ford those with the 8" open diff

[mustangmike6996 34]

who upgraded to a trac-loc/posi etc? I wont do a spool/mini spool. I really dont want to replace the whole rear end with an 8.8 or 9"

 

I have seen some posi units for 250-800 depending on if you get the 3rd member setup or just a trac loc unit or trac loc and gear set.

 

 

Just wanted some guidance before purchasing.

[SM69Mach 68]

My bother has a 8" in his 68 vert and didn't want to spend the money for the 9" upgrade either as it really wasn't needed power wise. He ended up buying the whole 3rd member with posi unit and new gears already installed and basically just swapped out his old one for the new in a couple of hours. Was a bit easier of a swap and the gears were already set up properly so no worries there.

[mustangmike6996 34]

I have set up 8/9 inch third members before so any of the paths would be fine for me. I was asking more based on brand/cost/quality. Are there some brands to stay away from or some that are cost effective with decent quality?

[stangs-R-me 121]

who upgraded to a trac-loc/posi etc? I wont do a spool/mini spool. I really dont want to replace the whole rear end with an 8.8 or 9"

 

I have seen some posi units for 250-800 depending on if you get the 3rd member setup or just a trac loc unit or trac loc and gear set.

 

 

Just wanted some guidance before purchasing.

 

Is your car an original Mach 1 or GT ... or originally built with a 351W or bigger ?? If so, it should have had a 9" in it from the factory.

 

Doug

[mustangmike6996 34]

not to my knowledge. It started life as a 302 auto drum/drum car. I wasn't aware they designated them as GTs in 69.

[rwcstang 201]

it sucks to have an open 8" behind my stroker...:( I've been debating to go with that ebay seller that sells posi 8" that can hold up to 550hp+ haven't herd any complaints and he answered all my questions.

 

I want 9" but to damn expensive right now.

[mustangmike6996 34]

it sucks to have an open 8" behind my stroker...:( I've been debating to go with that ebay seller that sells posi 8" that can hold up to 550hp+ haven't herd any complaints and he answered all my questions.

 

I want 9" but to damn expensive right now.

 

 

 

Yea that's how I feel for the most part, well that and I have all new brakes/lines etc on the 8" so it would be easier to just beef it up. Im not planning on racing light to light but I would like it to hold up. I don't think I have a need for the 9" other than to say "hey my car has a 9" Ford"

 

I have priced everything out and here are the ball parks/pros/cons

 

8"- I have the housing and everything is good except its open and the ratio is crap

 

9"- Seems like parts tend to be cheaper but that doesn't offset the cost of the new housing and brakes. This would most likely be a full rear end rebuild.

 

8.8"- trac locs are super cheap and easy to find. The 8.8 is getting harder to come by for the money but I can get a 4 lug drum 8.8 for $50 or a 5 lug with disc brakes for 500 right now but then I need to tear out my axle and brakes then fab up the 8.8. Some have an offset housing so that can be and issue as well depending on what is available.

 

With all of that being said, I think I would just like to get a 8" trac loc unit and a good gear ratio somewhere around the high 3.XX range. Im thinking 3.90:1

[rwcstang 201]

as long as you have a 5/6 speed I see no problem with 3:90's. also i would upgrade the axles.

 

but i have a built c4 behind mine and im not upgrading my rear end until i get my 5 speed. i'd prolly go with 3:80's on mine.

 

be sure to post pics with what you went with..

[1969vert 55]

As long as you have 5 lug 8" axels and drums they will fit into a small bearing 9" housing..all the same 28 spline stuff...the 28 spline stuff is not that bad.. I beat up on that stuff for years under my car.. but when it went mostly track axels started twisting..slicks and nitrous..the 8" will work on the street but if you beat on it hard..it will break..street tires and spirited driving should give you years of use...

[bryonbush 85]

im looking into the same thing now. the down side is it seems there is very little info on a solid 8" build because everything is all about the 9.

[mustangmike6996 34]

im looking into the same thing now. the down side is it seems there is very little info on a solid 8" build because everything is all about the 9.

 

 

Yea, that is true, most info about the 9 inch translates to the 8 inch as well other than sizes and strengths but they are set up and designed similar.