Ford 8.8 Build Help

[2001SilvrGT]

I have a 99 cobra with a 03 GT SRA swapped into it. Im pretty newbie to when it comes to these rears so any info or advice will help. Since my car is boosted and i take it on cruises and sometimes daily it i might stick with the 3.73 or go down to 3.55's. Also Im going to go with 31 spline strange axles and have my tubes welded too. Im also doing team z upper an lower control arms along with battle boxes. But Now for my differential part should i go with a Detroit locker or Detroit true trac? Pros cons on them both will help what do you think is best for my needs?

Thanks

 

[Stanger00]

Honestly, I would stick with a trac-lok. Buy the FRPP unit with Carbon clutches. It is the same build as a 03-04 cobra. I run one and have had zero issues with it until I built my motor and was running with a bad transmission tune. My converter would stay locked too long and wouldn't unlock until 3 mph causing my trac-lok to act like a spool. Now my stuff chatters and slips.

I'm going to rebuild with another carbon clutch kit. I don't want to deal with the noise of a locker or get bad luck with true trac making noise.

3.73 at minimum.

 

[cartec]

When changing the gear oil, check to see if you need a friction modifier. It was required to be added to my 8.8 SRA.

 

[KLeech]

If you want to cheap out and have a differential that is going to wear out over time and require you to open the rear end and rebuild it, buy a clutch pack unit like the ford diff.

Doesn’t sound real appealing does it? That being said, I run a Detroit True Trak, and I can tell you I’m 110% satisfied with it. I like it so much in my blown 01 that I have another brand new one waiting in the box for my foxbody turbo project. It locks up great when it needs to, goes around corners smooth and makes little noise. Remember when you’re trying to go to hardcore performance sometimes you have to sacrifice a little noise, its mechanical there are gears that mesh together. I would rather hear what my car is doing and know everything is working properly then not hear anything at all until something falls apart (that’s just me)

You will not be disappointed in one, and I can tell you if you want your car to hook hard but don’t want the ill side effects of a full locker it’s the route to go. Also I would order it from Drivetrain America, they are 40 dollars cheaper than any other retailer.

I also run 3.73's and would definitely stay with those.

 

[Stanger00]

If you want to cheap out and have a differential that is going to wear out over time and require you to open the rear end and rebuild it, buy a clutch pack unit like the ford

The thing works.

Knowing my luck I'll end up with of those noisy units from Detroit. It also costs 4x the amount of a clutch pack from summit racing and you can buy an explorer carrier used fairly cheap to install the new clutches and spring.

 

[KLeech]

The thing works.

Knowing my luck I'll end up with of those noisy units from Detroit. It also costs 4x the amount of a clutch pack from summit racing and you can buy an explorer carrier used fairly cheap to install the new clutches and spring.

It's not bad, but it all depends on what you're doing. The only complaint I've ever heard of about the True-Trak is some noise. But every single person I've saw review it absolutely loves it for what it does for planting the power. And I without a doubt wouldn't look back to anything else, that's why I bought another.

Sure the cost of an explorer carrier and the clutch packs are cheap. But it's the time. You're not going to have to pull that eaton unit out unless its broken, as opposed to you could be wearing out a clutch pack diff every year (depending on power and what you're doing with it) So in the end, spending 450 on a diff that I know is going to last until its broken is a no brainer. Very few people want to have to open the rear end multiple times, they want to put it together, leave it, and it work. That's why I suggest that one, because at the end of the day the guy that doesn't have to spend hours pulling apart the rear end, rebuilding it, and then setting everything back up frequently is the winner.

 

[Three21]

True Trac. Street friendly and reliable. I can't hear it over my exhaust and solid control arm bushings (those things are loud) except when coasting to a stop. Nothing real noticeable, just a slight whirring and occassional knock. Slap one in there and don't worry about it again.

I doubt I would drop down to 3.55s in your case, but I would put fresh gears in.

 

[Stanger00]

I'm looking more into the true trac. Have friends with cars that have this unit installed and they report the same as reviews. I'm not looking for something that has a ratcheting noise but I also don't want to experience the issues I'm having with 600hp to the tires. When the suspension starts to unload the one wheel takes over and wants to point me left. It's even worse when that 2-3 shift happens at 80mph, 4r75w problems.

 

[VA-Mach1]

A 99 Cobra should have came with 3:55's. A GT rear is normally 3:29 I think. So at a minimum I would go back to 3:55. In my Mach1 I went from 3:55 to 4:10 and its great.