8” IFS Clamshell w/FRS Torsen

Sorry I wasn’t clear or referred to anything, my bad lol. I’m talking about the torsion giving the desired outcome in reverse rotation.
I guess you could put one tire on pavement and the other on wet grass.

 

This shouldn’t really be a concern. The FRS unit is the same style of torsen as the TrueTracs, which are available for the older 7.5” front clamshell diffs and the TLC 8” front diff.

 

Dose not sound that easy.
https://www.rocksolidtoys.com/single-post/2017/09/04/Swapping-inputs-on-the-FJ-Cruiser-T-case

Unless it is and rst just dosent like center difs

 

This is another reason why I’m going with the T4R case and electronic switching, you don’t have to swap the input Wiring appears to be simpler, and you get 4LO without locking the center diff. I haven’t tried it yet, but if you have a TRD Sport 4x4, the center diff lock switch looks to be plug-and-play where the TRD OR rear e-locker switch should be. That is, the wiring harness should already be there and the two switches are the same just a different outer picture/wording.

 

It’s the same size and will plug into a stock blank. Just don’t know if the electrical plug is the same

 

Aw yeah, I think when I was researching this in the past they do look like different plugs, but couldn't confirm. I would probably just try to swap the outer cover from the center diff switch (PS, I think these are no longer available from Toyota) to a taco RR e-locker switch.

 

So are 3.9 gears the ONLY choice for this diff? And still need drilling?

FYI, the first gen Tundras have the same 3.9 gears plus factory LSD option in the rear in case you wanna save some dough. The pumpkin bolts straight into your axle.

Also current gen automatic Tacos have 3.9 gears. Might be able to get a whole junkyard axle with elocker. I know it's not an LSD but at least you'd get a stronger, larger ring gear (8.8") and the elocker design is far superior to the second gen. It uses an internal electro magnetic lock ring and 4 pinion Desong just like the ARB

 

Any thin gears for the 3.9+ carrier should work, if the 3.91 gears from the stock FJC case I’m having built work. I don’t plan on going to anything over 32” tires, so the 3.91 is fine with me for fuel economy. According to ZUK, the friction discs are likely worn out in the current LSD I have, so I was thinking about going with a TrueTrac torsen in the rear for easier maintenance.

Definitely good to know that the Tundras had 3.9 gears for anyone else looking to do this on a budget in the future though. Thanks for contributing that info to the thread!

 

I've read the cases or something is different between 3.91+ and 3.73, gears basically not interchangeable. Notice aftermarket 4.56 will make a note if they're 3.73 or 3.91 case

 

This is true for the front clamshell differential. a 3.73 and down ratios differential carrier requires "thick cut" gears for anything 3.91 and up to work. On the other side, if you have a 3.91 and up carrier, you requires gears that are designed to work with such carrier.

I recently re-geared my truck from 3.73 up to 4.30. Since the 4.30 gears were not available in a thick cut, I had to replace the front carrier from a 3.73 and down to a 3.91 and up.

This is only applicable for the front differential. The rear differential is compatible with all ratios.

 

This just in, @ZUK is a badass...

 

This is definitely getting very interesting. If only some minor milling and machining is all it takes to fit one of those bad boys in a clamshell, I will be considering the upgrade.

In reference with the first picture, did he cut the diameter down where the ring gear sits on the carrier?

 

I think OP said early on the ring sits there nice, I think just showing how he secured to drill base.

 

I test fit the FJC ring gear on the FRS unit before sending it to be rebuilt, they are the same ID. I did have to tap it on and off with a mallet, but I think that's pretty normal.

@05Taco4x4 is correct. These were just pics sent to me showing how he was able to lock the carrier down on his drill press. Thankfully the torsen carrier has a pass through the center that he was able to fit an 8" long bolt through.

 

OP do you know of any lower hearing ratios that would work? Like 4.10?

I'm not well versed in what's there to be had for re-gearing the FJ Cruiser

 

post #32 of this thread, page 2. Everything that says it fits the 3.90 & up carrier

 

Ring gear on. Had to clearance the ribs similar to what has to be done for the harrop e-lockers, which I expected.

 

Nice! What is left to get those in the truck?

 

That's exciting, I'm happy for you. Did he take measurements from end to the ring flange to see how exactly close they are? Or do a paint test on the gears?

 

Paint test is next, only thing left to confirm this works.