I know this issue has come up on the forum before, but I have tried some of the solutions and thought processes to remedy it and I'm still unsure. I am working on correcting the speedometer. My TJ has 3.07 gears and 32-inch tires. I have verified this ratio by checking the tags and turning the tire and watching the driveshaft spin.
I recently swapped the (I assume original) 29 tooth speedo gear for a 26 tooth gear as per the chart posted on this site. I got the gear from eBay and verified that it has 26 teeth. With the 29 tooth gear and 32-inch tires, the Jeep was around 5 to 6 mph fast compared to actual speed. Now, with the 26 tooth gear and 32-inch tires, the Jeep is 9 to 10 mph fast. I went for an 8.5 mile trip (according to the GPS app) and the trip odometer on the Jeep was off by about 0.15 miles.
Comparing ratios, the swap I did doesn't seem to make sense. For example (based on the first setup I had): 30 mph (Speedometer reading) / 25 mph (actual speed) = 1.2... 1.2 x 29 (original tooth count) = 34.8. This would mean I'd want a 35 tooth gear.
Does anybody have any idea what could be going on? Am I missing something here? I'm planning to swap to 4.10s when I locate the axles, so maybe it's not even worth chasing down right now.
Thanks
I recently swapped the (I assume original) 29 tooth speedo gear for a 26 tooth gear as per the chart posted on this site. I got the gear from eBay and verified that it has 26 teeth. With the 29 tooth gear and 32-inch tires, the Jeep was around 5 to 6 mph fast compared to actual speed. Now, with the 26 tooth gear and 32-inch tires, the Jeep is 9 to 10 mph fast. I went for an 8.5 mile trip (according to the GPS app) and the trip odometer on the Jeep was off by about 0.15 miles.
Comparing ratios, the swap I did doesn't seem to make sense. For example (based on the first setup I had): 30 mph (Speedometer reading) / 25 mph (actual speed) = 1.2... 1.2 x 29 (original tooth count) = 34.8. This would mean I'd want a 35 tooth gear.
Does anybody have any idea what could be going on? Am I missing something here? I'm planning to swap to 4.10s when I locate the axles, so maybe it's not even worth chasing down right now.
Thanks