QuestionQUESTION: I put a 1990 s-10 blazer 4by4 rear in my street rod.it is 7 5/8 ring gear.28 spline axel.i want to put a posi unit in it.the one in it spins both tires but has alot of slack.are there any units that will fit my housing.thanks
ANSWER: Eaton makes them, and Detroit locker has one, too. Check Summit or PAW (this is generally referred to as a 7.5 rear end). If you already have a posi which is just worn out, you can buy the parts to rebuild it from the dealer (just clutches, really). You might want to try draining the gear lube and replacing with a GL-6 rated lube and a bottle of GM Positraction additive. You have to use the additive if you want the posi to work properly, and it has to be refreshed every 10,000 miles or so.
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QUESTION: i have a posi unit out of a camaro 7 1/2 stamped on it.the one in it now has 7 5/8 on it.it does not have a cluch pack in it.i was told it was a ratach posi.never heard of this.will the camaro posi fit in this housing.if so it seems to me i would have to get 26 spline axels from moser to fit this unit.thanks
Answer That would work, but you would have to get axles with the appropriate spline count. I don't know why, but GM made both a 26 and a 28 spline setup in the 7.5 (7-5/8) rear end. Cost is the usual reason for GM doing things like that, but I find it hard to believe that leaving two splines off saved them any money (of course, when you make several million of something, every little bit helps). The differential you have sounds like a ratcheting differential, the most famous of the type being the Detroit Locker. These have disadvantages in the way they lock and unlock, sometimes leaving stripes that look like Morse code. I don't know if I'd invest in two brand-new axles just to use that differential. If you are running a V8, and are thinking of more power in the future, you might want to go ahead and save up for a 8.5 or 8.8 ten-bolt rear. S10s did use the bigger rear with the larger V6, so you could probably find one without a whole lot of fuss. Of course, if you're serious about speed, you are going to save up for a 9-inch Ford unit. If you're happy with your rear, just unhappy with the way it delivers power to the road, you might want to consider Eaton's helical gear differential. Basically a Torsen™ differential built under license, it is the bee's knees when it comes to putting all of the power down and still driving nice on the street.
