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Discussion Starter #1
While I have my wife's 1997 RAV up on the lift, I thought I'd check the operation of the locking center diff and the Torsen type rear differential.

I started the engine and put the trans in 2nd gear. With the center diff unlocked, the 2 passenger side wheels turned -- the front turned much faster than the rear.

With the center diff locked, both passenger side wheels turned at the same speed.

When I lightly applied the parking brake, both rear wheels turned, but the passenger side turned faster.

I know that with a large difference in traction between the rear tires, the Torsen diff will act as if it's open. In this case though, both wheels were in mid-air. I expected them both to turn at the same speed -- the way a positraction diff with clutch packs would behave.

Does what I described sound like normal operation?
 

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The Torsen is not a limited slip differential in the conventional sense, it's an auto-biasing torque-sensing (hence the name TOR-SEN) diff, it requires both wheels have at least some kind of grip to provide the bias multiplier, if one or both wheel/s has zero or close to zero grip then the bias multiplier doesn't have anything to go off of. That's why when you applied the parking brake, both wheels turned, the act of applying the handbrake gave the resistance the diff needs to send torque to the wheel with the most "grip". As for why one would spin faster than the other, that could be down to one side's handbrake being weaker than the other.
 

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Discussion Starter #3
The Torsen is not a limited slip differential in the conventional sense, it's an auto-biasing torque-sensing (hence the name TOR-SEN) diff, it requires both wheels have at least some kind of grip to provide the bias multiplier, if one or both wheel/s has zero or close to zero grip then the bias multiplier doesn't have anything to go off of. That's why when you applied the parking brake, both wheels turned, the act of applying the handbrake gave the resistance the diff needs to send torque to the wheel with the most "grip". As for why one would spin faster than the other, that could be down to one side's handbrake being weaker than the other.
Thanks Boden.

I made the classic forum mistake of asking a question without explaining that I have a clue. :wink

I understand how a Torsen differs from a "posi-traction" type limited slip diff with clutch packs -- that's why I applied the parking brake. I'd read about that being a trick people use to transfer some torque to the wheel that has traction, when (for example) the other is in mid-air or on ice -- when there is a huge difference in traction.

What has me confused is that there is NO difference in traction when both wheels are off the ground (on the lift).

In that situation I expected both tires to turn at an equal rate.

I'll admit though, I've looked at animated illustrations of how Torsen differentials work, and I can't entirely wrap my head around it. I expected it to act differently than an open diff though, when both tires have equal traction (zero traction in this case).

Of course there's always _some_ resistance to rotation -- bearing friction, inertia, gears turning through thick gear oil. Lightly applying the parking brake adds resistance, but it's not as if there was none to begin with. Maybe there's a certain threshold that must be reached?

In short, having a "clue" does not = complete understanding... :wink
 

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Try to pry an axle stub off the diff. If it pops out; you have a torsen. If it don't, you have an open diff. (The RAV4 open diff have snap-rings inside the diff to lock/unlock the stub axles.)
 

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Discussion Starter #5
Try to pry an axle stub off the diff. If it pops out; you have a torsen. If it don't, you have an open diff. (The RAV4 open diff have snap-rings inside the diff to lock/unlock the stub axles.)
Thanks Commando.

We bought it new, so I know it has the Torsen-type rear diff -- we searched the entire Mid-Atlantic region (had a friend with access to the Toyota database) to find one with ABS, the Torsen diff, and the manual transmission (with locking center diff). There was exactly ONE. The Torsen diff is listed on the build sheet.

It is good to know that there's a way to confirm whether a rear diff is open or Torsen though.

Wouldn't it be easier to remove the cover? I don't know, just asking.

Also, I seem to recall reading about a number cast into the differential case -- like a #2 -- that was an indicator, but I can't recall the specifics.
 

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You have to drop the diff from the subframe to remove the diff cover, so it's easier to try to remove an axle stub.


The diff code is written on the vin-plate when opening the driver door. Open is 01A (on mine). Don't know what should be the torsen diff code... 01B? On some other Toyota's, the diff code ending with A stands for open, B and C for lsd. I took my torsen from a GT4 Celica.
 
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Also, I seem to recall reading about a number cast into the differential case -- like a #2 -- that was an indicator, but I can't recall the specifics.
That is (most likely) true, "1" denotes an open diff while "2" a Torsen one:

4.2 Rav's have other markings though. I have seen a "7" (don't know what type was though) and an "8" which was a Torsen one..

I took my torsen from a GT4 Celica.
And I plan to take one from a Rav4 like yours! I'm still researching the matter but it seems that, at least in Europe, all pre-facelift 4.2 Rav's without VSC came with a rear Torsen diff as standard.
I have cross-checked part numbers and it SHOULD be a straightforward swap.

