View Full Version : Hi all, question, Posi Traction, or Limited Slip


Juicer28
07-14-2010, 10:10:30 PM
Me and my son are trying to figure out what to do. I gave him my 1980 camaro after I had my Posi traction rear end with 3.08 gears installed on the 80. now I purchased a 1978 Camaro and it has Limited Slip. I am wanting my posi traction from his 80. He is trying to figure out what to install on his Camaro. He is going to have 330 horses moving his car, Mine will not be near his. I will be putting a new 350 engine, with a few mods, but nothing like his. What would you recommend for gears on his car, and whats better, Limited Slip, Or Posi traction? and what Gear Ratio would you recommend. Please let me know what you think.

Gary S
07-14-2010, 10:12:22 PM
Posi-traction is just GMs name for a limited slip rear end. They are the same thing.

High Country Z
07-14-2010, 10:48:12 PM
I'm running 330 HP/4:11 ratio combo, it's ok around town, but a little to low for highway use. Better choice would be 3:73 rear.

80ZED28 EH
07-15-2010, 12:31:48 AM
Posi-traction is just GMs name for a limited slip rear end. They are the same thing.
Exactly! :bowtie:

z28rod
07-15-2010, 10:25:00 AM
limited slip and posi = same 3.42 for him and your 3.08's for you....

Juicer28
07-15-2010, 11:11:06 PM
Hi guys,, I did a test on the both Camaro's , I lifted both off the ground meaning the back tires, and below is what i found.

I lifted my 78 camaro off the ground on the rear, spun one tire forward, and the other tire went backwards,,

on the 80 with the Posi Rear 3.08 gears, we lifted it, and when pushing the tire forward on one side, causes the other side to turn the same way, not like my the current rear on my 78. so what does this mean? does the 80 with the 3.08 gears not Limited Slip?

How will this rear end do on Wet roads,, or like when it snows in TX, how will my traction be? My son is going to purchase a rear with 3.73 gears, and Posi,, meaning, that rear end will do like the current one on my 78 right now, and when you turn one tire forward the other will go backwards?

Can somebody please let me know what we have with what I said above.

Juice

Gary S
07-15-2010, 11:33:00 PM
It appears your 80 has posi. Since both tires turn the same direction, it is posi or there is a slim chance that it is a very bad condition open rear end with the spider gears seized up.
The 78 likely doesn't have posi. An open rear end will turn opposite directions when you turn one wheel. A totally worn out posi would do the same thing, but most likely the car just doesn't have posi.
The only way to know for sure is to open them up and see what is really inside them.
Either one will work on wet roads. Remember that probably 98% or so of the vehicles on the road have open rear ends, and we drive them every day.
I'm guessing that snow in TX is about as rare as a 100mph armadillo, so the odds of you driving it in snow much gets really slim.
The posi will have more traction in snow and rain, but unless you know how to drive a posi, you are also more likely to lose control of it on wet roads or snow.

Juicer28
07-16-2010, 03:09:19 AM
Well, I purchased the Posi rear end from a friend who sells Used camaro parts, and he checked it before sending it to me, I looked up our conversation in my email and I asked for a Posi, where both tires move at the same time, I wanted to build a camaro with a strong Rear end, and it has 3.08 gears,, I am pretty sure it is good, we have driven the car and the rear end is working fine, I spun the tires and two marks came out, Very strong,, so i doubt it is a messed up rear, My freind would never sell me a bad rear end. Also, how do I check if the fluid is correct in the rear, I have not driven it much, yet, And I would like to check it, how do I check the level? And make sure it is right.

and snow in TX have changed over the years,, we had 11 inches in my yard last winter, and so far, every winter, we get snow, and it appears to be getting worse over the years,, So Yes we have snow, but may not be every year. not sure why it has been for the last few.

I was told by someone, if I drove a posi end rear end where both tires are moving the car, then I would get stuck. I have never driven a Posi rear where both tires move,, can you tell me, what I need to know or concentrate on? I will be using this one,, very soon.

ronald66
07-16-2010, 04:42:06 AM
with an open rearend only one tire will lose traction, (unless you really get on it hard in the snow and rain).
with a posi rearend both tires will lose traction and you must be careful not to lose control of the rearend of your car..

z28rod
07-16-2010, 06:49:32 AM
An open rear end will turn opposite directions when you turn one wheel.ditto that !

cws455
07-16-2010, 10:57:55 AM
Posi-traction is just GMs name for a limited slip rear end. They are the same thing.


It always seems that somehow somewhere people started putting "open" and "limited slip" together like they are the same. I hear this a lot.

tom3
07-16-2010, 11:55:58 AM
To check the fluid, take out the fill plug and stick your finger in and down. Should contact the oil by the first knuckle of your finger. Sometimes the fluid will run out, good to go.

Juicer28
07-16-2010, 12:38:19 PM
Thank you Tom3, on how to check the fluid., Will take care of that today. And I will get my taste of using that Posi, I will drive very careful when raining, I will NOT get on the gas, much. I want to keep my Traction. I may end up taking that one out, and changing to Limited Slip, with 3.08 gears.. that may be my best option. But for now, I will install the posi (both tires pulling), and test it only when dry, for now. when the rain comes I may not drive it at all in fear of hitting a spot of rain that did not drain, and I find myself side ways.. Don't want to wreck my car.

80ZED28 EH
07-18-2010, 01:56:20 AM
And I will get my taste of using that Posi, I will drive very careful when raining, I will NOT get on the gas, much. I want to keep my Traction. I may end up taking that one out, and changing to Limited Slip, with 3.08 gears.. that may be my best option. But for now, I will install the posi (both tires pulling), and test it only when dry, for now. when the rain comes I may not drive it at all in fear of hitting a spot of rain that did not drain, and I find myself side ways.. Don't want to wreck my car.

I thought we all agreed that a limited-slip is the EXACT same thing as a posi-trac.?
Oh, and don't be fearful of losing control with a posi-trac in the rain, you won't notice any difference between an open rear end and a posi in the rain if you drive like you would with any other car. If you gun it going around corners and stuff then ya, you will, but if you just drive "normal" you won't have anything to "fear", so to speak. :rolleyes:

jasong
07-18-2010, 10:45:11 AM
I would go any higher than 3.73 for either car. It's really up to you though, depends on what type of driving you do. I put 3.55's in mine(see my pics under my homepage), but I have alot more torque than you to pull'em.

Cardinal
07-18-2010, 11:02:07 AM
Here's how a Eaton positive traction differential is supposed to work: when not under load (such as heavy acceleration) the clutches in it will let each rear wheel rotate independently of each other. When a load is applied to them, the torque of the wheels is transmitted to the cluch pack in the positive traction differential "stacking" them up effictively driving both wheels at near the same speed.

The biggest misconseption about a positive traction differential is that when you jack the car up, both wheels will rotate in the same direction. IF it is working correctly, they won't rotate in the same direction (acting line an open differential). THEE ONLY way (I've been able) to find out if a rear end has a posi differential is to take the cover off and look inside.