All rear drive cars have a differential assembly to allow the drive wheels to turn at different speeds when necessary. When turning a corner, the outside wheel speeds up while the inside wheel slows down. Although this allows smooth turning, it presents a problem if one of the wheels is on a slick surface. The wheel on the slick spot spins while the other slows or stops altogether. The result is no movement of the vehicle. In about 1957, the auto designers incorporated two clutch-like devices into the rear axle assembly (one on each axle) as an option. It was called a “limited slip differential”. Of course, the advertising people had to get some mileage out of this new development so they came up with unique names for each Make. Chevy was called Posi-Trac, Pontiac was Safe-T-Track, MOPAR was Sure-Grip, Ford was Equal-Lock, etc., but they are all limited slip differentials and they all function similarly. Read more

“Pontiac Intake Manifold Tests on a well tuned stock type 455 in a 3900# vehicle.”

Note; The following summary of intake manifold tests was prepared prior to the formal article in “High Performance Pontiac” magazine published several years ago.

After testing six different manifolds, I have began to understand the Aftermarket’s definition of “High Performance”. It generally means a series of engine modifications that allows/causes the engine to run at much higher RPM. It does not necessarily mean increased performance. Read more

Some of the technical information we read in car magazines is correct, but occasionally a real boner is printed. Recently, one of the better known magazines published tips for making our Pontiacs run better. One of the tips was to install colder heat range spark plugs for a substantial performance gain. While replacing defective of incorrect plugs with new ones of any heat range might well help performance, using colder plugs as compared to the correct heat range will not increase performance. Read more

Following is a tech. question and answer about speedometer accuracy.

Dear Tech guy,

I changed the rear axle gear in my Pontiac from a 3.08 to a 3.42. The car has a T-400. It seems to run better, but the speedometer reads about 6 MPH fast. What is the easiest way to fix it?

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