700r4 swap help

[cwp2]

Hello, I am thinking of swapping a 700r4 into my 83 wagon. It currently has 350c. How do I make sure the speedo is still accurate? Thanks

 

[Phoenyx]

I would like to know the same thing. In my case TH250 (weaker version of the TH350), is there any chance I can just swap the speedo gears over?

 

[Longroof79]

Check this out. There's other formulas on the web as well.

http://www.transmissioncenter.net/speed ... ____va.htm

 

[84cutspreme]

I had same problem, I checked after swap with GPS on highway @ constant speed and surprisingly I was most 2mph off lol, so I stopped worrying about it.