Diff gave up far from home, pinion nuts fault perhaps

[MikeyB Member Find all posts View Profile Close MikeyB]

So ive started the rebuild. First i measured the bearings to check they were the same size as the originals as any change here will affect pinion height which would cause a lot of complications. The outer bearing race/cup went in fine. The inner one didnt. Its hard to hit it in there due to the access angle and its super tight. Ive checked the OD with the original and its the same.

The pinion shaft bearing was the same issue. I did the heat up the bearing in the oven trick (90degsC). They have a service temp of up to 120degC.


The shaft went in the freezer overnight which was set to -18degC.
When i quickly pulled out the bearing and hit it with a pipe (on the inner ring) to try and get it to go down, it went down only so far.




So ive talked to a mate whos a retired bus mechanic and has kept most of his tools, he reckons he can press them in so I will try and get these two things sorted out by the weekend.
After that then it will be time to do the preload on the pinion and then just buttoning her back up and reinstalling her, the front driveshafts and prop shaft.
Il update as things go along but hopefully i can wrap up this extra long repair by this weekend.
For those needing to do this job, so far i suspect that buying a cheap press or paying a engineering/diff place to do the quick pressing jobs would be pretty cost effective compared to getting somewhere to do the whole job(About $1000 for just pinion bearings).
The money that goes into diff shops is when they need to measure things such as backlash etc, just pushing and pulling bearings is a quick job with the right tool.

[MikeyB Member Find all posts View Profile Close MikeyB]

There has being progress today. She is back together. There were quite a few things to get it to this stage, but none that were too absurd (well not too absurd for countryfolk shade tree/do it yourselfers!).I will write them up on how i got it done for anyone else who is considering giving this a go.


Well pressing on the bearing was very easy. A small press was all that was needed. I didnt add any more than the original shim. The new bearing had a bit of a lip on its lower which made getting it on straight very easy. The piece of metal next to it is the crusher sleeve. As ive written about before i decided to reuse this. So ive bashed it in the middle with a mini sledge to lengthen it out somewhat so it can be recrushed.



The next job was to put in the rear bearing cup. That was the hardest job of the day. To get it in it needed to be hit perfectly square on, but the position it sits in in the diff makes this difficult. I tried a slide hammer (heavy duty size) but this didnt work. The way that it got on in the end is that we undid the oil filler nut and put a slightly bent extension bar through that hole and then had an old universal joint (bearing cups removed) up against the end of the bearing race. My job was to hold the bar in the middle of the UJ while he hit the end of the extension bar with a large sledge. Non traditional method but to my great relief it worked and many bashes later it was seated nicely, flush up against its stop.

[MikeyB Member Find all posts View Profile Close MikeyB]

Next job was to install the pinion and put the pinion preload on.
This involved oiling the bearings and putting the pinion in then slide the crushing sleeve in then the top bearing, which presses in when you tighten the flange. The big washer/oil slinger went on next and then the seal. This again was tight but the flange makes an excellent seal install tool so i tapped it in with that. Before you do this job you may want to check the depth of the seal and the stop where it rests against that way you have a rough idea how far it needs to go before seating.
I coated its outer in a permatex sealant and drove it home.

The next step was to coat the thread of the pinion in threadlocker and put some grease on the seal lip and flange and then install the flange. I then put on the nut and started tightening it down. Here comes the most complex part of the day. As you tighten the nut it compresses the compression sleeve between the two bearings. This requires something solid to hold the Flange. Some people make tools, i used a massive pipe wrench i have. You keep tightening until the bearings become seated in their race and until the turning torque of the flange wheel reaches a certain spec.

New bearings require more than old ones. For reference I have new bearings at 10.4-16.5 inch pounds and old bearings at 5.2-8.7 inch pounds.. Yes thats inch pounds. This is without the carrier housing in there turning, its just the pinion.
So i dont have a torque wrench capable of such a tiny amount so what i did was i took a middlish figure of 14inch pounds and i took the distance from the nuts centre to a hole on the edge of the flange, which was 4cm. I converted that too 1.6 inches. I then converted the 14 pounds to 6.35kg.
I then divided the 6.35kg by 1.6 which gave me 3.9kgs.
Then what i did was i put my fish scale measuring hook in the hole at the 1.6 inch distance and tightened the nut until the turning torque was around 3.9kgs. ( I checked the accuracy of the scales on yoghurt containers). Since i used the middle figure i picked i could be a bit off.


I had to tighten it slowly as the bearings load up fast when they touch. Its hard to explain how it feels by hand to turn the flange at this torque... Perhaps about the lightest amount you would turn a tap off with.

