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Diff gave up far from home, pinion nuts fault perhaps

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  • Diff gave up far from home, pinion nuts fault perhaps

    Hello
    Ive a kzj95 manual diesel 560,000kms. Going over the Auckland harbour bridge I thought i was on the rumble strips which signal the side of the road, but i looked again in case i had somehow mistook what i was seeing but i was clearly in the middle of the road. I then thought the road must have a bad surface. Well after about 500m i realised my car was not well. I pulled off the motorway and I put it in neutral which isolated it down to the drive train and not the engine. I then stopped and checked all shafts for play. All were fine.

    The next morning i looked under the car and i had a small leak from the front diff flange and some play in it. Considering i lived 300k away i decided to remove the front propshaft and lock the transfercase into HL so i could drive, that helped quite a lot. However 40k up the road there was a bit of a clinking sound and then the pinion nut threw off under the car and into never never land. Luckily i still had the flange but she was dumping oil. I then stuffed her with a cut up rag and got her a few K to somewhere i could work on her which was a grass lawn.
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    Well i then removed the front driveshafts to isolate the diff from any movement (no inputs or outputs) and i covered up the now open wheel bearings.Well the front dustcap under the hub cap turns out it fits the inside of the wheel where the bearing hole is very well. All i needed was some tape to tape it up and bang it in there to make a good solid seal.
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    In case anyones front drive train gives out the only thing i think i needed thats not in a general tool box was the 35cm socket to undo the front nut on the driveshaft and a coldchisel to knock out the front axle (although luckily i had one of those)

    Well its driving well as a two wheel drive but i live up a gravel road, im a beekeeper and i need to tow my boat some point so i need to rectify this at some stage soonish and if the back diff gives up im really done for. I think what may of happened is that the pinion nut got lose and that meant the pinon shaft lost its preload and things deteriorated from there.

    Ive never gone near a diff before so im just enquiring as to some tips as to how i get it out and inspect it, such as do i need to be careful and mark anything, is it under any kind of pressure that i need to watch out for? The diff looks quite small compared to the rear since its arms are the removable front driveshafts/cvs, it doesnt look like its complicated to remove, just a few bolts?

  • #2
    Whatever you do dont do exactly as i ve done there. You critically need to do one more thing, ive found that out after driving 400km like that.
    Well i thought that removing all that stuff wouldnt cause another issue but talk about when a butterfly flaps its wings...
    I thought the wheel bearing would be ok, i mean you need a big press to remove it and i had done 230km in it ok. However mine didnt keep well, seems that big 35cm nut keeps everything in there tight so what you need to do is when you have the axle/cv/driveshaft out remove the boot and stick that stub of the shaft back in and tighten it back up.

    I ended up getting play in the wheel. First thing i noticed was some major brake fade followed by intermittent abs light coming on. I am so really lucky the whole thing didnt come apart- The brake calliper perhaps kept everything ie rotor etc from sliding out.

    What i think was happening was the wheel and rotor was wobbling due to being loose and that was pushing the disk pads apart which meant i needed to pump the brakes to get them to work. Once i figured out what was happening i kept doing this to keep the rotor in the centre, i did this for quite a few kilometres until i could find somewhere to stop.
    I now have the car parked on the side of the road and i will need to bus home and get the stub ends off the cv driveshafts and also the 35cm socket. Unfortunately this will have to wait at least a week due to other commitments.
    Im hoping i havent damaged the abs sensor, the light keeps coming on and then off so there is a bit of hope there and there is a touch of noise in the left bearing when turning at very low speed (im not surprised considering how loose it is) and the right is quiet but i suspect there might be some wornness going on in them, i wont know til ive retightened it up.

    My two front tires have had their tread mostly disappear over the 200k from home, thankfully they were due to be replaced very soon so i suppose i could be more peeved off at my mistake- uneducated i was but luckily you all arent now.
    Il update in many days when i get back to the poor prado.

    Comment


    • #3
      Well after ten days in Australia- Cairns to Melbourne im back home to the crippled prado. Ive bused up to get the short stubs to put back in the wheel housing and thus pull and hold everything together. Il write up what ive found for those who have a problem with there front drive train and also for anyone else curious as to what this front section is made up from.

