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Tech Question
Rojohn Soriano, Puyallup, WA, 1972 Dodge Challenger 318
Hello again. Thanks very much for helping me out with the ignition switch problem I recently had on my Challenger. As always, you hit the nail on the head! 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 used gear and pinion I got on eBay) and replacing the open rear of my 8 3/4 differential (489 case) with a Sure Grip unit. I was reading the article you did in the Feb. 1994 edition of MA where you did a similar swap on the Resto Runner, less the gear ratio swap. In the article, it indicated that as long as you didn't contemplate a gear ratio swap, installing a Sure Grip unit is a relatively simple task. My question is what additional steps or procedures must I take if I planned to do both swaps at the same time? How difficult of a task would this be? Is it something that could be feasibly done by a backyard mechanic such as myself? As always, I appreciate any assistance you can provide!
RoJo-
The trickiest part is setting the pinion depth. You can definitely do it yourself, but take your time. You will need a bearing kit with an assortment of spacers and a depth measurement tool. Places like Randy's and Ratech have these 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 only realistic way is to use a factory pinion setter kit, which you may be able to borrow from a local dealer ($20 in the service manager's palm can do wonders!)
There is a way to do this and come close to ideal without the tool, the usual "gas station mechanic's" approach is to re-use whichever spacer you find in there now. To me, this is a hassle since it means pressing off the old bearing. The accuracy of this procedure can be improved two ways: (1) be sure the new bearing is the same brand as the old one, and (2) compare the numbers written (in white paint) on the pinion head. E.G., if the one in the car now is marked "+2", and the new one is marked "-3", you'd need a spacer 0.005" thicker than what's in there now.
Using either method, confirm your work by LOOKING at the pattern. Gear marking compound is included in all the kits. If the pattern is wrong the FSM 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 the bearing you'll actually be using.
You should also be forewarned that getting used gears to be 100% quiet is not always possible, even if the gears are perfect. To a certain extent, it's a crapshoot. (This does not necessarily have a large negative influence on their longevity, however.)
You will DEFINITELY need a FSM, get a print one from Year One, or a CD-rom from www.moparmanuals.com
Rick
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