Posted by Tim Holloway [173.245.52.94] on Monday, September 24, 2018 at 19:47:04 :
So when we last left this, the pinion was known to be correct for my tire size and differential gearing, and a second speedometer was showing the exact same 20% slow reading. Only variable left was the gear inside the transfer case that drives the pinion. I looked through some parts and found a gear which was the correct one for my situation. I dug into the transfer case, fortunately don't have to drop the case or even drain it down, but still a lot to remove to get to the gear. Checked the gear I took out and the part number was illegible so I installed the known correct gear. Got everything put back together and took a drive through a radar that flashes your speed. I approached it with the speedometer dead on 40 and the radar flashed up 48! Damn, and double damn! Now ALL components are known to be correct, yet I have changed absolutely nothing! OK, next step would be a pinion with less teth to spin the cable faster. The one I had was 16 teeth, as Chris Case had suggested, one with 14 should work well. He also suggested checking a 2wd transmission for the pinion. I don't have many 2wd trannys but had one from a 65 D100. I pulled the pinion and low and behold, 14 teeth! Put the W-100 back on the lift and swapped the pinion out. Back to the radar and this time had the needle on the dot between 40 and 50 (45). The radar pops up right at 45!! Whoo hoo!
Not sure why, but problem solved.
Thanks for the help,
Tim
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