Ron94150

just swapped in 3.73's from 3.08's in my 94 f150 2wd 300 auto. I'm guessing I need to recalibrate speedo. Any idea on what number to use? I have 225/70/15 tires. Thanks.

Ron94150

Never mind. Just found out gear change doesn't effect speedometer with the vss set up. Makes sense now that I think about it.

mattbarron94

Idk if this is the same or not, but when I went from 28' tires to 31' tires my speedo wasn't affected at all. I was thinking about swapping my 3.08's to 3.73's, good to know its not gonna need adjustment. How hard was it to swap gears?

Ron94150

There are plenty of great write ups on 8.8 gear swaps. A quick google search and you can find everything you need to know. You can also YouTube it. It's not rocket science, but if your not mechanically minded, I would not recommend trying it. There's lots of little things and some specialty tools. you can get around some of these tools, but you will need a dial read inch pound torque wrench, micrometer with magnetic base, and at least a cheap set of dial calipers. I did not have a companion flange holding tool, pinion depth measuring tool, or a press. I got truck out and took it down the road. Sounds good and quiet up to 60mph. Still don't have bed on, so no tail lights. I'll know more when I get it back on highway.

Ron94150

If you changed tire size, your speedometer was most definitely effected. The vss reads off the tone ring, which is on the carrier beside ring gear. When you change tire size, it effects how many revolutions it makes, changing ring and pinion does not. Changing ring and pinion only effect how many rpms your motor is turning to turn the tone ring. Ring and pinion would effect speedometer if you are running a earlier model that had a speedometer cable running to the tailshaft of transmission.

Crownman

Here's a vid of a gear swap on a Mustang. We have the same rear end.

Crownman

Here's a vid of a gear swap on a Mustang. We have the same rear end. The only difference is that we have a toothed ring between the ring gear and the diff that the VSS reads for the speedometer.

mattbarron94

All I know is that I pass the same police speed detector every day to work for the past 2 years, and it reads 45 on the speedo and 45 on the speed detector everytime.