[MikeyB Member Find all posts View Profile Close MikeyB]

Next job was to stake the nut, and even for this seemingly menial job i can see why they use a specialised tool. It took a lot of time with a punch and screwdriver to get it in a form that i thought would make the nut unlikely to loosen off.
By the way the nuts size was 27mm.
I then put silicon around the diff casing and buttoned it back together.
Next job will be to install it, this may happen tomorrow, weather depending. To do that and the front driveshafts including regreasing the cvs I expect will be about 3 to 4 hours at a causal pace. I will report back on that and the test drive.

I thought i would add that i suppose i could of just tightened up the 27mm nut when this first happened. It would be a temporary fix as it wouldnt have the correct pinion preload but it may just get you home.

[MikeyB Member Find all posts View Profile Close MikeyB]

As again, things have taken a lot longer than expected, 7-8hours and a lot of that due to my own mistakes. I will run through a few tips for those doing this.
The diff is heavy so if you are by yourself a jack is almost a must in order to align up the bolts correctly. Make sure you use blue threadlocker on the back hex bolt as if that comes loose the diff will hit the gearbox in any reasonable bump.
When installing the driveshaft back into the cv joint do not bash down on the end of the driveshaft to get the retaining clip to fit through the cv. You may quite likely bugger the end of it like i did. To do it properly i ended up using a small flathead and pushing the clip in with the weight of the shaft helping by pushing down.
I redid the joints with new grease and used cable ties to do them up. I might try and get some other proper ones at some point but these will do for the moment

When putting the driveshafts in i managed to keep the brake calipers attached. I greased the seal and shaft and used the cv as its own driver to knock it in.
The one with the buggered end took me about two hours of banging to get it to go in properly, that was all my fault.
Make sure you put the short one in the driverside, the longer driveshaft goes on the passengers side.

Ive filled the case and luckily the seals seem to be holding. Tomorrow i do the prop shaft and test drive

[MikeyB Member Find all posts View Profile Close MikeyB]

Also to make this as comprehensive as i can i thought this further info could be useful.
If you think the nut has come loose yet your rear pinion bearing you think is ok, well to fix that you can actually just install a new spacer and seal. Just remove both driveshafts and the rotational torque specs for that is plus another 3.5-5.2 inch pounds on top of the new/used bearing figure (thats for the rotational inertia that will now have the addition of the crown wheel).
That would save pulling the diff out.
You could also pull out the outer bearing race with a puller of somesort and replace that race if that outer bearing had gone
I will update tomorrow

[MikeyB Member Find all posts View Profile Close MikeyB]

Well this is the never ending story.
Firstly zip ties are not up to the job on these cv boots. So i will need to get some metal bands.

I put back on the prop shaft and drove about a kilometre before the old whining sound returned. I thought maybe it was the bearings getting into alignment, i just wanted to think something positive about it. Well by 3kms i knew something was very wrong so i looked underneath and i felt the diff flange and there was movement.
Pretty despondent about it, i then proceeded to remove the propshaft. I thought id check how much the pinion nut had turned. Well to my surprise it hadnt.
What i think happened is as the new bearings were bedding in (which is why they require extra torque when installing the flange) well that loosened everything up. So i must of got the preload wrong.
There was one comment on just one website i read out of many that the preload figure is what you need to do to keep the flange rotating, its not the initial movement. If that is the case then i did underestimate the torque as i only used initial movement torque.

Well anyhow i could not be bothered at all taking things apart so what i did was i nipped the nut up some more and have being driving around like that. There is no noise or leaks. I will do this for a while and if all is well then i will will reinstall the prop shaft and see how it goes. The diff casing by the bearings isnt running as hot as the rear so thats a good sign i suppose.

Im glad i didnt add a shim on the pinion as i dont think that was an issue at all and it could of risk a lock up of pinion and crownwheel.
Il update in due course with whatever happens

[MikeyB Member Find all posts View Profile Close MikeyB]

Update. Ive done about 400km and theres being no noise from the diff or any change in the flange play(ie there is none) the bearings have loosened up and there is no oil leak.
What has being happening is the abs light has being coming on now again. I took the abs sensor out of the wheel housing which is really easy. Its a10mm bolt and then you just gently wiggle it out. It was covered in a bit of grease and a bit of metal from a spring. So what has happened is Ive ended up damaging the inner bearing seal while ive being putting the half shafts in and out. So i will need to replace that sometime. Looking at it itl be an easy job. I dont think the seal will be expensive.
The spring was clearly interfering with the magnetic signal which generates the abs. The warning light has not reappeared since ive cleaned it.
So if doing this job do be careful when replacing the front driveshafts into the wheel housing.




