What's the size of the hole on the transmission where the speedometer pinion goes. The transmission I have is leaking from it, and I'll just like to plug it up.

Why not simply REPLACE the O ring?

Well, I've done that, but it still leaks. I thought I'll just plug it since there's no speed-o cable going to it anyway.

According to Carl Munroe's 727 book, a 1-49/64" freeze plug fits.

x2 on the freeze-plug fix.

Also consider looking in a wrecking yard. SOME 4wd Dodge trucks had a blank plug in that hole, since the speedo actually connects to the transfer case.

did you change the small seal inside the speedo housing on the gear pinion shaft along with the big o-ring?

there are 2 seals for it,if you clock the housing so the gear is not spinning,it would help stop it from wearing and leaking.

the freeze plug will work fine also.

a cheap rubber core plug would be eazy and fast to remove if you went back to a working speedo.

Thanks for the info. I appreciate your help.

Thanks to everybody for your input. I went to advance auto parts and they didn't have a freeze plug to fit. Seeing how 1-49/64 is 1/64 bigger than 1-3/4 I got one of the rubber freeze plug that measured 1-3/4 to 1-7/8 for $3.99. It went right in, tighten the nut and walla problem fixed.