GBousley

Good day, ppl!

Would like to ask the community what the best option rear for my application would be. I am looking to get posi, 3.23 gears, and a rear that's strong enough to handle power from a mild 383 (future swap). I'm starting with the drivetrain upgrades first before I swap the engine and hear the rear is the weakest link.
So, I am only intermediately mechanically inclined and this will be my first rear swap. Is there a rear out there (new) that would be a direct swap with no fabs necessary that'll fit the bill?

PS: I've done some real searching but cannot find anyone answering the question above. Also, I'm aware of the 4th gen swap guide here on the forums and I've called around and found a few 4th gen Z's that have posi, but I wanted to kick up this discussion on a new rear that might last a bit longer than a used one. THANKS!

GBousley

Right now, leaning toward doing the 4th gen swap, with the added bonus that I get disc brakes, but having trouble finding how much Torque the 4th gen rear can handle.. anyone know this?
Would hate to to that work and get the posi and gears I want, but just shred it later on after doing the engine swap.

AlkyIROC

Your 92 diff is just as strong as a fourth gen diff. They both use the same 7-5/8" ( 7-1/2") ring gear. They both use 28 spline axles however the fourth gen's axles are slightly longer.

There are no inexpensive diff upgrade options. An inexpensive fourth gen swap is good for 82-89 cars that use 7-1/2" ring gears and 26 spline options but everyone will say the same thing. Don't waste money trying to upgrade the tiny little 10 bolt.

There are 3 aftermarket bolt in options. Ford 9", Chev 12 bolt and Dana 60. Expect to pay around a minimum of $1500 to get a diff installed and ready to roll. It all depends on which diff you use and how much you want to spend on options. About the cheapest upgrade is to buy a bare housing 9" bolt in for a third gen then provide your own center section which you can probably find locally.

QwkTrip

iTrader: (22)

I think a 10 bolt is fine with a mild 383 on street tires, especially with an auto trans.

GBousley

Did I read correctly that the 4th gen swap only works for 82-89 cars? I've heard a lot about the Ford 10 bolt, can u advise on the ease of swapping in the aftermarket rears? After reading the 4th gen swap guide I feel confident I can do it, but not sure what complexity is added going to new aftermarket rears.

AlkyIROC

No. Technically the fourth gen diff is the same as a third gen however around 1989, the ring gear size increased from 7-1/2" to 7-5/8". The carrier stayed the same but the ring gear diameter increased slightly. In 1990, the axles changed from 26 to 28 spline. These changes carried over into the fourth gen diffs but the fourth gen is wider so the diff was made wider. So other than the width, strength wise, a fourth gen diff is about the same as the 90-92 third gens diffs. They came with different brake systems and carriers (Torsen etc) but strength wise, they're the same. By the time you spend money on the diff to make it a lot stronger, you could have made a sizeable payment on an aftermarket diff. No matter how much you try to improve the 10 bolt, you'll still have that tiny ring and pinion gears which will always fail first.

The Ford 8.8 can be used but it needs a lot of modifications to make it fit just like trying to swap in any other diff not designed for a third gen.

The third gen aftermarket diffs are designed to be a direct bolt in and usually use the late model disk brakes but they can be ordered to use any brake system.

GeneralDisorder

iTrader: (1)

4th gen rear is not an upgrade for you.

Cheapest upgrade I could come up with was a good used 9 bolt with the Torsen carrier from Australia. They aren't larger than the 10 bolt but they are built a bit stronger.

Beyond that you are looking at an aftermarket offering and expect to spend $3k+

GD

AlkyIROC

Even then, a 9 bolt isn't that cheap. They were only made to fit into third gens for a couple of years. Finding an inexpensive used one that's in good condition will be hard as most will have a worn out posi and will probably come with 2.73 gears. If you're lucky, you might find one with 3.27 gears. If the seller knows what they have and it's in good condition, an aftermarket diff isn't going to be much more in price. Replacement parts need to come from Australia as there is very little if anything available in North America.

bigdavesiroc

You also have the option of an 8.8" that hawks provides. I currently run a moser 12 bolt but it was not inexpensive.