Nice work. Those 10mm hex plugs are a pain and they -are- easily stripped. Fortunately, accessibility is good, you can get on an edge with a chisel easily.

My life with old cars in NH changed completely after a pro took me under his wing and gave me a 20 minute lesson in the use of heat.

 

Nice work. Those 10mm hex plugs are a pain and they -are- easily stripped. Fortunately, accessibility is good, you can get on an edge with a chisel easily.

My life with old cars in NH changed completely after a pro took me under his wing and gave me a 20 minute lesson in the use of heat.

Thank you.

I had an issue with a 2011 Lexus RX350 AWD years ago with a similar rear differential setup with the same 10mm drain/fill hex bolts. Both hex bolts stripped out on me during the rear differential fluid change and I had to use a large spiral bolt extractor to grip the round edges. The extractor chewed up the bolts, but it worked. I am ready this time with my extractor and new hex bolts.

However I will keep the chisel method in mind just in case the bolt extractor doe not work
.

 

Today I finished the transfer-case gear oil change. I used Valvoline 80w-90 gear oil and a hand pump. I also added about an ounce of AT-205 Reseal to the gear oil to hopefully correct any minor gasket issues in the transfer-case. I was going to do the transmission pan and filter, but really did not feel like messing with the two corner pan bolts under the frame today. Those two 10mm bolts are a pain to access, however they can be accessed without lifting the engine/transmission. But requires patient due to having to use a small 10mm wrench to make small turns. I will save the transmission for tomorrow.

80w-90 being pump in the transfer-case. The transfer-case needed about 1 quart(.9 to be exact) to fill up.

The trans-case bolts look good as new after a couple of days soaking in Evapo-Rust.

The fluids I used. Valvoline 80w-90 gear oil and an ounce of AT-205 Reseal.

I also have to change out the o-rings on the transmission case plugs since it looks like one is leaking.

 

I finished the transmission pan and filter install today. The last two bolts under the frame was very hard to properly torque down to 69 in/lbs with an torque wrench. I had to use an long handle box wrench with a flex head and torque wrench-to-box wrench adapter. I ended up using about three different 10mm wrenches to get the last three bolts under the frame installed and properly torqued; however the last two had hardly any room to access under the frame. I was successful, so now i just have to fill the transmission with about 5 quarts on fluid. I used a Beck Arnley transmission filter kit that includes the rubber gasket and a new Dorman transmission pan.

I used orange loctite on the pan bolts since Toyota specify using blue loctite to secure the pan bolts. I only have orange, but it should work. Next will be the rear differential fluid change.

Make sure you lubricate the transmission filter o-ring with some transmission fluid.

I cleaned the rusty transmission pan bolts with Evapo-rust and they came out looking new.

New filter installed.

Torque-wrench adapter used to access the last hard to reach transmission pan bolt. You have to keep the torque wrench at 90 degrees to the box wrench to avoid messing up the torque wrench accuracy when tightening the bolts to spec.

The transmission pan installed.

The various 10mm wrenches and sockets used.

 

I’ve found that my 18v cordless drill ( not impact) with a 1/4” extension works well both for removing and installing the trans pan bolts. It doesn’t have enough torque to break or strip the bolts and gets them all relatively even. Then I just do the hard to reach ones by feel with a wrench. I skip the loctite, and so far, no leaks and no missing bolts after 3 filter changes.

 

I used to use methods like that years ago until a mechanic friend of mine educated me on the importance of using the proper torque for every bolt for uniformity for a proper seal. However, I am sure that that using an impact would have worked just as fine for the pan bolts. In my case, I only use a torque wrench to torque all my bolts to spec when possible.

As for the case for using Loctite, my old bolts did have blue Loctite on them so I just put some back on them when I installed them. I saw no real reason not to use Loctite since I did have some available. However, i am sure that the transmission pan would not fall of the transmission without it.

 

I now understand why newer cars have done away with transmission dipsticks. The reason is that they are hard as heck to read properly. I added about 3 quarts of fluid that brought my cold transmission fluid level to full mark on the cold area of the dip stick. However, after I let the fluid warm up to operating temp(158-172F) confusion happens.

