setups. I think I have convinced myself with the help of dirtyLarry that I have a all wheel drive setup with stabiltrac and NR4 transfer case...

EDIT: Called local Chevy dealer to see if they could help me out! They told me they couldnt give the type of Transfer case but its a NR4 and takes Autotrac 2 Fluid, Could not tell me what Tranny was in it but confirmed the M30 option, Confirmed that it had stabitrac control.... No wonder GM is in the crapper ! They cant even or willing to help a GM owner out ! So I guess the question still stands:

1- The NR4 Transfer Case does it trully take Autotrac 2 fluid or Dextron III?
2- Can any one tell me what Tranny I have?

1) NR4 requires Dextron III, not Autocrap fluid
2) 4L60E

Here are details of the StabiliTrak System from the Owner's Manual.

Transfer Case (All-Wheel Drive with StabiliTrak)
DEXRON®-III Automatic Transmission Fluid. Look for "Approved for the H-Specification" on the label.

StabiliTrak System

Your vehicle may be equipped with the StabiliTrak® system which combines antilock brake, traction and stability control systems and helps the driver maintain directional control of the vehicle in most driving conditions.

When you first start your vehicle and begin to drive away, the system performs several diagnostic checks to ensure there are no problems. You may hear or feel the system working. This is normal and does not mean there is a problem with your vehicle. The system should initialize before the vehicle reaches 20 mph (32 km/h). In some cases, it may take approximately two miles of driving before the system initializes.

If the system fails to turn on or activate, the STABILITY SYS DISABLED or SERVICE STABILITY message will be displayed. If the vehicle has gone through heavy acceleration or braking during the first two miles after starting your vehicle, the STABILITY SYS DISABLED message may appear. If this is the case, your vehicle does not need servicing. Turn your vehicle off and back on again to reset the system. If either message appears on the Driver Information Center (DIC), and your vehicle hasn't gone through hard acceleration or braking in the first two miles, your vehicle should be taken in for service.

The STABILITY SYS ACTIVE message will appear on the Driver Information Center (DIC) only when the system is both on and activated. You may also feel or hear the system working; this is normal. For more information on the stability messages, see Driver Information Center (DIC) .


The StabiliTrak button is located on the instrument panel.

StabiliTrak® and part of the traction control system can be turned off or back on by pressing the StabiliTrak® button. All-wheel drive vehicles must be in all-wheel drive mode to turn the system on or off. Four-wheel-drive vehicles must be in 2HI, 4HI or AUTO 4WD to turn the system on or off.

When the system is turned off, the traction off light will illuminate, and the STABILITY SYS DISABLED message will appear on the DIC to warn the driver that both the stability system and part of the traction control system are disabled. Your vehicle will still have brake-traction control when StabiliTrak® is off, but will not be able to use the engine speed management system. See "Traction Control Operation" next for more information.

When the StabiliTrak® system has been turned off, you may still hear system noises as a result of the brake-traction control coming on.

It is recommended to leave the system on for normal driving conditions, but it may be necessary to turn the system off if your vehicle is stuck in sand, mud, ice or snow, and you want to "rock" your vehicle to attempt to free it. It may also be necessary to turn off the system when driving in extreme off-road conditions where high wheel spin is required. See If Your Vehicle is Stuck in Sand, Mud, Ice, or Snow .

When the transfer case is in 4LO, the stability system is automatically disabled, and the STABILITY SYS DISABLED message will appear on the DIC. In 4LO, the StabiliTrak® button only turns the traction control system on and off.

Traction Control Operation
The traction control system is part of the StabiliTrak® system. Traction control limits wheel spin by reducing engine power to the wheels (engine speed management) and by applying brakes to each individual wheel (brake-traction control) as necessary.

The traction control system is enabled automatically when you start your vehicle, and it will activate and display the TRACTION ACTIVE message in the Driver Information Center (DIC) if it senses that any of the wheels are spinning or beginning to lose traction while driving. If you turn off StabiliTrak®, only the brake-traction control portion of traction control will work. The engine speed management will be disabled. In this state, engine power is not reduced automatically and the driven wheels can spin more freely. This can cause the brake-traction control to activate constantly. For more information on the traction active message, see Driver Information Center (DIC) .

Notice: If you have All-Wheel Drive with StabiliTrak® and the traction off light comes on due to heavy braking and/or because the traction control system has been continuously active, do not allow the wheel(s) of one axle to spin excessively. If you do, you may be causing damage to the transfer case. This could lead to costly repairs not covered by your warranty.

If the brake traction-control system activates constantly or if the brakes have heated up due to high speed braking, brake traction-control will be disabled and the TRACTION SYS LIMITED message will be displayed. In the limited mode, the traction-control system will only use engine traction-control and is limited in it's ability to provide optimal performance since the system will not utilize brake traction-control to control slip on the drive wheels. The system will return to normal operation after the brakes have cooled. This can take up to two minutes or longer depending on brake usage.

Notice: If you have All-Wheel Drive with StabiliTrak® and allow the wheel(s) of one axle to spin excessively while the traction off, ABS and brake warning lights and the SERVICE STABILITY message are displayed, you could damage the transfer case. The repairs would not be covered by your warranty. Reduce engine power and do not spin the wheel(s) excessively while these lights and this message are displayed.

The traction control system may activate on dry or rough roads or under conditions such as heavy acceleration while turning or abrupt upshifts/downshifts of the transmission. When this happens, you may notice a reduction in acceleration, or may hear a noise or vibration. This is normal.

If your vehicle is in cruise control when the system activates, the STABILITY SYS ACTIVE message will appear on the Driver Information Center (DIC), and the cruise control will automatically disengage. When road conditions allow you to use cruise again, you may re-engage the cruise control. See Cruise Control .

StabiliTrak® may also turn off automatically if it determines that a problem exists with the system. If the problem does not clear itself after restarting the vehicle, you should see your dealer for service.

[remist17]

Thanks all. DirtyLarry thanks a bunch you really helped me out.

Its a little concerning that everyone says I never saw this before in a Tahoe ! Not sure if thats a good thing or not. I hope this doesnt bite me in the backside.

[Huck]

My 2002 Silverado 2wd has positrac rear with StabiliTrac switch on the dash. In my truck, the StabiliTrac system senses which rear wheel is turning faster then the other when on slippery stuff and applies braking to the fast one. At some point, my poistrac kicks in to have both wheels turning. In reality, I would probably be just as well off with a couple 80lb bags of sand sitting over the rear axle in the bed of the truck and cost under $20. hehehehehehehe
Funny thing, I have had a 99 Silverado Z71 4x4 with posi, a 2000 Tahoe Z71 4x4 with posi and both of them can get stuck on WET GRASS!!!! Half the time the dash switch to kick in 4 wheel drive wouldn't work but even with the trucks in 4x4 and low range, the road tires they came with did not have an aggressive enough tred to pull a frog out of a pond! When I needed a 4x4 to help pull a neighbors vehicle out of a ditch, I pulled out my OLD 72 BLAZER K5--4speed, 350, 33"s---and could pull a sherman tank out of the grand canyon!! No comparison---old trucks RULE!!!!!!