      The front driveshaft cvs do come apart although it doesnt seem obvious at first glance. I took the boot clips off the outer end and that revealed the cv. The shaft is actually held in the end of the cv/short outer stub by a small clip. You cant see it as its inside the cv but if you grab the shaft and the outer stub and try and pull them apart you will see there is minor movement in there, ie they are not locked together permanently. To separate these, so i had only the stub left, i held the shaft against the towbar of my tractor and had the short stub facing down. I then smacked the end of the cv with a small mallet, once, twice, three times and then eventually the clip broke and i was left with the stub end to put back in the wheel housing. I put a glove over it to keep the dirt etc out and i taped it up. I did that to the other side too and marked one stubend with paint so i could match it up with the rest of the cv when i get back to installing the whole unit sometime in the future, in case they are matched as a unit etc.
      Here is the stub end when i was back at my car just before i put it in.
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      So when back at my car hundreds of Kilometres away i put the stubs back in and tightened them to 230Nm. Instantly there was no more brake travel issue and the bearings were pretty much quiet. I retorqued after five km and the right wheel took from memory no retorquing where as the left took about 20NM.
      I drove another 15km and things were good apart from a slight bearing noise when turning right on a slight rise. I retorqued and the right took none but the left took about 45Nm. On getting back in the car after that there has being no further bearing noise and the brake feels exactly how it has being prior to this whole issue. It took that last retorquing to get it totally to feeling normal.
      Ive now done another 200km to get home and there has being no issues. Ive checked the torque and both are what they were set at.
      Ive never stripped one of these down but i suspect the right bearing thing was holding tight yet the left had the hub slipping out with just the brakecaliper channelling the rotor in line as the wheel turned which saved me from calamity.

      The next job over the next day or so, when i can, is to drop out the diff.
      Any tips on what to look for expect on disassembly etc are still appreciated.

      Heres the stub ends in the wheel housing
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      • #4
        Ive dropped the front diff out. It wasnt too hard but like all things there was one thing that wasnt quite so easy. The front bolts were 19mm and the rear on the support were 17mm, i had to use spanners on these. The problem is you cant reach one bolt until you have undone the support and lifted up the diff. You do this by undoing the hex nut which requires a 12mm hex. It also has blue thread locker on it as if it comes lose i suspect your diff could smash into the lower oil pan if you do any decent wheel articulation. I heated it up with a paint stripping heatgun just in case it was too tight for my hex and might shear it. It came undone easy so you might not need heat.
        The only other thing is the diff breather which is easily seen clipped on and up the left wheel arch. It takes less than a second to pull out of the clips.
        Next job is disassembly. I will update as i go.
        Also note the diff is heavy so dont have yourself under it when its ready to drop.
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        • #5
          So ive split the differential. You dont need to undo any of the bigger sized bolts. Only the 14mm ones that hold the two halves need undoing.That means you can leave on the supporting brackets and the short axle housing. The diff has a lining of silicon in the joint so to break them apart i just tapped it gently with my mini sledge. ( i should clarify here that i used this to separate the CV too).
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          There are two dowel pins that act as a guide as it comes apart and when it comes apart its no problems, nothing drops out, its just like taking apart a sandwich, everything basically stays where it is.
          Heres what the diff looks like opened up.
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          Initially inspection shows some grounded filings collected on the bottom magnetic drain plug. The centre crown housing has a few wear marks/dents where the teeth from the pinion gear have knocked it as the pinion has come loose and pulled back a bit. There is no noticeable breakages of the spider gears or the crown wheel or the pinion teeth. I will next need to remove the pinion shaft and inspect those bearings before doing a more thorough inspection of the diff gears.
          At present the initial suspected diagnosis still stands that the pinion nut came loose and has led to the loss of pretension and thus the pinion shaft has moved.
          Will update as i proceed

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          • #6
            Well ive taken it right apart and inspected it. I slid the carrier housing off, thats all it takes to do that, no circlips etc. I wanted to check the roller bearing on its side and also i didnt want it hanging there putting weight on the shaft and axle and bearing in there while i sorted out parts.
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            To remove the pinion shaft was easy. I just put some wood on the end of the shaft and hit it with a mallet.
            The two bearings seem ok thankfully. Here it is with the crush sleeve in it (the middle bulging bit, it just slides off) and outer bearing and something called a slinger on top which just looks like a big washer.
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            The outer bearing and slinger come out the top end. So you need to remove the seal to inspect that bearing and race. The seals a bit of a pain, i had to take to it with a screwdriver to get it out. The race looked ok. The very end of a couple of the pinion shaft teeth a chipped. This is very minor though and this part of the teeth take very little load (ive read up a technical site on them) so im not concerned at all. The crown ring teeth are fine. The cars done almost 600000kms so im sure things are worn and any Diff specialist would say everything is worn but thats why i work on my own car so i can make that decision myself. At this point i will need a new nut $6, a spacer $35, a new seal $38 toyota or $18 aftermarket and a couple of clips for the cv shaft.

