Posi problems


#1

I have a 98 camaro z28 and im having some problems with my rear end. I am positive its a limited slip. Ive removed the cover from differential and know what a lsd looks like. My problem is when i turn and hit the gas only 1 tire spins. But if im going straight and hit the gas both tires spins. When i say spin i mean break loose. I removed the cover tonight and took a look. No metal shavings at all. It all looks in good conditon. It has a 390 gear in it. Owner before me put it in. I removed the calipers and the axels have a little play in them. About a quarter inch play going in and out. Was wondering if this was normal. Also while it was jacked up i could hold one wheel while spinning the other. And if i play with it i can make the back left tire spin by its self also not making the ring gear move. Is it normal for a wheel to spin and the ring gear not move? I have a lot of questions about differentials. But mainly why am i only getting one tire to spin when turning??? Completely kills the fun in having a strong car for me. Thanks for your time guys!


#2

I don’t have the answer for this question and if I did I would keep it to myself so as to not encourage this type of behavior except at a sanctioned track day.


#3

What kind of help is this? ^ two thumbs down for the smart alecky comment. Anyone else?


#4

+1 to @“VOLVO V70” This a lot of fun on a closed course, but not on public roads


#5

I never specified if this was on public roads or closed course. I am trying to fix a car that has been built for racing. Ive been building for quite a while and never ran across this problem. Thought i would try to get some advice since most people i talk to cant figure it out either. Obviously this is one that has everybody stumped bc of yall bashing me instead of helping.


#6

I had posi on my Olds. Someone may correct me but posi does not mean both wheels will necessarily spin. Posi transfers the power to the wheel with the most traction rather than with a standard that provides the power to the wheel with the least traction. So if both wheels would have similar traction such as on snow or gravel, then they both could spin, but going around corners could change that. A car with both rear wheels locked up would be very hard to control especially in slippery conditions.

Shortly after I got the car, we were pulling a camper up a long icy hill. I moved the car so that the right wheel was on the less slick shoulder and made it up with no problem. On a standard, the left wheel would have been spinning on the ice while the right had traction. I don’t think you have a problem.


#7

I am not extremely knowledgeable about limited slip differentials but aren’t they mainly for the dragstrip and that function seems to be working fine. I am wracking my brain thying to figure out how it clold let the outside tire travel a longer path and still put power to both axles at the same time.
I guess we need an expert that doesn’t mind someone using their car for fun. Some people would like to see us all sealed up in a plastic bag with air and food pumped in and waste pumped out to keep everyone safe until we die of old age. Guess what people, we are all going to die anyway.


#8

Limited slip means just exactly that: LIMITED slip. The two axles are connected to each other through a set of clutches that allows some slip, like when the car is going around a turn.

You should not be able to turn one wheel by hand without the other turning IN THE SAME DIRECTION. If the other wheel turns in the opposite direction the clutches are worn. If the other wheel doesn’t turn at all but the driveshaft does the clutches are worn. If neither the driveshaft nor the other wheel turns something is broken.


#9

No Oldtimer11, it was great for commuting in the snow. Great traction but ice could get a little scary, and you could never use cruise on ice or it could spin you around in no time. Used to have to add the whale oil to stop the clutches from chattering on a sharp turn so yes there are clutches or cones in there.


#10

The Posi-Trac in the diff is working as it should.

When driving straight, the diff will transfer power from the tire that’s spinning to the tire that’s not.

Where with an open diff, the tire with the least traction will just keep spinning.

The Posi-Trac also needs to allow the rear tires to rotate at different rates while cornering.

It’s that 1/4" play in the axles that allows the Posi-Trac to disengage while cornering.

Go on YOUTUBE and enter “Detroit Locker”.

Tester


#11

This car should not have a Detroit Locker as standard. It would have been installed with the gears.

If it has the standard LSD, it will be an Auburn cone-style LSD. You should NOT be able to turn one tire with the rear jacked up and holding the other. If the car has the Auburn, it is nearly shot. Since you can light up both rears going straight, there is still some anti-slip left but it needs rebuilding. IF you have an Auburn

Since the car has aftermarket gears (Chevy never offered a 3.90 gear in these) it MAY have a Torsen gear-type LSD. These were standard in 99 up cars but may be available in 98 or its been swapped in with the gears. If so, it would behave almost exactly how you describe. Jacked-up, you could turn one wheel. Straight-ahead would spin both tires. In a corner, if you have a really big rear stabilizer bar (1 inch or more) is may spin. The design needs some contact force by the inside tire to work. If the inside tire is very light because of a big stab bar, it will spin.

1/4 inch side play is too much on this axle. 0.040 inch should be about all the play it has. Likely your shafts are worn on the end-button near the C-clip.

BTW, I circuit raced a 3rd Gen Camaro for over 10 years.


#12

I think it’s time to rebuild the rear end and do it sooner rather than later. If the axle sideplay is too excessive (which yours appears to be) what can happen is that a C-clip can fall off.

That in turn can lead to the axle, along with the wheel attached to it, separating itself from the car; not a ton of fun at higher speeds.


#13

I think it’s time to rebuild the rear end and do it sooner rather than later. If the axle sideplay is too excessive (which yours appears to be) what can happen is that a C-clip can fall off.

That in turn can lead to the axle, along with the wheel attached to it, separating itself from the car and which will create some excitement at higher speeds.


#14

I happen to agree with Volvo on this, and your response suggests that you are, in fact, peeling rubber and/or drag racing on public roads. If you aren’t just say so and I’ll apologize. If you are, than I’m glad you don’t live in my neighborhood. There are kids here.

If you’re going to do this stuff, be a man and admit it.


#15

I admit to laying down a bit of rubber with my '04 T’bird. Jeez what is the big deal with that!


#16

If you live in a remote area, nothing. If you were doing it in a neighborhood, lots.


#17

I will freely admit to laying down quite a bit of rubber back in the day .


#18

I’m glad you’ve grown up.

And I will admit to having to had to hold my six year old son in my arms as the EMTs peeled him off the pavement in front off my house and ride the ambulance with him because some young clown thought he had the right to cruise through the neighborhood at whatever speed he felt like.

So if you think you’ll ever get me to accept hotrodding in a residential neighborhood… grow up.


#19

As for the statement about telling kids to not play in the street . You say - don’t play in the street - they hear - don’t play in the street when I am looking.


#20

That’s very true, but in my case my son was crossing the street to play with his buddy. The street itself ends in a cul-de-sac just three houses (perhaps 600-800 feet) down from where my house was.

Hotrodding in a residential neighborhood is totally absolutely unacceptable.