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Discussion Starter #1
What's the compatability of the GEARS in 8.4" and 8.0" rear thirds.

Can you take the R&P from a NON TRD Taco rear third member (8.4" housing w/ 8.0" gears) and put them in a TRD Taco rear third member (8.0" housing - same as a 4runner)???

Are the R&P totally different?? I could care less about the housings. I know they wont fit b/c they're different sizes. I know that the 8.4" uses a different ARB Locker than the 8.0" (RD89 vs RD23). I need to know ONLY if the R&P will swap over.

Thanks...
 

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Discussion Starter #3

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A factory option on 3rd Gen. 4Runners, Tacoma 4x4's, and Tacoma PreRunner 4x2's is an electric locking rear differential. This diff is a 4-pinon design based on the Turbo/V6 8" diff and uses the same gear sets.

This came from the site that bamachem found. It says that the gears are the same.

I just checked randy's ring and pinion website, and they don't list two separate gear sets, only a "Toyota 8" which I guess covers both. Marlin Crawler's website lists two different gear sets and two different prices (e-locker is cheaper).

I had always thought they were different, but I really can't say for sure.
 

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Jamier2 said:
A factory option on 3rd Gen. 4Runners, Tacoma 4x4's, and Tacoma PreRunner 4x2's is an electric locking rear differential. This diff is a 4-pinon design based on the Turbo/V6 8" diff and uses the same gear sets.

This came from the site that bamachem found. It says that the gears (and ONLY the gears) are the same.

So, either offroadr1 or the guy with the website don't know what they're talking about.
You mis-interpreted the quote. Only you are wrong :)

When they say it uses the same gear sets, they mean that the locking differential version uses the same gearset as the 8". They do not mean that the 8.4" gear matches the 8". Remember that the size designations refer to the ring gear.
 

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This diff is a 4-pinon design based on the Turbo/V6 8" diff and uses the same gear sets.

That's the part I'm going on - and I'm not saying the guy is right. I just want to make sure that the "turbo/v6 8" diff" is the 8.4 that non-TRD V6 Tacomas have. That's what I've read here on TTORA and other sites.
 

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The Turbo was a 4 cylinder-based truck, pre-tacoma. The V6 has always referred to pre-tacoma rear ends. The reason is that since the Tacoma there have only ever been two rearends from the factory. The magical 8.4" and the TRD electric-locking differential.

The TRD locking differential "is a 4-pinon design based on the Turbo/V6 8" diff." It has -NOTHING- to do with the 8.4" "open" rear end found in the majority of Tacomas.

Remember, 8.4" > 8.0". Those sizes refer to the diameter of the ring gear. If one is larger than the other then they are not the same.

A proof by contradiction:
Assume that the 8.4" diff is the same as the 8.0" diff. Then the diameter of the ring gear inside the differentials must be the same. However, the 8.4" diff has an 8.4" ring gear and the 8.0" diff has an 8.0" ring gear, hence, the ring gears are different and thus the differentials are different.
 

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Discussion Starter #8
BigBadBob0 said:
The Turbo was a 4 cylinder-based truck, pre-tacoma. The V6 has always referred to pre-tacoma rear ends. The reason is that since the Tacoma there have only ever been two rearends from the factory. The magical 8.4" and the TRD electric-locking differential.

The TRD locking differential "is a 4-pinon design based on the Turbo/V6 8" diff." It has -NOTHING- to do with the 8.4" "open" rear end found in the majority of Tacomas.

Remember, 8.4" > 8.0". Those sizes refer to the diameter of the ring gear. If one is larger than the other then they are not the same.

A proof by contradiction:
Assume that the 8.4" diff is the same as the 8.0" diff. Then the diameter of the ring gear inside the differentials must be the same. However, the 8.4" diff has an 8.4" ring gear and the 8.0" diff has an 8.0" ring gear, hence, the ring gears are different and thus the differentials are different.
partially right and partially wrong.

the 8.4" diff - or so it's called - isn't 8.4" afterall... it is a 210mm ring gear compared to the 200mm ring gear in the 8" diff. so, it truly isn't an 8.4" diff after all.

anyway, the point is that they are NOT compatable in any way, shape, or form. the gears from one CANNOT be used in the other. they are two totally different beasts and should be treated as such.

sucks for me, but that's the truth...
 

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I was actually pretty sure it wasn't 8.4 but was running with the tide of the thread. For kicks:
You have: 210 mm
You want: inches
* 8.2677165
/ 0.12095238

You have: 200 mm
You want: inches
* 7.8740157
/ 0.127
 

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BigBadBob0 said:
Remember, 8.4" > 8.0". Those sizes refer to the diameter of the ring gear. If one is larger than the other then they are not the same.
Apparently what I'm typing is not coming across right. I never said that they are the same size. I just said that I've seen the 8.4 called (incorrectly) an 8 inch rear. When I saw it discussed it was agreed that "Tacoma V6 8 inch rear" = 8.4 inch rear.

I understand that the ring gears have different outer diameters. But as for the two rearends not having anything in common, I know that I've seen a write-up of someone fitting a TRD carrier into the 8.4" rearend, so there has got to be some commonality there.
edit: I found the page, and it was retrofitting a TRD locker and carrier into the real 8" not the 8.4". D'oh!

I just posted what is on that webpage (that someone else referenced) and offered it for someone (such as you) to correct - as you did nicely.

Just trying to get the right info out here for everyone's benefit - even if it doesn't come from me.
 

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All 2wd and 4wd T100's, Tundra's, and Sequoia's use a newer/stronger 8" 2-pinion diff. Tacoma 4x4's and Tacoma PreRunner's that don't come with the electric locker, as well as V6 Tacoma 4x2's also came with this diff.
(from the same website cited above)

I finally see that you are talking about an older 8" diff.

In the past this diff has also been mistakenly called an 8.4" or 8.25" diff. The ring gear actually measures 8", but it is not compatible with the older 8" diffs at all.
It does make you wonder why the rear in my truck (non-TRD) is called an 8.4 when it doesn't measure that at all.
 

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BigBadBob0 said:
The V6 has always referred to pre-tacoma rear ends. The reason is that since the Tacoma there have only ever been two rearends from the factory. The magical 8.4" and the TRD electric-locking differential.
LMAO, you put it right in your second post and I missed it.

Thanks for explaining all that extra info anyway, I was just confused on the naming of the rearends. Ok, now that I see I'm having reading comprehension problems I'm going to go study for a while. :)
 

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An 8" TRD diff will fit in a 8.4" housing. You just have to do a lot of cutting, welding, and drilling and tapping.

I attempted it for shits and giggles a few summers ago with a junked center housing section and spare TRD 3rd I had.

I had pics but they got lost in a hard drive reformat a while ago.
 

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Jamier2 said:
LMAO, you put it right in your second post and I missed it.

Thanks for explaining all that extra info anyway, I was just confused on the naming of the rearends. Ok, now that I see I'm having reading comprehension problems I'm going to go study for a while. :)
It's coo.
:xbeer3:
 
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