            The technicality to this job is getting the pretension set on the pinion shaft. This pretension counteracts the forces from the crown wheel (i believe). What happens is that as you tighten the nut and press the flange down on the slinger and bearing it starts crushing the sleeve. This puts the tension on the bearings and the shaft. To do this you tighten it until you can start feeling the bearings being loaded and you then tighten it slowly until you get a very small resistance for turning the shaft. This is something small like 15 inch pounds and even less for used bearings. The torque to actually do the nut up is not specified as its the turning of the shaft resistance thats important. I suspect itd take over 200Ft pounds to get the bearings tightened down the shaft. Once you have it set you then hit the shaft at both ends to make sure they are seated. If you overtighten you need to loosen and put in a whole new crush sleeve.

            To get the tension right you need the pinon shaft to be freewheeling ie not connected to the carrier housing as that would change the whole turning torque.
            You can do all sorts of other stuff to get the diff set accurately, shims etc but ive looked at the teeth and there is nothing that concerns me much and as i said in a car thats done the kms this has you can end up replacing everything including the cabin roof lining if you arent weary to it.

            I will update when i get the parts, probably a few days a way at least. If anyone has any tips or wants me to clarify anything or take more photos of something they are curious in just let me know cheers

            Comment


            • #7
              Alright the plan is this, to get a nut from an engineering shop, reinstall the pinion shaft and spin the flange fast to test that the pinion bearings are still good (they seem ok). Then use marking compound on the ring gear and check the backlash and adjust that as needed. Why im doing this extra step is that i use to get a bit of a delayed shunting in the front diff whenever i changed gears or started moving the car. I dont get that with the front diff removed so im thinking it might be caused by too much backlash so i should try and reduce that. Its immensely much nicer driving the car with no backlash delay if thats what it is and i suppose excessive backlash would eventually cause problems too maybe back to the transfer case loading as well.

              I am getting a cheap nut so i can use the proper one when retorquing for the final job.

              I definitely was naively in over my head but i think I now see what i must do to do this adequately.. well hopefully.
              I will update as i go.
              I can see why diffs get sent out to specialist places, who would want this responsibility....

              Comment


              • #8
                So ive done some more reading/ringing diff shops and looking into these front diffs. There is enough going on in here to make me think only dealing with an automatic transmission could be more tricky, theres different things to adjust and doing one thing affects another; but i will give it a go. I figure that there is enough tolerance built into these things to handle something not perfectly right (its not like you need a NASA clean room to rebuild them) and also things dont make sense, ie im told you have to have the carrier housing out to set the flange spin torque (which i understand) and also the oil seal as that affects drag but you cant install the oil seal after you have the flange installed, so go figure...
                My plan is to do this as cheaply as possible which is my speciality and I will see how it goes.

                I will keep the require tools onboard so i can disengage the front diff again anywhere I need too. I figure that would take about an hour and if i do get this diff wrong i will then just install a second hand one.
                Its raining here today and its a saturday so today i should be able to check the bearings and backlash and then next week i order parts.

                On further looking at these diffs, to change the backlash you can move the crown ring closer to the pinion shaft. You need some backlash as there needs to be room for the gears to expand. I guess one way to know if your prados slight clunking might be backlash is to see if it improves slightly when you have driven a fair distance and the diffs heated up.
                To move the ring gear sideways so closer or further away from the pinion you turn this ring socket.
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                Heres the one from the other side with the short shaft that goes out along the short axle housing to where the front cv driveshaft slots in.
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                Theres one on either side. You turn them equally ie you turn one in and the other side out so that you keep the length between them equal otherwise you change the sideways pretension. The big issue with these are that you can see the race for the bearing is in the way so you have to knock that out and reinstall later but to get them out you need to first undo the ring socket as they are tight up against them, so this would mean lots of marking and making a new tool to undo this socket.
                I plan to check backlash by marking the ring gear and pinion to see if i really need to go through all that, ie is it so far out i can be reasonably confident it is causing the clunk.
                Alright, time to get into it

                Comment


                • #9
                  Well i put the pinion and flange back in and spun it and it seemed fine. I kept on spinning it while looking at something else and i heard a little chatter sound. I investigated more and every so often like once every thirty seconds there would be a chatter which would when you put your finger on the diff it would put vibrations through the case. Im unsure if this bearing issue is a result of driving after the pinion nut came loose or if it was actually what made the nut come lose. Im lucky i found it before going ahead.