The dipstick did not register any fluid when hot; so i added about a quart(4 quarts total). Still low; then i added another for a total of 5 quarts. Now, the dipstick has all kinds of fluid residue from the dip stick tube so reading the dipstick properly is impossible. I am now letting the fluid cool down and will try to read the fluid level again when the fluid all heat up at the same time and hopefully the tube residue drains into the pan so I can get a accurate hot reading.

So now I have about 5 quarts of new fluid in the pan(or system), but I am thinking that I will have to suck out about an half a quart of fluid with an extractor to get the level correct. I should have just measured what drained out the pan and filter; then just replaced that amount like i usually do on other cars. Now it is a guessing game.

 

Carguy:
The following is just for posterity - I know you know how to do this, but it is not in the owner's manual for others.
I agree - Toyota got tired of replacing transmissions under warranty from incorrect service so they removed the DIY serviceability to the extent possible. It also helps meet government environmental requirements by eliminating regular fluid changes.

How to check from the factory manual, with my annotations/experiences:
Correct fluid level is critical in these these transmissions. Even 500 ml too much or too little can affect shifting.
1) Check it hot. Transmission fluid temperature between 70C and 80C (158 to 176F). This can be checked with a good scanner. In my car, it can take up to a 20 minute drive. The cold lines are on the dipstick just to verify that there is approximately the correct amount of fluid after service before warming it up.
2) Park on a level surface. Engine should be at warm idle, about 650 to 750 RPM at normal operating temperature. .
Shift from PARK to LOW and back again. Hold each gear position for 1 or 2 seconds.
3) While idling in PARK, brake on, remove the dipstick, wipe with a clean towel, insert to the click, and remove and read. Make sure you are reading the meniscus line on both sides of the dipstick, and not the extraneous smears from inserting and removing the dipstick. A blocked vent may result in more smears on the dipstick.
I find that a UV light in a dark garage is very helpful in distinguishing the fluid on the dipstick.

Whenever making any changes affecting the transmission, I find it useful to reset the ECM adapt values by disconnecting the battery negative for about 10 minutes and reconnecting, then warming up the engine at idle, and then driving in various conditions for 20 miles or so. In my experience, the ECM adapts to worse conditions fairly rapidly by adjusting pressure and perhaps timing, but if the condition of the transmission improves through service, it may take a while for the pressure and timing to reset, if it ever does. There is a TSB on this.
Yes, you can heat up the transmission by power-braking, but I don't like putting that much load on the clutches.

 

Well I performed the transmission fluid level check again with all the fluid reaching the same temperature at the same time and with no residual fluid in the dip stick tube.

5 quarts seems to be about right on the transmission dip stick; so I will leave it as is. I used a Autel scan tool to check the transmission fluid temperature(ECT). I assume that 4.8 quarts or 4.9 quarts would be perfect.

The Autel temperature reading.

 

Sounds good. Given how dark that remain fluid in the transmission, maybe you'd want to do another drain and refill soon?

80W90 and 85W90 look like old dino weights. Maybe Valvoline 75W90 fully synthetic would be better?

+1 on Valvoline Maxlife ATF.

 

Thank you. I actually will do a few more drain and fills over time to remove most of the older fluid that was in the cooler and torque converter. My goal is to drain and fill about twice a year due to how easy the process is on the Highlander; except for reading the transmission dipstick.

I do not want any leaks from any old gaskets in my transfer-case from using a very light gear oil weight like 75w-90; so I will just stick with the thicker factory 85w-90 weight(or close 80w-90) in my transfer-case. The transfer-case is a pain to access if it does leak from its cover gasket. Remember, my transfer-case is 15 years old.

I may use 75w-90 in my rear differential since that cover gasket is easy to repair if a leak occur.

 

I used Valvoline 80W-90 gear oil & Valvoline Maxlife ATF (blue bottle) with good results so far.

