Well, with the necessary tools I was able to accomplish this operation in under 30min in a hotel parking lot (as so much of my repair work seems to be done nowadays ). Cost: <$25
Small plastic cup
Shop towels and nitrile gloves help too
3/8" drive socket wrench
12mm socket for 3/8" drive socket wrench
assortment of picks and punches
pliers (preferably of the locking type)
Items to purchase (P/Ns listed above):
24 or 22 tothed speedo gear depending on tire size
O-rings (if needed)
1. Back up the rear left wheel onto something or jack it up in that corner. This will help the gear oil in the transfer case drain away from the speedo assembly and won't create such a mess.
2. Unscrew the speedo cable sleeve from the speedo casing.
3. Remove the bolt for the retaining clip and pull out the speedo assembly. Have your plastic cup ready to catch any gear oil that will drain out. Make sure the area around the casing is clean and free of debris.
Once the speedo assembly is out...
4. Using a punch, drive out the spring pin holding the gear in place. This is the most difficult part of the operation. I accidentally chipped a piece of the casing off while doing this, but it actually made it easier to remove the pin. The spring pin can be reused if it is not too damaged upon removal. I got 3 for >$1, so I used a new one. Once that's done, simply pull out the old gear.
5. If they're worn (chances are they're not) replace the o-rings on the inner and outer casing. The one on the outside is pretty straight forward. The inner o-ring is a PITA. The old one is easily enough removed with a pick. Once that's done, you'll probably find it in perfect condition and kick yourself for removing it. Anyway - you've got a new one, so why not replace it (Hehe, I wish I could see you struggle to get the new one in place). Luckily, our evolved monkey brains allow us to come up with creative solutions to problems. Here's how I did it: fumble around until you can get part of the o-ring into the channel. Hold it there with a large punch from one end. From the other end take a smaller punch and roll it around until it pops into place. Any remaining bulge should be easily knocked into the channel. Good luck!
6. Generously coat the inside of the casing with gear oil as well as the shaft of the new speedo gear. Push the new speedo gear into place on the casing and drive in the spring pin to hold it in place. Voila!
7. Line up the mating mark on the tranfer case with the new gear size listed on the outside of the speedo casing and press it into place. It's a good idea to coat the outer o-ring with gear oil to help it slide.
8. Replace the clip and bolt it down. Replace the few ounces of oil you lost if you feel like it. Place the speedo cable into the slotted shaft of the new speedo gear. Screw the speedo sleeve back into place. Clean up your mess and drive away.
I tested the accuracy of the new gear while driving behind another vehicle while communicating on a cell phone. At 75mph displayed on my speedometer guage, the vehicle I was trailing was doing exactly 75mph.
So, it looks like this method will work! I'd be eager to see how well the 22-toothed gear works with 33" tires!
I'd also like to give credit where credit is due. Thanks Eddy!
Quote: The speedo driven gear is changeable. Remove the driven gear housing (where the speedo cable attaches) from the drivers rear of the transfer case (one bolt and retainer yoke) after removing the cable. The driven gear and shaft are retained in the housing by a driven roll pin thru the housing that engages a groove in the driven gear shaft. Drive out the roll pin and the shaft and gear come out of the housing. Mistu will sell you a new gear with almost any number of teeth. The one from the Starion with the 3.45 diff is about right for a 15% difference (23 teeth vs. 26). A 4wd 86/earlier truck with the 3.91 would serve for a smaller correction than 15%.
The speedo itself can be recalibrated with a magnetic tool at any good speedo shop (call your local law enforcement and ask them where they get their speedos "certified".
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