scubas_90rs

Ok this is on my 83 z. I was under it because i had to take the torque arm off to put on the 90. WHen I spun the drivers wheel the passengers didn't even move. I had some one tell me that this is normal. some do that and some don't. i have never seen that happen before. if it isn't normal what could be wrong with out pulling the cover and looking at the internals. thanks for the help.

RB83L69

Nothing is wrong. It's normal for a non-posi.

If you hold the drive shaft yoke still while turning one wheel, the other wheel will turn backwards. If the other wheel is sitting still while turning the one, the drive shaft yoke is turning.

TKOPerformance

Yeah, exactly. In an open differential the power always goes to the wheel that has the least resistance, and thus the least traction, which is the obvious flaw with an open rear end.

scubas_90rs

all right. thanks for the help. i just have never seen that happen before. but i have never spun the wheels with the drive shaft out of the car before.

FndmntlsOfPimpn

what it mean if your right tire is always the one that spins no matter what and occasionally both do?

TKOPerformance

That's an open rear. The right tire always has less traction than the left when accelerating from a stop on a surface where both rear wheels have equal traction.

When you accelerate the engine torques over the the right and twists up the chassis. This unloads the left front tire and loads the right rear tire with the more of the vehicles's weight than it has at rest. Sounds good right? More weight equals more traction. There's a catch. At the same time power is running through the driveline and starting the tires in motion. As the tires grip they compress the rear suspension when they begin to bite. This is why you'll see a car "squat" the rear end as it takes off. Contrary to popular belief this isn't good. When the supension compresses the tires lose traction, because the weight of the vehicle is being unloaded from the tires. The right side has more weight to begin with, and is now unloading that weight plus some additional weight as the suspension is compressed. This leaves the right rear tire with less traction than the left rear tire. The power just follows the path of least resistance in an open rear, so the right tire spins while the left tire remains stationary.

If you look at a properly set up drag car it does exactly the opposite of what is described above as it leaves the line. Instead of squating the rear suspension slams the tires into the pavement, forcing them to bite, increasing traction dramatically. This is the whole concept behind traction bars, slide-a-link bars, and southside bars. You can actually see the gap between the top of the rear tires and the wheelwell get bigger as it leaves the line.

FndmntlsOfPimpn

thanks you for that tko it was very informative i jus wonderd cause i was todl that it was impossible for an open rearend to sprin both tires

TKOPerformance

Oh no, that's not true. In a situation where both rear wheels have the same amount of traction the power will move side to side "hunting" for the least amount of resistance, and this can cause an open rear to leave two marks on the pavement. Typically the left mark will be shorter and lighter than the right one though. A worn out posi, or a posi with low breakaway torque (more common on european cars than american cars) will often behave very much like an open rear.

FndmntlsOfPimpn

hmm ok wellt hat would explain thanks alot

Off topic: are you still open for around mid-end of january for me to send my tranny in? this is camaro502power@yahoo.com case u ddint kno

TKOPerformance

Sure, whenever you're ready.

70BuickSleeper

Ive left two almost equal marks a few months ago in front of my friends house. At first I thought one might have been from his bike, but was informed that I left both of them. I have 3.73 open rear, the road was flat prolly equal traction on both sides. So as you like you said, this can happen and does.... Now only if I could do that everytime...

TKOPerformance

That's easy, just weld the spider gears to the carrier!

-That was a joke. Please don't feel the need to post in and say how foolish and dangerous welding the spider gears in an open rear is.

rbjones

TKO--remember the ancient trick of putting one air bag over the right rear wheel? 40 years ago folks used to force an open rear end into giving equal traction by finding the right amount of air pressure in that one bag to equalize traction under acceleration, then let the air out to drive home.

TKOPerformance

That's exactly how we set up the rear suspension on my Dad's Chevelle. The car ran a posi, but due to track variations and the torquing over of the chassis the airbag allowed us to tune the car so it would leave straight. That's the good thing about an airbag, you can alter the pressure to tune the chassis. 5.0 and 4.6 Mustang guys are still usign this trick today, because the suspension on their cars is nearly identical to an old GM A-body car.