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TheMAN
11-17-2013, 09:09 PM
Warning: long read. Skip below for the important bits!
In April 2011, I got a JDM Altezza LSD installed on my van. I'm pretty sure I am the first person outside of Japan to do this. My original diff went bad at around 310000km and a used replacement from the junk yard (unknown mileage; but best guess was around 250000km) was fitted as an emergency repair while I was in Toronto. That cost $500 a couple of years ago. Fast forward to last year; I was driving the bus on the highway and I heard the rear end started making a faint whining noise. It was very hot that day; around 100F, so that was a contributing to the diff/oil getting hot. I also noticed the diff making a clunking noise when shifting in and our of gear for a while before then and progressively more often after that day.

Great, so the junk yard rear end was going bad. I guess I'll rebuild it, NOT (keep reading)!
Since I was going to rebuild it anyway, I decided to add an LSD to the van. This increases handling ability and most important of all, increased traction in poor conditions. Better traction was what I needed as it sometimes sees snow in Canada (when I drive it up there during winter). I found this Japanese page long ago which gave me this idea: http://www.f8.dion.ne.jp/~youpapa/estima/torsenLSD/torsenLSD.html

With the help of my friend, I finally got to work on the van, after it was sitting for many months. Sounds easy right? No! You're supposed to unbolt the backing plates behind the brakes then attach a slide hammer to the wheel hubs to pull the axles out. That didn't happen. We spent a full day on the bloody thing and I even borrowed 2 slightly heavier slide hammers from my other friend who owns a shop. Without boring you with the details, both my arms and my friend's arms felt like jello at the end of the day, after breaking one of the slide hammers! :pissed:

There wasn't anything I could do except throw in the towel. I had to take it in to a garage after all; something which I wanted to avoid doing due to labor costs. First I took the van to a different friend who also owns a shop. First they laughed at me saying I didn't know what I was doing. :rolleyes: Once they got to work on it a few days later, they found out it wasn't so funny after all! :rol: They even borrowed a much bigger slide hammer than what I used to no avail.

Growing desperate, and running out of time (I was getting the bus ready for a camping trip out west), I searched on the Hilux/mini truck and Land Cruiser forums for gear installer recommendations. I wanted someone who does this every day and obviously are very experienced with work like this. I finally did find a shop across town that specializes in off road vehicle modifications. They work on everything from Jeeps to Land Cruisers. Perfect! :) I called over there and I told them flat out that this was not any 4WD vehicle and is actually a van! The owner said no problem, bring it down! So I paid the first garage $60 for their time and to replace the gear oil which was drained out (must do it before removing axles). Then I took it over there. They told me that they never had problems pulling stubborn axles out and they had various ways of doing it. Quite a reassurance!

Well a few days before I left town, I get a phone call from them letting me know that even they couldn't pull the axles out. They even rigged a 6000lbs hydraulic puller to it and it broke into pieces! Son of a gun! :shock: At that point, the only solution was to replace the entire rear axle assembly. I quickly located one which was specific for ABS and rear disc brakes over an hour away. So with the help of (yet) another friend whose father happens to have a Tacoma, we went over there and picked it up. $300 down the hole. :pissed:

Since I was already spending so much money (and costs were spiraling out of control), I decided I might as well replace the wheel bearings in the second hand axles and also replace the ring & pinion gears (I was already replacing everything else anyway). They couldn't locate an aftermarket 4.30 ratio 7.5" ring & pinion gear set to my disgust (which is what came with the van), so I had to settle with 4.11 and deal with the speedometer being slightly off. Oh well! Might as well get better fuel economy this way from the ~120rpm less on the highway. :wnk: It turns out it was a good decision to replace the gears after all. When the shop took off the 3rd member to inspect/work on it, they found lots of metal shavings inside the housing and significant bearing wear. Sounds like whoever owned the donor van before just didn't care about it (like most people it seems).


Well, that's pretty much it, after $1200 in labor costs, plus $300 of parts from Toyota (at a good discount), ~30000 yen for the LSD, and another $300 for the axle assembly, total cost for this disaster was around $2000! :wall: I hope to god I won't have to deal with this again as I'm now using synthetic gear oils from now on and changing it religiously every 60000 miles. Original budget was only ~$700. This is a classic case of Murphy's law at work!

Anyway, here are some pics of the LSD. I don't have pics of it installed because I wasn't around to witness the installation and the shop owner lost all the pics he took with his iphone when it went swimming :sleep: So for any "installed" pics, that Japanese page will have to do.
https://lh3.googleusercontent.com/_XtiJCLQ560k/TbuefmD9w1I/AAAAAAAAAUM/qD-qKhFWQ4M/s800/DSC_1742.jpghttps://lh4.googleusercontent.com/_XtiJCLQ560k/TbuegH3M0xI/AAAAAAAAAUU/d1zIIotCPOc/s800/DSC_1749.jpg
https://lh3.googleusercontent.com/_XtiJCLQ560k/Tbuefs3Vm6I/AAAAAAAAAUE/zJyyTPI0QUQ/s800/DSC_1745.jpg
https://lh4.googleusercontent.com/_XtiJCLQ560k/TbuefirGrII/AAAAAAAAAUI/D_0Ziu41gZU/s800/DSC_1744.jpg
https://lh3.googleusercontent.com/_XtiJCLQ560k/Tbuefx2wCPI/AAAAAAAAAUQ/1k8IxRhDlhM/s800/DSC_1748.jpg

