BigTex Posted September 9, 2003 Report Share Posted September 9, 2003 I posted this a while back on the LS1tech site, but some of you guys may want to take a look at it. New Venture Transfer Case in the SS: 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 as the input. The annulus gear connects to the rear output shaft and rear wheels. The sun gear connects to the front output shaft and front wheels through the chain and sprockets. The viscous coupling 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, and the outer drum to the sun gear. 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 ----- During normal operation, 100 percent torque is delivered to the input shaft from the transmission. The torque is split to 62 percent to the rear output shaft and 38 percent to the front output shaft, 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. 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. Link to comment Share on other sites More sharing options...
BenKey Posted September 9, 2003 Report Share Posted September 9, 2003 Thanks, BigTex. Link to comment Share on other sites More sharing options...
vette dude Posted December 29, 2003 Report Share Posted December 29, 2003 I posted this a while back on the LS1tech site, but some of you guys may want to take a look at it. New Venture Transfer Case in the SS: 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 as the input. The annulus gear connects to the rear output shaft and rear wheels. The sun gear connects to the front output shaft and front wheels through the chain and sprockets. The viscous coupling 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, and the outer drum to the sun gear. 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 ----- During normal operation, 100 percent torque is delivered to the input shaft from the transmission. The torque is split to 62 percent to the rear output shaft and 38 percent to the front output shaft, 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. 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. i have been looking for this for a while... Link to comment Share on other sites More sharing options...
detjoe Posted December 30, 2003 Report Share Posted December 30, 2003 ...The NVG 149 utilizes magnesium housings. Proper fasteners, brackets, and fill/drain plugs must be used to prevent galvanic corrosion. Did gm use the right fastners? Are we going to have any problems with corrosion? I do some plumbing and the problems from metals that are not the same causes alot of problems and relativly quickly(i.e. copper and steel). Does anyone have the build sheet to see what parts they are talking about as being in contact with the mag housing??? Could this cause our front end noise? Thanks for the information-I think too much info is better than not enough. joe Link to comment Share on other sites More sharing options...
vette dude Posted December 31, 2003 Report Share Posted December 31, 2003 ...The NVG 149 utilizes magnesium housings. Proper fasteners, brackets, and fill/drain plugs must be used to prevent galvanic corrosion. Did gm use the right fastners? Are we going to have any problems with corrosion? I do some plumbing and the problems from metals that are not the same causes alot of problems and relativly quickly(i.e. copper and steel). Does anyone have the build sheet to see what parts they are talking about as being in contact with the mag housing??? Could this cause our front end noise? Thanks for the information-I think too much info is better than not enough. joe good questions.... Link to comment Share on other sites More sharing options...
MustBBrent Posted December 31, 2003 Report Share Posted December 31, 2003 I posted this a while back on the LS1tech site, but some of you guys may want to take a look at it. New Venture Transfer Case in the SS: The NVG 149 RPO NP3 is ... deleted to get to the good part... 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. Gosh, no hard acceleration from romping on the GO pedal. It could keep the viscous thingy from operating properly. We can't have that now, can we?! Link to comment Share on other sites More sharing options...
ledfootss Posted December 31, 2003 Report Share Posted December 31, 2003 good info big tex thanks and detjoe you should cut that fat chick out of you sig picture Link to comment Share on other sites More sharing options...
BenKey Posted December 31, 2003 Report Share Posted December 31, 2003 good info big tex thanks and detjoe you should cut that fat chick out of you sig picture Man, I've been wanting to say that forever Link to comment Share on other sites More sharing options...
whitebowtie Posted January 4, 2004 Report Share Posted January 4, 2004 "I like women like I like my chicken; A little bit of fat on the end! Not too much and not too little; Just enough to make me grin!" Ahhh, Rodney! Link to comment Share on other sites More sharing options...
BigTex Posted January 4, 2004 Author Report Share Posted January 4, 2004 I saw Rodney at a comedy club a while back. Of course, I drove home singing the chicken song. Funny stuff. Link to comment Share on other sites More sharing options...
383ss Posted January 4, 2004 Report Share Posted January 4, 2004 great post Link to comment Share on other sites More sharing options...
2bseen Posted January 6, 2004 Report Share Posted January 6, 2004 Is this the same transfer case as the denali, just wondering. Link to comment Share on other sites More sharing options...
BigTex Posted January 6, 2004 Author Report Share Posted January 6, 2004 It should be the same for the C3 / Sierra Denali, but the Denali and Escalades use a borg warner unit. Link to comment Share on other sites More sharing options...
smithl3 Posted May 5, 2004 Report Share Posted May 5, 2004 So in light of these stats, BigTex has generously given us, we shouldn't run our trucks on the dyno without the front drive shaft. Or do you think that the time on a dyno run is so small that the excess heat created wont really cause any long term damage with our transfer case???? Just don't want more problems..... Link to comment Share on other sites More sharing options...
Vett Tech Posted June 10, 2004 Report Share Posted June 10, 2004 I have worked at a Dealership for 14 years and not had any problems with this transfer case except noise concerns form front axel. Turn up your Bose cd changer!! Link to comment Share on other sites More sharing options...
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