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Discussion Starter #1 (Edited)
So I drive a 04 factory 5 speed. And the rear diff ration is a 3.7 if I'm not mistaken. And factory autos have a 3.9. I know people swap brz and frs diffs in because its a higher ration of 4.1+s to drift with. (Which I dont understand because 2nd and 3rd are fine with the factory diff.)

Anyways, my question was going to be, is there any other options other then those few that I always hear about? Honestly I am looking for something a little lower. I do a lot of driving for my job and doing 70+ on the freeway with my rpms well over 3k is getting annoying. My wifes e36 has a zf trans a 2.9 rear diff and goes 80 with it just under 3k rpms and thats amazing for freeway driving.

Did research on this and just came up with the couple options I always hear about that I listed above. If anybody knows of any lower ratio diffs or gearing I could swap out let me know!

Thanks!
 

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You are correct, you have a 3.73 if your car is stock 5MT. The only option that will fit the stock pumpkin and is taller is a 3.56. I think I turn [email protected] ish with the 3.56. You will of course sacrifice a little low-end for the taller gearset. To go any taller, you have to go with a GS/SC/Supra diff which requires custom mounting and different axles and a driveshaft flange for the diff. Quite a bit more work but could get down to a 3.26 with this route. There’s also the Grannas-Ford 8” but that’s probably out of the scope of this haha it’s like 2900$ but bolt-on, no custom so there is that aspect.
 

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There’s also the Grannas-Ford 8” but that’s probably out of the scope of this haha it’s like 2900$ but bolt-on, no custom so there is that aspect.
I didn't know this was bolt on!

I can confirm everything else except my rear end is 3.54 :)
 

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Yeah it’s bolt on. Pretty bad ass and makes for pretty much infinite ratio options haha.

Well it may be 3.54, then. I don’t remember for sure. It’s from a Tacoma, I think I got my set up from Nitro Gear brand new.

Just Differentials is where I got it. It’s a Nitro Gear brand. They are calling it a 3.58 😝Toyota 8'' 3.58 Ratio Nitro Ring & Pinion
 

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Discussion Starter #5
I can confirm everything else except my rear end is 3.54 :)
Where did you get the 3.54?!

Just Differentials is where I got it. It’s a Nitro Gear brand. They are calling it a 3.58 😝Toyota 8'' 3.58 Ratio Nitro Ring & Pinion
Oh okay so the 3.58 is actually what your running.😆 That site looks awesome! So as long as it’s a Toyota 8” with the right splines it should work right? That site seems pretty straight forward with what gears work with what vehicle.
 

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Where did you get the 3.54?!



Oh okay so the 3.58 is actually what your running.😆 That site looks awesome! So as long as it’s a Toyota 8” with the right splines it should work right? That site seems pretty straight forward with what gears work with what vehicle.
From 3.73 to 3.58. Is only about 150 rpm difference. You will not see a significant difference in mileage.
 

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Oh okay so the 3.58 is actually what your running.😆 That site looks awesome! So as long as it’s a Toyota 8” with the right splines it should work right? That site seems pretty straight forward with what gears work with what vehicle.
Yep that is the exact one I used. You’ll need to make sure there are 29 input splines on the driveshaft side of the old diff pinion (my 04 had 27 splines even though the Just Diff site states that after 02 Toyota went to 29 splines). You’ll need that new YokToyFitkit-29 otherwise. It’s a good time to replace bearings but not absolutely necessary. I also used a solid spacer instead of a crush sleeve.

From 3.73 to 3.58. Is only about 150 rpm difference. You will not see a significant difference in mileage.
Yep you are right, and I have a lower final drive because of my transmission swap to the AR-5. Forgot about that. The turbo sure likes the taller gearing it loads it up a lot sooner.


This is a good site with the common transmission and diff combos and respective data.
 

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Where did you get the 3.54?!
Weir Performance. I believe they did the R&D for us to find out the largest pinion that would fit without modification.

From 3.73 to 3.58. Is only about 150 rpm difference. You will not see a significant difference in mileage.
Exactly - It's minuscule. I was just poking fun by calling my exact ratio out. I came from the Auto 3.9 though.

Honestly, I need ~3.2 but never got around to it... At least not yet.
 

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I think I tried Weir but they did not have any used or new at the time. My car while an original 5MT did not have LSD. So I had swapped to an 04 auto LSD 3.9. So it was significant to go from the 3.9 to 3.5 ratio. That, and the AR5 final drive gets cruising rpm low. I’d like to see if a 2jz could actually cruise at 1600rpm with the T56 trans and 3.5 diff as mathematically implied on the site I linked. Way out of its powerband so I bet not.
 

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Well I didn’t know this existed... GS400 adapter ...some custom work but still quite a game changer.

I think the caveat here is that the GS400 did not come with an LSD stateside. I believe the NA MKIV and TT Auto MKIV had an LSD, so you could do some swapping of parts to get that 3.26 ratio with LSD.
 

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Wow! I haven't seen that yet. I was planning to cut and weld everything myself.

You are correct... An LSD for that diff can be more expensive than sourcing it... at least when I was looking.

Or did the 430 models come with LSD?

Edit: Also I think you need the Supra TT axles.
 

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Yeah you’re correct, it will need the offset TT axles. The link also says you can re-use the IS diff cover and no welding of the GS adapter plates-to-IS subframe is needed. I bet a new pinion-to-driveshaft yoke is needed as well, may have to shorten the driveshaft too?

I don’t think the SC430 had an LSD option, but I may be wrong. TRD and Kaaz for sure made them.

I am tempted to order the Figs adapter just to have it. In case I ever want to do the swap. It would only be like a 8% decrease in cruising rpm, but it would load the turbo up in the lower gears quicker.
 

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I'm kind of a little bit not happy you showed me this.
haha, well it’s only 150$ buy-in. You could sit it on a shelf and it’s there when/if you want to do it. I’d have to do some math and see what total cost would be. Diff, lsd, half axles, modded driveshaft, etc. I just did cams/springs/retainers + retune, so I can’t drop the whole amount yet. I could sneak that adapter through, though...
 

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haha, well it’s only 150$ buy-in. You could sit it on a shelf and it’s there when/if you want to do it. I’d have to do some math and see what total cost would be. Diff, lsd, half axles, modded driveshaft, etc. I just did cams/springs/retainers + retune, so I can’t drop the whole amount yet. I could sneak that adapter through, though...
I have way too many other projects going on to even begin thinking about swapping rear ends again...
Although, I'd hate to miss out if these aren't available when I do. I'll add it to my list I suppose.
 
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