Broc Luno

Posi (Limited Slip Diff) for your RX ...

Recommended Posts

Ot seems there was/is a mythical Unicorn among RX's.  In the early model years there was an optional Torsen posi-traction rear differential.  I'm very keen on finding the parts to make that happen in a 2009 RX 350.

So I went looking in the Toyota parts stream. I was searching the parts at a web site called Toyota Parts Overstock, or something similar. I was looking to see if some, or all, of the internals from an earlier rear diff would fit in a latter one? So I concentrated on the center section (the casting that carries the ring gear) P/N 41311J in the diagram. As I honed in on that part, I got a parts diagram with notes that that listed the years and models.

The internals seem to be an 8" 2-pinion (spider gear) "V-6" diff that was commonly used on most everything: TOYOTA: 7 models, 305 variants between 1982 and 2010. Fits CAMRY, CELICA, HIGHLANDER, PREVIA, RAV 4, SIENNA, VAN

And on page 1 at the bottom are some variation notes about the shape of the spider gears. And under that is a note about the model RX300 ... The rear end in a Lexus RX might be designated as an MCU15 ... [Nope - MCU15 is the designation for the Lexus Service Manual for the RX 300.  I can be found on-line by Googling in MCU15 and Manual]

Tthis is not conclusive proof of course, but aken all together, it seems to indicate that minus some variations in attachment, rubber isolation supports, and spider gears; this same rear end (internals) have been used in RX's from day one through some time in 2010. So the idea of finding a rare early RX 300 posi rear diff is possibly a good one. And with changing the external bits that make up the year model mounting variations, might actually fit a Gen II RX 350 ...

I have to do more research, and prolly digging at Pick-&-Pull looking at Highlander and RX models from various years. But if what I'm reading is true (?), we could use the RX 300 Torsen posi in later models ...

The trick will be to get a VIN number from an early vehicle with a Torsen factory installed. And use that VIN number to order the internal parts through Toyota's various web sites to build up a modern version (housing & mounts) to fit the vehicle of interest.  Or rebuild the one we have with selected new internals.

See attached for info:

Lexus RX Rear Axle Housing.pdf

Share this post

Link to post
Share on other sites

OK, I been digging and digging.  Been to all sorts of off-road after market and race after market vendors, and no Posi's available ...  It is believed that this is the Toyota 6.7" ring gear diff ... But Toyota made lots of OEM Posi's it seems. 

The RX uses a differential carrier and gear selection designated -02A as shown at the bottom of the build plate in the door jam.  This rear carrier and differential were available with a Posi (Torsen), all gear - no clutch, center section in RX's from 99 to 00.  Then Lexus dropped the option.

The same rear end was used in RAV4's, Highlanders, and RX's for many years.  Any independent suspended vehicle that shows -02A can prolly use this rear end ...

If you put this phrase into the search block in eBay, you will come up with a selection of used OEM LSD differential carriers.  The wrecking yard interchnage number is  440-58865A

Carrier Rear 2.928 Ratio Locking Fits 01-03 HIGHLANDER 

Build Plate 2002-b.jpg

Share this post

Link to post
Share on other sites

Well I found one in Oregon with 158K on the ODO. Seller (B&D Auto Wrecking) confirmed that it was/is a locker. So after the previous three vendors failed to check well enough and either sent the wrong part, or just refunded my money after double checking, I pulled the trigger and got it. Yup, it's a Toyota OEM Limited Slip Differential carrier complete. Raining right now, so don't want to open it up, but will in a few days.

Looks like the right rear stub axle seal was weeping, so before it goes into my RX, I'll have the shop install all new seals and double check the lash. I don't want a noisy one replacing a dead silent existing one...

So I got a photo of the "Build Plate" off the drivers door jam (sticker) from the donor vehicle (Highlander) :
So you see the axle data in the lower right hand corner? It says -04A for this axle. My existing one is a std open diff (-02A). It's the thing you are looking for when out shopping. -04A is the axle code to look for in the field when hunting for one of these.

I have seen one door sticker with an -03A on it, but was not able to get any more info about what axle that might be ...

Share this post

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.