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Thread: F body Rear Diff Question

  1. #1
    Join Date
    Mar 2010
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    Rural Alberta
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    Default F body Rear Diff Question

    Looking for advice please. Have a 2002 Trans Am WS6. Looking to upgrade the rear diff. Not sure which diff to go with. 12 bolt, 9", 8.8? Pricing with our shitty dollar is also discouraging. Anyone have any experience in buying built diffs? Any local shops build them for a decent price? Really have no experience with diffs. Any help is greatly appreciated. Thanks
    Mustangs are like Hemorrhoids, sooner or later every asshole gets one.

  2. #2
    Join Date
    Apr 2007
    Location
    Calgary, AB
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    With the torque arm setup, you need a specific housing. There are a few companies that build brackets for the 9" that can be welded on and used with their torque arm.

    If your going new, check out the Strange S60. You can either send them your brake backing plates or buy from Rockauto and have them shipped direct to Strange for install with axles.

    Contact Carl here for purchasing support and a great deal.
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    Another option is buy the housing only, then fill it with parts locally. After all the research I had done, the built S60 was still the best deal I found.

    I had mine shipped to the Sweetgrass border, then picked up from Montana Shipping Outlet.

  3. Default

    There are no inexpensive options for a better diff. Currie once sold a kit to attach the torque arm onto a 9" housing. It required welding heavy wall tubes onto the housing that the torque arm was able to bolt to. As far as I know, they won't sell the kit any more except with their housing.

    Aftermarket choices are 9", 12 bolt and S60. About the cheapest is going to be the 9". You can buy the housing with axles for a little more than $1000 USD. You then provide the center section and brakes.

    Buying a fully assembled diff ready to bolt in will cost you a minimum of $2500 USD.

    OEM options are building up the factory 10 bolt. You can easily invest $1000 to make it better and you still have the tiny 7.5" ring and pinion which will still fail. Your 2002 will already have 28 spline axles but factory axles are weak compared to any aftermarket axle.

    The 1987-1989 Borg Warner 9 bolt is a slightly stronger diff but performance options are virtually zero unless you buy stuff from Australia.

    GM once offered a Dana 44 as a performance diff over the counter for third gens. 8.5" ring gear. If you manage to find one in almost new condition, it would be cheaper to buy an aftermarket diff instead.

    Any other junkyard diff option requires a lot of work to install. First you need to find one narrow enough to fit under the car then you need to find some way to attach the torque arm. You can completely change the suspension to something else like ladder bars to eliminate the torque arm but then that means a whole lot more money to invest to make everything work.

    There have been people who have modified an 8.8 to work but it's not an easy or inexpensive option to do.

    Your fourth gen diff is also about 1-1/2 to 2" wider per side than a third gen diff so using a 9 bolt or Dana 44 in your car means your wheels will be tucked under and may rub the inner fenders.
    Last edited by AlkyIROC; 03-31-2016 at 10:21 PM.
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  4. #4

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    They make a thing called a hilti bracket, it welds on to a truck 8.8 housing to allow the use of a stock style torque arm. then you just cut all the brackets of the stock diff and weld them on the 8.8.
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  5. Default

    I ended up putting a 12Bolt Moser diff in my 95 Z28, it wasn't cheap though, I think around $3400cad all said and done back in 2006 or 2007. 33 Spline axles and Detroit Trutrac posi.

    It's for sale as well...comes with a 95 6 speed Camaro with bolt ons if interested..

  6. #6
    Join Date
    Mar 2010
    Location
    Rural Alberta
    Posts
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    Default

    Thank you guys so much for the responses. I'll do some more research and hopefully everything works out and doesn't cost $5000!!
    Mustangs are like Hemorrhoids, sooner or later every asshole gets one.

  7. #7

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    If you're looking for something relatively local, PPP in Lethbridge: http://performancepowertrainproducts.com

    I didn't see anything specific to your year of Trans Am, but the site may not be updated. I'm partial to the Ford 9", have one in my square body Chev pickup + my '05 Mustang.
    If you can read this, thank a teacher; If you can read this in English, thank a soldier.

  8. #8

    Default

    Midwest chassis makes a nice piece, Hawks third gen also makes the 8.8 setup that will work. And stay away from ppp

  9. Default

    It doesn't matter if you choose a 9", 12 bolt or S60. They are all good and each one is also considered bad for any number of reasons. The 9" is very common and parts are very inexpensive. Best part about the 9" is the carrier (posi). One size fits all. Doesn't matter of you have 2.50 gears or want 6.00 gears. They all fit the same carrier.

    I run a 9" in my Camaro (custom narrowed, 45" axle flange to axle flange). I use a Moser bolt through aluminum center. Aluminum Dayton pinion support and an aluminum spool. I can lift the center section into the diff with one hand. Removing all that unsprung weight is a huge advantage. I only run 31 spline axles but with a powerglide, that's all I need. If I was using a 3-4 speed trans, I'd go with 33 or 35 spline axles. 40 is overkill even for my car. My center section is for the smaller bearing so the most I could upgrade to is 33 spline. If I wanted to go to 35 spline, I'd need to buy a center and carrier with the bigger bearings for the larger axles to fit through. Technically I could use a special steel spool that can handle 35 spline axles in the small side bearings but I wouldn't trust it.

  10. Default

    I've been thinking about upgrading myself. I currently have a Borg-Warner 9-bolt in my 3rd gen. The only feedback from someone I know is that the Currie or Moser housing with a 9" was noisier than the OEM rear axle. If and when I decide to replace rear axle and housing I'll go with the Ford 9" Center section. It's proven and lots of parts available. BTW ALKYIROC, that 3.27:1 rear diff I got from you is still running strong!

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