 

Well, the rear differential 10mm hex fill bolt proved to be as stubborn as I suspected that it would be. The fill and drain bolts are both rusted to the rear differential. I only have been working on the fill bolt since it would be a major problem if I can not remove that bolt since I would not be able to fill up the rear differential. However, the fill bolt is located in a very tight area and have only the bottom section of the bolt exposed; which make using a large spiral extractor socket useless.

So far I have used an air hammer to hammer in a 3/8in10mm hex socket and is waiting on an impact rated 1/2 to 3/8 drive adapter to arrive by mail so that I can use one of my 1/2in drive breaker bars or 1/2in air impact to hopefully break the fill bolt free. The only 1/2 to 3/8 drive adapter I have is a cheap chrome version that will not hold up to the amount of torque needed to break this rusty bolt free; hence impact rated one I ordered. I hate rusty bolts.

Rusted out rear differential and fill/drain bolts.

10mm hex socket air hammered on the fill bolt for snug fit. Hopefully the fill bolt will give with some leverage without stripping out.

 

When i changed the rear diff. oil i had the same problem so i sprayed it with penetrating oil and let it sit for an hour then used a pick tool to clean the inside of the hex bolt, i got most of the rust out so the hex socket went in almost all the way.

 

That rust looks nasty.

+1 on a rust penetrant like Kroil or PB Blaster. Spray and let it soak, then spray it again and let it soak again.

 

I would definitely use the heat wrench as well on that one. Due to the PITA factor if that plug strips out, you don’t want to leave anything on the table! 😬

 

I can heat up the bolt with my induction heater, but 1/4 of the bolt is recessed under a top lip in the differential case so it does not heat up as hot as if it the coil was going completely around the bolt so that it gets red hot. But it does heat up the bolt so that it smokes.

I do have a 1/2 in drive 10mm hex bolt removal tool if it does strip out which should work. I also have a large 13/16in spiral removal socket(with a very large wrench) that I used on a stripped 10mm 2011 Lexus RX rear differential fill plug; however that rear differential fill plug was more exposed than the Highlander differential so it may not work.

The hex removal kit that may work if the 10mm hex bolt strip.

The other option that may work if the socket can get a good grip on the sides of the fill bolt. Worked on a Lexus 10mm fill bolt.

 

I used some PB Blaster and heated up the bolt up with my induction heater device, but the bolt would not turn with my 12in long 3/8 wrench or with my 12in long 3/8 breaker bar I used, hence the need for more leverage.

I should have purchased a 1/2in drive 10mm hex impact socket and used that. However, I hammered in a 3/8 socket which limited my use of breaker bars. The only breaker bar I have that have both 3/8 and 1/2 ends is a 24in long one that is too long to be used while laying on my back due to the fill plug location. I do a have 24in long breaker bar with a racket end that would work perfectly, but it have a 1/2in drive end.

Both breaker bars are too long, but the racketing one allows for some more movement to hopefully break the nut loose. If that does not work then I will try a stripped hex removal socket with an air hammer bolt breaker to vibrate the bolt loose.

I am hoping that I can use the 1/2in racketing breaker bar on the bottom with a 3/8 impact adapter.

 

After heating up the area you can put a jack under your breakerbar and let the jack do the work.

I wonder how much our cars are worth now after all these work.

 

Good idea, but there is no space on the opposite side of the differential to force the handle up with a jack to break the bolt loose. I have to use downward force to crack the bolt free on one side. If I had a car lift then I could just use my 30in breaker bar and pull down. However, not much room to use any good tools with the current setup.

I could sell my 2007 for good profit for sure. Used Highlanders in my area in good running condition with just over 200k miles are still going for about $6000-$8000 for older 2002 and 2004 FWD models. 2006 and newer AWD models are rare and cost about $8000-$10000 in good running condition in my area. I paid only $5000 for this one in poor running condition. So I could still pickup about a few thousand minus what I put into it if I did sell this Highlander.

 

I finally removed the rear differential fill plug. I ended using a 1/2 drive set(including 24in racketing breaker-bar) with a 10mm damaged hex removal socket. The set up worked perfectly. I should have just used the hex removal socket from the beginning, because the normal hex socket just stripped the fill bolt anyway. It was a waste of time hammering in a normal 3/8in hex socket to this rusted bolt. The hex removal socket bites harder the more you apply pressure even if the hex opening is stripped which did the job perfectly.

