I am having a problem with rear end selection. As I understand, I guess my rear end is a 8 3/4. I took it out of a 57 4dr wagon years ago and saved it. I never needed it until I found my Del Rio 2 dr wagon (rear was already gone). My problem is I am going with about 300 horse 390 and this rear is a 4.11. I want a comparable ratio so I can at least drive it a 100 miles without breaking everything. I have a 68 Galaxie with the ratio I want and a posi to kick. Can I take out the 3rd member and put it in my 57 rear assembly? I am also not sure of axle spline, which to use, if I have to have the one in the Galaxie shortened etc? Poor Boy just wants to drive my 57 wagon. Thanks for any help.
ok heres the story, all ford third memebers from 1957 til whenever are all considered 9" tho 57and 58 do have a small ring gear. you can put any 9" ring gear in a 57-58 third memeber but alil trimming may be required. my 57 third member needed alil grinding for a 3:55 to be installed but no big deal. now on to axels. your 57 will be 28 spline and i bet your 68 are to. i'd say , slap your 68 third memeber in your 57 housing and go.
I second that. Mines had everything from 3:0's to 4:88's and they all fit fine. If that 68 isn't a
H.P. model it'll be 28 spline also.
Thanks for all the info. I have heard strange stories about the rears being so different. I figured the best way to know for sure is to ask here, where the info is reliable.