                  Im unsure which bearing is damaged out of the two on the pinion so ive removed both their races from the diff housing and will price them up and compare that to a second hand one. Only doing one bearing is too reckless as im picking even if i figure out the worst one, the other one is probably not far behind.
                  Looking at the rollers it doesnt indicate which is the worn one.

                  I figure i can reuse the crush sleeve as that only keeps the tension to hold the nut on, its not the bearing torque.(this took me quite a while to understand).
                  Heres a good thread on that for anyone who is interested.
                  http://www.chevelles.com/forums/33-t...sh-sleeve.html

                  I will update when i get the parts or the 2nd hand diff. At the moment she drives fine in rear 2wd and even up gravel roads, i just dare not tow anything heavy as i dont want to load up the back diff.

                  Comment


                  • #10
                    Time for an update. A secondhand front diff costs about $600 so im going to put this current one back together. Also wreckers a not convincing they know enough about their diff ratios and thats something im not willing to take a chance with. Id have to take the new diff apart and count the teeth and i bet that would probably void any implied warranty anyway.
                    Cost to rebuild are as follows. Ive put the quote for each part from Toyota in brackets next to it. The bearings interestingly are the same brand Toyota was going to give me so even though toyota parts are normally much better quality it seems like they like some decent cream on top for the price too.

                    Pinion bearings $42 and two of them (Toyota $200 plus $140)
                    Seal $14 ($38)
                    Pinion nut i bought from Toyota $7, I bought it because it has a built in washer and is easy to preen into the indentation in the pinion shaft so that it wont likely come undone .
                    Silicon gasket maket for sealing diff $12
                    Diff fluid $12 (1.1L needed approx)
                    Shim $3 ($12)
                    Clips to go back on cv joints $1.60each ($17 each)
                    Locktite and a bit of Permatex aviation form a gasket i already have.
                    So total parts about $120. If i went to a diff shop labour would be about $350 plus whatever other parts they would say were a must..

                    Comment


                    • #11
                      Heres the pinion and the nut, the washer down the bottom is the shim they put in at the factory to set pinion depth. What im going to do is put another small shim on top of that so that the pinion will push a touch more into the crown wheel and thus slightly reduce backlash which i think has happened over the course of this diffs living. Pretty cowboy stuff but im fairly confident about it. The main thing is checking there is still backlash, ie so the gears dont lock up when they heat up.
                      Click image for larger version

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                      The bottom bearing i tried to grind off but its so solid that i ended up dropping into a diff shop and a guy did it for free, took him about a minute and saved me a lot of hassle. I hope to be able to put the new one on without needing to go to a engineering press shop, but more about that later. Bearings will be here in a few days so i will update then as i need her to be a four wheel drive again.
                      Last edited by MikeyB; 10-07-2016, 05:59 AM. Reason: reloaded photo

                      Comment


                      • #12
                        Well ive recieved an excellent tip that the clunk when i start movement could well be from the spider gears and on investigation that looks to be quite likely.
                        The gears a worn and you can see if you look closely on the right handside some daylight between the gear and housing. A washer is in there and so if i was to shim that then there wouldnt be so much loose fit.

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                        To sort this out will mean taking off the crown wheel teeth and taking the carrier apart. I think having a go even though this is well over my head will be good in case it actually does work.... as its annoying and a bit disconcerting the clunk when power goes on initially and between gears. Interestingly Toyota only sells shims for this bigger gears not the smaller side ones so i will try and shim the big ones only just in case theres some engineering reason im not aware of. My feeler guage indicates about a 0.3mm gap to shim on both sides

                        First i will need to mark where the crown wheel teeth are and undo these bolts and retaining devices
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                        • #13
                          Well another disappointment, i cant get the bolts undone, they must be covered in red locktite. I tried my heatgun so much that its now broken and even my arc welder isnt doing the job, the loctite on the threads seem too deep.
                          So i will just put it back as is unless i think something up during the day but i doubt it as these bolts are clinging on with all their might.

                          Comment


                          • #14
                            A lot of crown wheels bolts are left hand thread... Do they have a L stamped on them?

                            Comment


                            • #15
                              Originally posted by Piggy View Post
                              A lot of crown wheels bolts are left hand thread... Do they have a L stamped on them?
                              Thanks for the suggestion, ive had a look and unfortunately they arent stamped, ive also since tried turning right to loosen but no success.
                              Il look up the part number and see if i can see if they are left threaded, il report back if so.
                              I plan on picking up the bearings tomorrow as its getting beyond time to get her back working even if it isnt ideal..

                              Comment

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