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

[Broc Luno]

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

[Broc Luno]

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 

[Broc Luno]

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 ...

[paulsRX300]

How do you like the locker? 

I drive an '01 Rx 300. I guess I just missed getting a locker if I'd bought a little older RX.

What little time I've spent off roading my RX it sure needs that locker!!

[Broc Luno]

OK, here is the long over due update.  I have an 03 and I contacted Jimmy Vasser Toyota (JVT) in Napa Calif to see whether they would do the swap for me?  Yes, they would.  So I found a Torsen rear diff at B&R Auto Wrecking in Oregon (excellent source of good parts: https://www.autowrecking.com/  ).  Bought it and had it shipped.  Around $240 by the time it got here.  I had already been shipped a couple of non-posi's by other vendors (advertised as posi's), and refunded my money when I pulled the rear covers and found them to be std open diffs.  eBay adverts can be misleading ...  But they all made it right, just annoying.

In case anyone is looking at door stickers and build codes, and trying to decode stuff, that is a gamble.  The only way to make sure is to put the VIN # into the Toyota "as delivered" database and see if it comes up with a posi as an installed option.  The donor vehicle for these parts was:  JT6HF10UXX0090348   I do not know which number in this sequence denotes posi ...

I took the car in to JVT to have some other service work done last month.  I needed the dash dissembled to fix a non-functioning blend door, an engine service, etc.  The car has less than 100K on the ODO, so I'm letting dealer do the work for now.  That way it's all in the Toyota/Lexus system.  This is planned to be our travel car, so I want any Toyota dealer to see what has happened so far, if I need a fix on the road ... I had them pull the rear cover and inspect (all good), install all new seals, etc.  In about a week, they called and said they had finish everything but ...

They could not get the axles to fasten up. The Torsen Posi has larger axle shafts and bigger differential flanges than a stock open diff.  So they "one bolted it" so it could be moved outside while I went on the hunt for used proper axles and hubs.  They quoted $4K if they had to order all new parts from Lexus.  That's a big ouch if I could not find what I needed ...

While this was going on, the Hennessy Lightning Fire blew up and became the LNU Complex Fire, and then parts of southern Oregon started burning too.  So B&R found the correct parts in one of their yards, but the yard was in a fire zone.  By the time we all slowed down from burning enough to resume business, weeks had gone by.  But JVT was kind enough to store the car and wait.  Another $180 for both rear axles, CV joints and hubs finally got drop shipped to JVT. 

While that was going on, the Glass Fire started.  We were in the fire zone and had to fight the fire to keep our house, so glad the car was safely away.  You can read about it here:  https://www.mercurynews.com/2020/09/29/as-famous-wineries-burn-around-them-not-so-typical-napa-valley-couple-fights-all-night-to-save-home/

After the fire was under control and travel could resume, we fetched the car.  JVT's charges were around $800 split over two bills due to the delay in parts sourcing.  I have since driven the vehicle a little less than 1,000 miles and it acts just like a regular RX 300 on the road.  No chirping, shudder, whine, or any other sign it has a posi.  But on the dirt or gravel it is different.  99% of the time you can not get it to turn a wheel from a standing start.  Granted I have not hit hard from dead stop, but I have a pretty steep part of my gravel drive (35* slope) and it'll go up that from a standing start on slope w/o so much as hearing one little rock roll over.  It is uncanny how grippy it is.

This car will be used to pull my 16' fiberglass runabout, hopefully to Lake Chelan next year, and launch it on some "primitive" ramps (gravel).  I expect it to perform perfectly, but I'll test that here on slippery tidal ramps in the next week or two. 

Anyway, anyone contemplating this should not be put off.  The parts are out there.  My stuff came off a nice clean wrecked 1999 RX 300.  But there were no fitment issues other than needing the correct axles and hubs.  There are no error codes.  The ABS seems to act normally.  I can't see why or how it is not a 100% improvement over stock open diff vehicle 🙂

[GioB]

On 4/5/2020 at 12:50 PM, Broc Luno said:

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 ...

That's bs about the code. I have a 99 rx300 that I bought about a month ago and I too was curious if it has the posi. Was disappointed when I ran across this post and saw that mine has the 2A code on the door sticker, until I checked it today on a gravel road, floored it from a stand still and guess what? The rear tires dug two holes.

[GioB]

On 4/5/2020 at 12:50 PM, Broc Luno said:

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 ...

Beg to differ. I just bought an AWD 99 RX300 with 80,000 kms and was curious about this as well. Door sticker code is O2A on mine but I can tell you with 100% certainty that it's not an open diff on the rear end. I've taken it off road a couple of times already to test it and put the gas pedal all the way down from a standstill on anything but dry pavement and I leave two distinct gouges in the dirt from the rear wheels. Definitely a positive rear end on mine, so I don't think the O2A code has anything to do with the rear diff.

[Broc Luno]

OK, but the only way to really know is pull the rear diff cover and look.  Might do that when you get ready to change the rear diff fluid ...

Easy to reseal as Toyota/Lexus only uses a bead of RTV around the edge to seal the rear cover, even from the factory.

[GioB]

1 minute ago, Broc Luno said:

OK, but the only way to really know is pull the rear diff cover and look.  Might do that when you get ready to change the rear diff fluid ...

Easy to reseal as Toyota/Lexus only uses a bead of RTV around the edge to seal the rear cover, even from the factory.

Fluid changes are due but no way its an open diff leaving two distinct ruts. Tested it multiple times after seeing the O2A code on the door sticker and I'm convinced that code must be for something else. Could also be that the code doesn't apply to Canadian market vehicles since SUVs sent here usually are only available in higher traction package levels. 

