Change 8.5 rear end ratio from 3.42 to 3.73 or 3.91

With a Gear Vendors,I would run a 3:91.
The stock 28-spline shafts can take some abuse,but it all depends on how hard you hit them. Obvious things like a trans brake or stick will throw more blunt force at them and there for more stress with not as much power needed. If it is anything running 11:80’s or quicker,I just upgrade it to 30-spline parts and be done. As far as posi units,I would just do a Tru Trac helical unit. ALL of the clutch style units come out of the box with junk clutches,not like the old ones from the 70’s and 80’s. By the time you install good clutches and tune the unit,you might as well just get a Tru Trac. The stock yoke is fine. A stock cover is fine,if you are wanting to keep the stock appearance. I’ve gone well into the 10’s with a stock cover and have found no signs of stress or fatigue. That also has stock cap bolts. ARP studs are an option and will be hidden.

 

I use wavetrac posi units in my high hp cars. Fantastic units and lifetime warranty.

 

Sub'd......

 

4.10 for sure

 

So, if I go with the Tru Trac, what's involved in changing from the Eaton Posi to Tru Trac? And, where's the best place to buy one?

 

It's been suggested that I consider just replacing the current Eaton Limited Slip carrier with a new unit rather than overhauling the current Eaton unit. Is this a smarter and/or lower cost option? The current unit is Eaton p/n 19557-1 manufactured Nov. 1997. Here it is:

 

What's involved, its just like replacing any other carrier. Just put the new bearing on it bolt right g gear on and have it setup

 

If you had to choose between that Eaton unit and a new one,I would just keep that one and put good clutches in it. With the right pieces,it doesn’t even need the spring pack.
The Tru Trac install is no different than any other unit.

 

My son runs 3:90 gears in his ‘71 GSX with a 4,000 stall Switch Pitch transmission and the Gear Vender overdrive unit. His rear tires are 28” tall. It makes a nice combination for street driving and highway cruising.

I run 3:90 gears in my ‘70 GS 455 with a M22 4-speed and 29” tall tires.

 

I run 26.5 in. MT drag radials almost all the time so the rear tires match the fronts like original. I show much more than race.