5th Gen 4Runner Drivetrain Rebuild: Rear Axle Assembly Rebuild + Rear Axle Seal Replacement

Table of Contents

Drivetrain

• Rear Axle Assembly Rebuild + Rear Axle Seal Replacement
• CV Axles Rebuild + CV Axle Seal Replacement + Front Wheel Bearings Replacement
  
• Driveshafts Rebuild

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Can somebody explain this to me? I am having a strange leak into the parking break. The break system is in good shape. No leaks anywhere. Parking break on the passenger's side is consistently covered in something oily. I have been monitoring break fluid for the past year. No problems there. Every time I check the rear breaks I see parking break assembly all covered in something.

If it was related to parking break cable, the driver's side would also be affected as well.

Here is the video of what I am talking about:

https://m.youtube.com/watch?v=tEPoRrDtEuo

 

Maybe gear oil from the differential.

 

Caliper piston seal looks intact as well as the banjo fitting. Seeing as how the 'stain' appears all around the brake housing (backing plate) I suspect a possible rear axle seal.

 

Not a brake issue. I'd be looking at axle seal.

 

Thanks! Never would have thought. I will have to check rear axle seal out. I've heard it is a nightmare to change that.

Is there an easy way to confirm this without dismantling everything?

 

Unfortunately not.

 

Looking at this video, it will be a lot of work. It also seems to be very expensive if done at a shop, so it will have to be a DIY project.

https://www.youtube.com/watch?v=xvQybhW

What type of press is good for the job? Do I need a 12T, or 6T will do? I was looking at these from Amazon for a very reasonable price. 6T may be a bit too short.

$160 VEVOR Hydraulic 12 Ton H-Frame Garage Floor Adjustable Shop Press with Plates, 12T, Orange

https://www.amazon.com/VEVOR-Hydraulic-Adjustable-Shop-Press/dp/B0BZ7YY3CP?crid=2WF71YM5VZHDV&keywords=VEVOR+Hydraulic+Shop+Press&qid=1707608631&sprefix=vevor+hydraulic+shop+press%2Caps%2C471&sr=8-3

 

I would go with 20T HarborFreight $250. you risk to pay twice with 12T, or hassle return in a middle of job. all auto shops using 20T

 

Yes, probably diff oil. Check your breather first, you probably need the seal also but start by verifying that breather works. I had this problem on a Tacoma, shop (not dealer) replaced both seals for about 350.00.

 

It seems that seals are not a problem to replace at all. Parts cost $25, and replacement can be done without removing the parking brake assembly. I found this video, and comments to it very informative.

https://www.youtube.com/watch?v=__PSNbupxBc

I am still debating if I should go ahead and replace the wheel bearings or wait until they fail. My decision is leaning strongly towards replacing them while I am working on the car in my garage. It seems like not every shop has the equipment to pull and press Toyota rear wheel bearings, and dealer wants an arm and a leg to get the job done. I have calculated the cost of all the parts and tools, and it came out to be around $1,000.

 

After doing some research, I finally figured out what caused the axle seal to blow out.

...

Water in the rear differential fluid

• If you ever drive through deep water that may submerge the entirely axle, it doesn't hurt to go ahead and do a drain/check unless you are sure your axle seals are good and you've extended the differential breather to a higher drier location.
  • When you put a hot axle into cold water the temperature change creates a sudden vacuum inside the axle assembly.
  • If there are leaks or the breather itself is under water, it will draw water into the axle.
  • The gears will turn the water/oil mix into a gnarly sludge.
  • Also, once the axle gets hot from the poor lubrication the water will boil and the steam can potentially blow out seals.

https://www.reddit.com/r/4Runner/comments/ujvqtf/how\_often\_does\_differential\_fluid\_need\_changed/

...

I discovered rear axle seal leak the first time after a long road trip that involved many water crossings. I never did rear differential breather mod. That is probably another thing that I should do as well as replacing the seal.

Not sure how much water got in, but the fluid is definitely due for a change. I came across another video where a guy does drain and fill several times after water got into his rear diff. Not sure if this is necessary in my case. Mine doesn't look like milky sludge.

https://www.youtube.com/watch?v=pylitmMEsLw

 

Rear Axle Overhaul



Rust has slowly made its way to mating surfaces of the hub and rear axle housing.