I also removed the drain bolt as well with the hex removal tool; broke it loose really easy with the breaker bar. However, the tool does damaged the hex bolt so I would not use it on a hex bolt you want to reuse. I bought new drain and fill bolts so not an issue for me.

The fluid was a dark amber color; which was what the transfer-case was as well, but in better condition. I will replace with 80w-90 fluid like the transfer-case. The magnet on the drain bolt only had some fine metal ; so it seem that the rear different is in good working order.

Air hammered the 10mm hex removal tool on the stripped fill bolt and use my 24in ratcheting breaker-bar to break it loose.

The same process worked for the drain bolt as well.

The rear differential 10mm hex drain and fill bolts removed. The drain bolt magnet only has some fine metals and the fill bolt is very very stripped out so it is unusable. The drain bolt hex opening was good when I hammed in the hex removal socket; so it has a extremely tight fit so that I will have to find a way to remove the extractor tool. The drain bolt is unusable as well now.

 

I forgot to add that I did change one of the transmission case plug o-ring before adding new transmission fluid that seem to leaking with a new 010 size o-ring.
However, after further inspection I may have an weeping transmission cover that is also the transmission mount bracket; since it does have some orange RTV sealing it near the oil residue area near the case plugs. The upper case plug did seem to be "wet", so it may the source or one source of a transmission leak. I will keep an eye on the area and see if the leak is bad. It looks like i may be removing the transmission case cover to reseal it with RTV later on, but not now. So far no new transmission fluid leak leak occurred while the engine is idling so maybe the case plug was the only issue.

The transmission case plug o-ring(010 size) I replaced.

 

As many may know ; I recently purchased a poorly maintained 2007 highlander with 226k miles and have been bringing it up to my standard of operating condition which required major work on the engine and power steering system. Luckily, the transmission and transfer-case seem to be in good condition even if the oil in both units does not appear to have ever been changed. I will fill the transmission with Valvoline MaxLife transmission fluid and the transfer-case with 80w-90 Valvoline gear oil since the fill plug sticker states the transfer-case requires 85w-90 gear oil.

I have now started draining the transmission and transfer-case fluids. Both fluids were black and well used, however the magnets only had fine metals in both units. I also had some very rusty bolts on both units. The good news is that a good long soak(2 days) in Evapo-Rust have the bolts looking new. Next I will tackle the dreaded rear differential with it rusted bolts(fill and drain) that can only be removed with a 10mm hex. I am sure that both hex will strip before breaking the rusted bolts free.


My black transmission fluid(should be red) draining and rusty 10mm pan bolts.

Transmission pan magnets with only fine metals.

The rusty transfer-case and black gear oil (should be amber)draining out.

The 24mm transfer-case drain bolt with fine metal on the magnet. 24mm fill plug with 85w-90 sticker.

The transmission pan bolts after a few hours in Evapo-Rust.

The transmission bolts and transfer-case bolts after soaking a day. They are all nearly perfectly clean.

Before you buy new bolts if your old bolts are rusty try soaking them in Evapo-rust. Good product if you got time to wait for it to work.
guy

Hello carguy75,
How did you get the rusted pan bolts free? What penetrating fluid/oil did you use? And how did you use it? Thanks for sharing the valuable info.

 

Hello carguy75,
How did you get the rusted pan bolts free? What penetrating fluid/oil did you use? And how did you use it? Thanks for sharing the valuable info.

The transmission pan bolts came free pretty easy without any rust remover; just needed a 10mm driver. However, I used PB blaster on the transfer-case and rear differential fill/drain bolts. I just sprayed PB blaster on the rusty bolts and let it sit for a few hours to help break the rust bond.

Note: It may be best to spray the 10mm transmission pan bolts with rust removal like PB blaster before you attempt to remove them to prevent snapping off a bolt head on the transmission pan. I did not, but it could have went sideways if one of the rusty 10mm bolt head snapped off.

