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Discussion Starter #1
Can someone explain to me all the different options for my 8" rear end? If seen limited slip, true lock, detroit lockers and a bunch others. I'm looking to replace my 2:80 gears for something quicker. Doing a T5 swap and need to change the rear end. Thinking about 3:50 gears. Street use no strip. Just looking for more spirited driving around town.

Also anyone have recommendations where to get new third member?
 

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i have a ribbed case 3.55 posi (brand new unit and gears) just rebuilt by a very reputable local builder - i decided to replace the entire rear - it has never been installed or run - i live in western ma - pm if interested - $800
 

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Discussion Starter #5
It always looks "odd" to me when a new user's first post is like the one above.
I was wondering how long it would take for that response. Rufus, you make me proud!
 

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your loss then - buy one from ebay - figured you were in ma and i had somthing you may be looking for - lurked on here for a while and recently registered - recently got a killer deal on a '65 im putting back together - just trying to help but go **** yourselves
 

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Well....everybody is probably going to have a different opinion. Assuming you will be going to a 2.95:1 first gear T-5 then I'd divide 2.95 into 10 to select your rear gear ratio, which would be 3.3898, so I'd pick 3.40's. That will give you a good "pull" from a stop. If you're buying the T-5 from a "builder", I'd have them go to a .80 5th gear instead of the .63... that will give you a 5th gear final drive ratio that is close (2.72:1) to what you currently have AND much more evenly spaced shifting up through the gears, instead of a clumsy drop from 4th into 5th. That's just IMHO though...

As far as limited slips go... I like the Eaton-Detroit TrueTrac helical unit. No clutches and no "locking" so much easier on the drivetrain and the ride, plus no need to invest in a new differential carrier assembly....
 

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Why run a limited slip of any kind if you aren't planning on spinning the tires? It won't change how fast you get to a car show or the grocery store. Woodchuck's suggestion of 3.40 is great , no more than 3.55 or first gear will be virtually useless.
 

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There is always the practical benefit of having a limited slip for decreasing the chance of getting stuck if one rear tire is on a slippery surface. With the open diff, both rear tires need traction so whenever given the choice, choose the limited slip.
 

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Worth noting that not all T5’s are the same. Mine is out of an ‘85 Mustang GT and with 3.73’s, first gear is perfectly usable.

It’s really the perfect setup in my opinion, provided the first gear ratio is the right one.
 

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Discussion Starter #13
your loss then - buy one from ebay - figured you were in ma and i had somthing you may be looking for - lurked on here for a while and recently registered - recently got a killer deal on a '65 im putting back together - just trying to help but go **** yourselves
Actually I mis read his post. I thought he was referring to my title of this thread about my rear end NOT that you offered my your parts. I actually think that was pretty nice of you and I was thinking about it. I just don't know the difference between all the different types rear ends for a Ford 8" and I wanted to do some research first.
 

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Discussion Starter #14
Well....everybody is probably going to have a different opinion. Assuming you will be going to a 2.95:1 first gear T-5 then I'd divide 2.95 into 10 to select your rear gear ratio, which would be 3.3898, so I'd pick 3.40's. That will give you a good "pull" from a stop. If you're buying the T-5 from a "builder", I'd have them go to a .80 5th gear instead of the .63... that will give you a 5th gear final drive ratio that is close (2.72:1) to what you currently have AND much more evenly spaced shifting up through the gears, instead of a clumsy drop from 4th into 5th. That's just IMHO though...

As far as limited slips go... I like the Eaton-Detroit TrueTrac helical unit. No clutches and no "locking" so much easier on the drivetrain and the ride, plus no need to invest in a new differential carrier assembly....
Thanks Woodchuck, that's what I was looking for. I'm planning on a Modern Driveline kit. Gears they quoted me for a 3:50 and 15 " tires were 2.95,1.94,1.34,1,0.63. (1st-5th). I can ask them about the .80 5th gear. Not planning on a ton of highway driving, but you never know.

Is the Eaton-Detroit True Trac a complete third member or do I use my current third member and swap out the guts?
 

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As far as limited slips go... I like the Eaton-Detroit TrueTrac helical unit. No clutches and no "locking" so much easier on the drivetrain and the ride, plus no need to invest in a new differential carrier assembly....
I second the TrueTrac recommendation. I had a TrueTrac installed on my '70 Mach 1. When driving around town, and even on an autocross course, it's like a single track. If I punch it in a straight line, it's like a Detroit Locker; but without all the click, pops, bangs and chirps.

My take is a limited-slip diff should be one of the first mods to any performance build. If you have any power up front at all, an open diff will simply roast the right rear tire. And that's lame.
 

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1965 Mustang Fastback GT350-Tribute Restomod. 2019 Shelby GT350.
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Another LSD option is the WaveTrac from Moser Engineering. Like the Eaton, it is also a helical torque-biasing differential, but is claimed to work better when one wheel is in very low or no-traction conditions such as on ice or when one wheel is off the ground (think rock-crawling or jumping a curb at the racetrack). It costs a bit more but comes with a lifetime warranty regardless of horsepower.

Back in the 80's and 90's I was running a Trac-Lok in my Ford 9" for AutoX. When I took the car down for a rebuild, I originally bought a Detroit Locker to preclude the need for a Trac-Lok clutch-pack rebuild.

My 65 Fastback languished for years in various stages of construction. When I recently restarted the project, my axle guy educated me about the new LSD technology available and suggested the Eaton or WaveTrac helical gear variety. I stashed the Locker and upon his recommendation, chose the Wavetrac unit. I haven't got the car running yet, so have no personal experience to share yet.
 
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