The other thing i should mention is that i got some hose clamps for the cv boots and they are holding fine. I put the screws at 180degs to each other to help with balancing and you do need to take a bit of care when installing to make sure that when they spin they dont hit the bolts on the bottom wheel joint.

I will update with how the diff goes. At the moment im waiting for some epoxy resinto dry around the nut as i could not remove the nut to put threadlocker on as that would lose the preload

[MikeyB Member Find all posts View Profile Close MikeyB]

Ive put the front prop back on and ive done about 30km. Its not making any sounds, or developed any play. It is running hotter than before, that i suppose is due to the torque now going through it. It is noticeably hotter than the rear diff. I think the rear diff has dropped in temp now that the front diff is taking up some load. Im not surprised the front one is running hotter as its in a much more confined space than the rear diff, it has the oil pan right above it and it doesnt have the long cooling fins that the rear diff has and also it has less than half the oil capacity as the rear one.
It is not running hotter than the gearbox so im not going to be too concerned about it when i think about this diff.

I will now just run it as usual and will update if i come a cropper or when i get the wheel bearing seal done

[MikeyB Member Find all posts View Profile Close MikeyB]

Time to do the inner hub seal. An update on the diff first. Its being running quite well, ive done about another 60km and the temperature in it has actually reduced. Im not sure if thats due to the heat and cold cycle affecting the bearings settling down into their seats. I know that on new ring gear setups you have to stop the car and let it cool during its first few runs. Ive had to remove the prop shaft, not because anything is wrong, its just because ive some very important meetings i cant be late too so i thought id remove it and then put it back on once those are done. Checking the preload on the diff pinion now it has freed up some more. The nut is in the same place. Previously it took a bit more than a touch of a force to get it to turn, now it turns freely but not too freely. Hard to explain but it feels promising.
Now on to the seal. It was a very easy job and a pleasure actually to get it done, plus a necessity as moisture in there could wash out the bearing and also it will allow for rust.
To remove the old seal just took a small flat edged screwdriver and tapping with a hammer

Once removed i could see all the mess from the old seal, it definitely needed cleaning out. All that rubbery stuff is actually embedded with the metal spring particles which could well cause more problems down the road. I brought the hoover out to clean it up as best as i could.

Installing the new seal wasnt too difficult. I had tied up the brake caliper out of the way and also slid off the rotor so i could rotate the wheel hub housing on the top ball joint enough so that i could get to the back of the hub quite easily. I just pushed it in by hand and then tapped it in with a hammer around the edges using wood when i could. I also put a bit of permatex around the outside of the seal.
Last job was to clean the abs sensor


Job done. And car drives well.
The part number was 90316-69001. It was $137 from Toyota or $13 from a parts shop. Its a good quality metal one the $13 too.
Actually ive noticed that the backlash shunting i use to get has about 90% gone since ive had the new diff hooked up and working. Perhaps its from the new bearings or perhaps i had tightened the diff housing up more than it was and that has somehow affected side to side backlash, i didnt use any torque reading on that one. Just another mystery but this time hopefully not a bad one.

I will update after ive reinstalled the prop shaft and done some decent kilometres on her. After all this i still think they are a great vehicle.

By the way after more reading on the diff, if you use synthethic fluid it will make your diff run cooler. I saving a few dollars used mineral which although exceeds specification has not being the best money saving choice.

[williamturner1 Lurker Find all posts View Profile Close williamturner1]

WoW! Thans for that. I've got a 90series Prado here in WA and just taking the front apart. Great read.
Thank you for taking the time to write that up and share!

[MikeyB Member Find all posts View Profile Close MikeyB]

WoW! Thans for that. I've got a 90series Prado here in WA and just taking the front apart. Great read.
Thank you for taking the time to write that up and share!

Hi,no worries, im glad its of some help, i dare not read how garbled it probably is in hindsight, I was under a bit of pressure to fix it quickly in winter at the time.
Just to update on mine, the repair is working really well and ive done quite a few thousand kilometres since, ive even done some towing up some steep hills and the front diff is keeping just like it should do. I havent had to do anything more since the last post.

Good luck, its not a small job but its a rewarding one... when you are cruising at over 100kph and you sudddenly remember that your front diff was put together by yourself and its still working fine and you havent needed to be paying attention to it anymore, then that does makes for a really great driving experience.