PontiacJim

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.

geeteeohguy

Great post. I've had 9 GTO's over the years. 6 of them came with "safe-t-track" limited slip, and 3 of them didn't. The ones that didn't were automatic cars, the ones that did were 4 speed cars. I have spun out more than once in the wild days of my youth. Not hard to do.

Groundczero

Interesting read, but no one put up quarter mile times, what are you guys thinking is fast, I know in High school (late 90's) if you were in the 13's you were moving, collage it was 12’s. Now better be running mid low 11 or 10, keep in mind these are street cars driven to track, on DR’s not even slicks.

ppurfield001

Bought my first GTO (a 1967 hardtop) in 1971. My Mom said it was too dangerous for a 20-year old but my Dad said "let him have a little fun." Mariner Turquoise with a white painted top. Once clocked at 105 MPH in upstate NY returning to college going up a hill. The cop took pity on me and gave me a ticket for 24 MPH over the 70 MPH sipped limit (I.e., no reckless driving ticket in addition to speeding ticket). Learned to love American muscle with that car..........

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PontiacJim

1964 GTO - Car & Driver: 1/4 mile - 13.1@115mph tri-power 4sp/3.90 gear Note: engine prepped by Royal Pontiac
1964 GTO - Car Life: 1/4 mile - 14.8@99mph tri-power 4sp/3.23 gear
1965 GTO - Car Life: 1/4 mile - 14.5@100mph tri-power 4sp/3.90 posi gear
1966 GTO - Autocar: 1/4 mile - 15.3@90mph tri-power 2sp auto/3.55 posi
1967 GTO - Car Life: 1/4 mile - 13.9@102.8 4bbl 4sp/4.33 posi gear Note: this was a Ram Air car
1968 GTO 428CI - Car & Driver: 1/4 mile - 13.8@104 4bbl TH400/3.55 posi gear Note: engine swap/prepped by Royal Pontiac
1968 GTO - Car Life: 1/4 mile - 14.53@99.7 4bbl 4sp/3.90 posi gear Note: this was a Ram Air car
1970 GTO Judge - Road Test - 1/4 mile 14.77@94.42 4bbl 4sp/3.55 posi gear Note: this was with the standard Ram Air III engine
1970 GTO 455CI - Car & Driver - 1/4 mile 15.0@96.5 4bbl 4sp/3.31 non posi gear

geeteeohguy

The 1964 GTO in the Car & Driver test was powered by a 421 engine. It was one of two "Ringer" cars used in several high profile tests of the day. Both were fitted with 421" engines and passed off as 389's.

PontiacJim

I think I recall hearing about that, but did not know what car/year. The 1/4 mile time seemed to be way better than what I posted for most "stock" 1/4 mile times. Even with these "stocK" time figures, all I knew was by the seat of my pants, and if all I had was a car capable of mid 14's, it still felt damn fast and beat a lot of other "fast" cars of the day! I think it really boils down to not 1/4 times from a standing stop, but passing speeds and the "rolling race" when you met another contender. I guess its all about perception and the thrill of experience. GTO-Gas Tires & Oil as we used to say.

Groundczero

Ok so they were fast compared to what ever else was out on the street, but not realy fast. But I would not brag about a roll race that is what we laugh at all the ricers for doing.

geeteeohguy

I respectfully disagree, Groundczero. They WERE really fast, at the time. Not compared to today's monster cars, but back then, pretty well untouchable. And I'm talking from the time they were new until the early '90's, when muscle re-appeared. I remember driving a brand new 1987 Buick Grand National and being impressed that it felt as fast/quick as my '65 GTO. A 14 second car WAS a fast car back then, and a 12 or 13 second car was a real street sweeper. I had a '66 GTO that did mid 13's back then, and that car was a terror.

BearGFR

And there was always potential there for more. My 69 GTO today, at 4000 lbs running weight running the engine it was born with, TH400, 3.50 rear gears is an honest 11-second street car on drag radials and 93 octane pump gas. That's running in 'drive' with the upshifts happening around 4900 rpm. Yes, I've "enhanced" the engine with some modern parts but it's still naturally aspirated, running a Quadrajet, no bottle, nothing super-fancy.

Just this morning I was on my way to a doctor appointment, sitting at a traffic light just prior to the on ramp. In my mirror I saw a guy in a black late model Camaro cross 3 lanes of traffic just so he could get behind me. I admit, once the light turned and I was about halfway down the on ramp, I took it to about half-throttle and watched him get really small, really quickly. I back out of it around 85 and let it fall back down to the limit. He pulled up beside me and wanted to play, but I didn't take the bait - there was no need - so he pulled away. It was funny because I'm sure he was thinking he'd just "showed me", when the reality was that I knew he just wasn't worth the effort.

Bear

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BearGFR
Garland, TEXAS