Converting Clutch-Based LSD to Geared LSD on a Tacoma PreRunner

I have been driving my early TRD with a TrueTrac in it for some time. That is advertised to fit and was installed without issue.

TRD Sport 8.4” which should be what prerunner has except open diff.

don’t know what’s offered for the weaker OR 8” diff. Nor reason to change that to an LSD given 8” OR means Elocker stock.

whoops yeah correct my bad didn’t understand.
Yeah if it’s 8” idk what they list for that. ECGS has drop down menu diff parts selector.

 

Trd sport prerunners had the 8.4"
Trd OR prerunners had the 8"
Truetrac only fits the 8.4"
https://www.tacomaworld.com/threads/sumo-tnk-08-dcsb-trd-or.757165/page-3#post-28476945

If OP has a trd OR prerunner, the mechnical diff lock is not bad but the upgrade options are an air-operated locker or swap the whole rear axle to an 8.4". Not much else.

 

Thanks for sharing.. Just to double-check, does it behave like a normal open differential when turning corners on pavement? I know air lockers have to be turned off for street driving since they don’t work well for cornering, so I just want to make sure the TrueTrac is smooth in that situation.

 

so if the TrueTrac doesn’t fit the early 2nd Gen TRD OR PreRunners, what would be the requirements for the rear differential to make it compatible?

 

Totally smooth and seamless in street operations. They behave and perform like an open diff until they don’t need to and then it seamlessly moves power to the wheel with traction as a limited slip. Even then it is seamless in operation.

Note - they are not a locker, they are limited slip so if one of your rear wheels is in the air with zero traction that is the one place it can’t/won’t assist. For the vast majority of users this is very, very rare.

Aside from swapping out the highway tires the TT was my single best modification.

 

Rear axle swap

 

So, it looks like I need a complete rear axle swap to an 8.4. I’d like to find out how much it really costs and see whether it’s worth it for me or not.

 

NO... you have the 8.4.

The 8.0 is only the Offroad (OR) axle, that has the e-locker in it.

 

@Yoco07

Do you have a TRD OffRoad or TRD Sport PreRunner? And what year is your truck?

Or a non-TRD base model 2wd? And what year?

I think you're getting a lot of convoluted answers because you havent provide necessary details about your truck.


If you have a TRD OR, you'll need a rear axle swap to fit and Truetrac.

If you have a TRD sport, you can install the TT with your existing axle.

If you have a non-TRD 2wd base model, then I don't know what rear end that has. But if you say that you currently have a non-elocker lsd, then I would fathom that you have the 8.4" and can use the truetrac.

I always thought non-trd base model early 2nd gens 2wds came with an open diff. But I could be 100% wrong on that.

OP, you mention the dealer told you about your rear diff. Are you sure they weren't talking about ATRAC, etc. I think you may want to reconfirm what rear axle you have.

 

OK, so if I already have an 8.4", and since my truck also comes with a clutch-based LSD, also known as "POSI" (I just confirmed this with an Eaton TrueTrac rep), they said I don’t need to upgrade to TrueTrac because "POSI" functions similarly to TrueTrac, meaning you have to apply the brakes or give it gas to activate it when coming out of a break.

 

Bueno.

In mine the factory LSD clutch pack was worn enough that I was digging one wheel holes on hills/trails that my Taco should have been able to do in 2WD.

So, for the future you know it is a path if you need upgrade.

 

No.

posi is a thing. It has springs. The Tacoma does not have that.

an Eaton rep is an Eaton rep. Not a Toyota engineer who worked at Toyota during the development of the 2nd gen.

 

Respectfully, TacoTuesday, you're wrong here. The mechanical LSD in the 2005-2008 TRD Sport 8.4" rear diff is a posi-style clutch pack limited slip rear diff. Take a look at the rebuild thread that I posted above.

 

I believe I have the non-TRD base model 2WD. It’s a 2007 Toyota Tacoma Pre-Runner with a 4.0L V6 Double Cab Longbed. So, this should be the base model for that year of the 2nd Gen Tacoma. That said, I’m not entirely sure how accurate the dealership was about this. Another Toyota dealership I spoke with actually recommended I go to a shop that specializes in aftermarket upgrades instead.
Now, I’d like to ask everyone here in the forum who owns a similar vehicle to help me confirm what type of rear differential this truck has. Your input would be greatly appreciated. thank you!

 

My money is on you have an 8.4 non LSD without the red sticker that says LSD that would denote LSD or the elocker that would denote 8”.

I took out my TRD Sport 8.4
and put in an 8.4 off a gardener truck
with a TrueTrac in it

 

I agree with you there!! 8.4 open diff if it's not a Sport, 8.4 LSD if it is.

And the True Trac. I just had ECGS install one for me last month and just now getting my front diff sorted so excited to see how the new gearing and True Trac work.

 

curious, front diff sorted how?

 

Honestly, you are pissing away $ here changing to another style of LSD if you already have the clutch type. A clutch style LSD is totally capable and not going to be the deciding factor offroad- lack of a low gear and 2WD is going to be. Clutch style LSDs can be dangerous on slick pavement- very easy to fishtail or swap ends.

 

Yes, my truck is indeed equipped with an LSD, as shown in the picture. Given that it’s an LSD differential, can I assume it has an 8.4" diameter ring gear?

 

8.4 is what it’s called when it has a stronger carrier with the girdle handle looking thing. Which is what you have.