 

I finished the rear differential gear oil change. I used Valvoline 80w-90 as with the transfer-case. I went with thicker gear oil due to its being closer to the 85w-90 that Toyota specify and it reduces the chance of developing any weeping leaks from the old gaskets that can occur when using thinner gear oils like 75w-90.

The rear differential and transfer-case covers look a pain to remove if a gasket does leak. The transfer-case cover is the worst since it looks like you will have to remove the transfer-case off the Highlander to replace a gasket. The rear differential cover is a part of the support so it also looks like a very involved repair as well to a lesser degree.

I also cleaned off the rear differential breather; which was covered in crude. Now it moves like a new breather. A working breather is very important since it prevent pressure inside the differential from blow out seals which cause leaks.

Rear differential filled up(1 quart) with hand pump. New 10mm hex bolts are tighten down to 36ft/lbs.

Rear differential breather located on top of the rear differential just above the fill bolt. Inspect and clean these often to prevent seal leaks.

The transfer-case and rear differential cover. Both are hard to remove if a leak occurs, so I would just stick with the thick gear oils in an older Highlander.

Rear Differential Cover

Transfer-case Cover

Tip: To get all the gear oil out of a quart bottle with the cheap hand pumps add about 2inches of 5/16 tubing or hose to the pump feed tube. For some reason the cheap hand pump feed tubes are too short and leave a good amount of gear oil in the bottle. I used to have to buy an extra bottle just to properly fill up my differentials before I learn this trick.

5/16th coolant line used to extend the hand pump feed tube. Works like a charm to get all the gear oil out of the bottle.

 

I stand corrected. The damaged-hex removal tool did not damage the hex opening on the rear differential drain plug. The fitment was tight, but no harm done. For now on I will use this hex removal tool as my go to hex removal tool for rusty hex fittings instead of using a normal hex socket.

The drain bolt (left)with the hex removal socket removed. Still looks good. I could have just cleaned off the rust and reused it. The fill hex bolt (right)is completely stripped after first trying to use a normal hex socket, but the hex removal tool still got it out even with a large amount of torque.

 

I stand corrected. The damaged-hex removal tool did not damage the hex opening on the rear differential drain plug. The fitment was tight, but no harm done. For now on I will use this hex removal tool as my go to hex removal tool for rusty hex fittings instead of using a normal hex socket.

The drain bolt (left)with the hex removal socket removed. Still looks good. I could have just cleaned off the rust and reused it. The fill hex bolt (right)is completely stripped after first trying to use a normal hex socket, but the hex removal tool still got it out even with a large amount of torque.

Sounds very good. What is the brand of the hex removal tool and where did you buy it?

 

I finally finished up the fluid changes on this Highlander with an engine oil change. I saved the easiest job for last. I used Valvoline Maxlife 5w-30 full synthetic high mileage oil with an Denso 150-2010 oil filter that looks very much like the Denso made Toyota OEM filter. I like that the Denso oil filter o-ring comes pre-lubed with a plastic cover.

My drain plug did not have an washer; so I assume that the last person who did the oil change was not a true mechanic or not very good at keeping this old Highlander running well since they forgot or chose not replace the washer. They also used a low-end STP oil filter, which is not a concern if they changed the oil before 5k miles;I doubt it. I replaced the drain plug washer with a Toyota blue washer.

The job was a standard oil change without any special methods needed. Remove the 14mm drain plug, let the old engine oil drain out, replace 14mm drain plug with new washer and tighten to snug, remove old oil filter, replace with new oil filter, hand tighten oil filter and then tighten oil filter with a rubber strap wrench to snug, add 5 quarts of engine oil. Done.

Now my old Highlander is road ready after many months of repairs.

Drain plug with no washer and dirty oil draining out.

New blue washer on drain plug.

Old STP oil filter draining the old oil out of the built-in oil filter drain system. New Denso filter installed by hand and then with a rubber strap wrench.

The 5 quarts of oil I used. Good stuff for any engine especially older high mileage engines.

 

Congrats!