I cleaned it up a bit the best I could with angle grinder and wire brush attachment. The pitting is very minimal.


Wheel bearing and the axle have seen better days. ABS sensor was completely stuck inside of the hub, and ABS sensor stud nut was seized onto the stud. All of these components were far beyond repair and would need to be replaced.



Parking brake bracket bolts broke off.



I had to drill out through holes to secure it in place.

 

Trying to get a stuck ABS sensor, I managed to damage ABS sensor ring. Initially, I was hoping to just change out axle seal that was leaking, but once that damage was done I had no other choice but to do a complete overhaul of both sides.

It was a difficult decision to make. I understood that no matter what, I will have to bite the bullet and get it done.

• In the past, every mechanic that I spoke to refused to work on my car because of rust. I doubt I would be able to find anyone who is willing to even get near an axle like this in the arid Southwest region of the country.
• Pressing the wheel bearing off and a new one on is certainly not enough. The axle needs to be completely rebuilt, including rust removal, painting, etc. Who is going to do that?
• The price of pressing these parts in and out would bout about the cost of the press and the specialty tool for wheel bearing removal.

In total, together with the all the tools, this complete overhaul cost me around $1,500. The hardest part was making the decision to get 20 ton press. This is the first time in my life that I needed one, and I am not sure if I will ever need it again. Harbor Freight Tools had a parking lot sale that week, so I managed to get one for $250 out of the door. Specialty tool cost me $50. The only way I could justify the costs was by come comparing them to how much it would cost me if I paid someone else to do the job. Use value of these items is very minimal.

The major drawback of this sort of repair is time. I have decided to go in steps and first take everything apart to see what needs to be replaced. Disassembly, rust removal and painting took several days. After concluding that the situation demands extreme interventions, I ordered the parts. It took about a week to gather them all together for reassembly.

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I felt a bit safer using repair manual for the specs rather than completely relying on YouTube videos. I referred to this video for the methods, which made the job a lot easier.

https://www.youtube.com/watch?v=xvQybhW_nbI

It is interesting to see how many different methods there are for getting the remaining wheel bearing part off of the axle shaft.

This one is the most creative way, if you have a torch. I tried it with regular butane torch, and it didn't work.
https://www.youtube.com/watch?v=bqKmvhbh1eY

This is the way that is described in the repair manual.
https://youtu.be/G3K215iPPOE?si=4fqvb-LNMhC16x_w&t=912



Using wheel bearing puller turned out the easiest one for me. AutoZone is just around the corner, and you can't beat their loaner tool program. I loaned wheel bearing puller and bearing race.

I didn't like using bearing race as a race to install the axle seal. Instead I used the part of the wheel bearing that was left on the axle shaft after wheel bearing was pressed off. It seems to be the tool of choice for many, as Instead of hitting in the center, it allows you to hit along side of the seal. It makes it easier to make corrections, plus you can see exactly where you are hitting.

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Notes from the Repair Manual

Rear Axle Shaft Removal: pg 1325

Orientation of the Washer and Spacer: pg 1331

• Install the washer with its tapered surface facing downward.
• Install the retainer with its chamfered surface facing downward.
• Torque for 4 Wheel Hub Nuts: 44 ft-lbs (pg 1332)

 

Pressing the wheel bearing off with 20 ton press was not as easy as I imagined. The harder I pressed, the more the red plate bent under tension. I ended up using torch to heat up the wheel bearing until it was red hot, and then pressing it off the axle. It worked like a charm.



With a loud bang not only the wheel bearing, but also all the rust on the dust shield came off. The red plate on the specialty tool was bent, but still usable.



Condition of the wheel bearing after 185k miles.



All the parts, including hub studs were rusted and had to be replaced. I just hammered everything out without a second thought. The guy in the first video directly hits the studs with a mallet. I would not knock out hub studs by hitting them directly with a mallet. Upper threads may get compressed, making it impossible to screw on a flange nut. Ask me how I know.



Condition of the spacer and the washer. The spacer had a noticeable grove, and the washer was rusted. I replaced both of the parts with new ones.