[MattRX]

Gio, sorry but that is just objectively false unless your car does not have traction control or your rear diff cover says "17TU".  You'd think us Canadians would get the LSDs, but we don't even have them here, at least for the 2001-2003 Highlander as VSC is standard here along with AWD.  I would assume the RX300 is in a similar boat.

I have been trying for a solid 6 months now to get a pair of these limited slip differentials for my 2002 Highlander and 2008 RX350.  Three out of three were the "17SU" open diffs and were not a Torsen at all!  I forced every single one of them to give me a full refund too.  Every junkyard car I have seen here personally has the open diff as well.  I can confirm these diffs can be mounted on both cars, on my Highlander I just pulled the side flanges out and swapped to the 04-09 RX rear CV axles which plugged right into the diff. This is a very involved job as you'll need rear knuckles, brakes, ABS sensors backing plates and some modifications to get the parking brake to line up on the driver's side. 

I was using the 2008-2013 Highlander rear end parts anyway (basically beefed up 2004-2007 Highlander / 2004-2009 RX parts) so this was not a problem, however you can just swap the side flanges or buy the appropriate 99-00 RX AWD rear CV axles for your 01-03 model RX.  On a 2004-2009 RX, you will just need to pull the side flanges out and swap the CV in, as the axle is one piece on the 04-09 RX and 04-07 Highlander.

I have found an easier way to confirm if it's open or Torsen without pulling the cover.  Just pop open the bottom drain plug and stick in a digital inspection cam (preferably one with a light), and you can easily see if the gears are that of an open diff, or a Torsen

Here is a cutaway of a Torsen LSD that I had the pleasure of seeing in person.  Google a standard Toyota open diff and compare it to this, and you will easily see the physical differences. A Torsen will spin just like an open diff at the pinion or at one of the side flanges, but if you put a lot of pressure on the adjacent flange while the other is moving, you may get the Torsen to lock up slightly.  However, this is not a proper test, and you will want to either pull the cover or confirm via access through the drain plug with a camera before pulling the trigger. DO NOT trust the eBay sellers unless they can prove to you 100% that it is an actual Torsen diff!

Cutaway of a Toyota and Lexus Torsen Type 2 Limited Slip Differential

 

[Thechondo]

The O2A vs 04A, and the TU vs SU method of identifying models that had the LSD, is totally false. 

In the past month, I have found 6 RX300's with the LSD. All of them had 02A on the sticker, and all of them had SU on the diff cover. This has been in northern California 

Pulling the drain plug and using a bore scope is definitely the easy way to confirm without pulling the diff. 

And on that note I still have two for sale 😁

Edited April 18, 2023 by Thechondo

[MattRX]

Hot dang! Two for sale? One for my '02 Highlander and '08 RX350!  How much are you asking and would you be willing to ship to Canada (Ontario)?

[Thechondo]

Shipping to Canada is more expensive, but I've sent two, sending one Monday actually. For Canada, I charge $500 shipped. 

This includes the differential with ring gear, and stub axles. The bearings remain installed, and I also throw in the races and shims just because. 

This does not include the housing. 

I am currently out of stock, but I've sold about 10 now. I found one today, first try again. If you're interested, shoot me a message and I'll hit the yard next weekend. 

[Thechondo]

I should add, I can pull the axles and hubs too, but that will obviously cost more, available upon request 

[Patrick Campion]

Late to the thread, but this is the closest I have come to finding good information on the subject, so any help would be extremely appreciated. I bought my 2000 RX300 a few weeks ago, and managed to run the rear end dry (not a huge leak, so obviously been very low for a long time). I only put a few hundred miles on it before the vehicle began to drive really strangely, the back end "stepping out" and wandering around and such. I've decided to replace it. Could anyone tell me if a 1999-2000 rear end could be replaced with a 2001-2003 part? I'm finding them with the same ratio, but worried there are differences in the case or axles? I haven't taken the cover off yet, so unsure if it's one of these mythical posi units or not.

Edited June 6 by Patrick Campion
Auto correct

[Thechondo]

According to Broc's post above, the axle flanges are larger on the units with LSD, though specific numbers aren't provided.

I can measure the flanges when I get home, I just picked up 3 more LSD's last weekend 😁

So if you have a torsen LSD diff, you need to replace it with one, or replace the associated parts as well if you're switching to non-LSD. 

If you don't have LSD, you're fine to swap with another non-LSD

A dealer should be able to tell you what you have based on your vin. Or you can pop the drain plug and stick a bore scope up there, there are cheap ones available nowadays. 

 

If you end up needing an LSD diff, or want to upgrade to one, send me a message, I have found over 15 now

[Patrick Campion]

13 hours ago, Thechondo said:

According to Broc's post above, the axle flanges are larger on the units with LSD, though specific numbers aren't provided.

I can measure the flanges when I get home, I just picked up 3 more LSD's last weekend 😁

So if you have a torsen LSD diff, you need to replace it with one, or replace the associated parts as well if you're switching to non-LSD. 

If you don't have LSD, you're fine to swap with another non-LSD

A dealer should be able to tell you what you have based on your vin. Or you can pop the drain plug and stick a bore scope up there, there are cheap ones available nowadays. 

 

If you end up needing an LSD diff, or want to upgrade to one, send me a message, I have found over 15 now

Awesome, that's a big help. I'll have to figure out what I have and go from there. Thanks for the quick reply!

[Thechondo]

Maybe this will help.

[SoccerDadrx]

Would this work on a 2007???? That would be amazing!

[Thechondo]

I think it fits 99-09 lexus RX.