In the continuing saga of the speedometer reading incorrectly on the IROC I received some answers today.
I took the differential cover off. Thankfully the ring gear had the teeth numbers etched into it, 13:42. What does that mean? That means there are 13 teeth on the pinion gear, 42 on the ring gear. If you divide the teeth on the ring gear by the teeth on the pinion gear, you get the ratio. In this case, it equals 3.23 which is a widely used ratio.
From that, I now know what gears my transmission needs in order to display the speed traveled correctly thanks to this post on the 3rd gen forums. I went ahead and ordered a 38 tooth (blue) driven, and 15 tooth (gray) drive gears from eBay. These gears are commonly known by their colors.
I was a little apprehensive about taking the cover off, as it’s something I’ve never had to do before on a vehicle. I had a plan however. I purchased a different cover that has a fill and drain plug, the OEM one does not. The Dana 44 axles on my Jeep have them.
This differential cover is sold all over under different name brands, but all of them are made by the same place, LPW Racing Products. I purchased it directly from them through, you guessed it an auction on eBay. Besides having fill & drain plugs, it also has a girdle to help strengthen the already “weak” 10 bolt rear end this car has.
I also received the gauge clusters I had purchased from eBay, and was able to successfully remove the needle on the speedometer from one of them. I then used that needle and shaft from the donor cluster to rebuild my original.
I still need to purchase bulbs for my cluster. Not knowing how long they have been in there, but knowing how hard it is to remove the cluster – I want to replace them all. 1 of them is missing/broken.
In other news, I have removed the headliner with the help of my daughter. It definitely went better with the help of someone than had I attempted to do it alone.
Last night, I took all of the old material and foam off. The backer is quite fragile, some small spots came off with the material or while I was taking the foam off with a combination of a vacuum and sponge.
By the end of the weekend, I hope to have the car back together. When I receive the gears for the transmission I plan on having a shop change them. I might then have to remove the cluster again if it requires more calibration.
Whew. So much going on in such little time.