Merc Dr. Posted October 21, 2009 Report Share Posted October 21, 2009 It was raining the other day and I was driving my awd sss. I had my work supplies in the bed(700-1000 pounds). I was doing about 25-30mph coming down the off ramp. When I stood on it I felt the front end loose traction. The rear didn't seem to loose traction at all. From what I understand, the rear turns faster and the front should only break loose if the rear does first. Am I missing something? I've had the front end get loose before in the rain/snow, but it was after the rear broke free. Quote Link to comment Share on other sites More sharing options...
fox_forma Posted October 21, 2009 Report Share Posted October 21, 2009 with all the weight in your bed is it compressing the rear suspension enough that it is making you front end light. The weight was balanced enough so the front was prob walking a little on you. Quote Link to comment Share on other sites More sharing options...
mcmahan Posted October 21, 2009 Report Share Posted October 21, 2009 with all the weight in your bed is it compressing the rear suspension enough that it is making you front end light. The weight was balanced enough so the front was prob walking a little on you. the weight made the front end light thats why it seemed that way Quote Link to comment Share on other sites More sharing options...
Merc Dr. Posted October 21, 2009 Author Report Share Posted October 21, 2009 But why would the front end spin the tires and not the rear? From what I know, the differential has a 62/38 split(or something close to that). So if the front spins roughly 1/3 slower then the rear, how can they loose traction and spin if the rears aren't? Quote Link to comment Share on other sites More sharing options...
SSplaytoy Posted October 21, 2009 Report Share Posted October 21, 2009 But why would the front end spin the tires and not the rear? From what I know, the differential has a 62/38 split(or something close to that). So if the front spins roughly 1/3 slower then the rear, how can they loose traction and spin if the rears aren't? Weight distribution, momentum, centrifugal force, surface friction...simple physics It has happened to me numerous times. Nothing to be alarmed about Quote Link to comment Share on other sites More sharing options...
Merc Dr. Posted October 21, 2009 Author Report Share Posted October 21, 2009 I wasn't really worried. Just trying to educate myself. After it happened I spent a 1/2 hour tryin to figure it out in my head. The physics don't make sense to me. Quote Link to comment Share on other sites More sharing options...
SSplaytoy Posted October 21, 2009 Report Share Posted October 21, 2009 I wasn't really worried. Just trying to educate myself. After it happened I spent a 1/2 hour tryin to figure it out in my head. The physics don't make sense to me. Take into account the angle at which you were turning, at what speed, with how much the truck weighed and how that weight was distributed, the amount of water, oil, and other sh!t on the road, the traction of your tires, psi of the tires, water displacement of the tires, distance slid,...and a lot of other little things, and it will I was doing a slight turn once with a slightly wet road with about 600 pounds of Durock in the bed and I turned slight left but the truck went straight about 10 feet right as I had to turn right slightly when the front hooked and the bed swung out. Bottom line is that it does happen sometimes even with awd, regardless of displacement of power to the wheels. Quote Link to comment Share on other sites More sharing options...
Merc Dr. Posted October 22, 2009 Author Report Share Posted October 22, 2009 It sounds like you had a push. Put a round of wedge in the rear and take a 1/2 pound out of the right front. I was going straight when it broke traction. I'm actually looking for the technical reason. I'm a boat mechanic, so I'm always interested in knowing how things work.Any GM mechanics out there? I would completely understand this happening if the front end was the primary drive and the rear turned slower. This is not the case.(from what I know) Picture 2 gears. 1 big(front),1 small(rear)turning together. If the small one is turning 1000rpm and the big is at 650rpm, how can the big one exceed the rpm's of the little one? Regardless of how much wieght you put on it. Quote Link to comment Share on other sites More sharing options...
SSplaytoy Posted October 22, 2009 Report Share Posted October 22, 2009 It sounds like you had a push. Put a round of wedge in the rear and take a 1/2 pound out of the right front. I was going straight when it broke traction. I'm actually looking for the technical reason. I'm a boat mechanic, so I'm always interested in knowing how things work.Any GM mechanics out there? I would completely understand this happening if the front end was the primary drive and the rear turned slower. This is not the case.(from what I know) Picture 2 gears. 1 big(front),1 small(rear)turning together. If the small one is turning 1000rpm and the big is at 650rpm, how can the big one exceed the rpm's of the little one? Regardless of how much wieght you put on it. If something breaks Quote Link to comment Share on other sites More sharing options...
Bear Posted October 24, 2009 Report Share Posted October 24, 2009 But why would the front end spin the tires and not the rear? From what I know, the differential has a 62/38 split(or something close to that). So if the front spins roughly 1/3 slower then the rear, how can they loose traction and spin if the rears aren't? While your right on the normal split, the transfer-case has the ability to shift the split front to back up to 100%. A little info from the General on the operation of the NVG-149: 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. Quote Link to comment Share on other sites More sharing options...
Krambo Posted October 24, 2009 Report Share Posted October 24, 2009 Nice description Bear. I would commonly blow off the front right tire at the strip through the 60ft lights while the rears would hook. Quote Link to comment Share on other sites More sharing options...
Merc Dr. Posted October 30, 2009 Author Report Share Posted October 30, 2009 Thanx alot! That's the kinda reasoning I was looking for. Quote Link to comment Share on other sites More sharing options...
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