ok so i have ruled my speedometer problums down to the gear in the extension housing.
i belive my 77 f350 has a 4 speed with a very low first gear. I jacked up the truck and spun the drivshaft and found the gear in the extension house to be egg shaped and missing a chunk.
so does any one have a picture of this gear. or the part numbers for it.
Were would the id tag be on the tranny I cant seem to find the one on mine.

 

Check your trans agains pics here. Look at the BW T18, T19 and the NP435. Your trans will have numbers cast into the sides as well, which will help determine T18/19.

Is your first gear synchro? If so, T19.

Pics here:

http://www.motivegear.com/tech_info/...nny_guide.html

Now that same site has blow ups of all the trans. Just below the pic of the gears and gaskets, click on 'Download our manual transmission....':

http://www.motivegear.com/pages/tran...ansmission.htm

FTE partsguy might be able to help with the part once you id the trans--note he is now 'partsguyed':

http://www.trademotion.com/partlocat...?siteid=214072

 

just by looking at the picture mine looks very close to the the new processs 435.