This LSD is off of the 1st generation Toyota Altezza (1998-2005 models). Some Lexus IS200s in the UK also have this same LSD. It was an optional unit in Japan just like the UK. Only the GXE1*/SXE10/JCE1* has the LSD; which are the model codes for the Altezza/IS200. IS300s (JCE15) all had no LSD. Not sure why anyone wants to do it, but if a brand new unit is desired, the part number is 41301-53010 from Toyota. This LSD was made by Zexel Torsen Japan and is a Type 2 Torsen LSD. After lots of searching, I found out that the torque bias ratio for this diff is 2.5:1; a low ratio for RWD, which makes for safety on the conservative side.

TRD Japan also has a 2 way clutch type LSD for the Altezza, which means it will also fit in the Estima/Previa. Part number is 41301-RA010 and has a similar price to the standard Torsen unit. A customizable "selective LSD" from TRD Japan was also available, which requires building to get the desired lock up. Part number is 41301-SE100 but is no longer available, however service parts are still available for it. I honestly don't see a reason to use clutch type LSDs as that requires constant servicing and is for racing applications only. They also require the special TRD LSD oil.

For serious traction needs, you can fit an Aussie Locker (XD-27527), ARB (RD90) locker (requires serious modifications as it requires an air line fitted), etc into the van. The 86-95 Hilux front diff locker is what you need as they are 7.5" ring gear size, and that is what the Estima/Previa uses. The Hilux uses an 8" ring gear for the ring diff, which is why you can't fit the Hilux rear diff bits into the bus. I'm not sure what the Estima/Previa front diff uses (4WD models), but my guess is they are also 7.5". Mine is RWD only, so I will never know. I know the Lexus RX300/Toyota Harrier, RAV4, or Highlander (all early models) has rear diffs that will fit into the Estima/Previa's front diff. Toyota part number is 41301-48020, but the torque bias ratio might be wrong for a front diff application. I don't know!



To fit the Altezza LSD into my bus, I used FJ80 Land Cruiser carrier bearings following what the Japanese guy did. They have more rollers compared to the original bearings (25 vs 20) which means they can handle heavier loads. :thmbup:
https://lh6.googleusercontent.com/_XtiJCLQ560k/TbuegMwqbaI/AAAAAAAAAUY/ntxFLOF-4vE/s800/DSC_1753.jpg

As for the ring and pinion gears, I used Nitro gears, which is an excellent maker of aftermarket gear sets that many Hilux/mini truck off-roaders use.

And finally, here are some pics of the original diff:
https://lh4.googleusercontent.com/_XtiJCLQ560k/TbuegH58GfI/AAAAAAAAAUc/YhqC81NbkWU/s800/DSC_3778.jpg
https://lh5.googleusercontent.com/_XtiJCLQ560k/TbuegatMBCI/AAAAAAAAAUg/7KRGgh8fUtg/s800/DSC_3779.jpg
https://lh5.googleusercontent.com/_XtiJCLQ560k/TbuegvNLe1I/AAAAAAAAAUk/vRBB__Vi-fE/s800/DSC_3784.jpg


The initial break in period required constant temperature checking. I first drove 5 miles then did a feel test on the diff housing, and then did 10 miles to make sure it was still okay. After 20 miles, the diff finally got very hot and necessitated the vehicle not be driven as high temperatures would damage the bearings and break down the gear oil. Hot means above 130 degrees (I used a laser thermometer gun to figure out what "warm" and "hot" meant in actual numbers). I tried to stay below 120 degrees. The temperature cycling was also necessary to help reform the metals and to strengthen them. The first 100 miles was very crucial and the distances that I could drive at any given time progressed more and more as I put on more miles. Anyway, I had the diff inspected today at the shop and everything was good. New oil was put in, and now I am running Redline 75W90 GL5 synthetic.

I hope you all enjoyed the long read. I would love to hear if anyone else will do this!

TheMAN
11-17-2013, 09:13 PM
Due to the axle ratio change, the speedometer was 5-6% off, which means when my speedometer was saying I was doing 90mph, I was really doing around 95! :no: This is unacceptable if I ever am driving the van on long trips.

I spent a couple of nights looking through the parts catalog and determined that the Previa's speedometer gear is the same as the early 90s Hilux/mini truck. Then using this handy calculation tool on this site:
http://www.tciauto.com/Products/Techinfo/speedo_gears.asp I determined that I needed a 19 tooth speedometer gear. Perfect, some of the 1990 VZN85 Hilux V6s have a 19 tooth speedometer driven gear with 6 tooth drive gear setup. The Previa has a 20 tooth speedometer driven gear with a 6 tooth drive gear, this meant the Hilux gear ought to fit.

