Tech Question
Rojohn Soriano, Puyallup, WA, 1972 Dodge Challenger 318
Hello again. Thanks very much for helping me out with the ignition switchproblem I recently had on my Challenger. As always, you hit the nail on thehead! At any rate, I have another issue that I’d like to get your $0.02.I’m planning on doing a gear ratio swap (2.76 to 3.23, using a good usedgear and pinion I got on eBay) and replacing the open rear of my 8 3/4differential (489 case) with a Sure Grip unit. I was reading the articleyou did in the Feb. 1994 edition of MA where you did a similar swap on theResto Runner, less the gear ratio swap. In the article, it indicated thatas long as you didn’t contemplate a gear ratio swap, installing a Sure Gripunit is a relatively simple task. My question is what additional steps orprocedures must I take if I planned to do both swaps at the same time? Howdifficult of a task would this be? Is it something that could be feasiblydone by a backyard mechanic such as myself? As always, I appreciate anyassistance you can provide!
RoJo-
The trickiest part is setting the pinion depth. You can definitely do ityourself, but take your time. You will need a bearing kit with an assortmentof spacers and a depth measurement tool. Places like Randy’s and Ratech havethese cheaply, but, since 3.23’s are not available in the aftermarket,you’ll be using NOS or, as you indicated, used factory gears, so the onlyrealistic way is to use a factory pinion setter kit, which you may be ableto borrow from a local dealer ($20 in the service manager’s palm can dowonders!)
There is a way to do this and come close to ideal without the tool, theusual “gas station mechanic’s” approach is to re-use whichever spacer youfind in there now. To me, this is a hassle since it means pressing off theold bearing. The accuracy of this procedure can be improved two ways: (1) besure the new bearing is the same brand as the old one, and (2) compare thenumbers written (in white paint) on the pinion head. E.G., if the one in thecar now is marked “+2”, and the new one is marked “-3″, you’d need a spacer0.005” thicker than what’s in there now.
Using either method, confirm your work by LOOKING at the pattern. Gearmarking compound is included in all the kits. If the pattern is wrong theFSM will explain the fix. Sometimes this means pressing off the bearing -usually destroying it – and pressing on a new one with the “revised” spacer.That’s why the factory tool is so cool – it makes the measurement with thebearing you’ll actually be using.
You should also be forewarned that getting used gears to be 100% quiet isnot always possible, even if the gears are perfect. To a certain extent,it’s a crapshoot. (This does not necessarily have a large negative influenceon their longevity, however.)
You will DEFINITELY need a FSM, get a print one from Year One, or a CD-romfrom www.moparmanuals.com
Rick
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