After a few hours of work, I managed to clean up all the rust from the axles and brake shields using angle grinder with wire wheel attachment.



I decided to paint all the parts with several layers of paint. Wheel bearings have been ordered through NAPA, whereas other parts through Toyota dealer. I went with aftermarket ABS sensors from RockAuto. All the parts should arrive next week, and will be time for assembly.

I already purchased 1-1/2" pipe coupling from Home Depot to drive the new wheel bearing onto the axle shaft, just like shown in the first video. It fits great over the hole on the metal support plates, and is also an exact fit over the spacer.

 

Wow! Now that’s corrosion. Might have been easier to replace the whole rear end

 

Nice work

 

I don't think he goes the easy way very often.

 

Never thought of replacing the whole rear end. At this point most of the corrosion is taken care of and all the parts that were exposed to years of snow and salt have been replaced except a few. I am contemplating of replacing front drive-terrain components entirely.

One of disk break dust covers has completely fallen off. The other one is barely hanging on whatever metal is left to support it. I found both left and right for $100 on eBay and already ordered them for this rebuild.

My plan is to replace the front wheel bearings completely. I already ordered SKF BR930978 from RockAuto along with o-rings from Toyota dealer. ABS sensor is, most likely, stuck in the knuckle. If I will ever need to replace it, the wheel bearing/hub assembly will have to come off. The rear ABS sensors were stuck in the hubs so tightly that I could barely knock them out. I am thinking of replacing them right away, so I don't have to deal with two problems in the future. The price is the only deterrent.

Looking at the condition of the axle seals in the rear, I can only imagine what the front ones look like. If they are not leaking right now, it may be just a matter of time until they will. Although inner CV axle boot and CV axle seals are covered by the skid plate, so I wounder how much exposure to the elements they had over the past 14 years.

CV axle boots are still in good condition. Since I am at it, I may just rebuild CV axles completely. Toyota 04427-60130 Front Cv Joint Boot Kit, In Outboard is around $45.

$14 Valvoline - VV986 Moly-Fortified Gray Full Synthetic Grease 1 LB

Valvoline - VV986 Moly-Fortified Gray Full Synthetic Grease 1 LB is $10. Front axle seals are $15 per seal. For around $150 and a few days of work everything can be refreshed and given a new beginning.

 

Yeah, with as much disassembly as you'll be doing, you might as well go all the way. That will prevent having to revisit anything for ages.

 

Great job...nice to see another DIYer.

 

What was supposed to be an axle seal replacement slowly turned into complete drivetrain rebuild.

It took a while to get all the hardware for rear axles. Someone on their side read number 8 as 3 and I ended up recieving only 3 nuts to secure the hub to the axle housing. I ended up reusing the old one, which were still in good condition.


A nut and a few washers seemed to make installation of new hub studs a little easier.


Wheel bearings pressed in very smoothly. There seems to be a debate regarding using the grease to press new wheel bearing onto the axle or press them on dry. I decided that I will be using grease on everything that gets pressed.


Completely rebuilt rear axle assembly.


New axle seal in place. That is where it all started.


Rebuilt rear axle assembly installed into the rear axle housing. The thing that is wrapped in a plastic bag is the parking brake cable.


I ended up removing parking brake cable completely because of my previous experience of driving around with it loose. It eventually gets caught by the spinning axle and stretched beyond its limits. I also decided to hold off on installation of the parking brake assembly because of another issue that I discovered when axles were already in place. There is cardboard material that is sandwiched between the part of the axle into which studs are inserted and a thin metal sheet. I am not sure what the name of it is and why it is there. Anyway, it got soaked in gear oil so the extent that gear oil is still slowly dripping down into the rotor where the parking brake assembly is located. I decided to let all the oil drip down as the axle spins, otherwise I will ruin another parking brake assembly by coating it in gear oil.


I just removed the cable, wrapped it in ziploc bag, and secured it with a zip tie. The next time I do an oil change, I will install new parking brake assembly.


I taped up the hole with duck tape to prevent dust from entering the parking brake assembly housing.


For now I am using ratchet straps wrapped around the wheel and secured to the rock sliders. Seems to work better like a charm along with wheel chocks.