triloma Posted July 10, 2003 Report Share Posted July 10, 2003 Here is a simple questions for the techies... How does the AWD actually work? Is there an all time split between front and rear at some % or is the computer looking for slipage then engaging the front axle? Link to comment Share on other sites More sharing options...
ctrow Posted July 10, 2003 Report Share Posted July 10, 2003 I read somewhere that it was something like 36% front and the rest rear. Don't know where I read it otherwise I would post a link for ya'. Link to comment Share on other sites More sharing options...
ridnlow135 Posted July 10, 2003 Report Share Posted July 10, 2003 i saw that too.... Link to comment Share on other sites More sharing options...
GnatGoSplat Posted July 10, 2003 Report Share Posted July 10, 2003 It 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...
ctrow Posted July 10, 2003 Report Share Posted July 10, 2003 Very interesting... Kinda makes me wonder who finally figured that one out. Link to comment Share on other sites More sharing options...
triloma Posted July 10, 2003 Author Report Share Posted July 10, 2003 WELL THAT MAKES IT CLEAR Thanx for the answer....I think I got the basics but will have to read this a few hundred times to fully understand.... Again thanx everyone for the input Link to comment Share on other sites More sharing options...
BenKey Posted July 10, 2003 Report Share Posted July 10, 2003 ....I think I got the basics but will have to read this a few hundred times to fully understand.... I'm with you there Link to comment Share on other sites More sharing options...
GnatGoSplat Posted July 10, 2003 Report Share Posted July 10, 2003 Hahah! In summary: Front gets 38% torque, rear gets 62%. There is viscous fluid in the differential of the transfer case. This fluid is some kind of silicone that firms up as it gets hot. If the front wheels lose traction, the fluid causes more torque to be redirected to the rear wheels and less to the front. If the rear loses traction, the fluid causes more torque to be redirected to front wheels and less to the rear. Link to comment Share on other sites More sharing options...
2xtreme Posted July 10, 2003 Report Share Posted July 10, 2003 that's neat Link to comment Share on other sites More sharing options...
xlman Posted July 10, 2003 Report Share Posted July 10, 2003 I love readin' this stuff........................... what? Link to comment Share on other sites More sharing options...
johnsen Posted July 12, 2003 Report Share Posted July 12, 2003 Link to comment Share on other sites More sharing options...
ledfootss Posted July 12, 2003 Report Share Posted July 12, 2003 I have not got my SS to break lose yet even on wet pavement. i have only had it for a week about 1000 miles. I love it. I owned and built a 90 gmc stepside it ran high 9's in the 8th my only problem was i could not get it to stick to the ground. I love my SS it does not have that problem! Gary. Link to comment Share on other sites More sharing options...
03BlackSS Posted July 14, 2003 Report Share Posted July 14, 2003 Spun a wheel tonight on the way home it was a down pour and thought I would have a little fun. From a rolling start stomped on it while going around a slight turn. The rear wheels spun a little then the front wheels straited the SS out and that was the end of the spining. Link to comment Share on other sites More sharing options...
pharmb Posted July 14, 2003 Report Share Posted July 14, 2003 Have got the front wheels to spin briefly on dry pavement while making a u-turn...with a lot of throttle! Link to comment Share on other sites More sharing options...
SSilverado60 Posted July 14, 2003 Report Share Posted July 14, 2003 I have not got my SS to break lose yet even on wet pavement. i have only had it for a week about 1000 miles. I love it. I owned and built a 90 gmc stepside it ran high 9's in the 8th my only problem was i could not get it to stick to the ground. I love my SS it does not have that problem! Gary. now you should be running mud 9s with no traction problems ever again Link to comment Share on other sites More sharing options...
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