MN C5 Posted July 23, 2003 Report Share Posted July 23, 2003 (This is My understanding of the AWD and isn't based on anything but my ASSumptions) The AWD system in our trucks is not locked in 100% of the time. If the transfer case senses slip it will lock in and send power to the front shaft. It takes a variation is shaft speeds to cause the viscous to send power to the front shaft. This takes a second or so (a small amount of time) but is not instantainiously locking the fronts in. Thus if you've got a good tune in the computer you should be able to at least bark the rears. I have noticed that when I accelerate hard on a hill in the rain, the front wheels will spin on me, so I am not sure if your statement is correct. Perhaps the elastomer reacts faster than you stated. On dry pavement, the only way I have been able to get my wheels spinning is to floor it while making a sharp turn. Of course you can't do this long as you start slipping out of the turn I have not yet removed torque management, so I expect better results when I do. Still waiting for LS1Edit to come out for the 03 trucks. Ok, here is some info from GM about how our transfer case works.. And yes I was Wrong it is putting power to both axles F/R full time... Transfer Case Description and Operation The Borg Warner (BW) model 4481, RPO NR3 transfer case is a one-speed, full time, all wheel drive (AWD), transfer case. The transfer case provides power to both axles, through 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 both axles are constantly being driven for maximum traction in all conditions. 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, the front propeller shaft can be rotated by hand. The vehicle cannot be driven if one propeller shaft is removed. Operating the vehicle on the hoist can damage the differential pinion gears, by over-spinning. Operating the vehicle with one propeller shaft removed causes over-spinning of the differential pinion gears. The BW 4481 design of the planetary differential allows the 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. The BW 4481 case halves are high-pressure, die-cast magnesium. Ball bearings support the input shaft, the front output shaft, and the rear output shaft. The transfer case requires DEXRON®III ATF GM P/N 12346143 (Canadian P/N 10952622), which is red in color. When the BW 4481 is operating in the AWD mode, the power flows from the transmission to the transfer case input shaft (1). The input shaft (1) delivers the power to the planetary differential (4). The case of the planetary differential (4) is splined to the input shaft (1). The planetary differential (4) splits the torque 40 percent through the front differential pinion gears (3) to the front sun gear (8). The front sun gear (8) is engaged with the drive sprocket (2), which drives the chain (9) to the front output shaft (10), and power is delivered to the front propeller shaft. 60 percent of the torque to the rear output shaft (6) goes through the rear differential pinion gears (7) and rear sun gear (5), which is connected to the rear output shaft (6) and to the rear propeller shaft. Link to comment Share on other sites More sharing options...
2drTahoe Posted July 23, 2003 Report Share Posted July 23, 2003 Hey if you can find a bigger diagram of the transfer case can post it for us Seriously though, thanks for the info! I always prefer bigger pics to small pics. Link to comment Share on other sites More sharing options...
blackhawk Posted July 23, 2003 Report Share Posted July 23, 2003 LOL, had to scroll left and right to read, thanks for the info. Link to comment Share on other sites More sharing options...
MN C5 Posted July 23, 2003 Author Report Share Posted July 23, 2003 Well, I finally figured out how to size a picture. Had to buy PhotoShop to do it, man they really nick ya for that.. Link to comment Share on other sites More sharing options...
jwest1975 Posted July 23, 2003 Report Share Posted July 23, 2003 Well, I finally figured out how to size a picture. Had to buy PhotoShop to do it, man they really nick ya for that.. Cool! I hope the new software comes in handy for you.........I am sure it will! Well, I think we have all figured out by now that anything remotely related to being and owner of an SS truck will cost lots of money. Justin Link to comment Share on other sites More sharing options...
MN C5 Posted July 23, 2003 Author Report Share Posted July 23, 2003 This was Posted by GnatGoSplat Are these two transfercases different? they appear to be different This looks to be the correct info Posted by GnatGoSplatIt is a 38/62 split and has no electronics whatsoever. This is from GM: Document ID# 873908 2003 Chevrolet Chevy K Silverado - 4WD -------------------------------------------------------------------------------- Transfer Case Description and Operation The NVG 149 RPO NP3 is a single speed, single mode transfer case. The mode is full-time all wheel drive. It has a planetary differential gear set that splits the torque, normally 38 percent to the front wheels and 62 percent to the rear wheels. The NVG 149 utilizes magnesium housings. Proper fasteners, brackets, and fill/drain plugs must be used to prevent galvanic corrosion. The planetary differential uses the carrier (6) as the input. The annulus gear (4) connects to the rear output shaft (5) and rear wheels. The sun gear (3) connects to the front output shaft (7) and front wheels through the chain (8) and sprockets. The viscous coupling (2) consists of a sealed housing filled with a high viscosity silicone fluid and thin steel plates alternately splined to the inner and outer drum. The inner drum is connected to the input shaft (1), and the outer drum to the sun gear (3). Whenever there is a speed difference between the front and rear wheels, the inner and outer plates of the viscous coupling spin relative to each other and the silicone fluid provides resistance. The resistance was tuned to be high enough to bias power quickly to the wheels with traction, and low enough to prevent binding in a tight turn on dry surfaces. This is the most common way the viscous coupling is activated, the shear mode. If the speed difference is high, the coupling can lock or hump. This "hump" occurs when the heat generated, expands the fluid inside the housing, changing the fluid dynamics between the plates. This results in pressure between the plates, forcing them into contact with each other, similar to a clutch pack. In the hump mode, the coupling can bias torque 100 percent to one axle, if required. Situations requiring this are extreme such as backing up a steep gravel grade or climbing over off-road obstacles. The viscous coupling is not serviceable; it must be replaced if defective. This is because each viscous coupling is calibrated for optimum vehicle performance for both the shear and hump modes. If the viscous coupling is in the "hump" mode too long, severe damage will occur. To prevent damage to the viscous coupling, DO NOT: Tow with only two wheels down Drive without one propshaft Drive with a "donut" spare tire for an extended period of time Operate the vehicle on a hoist to diagnose the driveline components Power Flow - No Wheels Slip During normal operation, 100 percent torque is delivered to the input shaft (1) from the transmission. The torque is split to 62 percent to the rear output shaft (2) and 38 percent to the front output shaft (3), by the planetary differential. Because there is not a loss in traction or slip in the front or rear wheels, the viscous coupling is locked in place and there is no "shear" mode or "hump" mode involved. Power Flow - Front Wheels Slip When traction is lost at the front wheels, the viscous coupling works in conjunction with the differential to bias the torque more to the rear wheels. The rear torque goes higher than the 62 percent, and up to 100 percent torque to the rear output shaft (2). The torque at the front output shaft (3) is lowered from the 38 percent, to as low as 0 percent torque. Power Flow - Rear Wheels Slip When traction is lost at the rear wheels, the torque is biased to the front wheels. The torque to the front output shaft (3) goes higher from the 38 percent, up to 100 percent torque. The torque at the rear output shaft (2) is lowered from the 62 percent, to as low as 0 percent torque. Customers may have concern that the transfer case is not operating properly because one set of tires spun for a brief period. It is normal for one set of tires to spin until the viscous coupling engages. Turning off the traction control switch, if equipped, enhances the function of the viscous coupling. The viscous coupling, as described above, engages by heat. Allowing one set of tires to spin or slip for a brief period will generate heat in the viscous coupling. The engine speed should be kept at a constant speed during the brief spin of the tires. Pulsating the engine speed or hard acceleration will not allow the viscous coupling to operate properly. -------------------------------------------------------------------------------- Document ID# 873908 2003 Chevrolet Chevy K Silverado - 4WD Link to comment Share on other sites More sharing options...
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