Differential Gear Ratio

[texasmike]

I jacked up the drive wheel and turned the tire twice and got 2-3/4 turns on the drive shaft so it looks like I have 2.73 gears. I'm going to switch to 3.42 gears so can someone tell me what the 8.5 and 8.6 designation means and how I can determine which I have. I frequently break loose the drive tire without trying (not enough weight in the long bed, I guess) so I'm considering installing posi traction while I have it apart. Any recommendations on a good unit?

 

[Redfish]

I cannot help you on the designation but I will say that you should definitely feel some improvement if you go from 2.73 to 3.42 gears. I remember driving and riding in several '83 and '84 trucks very similar to yours and it was difficult to break the tires of that era loose with the 160HP 305s of that era. My Mom's '84 Blazer had 3.08s and it would NOT spin a tire on dry pavement even after we added headers and a better cam. Lower gears would have really helped.

I personally like the idea of the factory original limited slip units. They worked pretty well and were not bad to drive around on the street, they didn't lock up and make a bunch of noise during regular driving.

 

[texasmike]

Do you know if the factory units are still available (part number) and how many splines (28 or 30) my axle shaft might have? I have a suspicion the 8 numbers have to do with the ring gear. Thanks for your reply.

 

[Snoots]

When you change them be sure to wear black. You'll be mourning your lost MPG.

 

[Turbo4whl]

...... so I'm considering installing posi traction while I have it apart. Any recommendations on a good unit?

An Eaton True Trac is a good choice for a street truck.

Do you know if the factory units are still available (part number) and how many splines (28 or 30) my axle shaft might have? I have a suspicion the 8 numbers have to do with the ring gear. Thanks for your reply.

The parts are available, buying all of them will be more than a complete aftermarket diff. Axles are 28 spline.

I personally like the idea of the factory original limited slip units. They worked pretty well and were not bad to drive around on the street, they didn't lock up and make a bunch of noise during regular driving.

The Eaton Governloc was designed for mom and pop America. Not good with big tires or lots of hard driving that some of us may do. Yes driven sanely it will last.