Join Date: Dec 2012
Location: Gastonia, NC - Born & raised in Connecticut - 31 years
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Today's remembrance is of "Posi-traction", or the limited slip rear end. I saw a U-tube video of a GTO burn out and one of the comments was, "only one tire was smoking, I thought all GTO's had posi-traction." No, most of them did not. Of the 3 GTO's I drove, none had posi, not even my 3.90 factory geared '67. Posi was an option that most GTO's did not have. I suspect like today's cars, you bought off the dealer lot what they had in stock, and extra options meant added price, and special orders took more time to deliver.
Here are a few road tests found in magazines of the day. Of the 1966 GTO with powerglide/3.23 gearing: "Such is the cars tremendous power that the back end can be popped loose almost anywhere. Despite the limited slip diff, the car fishtailed right up to 80 and 90 mph under full acceleration." Of a 1968 Ram Air GTO with 4 sp/3.90 posi gearing: "Driving the GTO on wet roads with this deep geared axle was thrilling. Rear tire breakaway could be provoked by a slight jab at the accelerator, sending the car into a minor skid that usually used up more than one lane of space." And how about a Royal Pontiac 428 CI in a 1968 GTO with auto/3.55 posi gearing: "In the hands of an inexperienced or irresponsible driver the 428 GTO would be as dangerous as a basket of hair-trigger hand grenades. Too much throttle at the wrong time will spin the car, or send it rocketing off the road into the farmer's field. You can light up the cars' tires like it was an AA-fueler anytime the notion seizes your fancy."
I love these road test articles as they are fairly true. They also speak of handling that was not the best and understeer. Couple the torque the Pontiac engine produces with just adequate handling, and it does not take long to get into trouble, especially with a POSI rear axle. I can speak from experience as I have driven other cars with posi. If you have the torque of a Pontiac engine, and the road is anything less than dry, it takes very little to get your car out of control - and this was based on stock factory horsepower and not those of us who build more HP on that. Many "muscle cars" of the day found themselves in the "farmer's field", wrapped around a tree or telephone pole, rolled over, or simply crashed. I used to frequent the junk yards to pic parts off cars to resell at swap meets. Saw many a "muscle car" destroyed from just an incident. Some I figured the drivers were OK, others were mangled where you wondered if they lived.
And this is not entirely limited to a car having a posi rear end, I can attest to GTO's and other motorhead cars I owned that given enough horsepower/torque in less than ideal road conditions, you may find yourself sideways. It was always cool when I planned to do it and no other cars were around. Not so cool when I was just standing on the gas when the direction of the car took on a mind of its own! I'm talking "pucker factor 10" here. Many first time Pontiac owners today are not aware of the trouble you can get into real quick with simply the stock factory torque of a Pontiac -until you experience first hand at a time your wish you had not. The old muscle cars took some skill, and sometimes luck, to keep you out of danger or endangering others. Now I am not writing this to scare anyone or sound like a "goody two-shoes", because I still like to smoke tires and go sideways, but even when I know what I want to do it doesn't take a second for the car to do what it wants to do - so just be aware and expect the unexpected from your car.
So, my opinion on a posi rear is that they are great for straight line acceleration on a dry road. Otherwise, I like a single track for the everyday driver - you can light up a tire and it is much more controllable(typically). If you have one, be cautious on icy, snowy, wet, damp, sandy, bumpy, and leaf covered stretches of road and don't nail the gas when in a curve. My experience with a posi rear is that it always kicks out to the right on you. If this happens at a bad time, your pride and joy may become a parts donor like so many other "muscle cars" I have seen over the years. Upgrading your suspension, brakes, and tires, is the smart way to go if you gotta have the posi.