Time for a power-lok!!! They're the factory posi- track setup. Probably easiest to find a used one- with a '93 I believe you have a 70u rear axle, which is a 32-spline, so look for either a whole axle with a power-lok setup or just a used power-lok from another intercooled truck (I believe the use of the 70u as a rear axle began in the intercooled era- non-ic trucks ran a 70b with 35 spline shafts). I have power-loks in all 3 of my trucks and love them- only 1 of the trucks came with the option. I recently picked up a power-locked 70u for my crew cab and paid $100 for the complete axle- waaaay cheaper than any other locker option- i put the whole thing in my truck to avoid having to setup the gears and am good to go! As a non-ic truck, it originally had the 35-spline 70b, but the power-lok is way worth the sacrific of 3 splines!!! If you need to rebuild the power-lok (i.e. replace the clutches) the cheapest I've found the rebuild kit is through Jeff's Bronco Graveyard- at about $72 shipped. Street manners are superb, and power-loks go for a long time before needing to be rebuilt- my '90 with the 1974 W200 body is the only truck originally equipped with it, and it has 300K miles on the unit- there is no slip whatsoever!!! Hope this helps!
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'66 Dodge Crew Cab long bed on stretched 1990 Cummins W250/getrag 5spd. frame- 335k mi, 36" IROK's, 5" straight pipe, 3.54 gears w/ rear posi.... '90 Cummins W250 5 speed ('74 W200 body), 300k mi., 4.10 gears w/rear posi, Braden LU2 PTO winch