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Discussion Starter #1
My 2006 highlander is still running great but having some experience with cars now I would like to maintain this vehicle. Vehicle has been driven on mostly highways with little city for most of its life. Never towed anything with it. its a 3mzfe Sport with a 3rd seat. Did the timing belt and all seals at 180k last year. I also plan to change the transmission fluid (never changed before but trans shifts fine) this week using the drain and fill method as I have heard a complete flush can hurt the trans due to the high mileage so was wondering same about the diff and transfer cases.

Is it safe to drain and fill the transfer case and diff? the fluid was never changed before.
 

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Yes. They are all simple open differentials. No clutches or solenoids. Traction control comes from brakes and ABS controller. Technically a center differential and not a transfer case. Very important to keep them full. Clean the vent while you are there.
 

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Note that above comment only refers to 2004 to 2007. Earlier HL’s have a viscous coupling in the center diff.
 

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Ok. Not what the TIS documentation says. Which does your 2001 have? Open diff or viscous coupling?
 

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The TIS information states that the 2004 discontinued use of the viscous coupling. I could be wrong because I have not specifically checked the 2001 and 2006. This is information for the 2004 and it says the 2005 is the same. I assumed that they mean the 2003 has a viscous coupling LSD. By extension I assume that the 2001and 2002 also have the same LSD and that by extension the 2006 and 2007 share the 2004 and 2005 open differentials. When I get time I will double check the TIS documentation for those years too.
TIS seems to indicate that they used the same case but substituted a normal ring and bevel gear for the viscous coupling. So they would look the same but have different functionality.
 

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Discussion Starter #7
Yes. They are all simple open differentials. No clutches or solenoids. Traction control comes from brakes and ABS controller. Technically a center differential and not a transfer case. Very important to keep them full. Clean the vent while you are there.
Thanks for the tip. I actually have all 3 breathers (trans,diff,transfer) on order. Any pics of the locations of the breather vent?

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Thanks for the tip. I actually have all 3 breathers (trans,diff,transfer) on order. Any pics of the locations of the breather vent?

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The vent on the rear diff can be seen (just) from under the car. It's at the back end of the diff, you can get a 17mm open end wrench on it, no problem. The vent on the transfer case is --- near as I can tell -- basically inaccessible. It's at the front of the transfer case, right side (more or less). If you figure out how to change that one out, I'd love to know how. Is it the same PN as the rear?

I haven't gone looking for the trans vent. not a bad idea...
 

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Oh, and... I did my first trans fluid change (via "self flush) at 217K (06 limited 4WD). This vehicle has done a lot of towing. No issue, fluid didn't even look particularly bad.
 

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Discussion Starter #10 (Edited)
The parts numbers are as follows (2004-2007 3mzfe engine):

9093003133 - transfer case breather
9093003129 - diff breather
9093003157 - trans breather

The trans breather has a hose that connects to it, if your hose is cracked or broke you can also order that. There are 2 kinds, a straight and a L shaped.

L shaped hose - 3512145010
Straight - 3512148030

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Discussion Starter #11
Oh, and... I did my first trans fluid change (via "self flush) at 217K (06 limited 4WD). This vehicle has done a lot of towing. No issue, fluid didn't even look particularly bad.
When u say flush, do you mean you took out all the old fluid (around 10 quarts or so if I remember) or just dropped the pan. I plan to drop the plan and change filter w/gasket, clean magnets, and replace whatever comes out. Should be 3.5 qts give or take. I really dont want to flush and have to regret it although my trans fluid is still red in color with 200k miles atm and shifts fine.

Surprisingly the original timing belt also lasted upto 180k, maybe would of lasted longer if I didnt change it. And it's still on it's original spark plugs. Will tackle that once they go bad and do valve cover gaskets at the same time as well as a minor p/s leak.

So far this lander has served us well. Only recently did I dump $2,000 at it doing quick struts, brakes, tires, and common fluid flushes. The timing belt was done by myself so that saved me a bunch.

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When u say flush, do you mean you took out all the old fluid (around 10 quarts or so if I remember) or just dropped the pan. I plan to drop the plan and change filter w/gasket, clean magnets, and replace whatever comes out. Should be 3.5 qts give or take. I really dont want to flush and have to regret it although my trans fluid is still red in color with 200k miles atm and shifts fine.

Surprisingly the original timing belt also lasted upto 180k, maybe would of lasted longer if I didnt change it. And it's still on it's original spark plugs. Will tackle that once they go bad and do valve cover gaskets at the same time as well as a minor p/s leak.

So far this lander has served us well. Only recently did I dump $2,000 at it doing quick struts, brakes, tires, and common fluid flushes. The timing belt was done by myself so that saved me a bunch.

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I drained the pan (didn't bother to drop it), refilled with 5 qts, then pumped out a quart at a time from the return line off the radiator. Procedures have been published (search, you will find). When the fluid cleared up (~ 10 qts iirc) I pumped one more quart, then precisely adjusted fluid level with my 12th. Nothing wrong with dropping the pan, but likely unnecessary. Magnets and filter have ample capacity... and they don't mind that they aren't "clean". Highly recommend OEM Toyota fluid.

I'd caution against waiting for plug problems. I changed mine at 122K, they looked like they'd been driven twice around the block... amazingly good shape... but still: misfires are baaaaaad news on modern closed loop control cars. Beware all the counterfeit Denso and NGK Iridium plugs out there, too. Buy only from well trusted source.
 

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Discussion Starter #13
The manual and dipstick says type "T-IV". I ordered exactly that. Did you change the coils as well. Man those coils are expensive and I dont wanna take any chances with cheapos. I think it was like $60 a coil on amazon (denso 6731301). Dealer wanted like $800 for just coils.

Did you also change the valve cover gaskets. Any idea what brand you used and how much those were?

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The manual and dipstick says type "T-IV". I ordered exactly that. Did you change the coils as well. Man those coils are expensive and I dont wanna take any chances with cheapos. I think it was like $60 a coil on amazon (denso 6731301). Dealer wanted like $800 for just coils.

Did you also change the valve cover gaskets. Any idea what brand you used and how much those were?

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I haven't changed coils or VC gasket. Why do you think you need coils?
 

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+1 on change the spark plugs soon. I don’t like misfires so I have been replacing coils with plugs. I once had a coil fail at 120k miles and it failed fast- within 20 miles of first feeling a stumble I had a flashing CEL. Root cause of failure was a loose valve cover allowing oil to seep into the spark plug well. The dealer had replaced the gasket about 20k before and didn’t torque the middle screws.
I recommend getting the parts online from one of the dealers like McGeorge Toyota or Denso from RockAuto. Best prices I have found with low / no risk of counterfeit.
 

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Discussion Starter #16
Just high miles and I would rather not take off the intake manifold again if one coil fails back there.

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