EDIT: Check this link for 4.2 open to 4.2 Torsen swap:
http://www.rav4club.gr/forum/viewtopic.php?f=110&t=3477
I know it's all Greek to you, but "StuparArt" did a great job taking pictures.

Eodgator, I am waiting for you to tackle this mod as well (and eliminate guesswork from my part)!!!
 

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Discussion Starter #8
That is (most likely) true, "1" denotes an open diff while "2" a Torsen one:
Rav4 1995-2005 lsd torsen diff vs std diff - YouTube

4.2 Rav's have other markings though. I have seen a "7" (don't know what type was though) and an "8" which was a Torsen one..


And I plan to take one from a Rav4 like yours! I'm still researching the matter but it seems that, at least in Europe, all pre-facelift 4.2 Rav's without VSC came with a rear Torsen diff as standard.
I have cross-checked part numbers and it SHOULD be a straightforward swap.
Thanks -- that's the video I was referring to.

I'm thinking the Torsen in our RAV4 was acting normally. You can see in the video that it acts like an open diff on the bench -- the outputs rotate opposite directions -- so having one wheel rotate while the other remained stationary while both were in mid-air is to be expected. That's how an open diff acts. I guess the 'torque sensing' only comes into play when there is a difference in traction -- up to the point where it is too great for the Torsen to overcome. IIRC that's usually about a 2.5-3.5:1 ratio -- beyond which the Toren is no longer effective.
 

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Europe, all pre-facelift 4.2 Rav's without VSC came with a rear Torsen diff as standard.
I have cross-checked part numbers and it SHOULD be a straightforward swap.

Here in Canada, it's seems that only ''Limited'' 4.2 were equiped with the torsen rear diff.


For the swap it was very easy, it took me 2 hours top chrono including road test (I work in a garage and have lift and air tools).


I used the GT4 torsen unit and installed my RAV4 ring gear on it. I kept the Celica side bearings and races. The backlash was spot on using the RAV4 bearings shims. I installed 2 new oïl seals.


The ''problem'' now was that RAV4 stub axles have smaller splined shafts diameter than the Celica.... so I used the Celica stub axles. The studs of the Celica stub axles did not bolt to the RAV4 axles (not exactly the same bolt pattern, just a few millimeters off). So I drilled the holes in the RAV4 axles until they bolted to the Celica stub axles. It was perfect, absolutely no vibrations. I made about 30,000 km of abuse with it up to now, and still no problem! :)
 

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Discussion Starter #10
Here in Canada, it's seems that only ''Limited'' 4.2 were equiped with the torsen rear diff.


For the swap it was very easy, it took me 2 hours top chrono including road test (I work in a garage and have lift and air tools).


I used the GT4 torsen unit and installed my RAV4 ring gear on it. I kept the Celica side bearings and races. The backlash was spot on using the RAV4 bearings shims. I installed 2 new oïl seals.


The ''problem'' now was that RAV4 stub axles have smaller splined shafts diameter than the Celica.... so I used the Celica stub axles. The studs of the Celica stub axles did not bolt to the RAV4 axles (not exactly the same bolt pattern, just a few millimeters off). So I drilled the holes in the RAV4 axles until they bolted to the Celica stub axles. It was perfect, absolutely no vibrations. I made about 30,000 km of abuse with it up to now, and still no problem! :)
Excellent!

I'd think the Torsen rear diff would have been standard equipment in Canada.

Since you mentioned the oil seals -- our Torsen has an oil leak. I think it's coming from where the right side stub axle enters the case. Of course the gear oil goes everywhere so I couldn't tell for sure. While I had it on the lift I cleaned it up so hopefully the source will be obvious. If it is the right side stub axle, how difficult is it to replace the seal?
 

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Since you mentioned the oil seals -- our Torsen has an oil leak. If it is the right side stub axle, how difficult is it to replace the seal?


Very easy with the torsen. Unbolt the axle off the stub. Don't need to remove the axle from the knuckle. Pry the stub off the diff, pry the old seal to remove it. Install the new seal do the opposite operation. Adjust oïl level. Good time to flush the diff and put fresh oïl!
 
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Very easy with the torsen. Unbolt the axle off the stub. Don't need to remove the axle from the knuckle. Pry the stub off the diff, pry the old seal to remove it. Install the new seal, etc,etc.
Sweet.

So the stub axle just pops out of the diff case? Is there anything holding it in there?

I appreciate your help -- I have an old Haynes manual but it isn't the best because it covers several model years.
 

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So the stub axle just pops out of the diff case? Is there anything holding it in there?


Yes. There is a spring clip exactly like on a front axle.
 

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No, but it would be so much easier to do the job if there was spring clips on open diff also!
 

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Discussion Starter #16
No, but it would be so much easier to do the job if there was spring clips on open diff also!
That's what I was thinking -- why use C-clips at all since spring clips work?
 
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