Since this arrangement is rare on the Hilux (most have high gear numbers as many had large tyres or short axle gearing), I had a hard time finding it from any junk yard. Those that had them were across the country and after shipping the cost was about the same as buying a new gear from the dealership. So I ordered it from the dealership and I didn't even expect it to arrive today (it's a back ordered part apparently).

The new gear even came with a new o'ring for the gear housing! :thmbup:
https://lh3.googleusercontent.com/_XtiJCLQ560k/Tc4X0rmmTwI/AAAAAAAAAWI/1zIfTKlizQI/s800/DSC_3865.jpg

Next I raised the back of the bus as high as I practically could in order to get the transmission fluid to drain towards the front of the van. This is necessary in order to prevent spillage when I remove the speedometer gear.

Then I located the speedometer gear. It is on the right side of the transmission's extension housing. The sensor on the left side is a secondary sensor, don't touch it!
https://lh3.googleusercontent.com/_XtiJCLQ560k/Tc4X0Rd7SMI/AAAAAAAAAWA/pGz092gvmc8/s800/DSC_3870.jpg
There is a rubber boot protecting the wire connector. I moved it out of the way in order to disconnect it easier. Then I removed that rusty 12mm bolt that holds the little retention plate in place. The bolt was actually seized and took some good muscle to get it off (I retapped the bolt hole later on as I reassembled everything).

The whole assembly actually didn't want to come out. The rubber o'ring has essentially "glued" itself into the aluminium case over the past 18 years. I had to get some large pliers to twist it a bit in order to break it free. Then it slid right out.

The original speedometer gear assembly isn't really held together by anything except for surface tension/vacuum from the ATF. The gear just pulled right off:
https://lh4.googleusercontent.com/_XtiJCLQ560k/Tc4X0QOs0MI/AAAAAAAAAWE/gIqw9yh0ZX8/s800/DSC_3873.jpg
I didn't notice the little gold linkage piece in the middle of that pic oriented the wrong direction when I took the pic.... in any case, the small end goes into the gear housing.... pretty obvious once you have it apart.

New and old speedometer gears side by side:
https://lh4.googleusercontent.com/_XtiJCLQ560k/Tc4X0nD3otI/AAAAAAAAAWM/Jv2KF_v4GZ8/s800/DSC_3876.jpg
https://lh3.googleusercontent.com/_XtiJCLQ560k/Tc4X0h9miNI/AAAAAAAAAWQ/bUaXaTrcI4k/s800/DSC_3877.jpg

It's hard to see in this pic, but you can barely see the speedometer drive gear.... it's a giant worm gear inside the gear box's extension housing. Sorry, it was hard to take this pic.
https://lh3.googleusercontent.com/_XtiJCLQ560k/Tc4X0tCuj1I/AAAAAAAAAWU/qHYIWt-LU0I/s800/DSC_3878.jpg

The new gear just pops right in and it went into the extension housing like warm butter!
https://lh4.googleusercontent.com/_XtiJCLQ560k/Tc4X05paohI/AAAAAAAAAWY/CRFWnpMFbRc/s800/DSC_3881.jpg



I drove the van around and went by one of those speed check signs, and it is reporting what I was expecting... the speedometer is accurate! I still need to get it GPS checked but I'm confident it's within 1/2mph accurate :) Accurate speedometer again for only $20! The gearbox shifts at the correct speeds again too. This is no surprise because the speedometer signal first goes into the ECU then the ECU sends the signals to the speedometer.

TheMAN
11-17-2013, 09:17 PM
Some of you may choose to get a different axle ratio than what I used. The lowest ratio you can go is 3.72, but you can switch to a 4.10, 4.56, 4.88, 5.29, or 5.71.... it's all the matter of how big of tires you want to go :LOL2:
I believe 3.72 was stock on the S/C Previas

the only problem you have to face is the speedometer... unfortunately there aren't any speedometer gears greater than 20 teeth from what I can tell, but that doesn't mean they don't exist... so if you go with higher ratio, you will need to buy an expensive speedometer correction box

for 91-93, you need a mechanical box: http://www.yotatech.com/f116/mechanical-speedo-correction-box-install-pics-195986/
for anything newer, you need the electrical box: http://www.4x4wire.com/toyota/tech/tacoma_speedometer/

pdgizwiz
11-19-2013, 09:56 PM
Wow, that's a ton of work! I'm impressed. With a rear drive van, it seems like a good idea. All of my Previas have been AllTrac, so such a project hasn't even come to mind.
I did go through something similar with a Cressida, but since LSD rear ends were an option, I had only to find one. (It's not a Torsen, though..)
I also changed ratios, and dealt with the speedo gear thing. The gear in the transmission isn't too hard to swap, but only if you have the transmission out of the car! Also, although a lot of ratios are available, you can only change the nylon driven gear in a range of a few teeth before you have to change the transmission gear as well. Ideally the pitches of the two gears should be the same, so there's more to it than just the number of teeth.
The adapter boxes you found are good to know about.