the test was where you have one person hold the left wheel preloaded against the drive line and the other person spind the right wheel in the oppisite direction to try to let the unit unlock. It took a good jerk on the right wheel to get it to work but it did work like a champ. I bought the expensive one and it is pretty smooth. I'm pleased with the purchase and can't wait to get to the strip with it now!
Don-Too bad that Richmond shows the Rivs as a 8.2-stupid mistake. As you found, not even close to the big car monster. These rears rarely give trouble, but nobody is making the power you are either. FWIW-this ring and pinion are used in the Rivs-cats 225s for many years up to 1970. There are no aftermarket gears available and nos is rare to find. The cars used the dropout rear thru '65 and then with the integral carrier/banjo starting in '66. Since the earlier rears are easy to pull and swap, you might grab a few from the boneyards(spares) I'd go for an Electra with no trailer hitch as good candidates. Most will be 3.07 ratio, with some 3.23 2.93 2.78 and a few 3.42 out there. Clutch type posi seem to be in 10-20% of the cars-good luck.
Power trax The Powertrax listed for the '63 - '70 Rivieras is incorrect, they do not have one to fit and it is not an 8.2. The buick '63 - '70 9 3/8 rears are big and strong, stronger then the ford other than there are no after market parts, nothing. I wasted two 9 3/8 rears, spiders siezed on the shaft and sheared the roll pin then all hell breaks loose. Searched long and hard for after market tracklok or something to eliminate the spider gears, but there is nothing really available now. I had Richmond gear engineering look and all kinds of options and combinations and nothing would fit. I ended up narrowing and putting a ford truck rearend into my 65 Riv.
