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Front diff remove/repair

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13 Jun 2019 19:58 #209924 by 2013gary
Hi all,

Back story: A while back I hit a big rock at speed. There was no visible sign of damage apart from a bent panhard rod, which I replaced with a heavy duty one. However since the accident the Jimny has shaken violently at speeds over 20mph. I have since changed the King pin bearings and track rod ends but the wobble is still there.

I took it to QwikFit for an alignment test to see if anything like chassis damage became apparent. The mechanic took it for a drive and said that I need to see a gearbox specialist as the shake appears to originate from the front diff. So I'm guessing I've damaged the part where the axle joins the diff. Is this something that an average DIY mechanic can fix? I assume it would cost a fortune for someone else to do it so I'm thinking about having a go myself. However the most complicated thing I've done to date is the King pin bearings. Has anyone done anything similar?

Gary

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13 Jun 2019 22:49 - 13 Jun 2019 22:53 #209928 by Scimike
Replied by Scimike on topic Front diff remove/repair
Just thinking.
Shaking could be the following:

Something's no longer connected, broke or loose on the front end = should be easy to see and check visually if you jack the front end up. Also while its in the air check your tyres and wheels are still round etc.

Something that rotates is bent - check wheels above and make sure the front drive shafts and prop are not rotating, ie in RWD only. If they are turning try to find out why (jammed hub etc) disconnect and test drive again. If it still wobbles then disconnecting them has eliminated their influence. If it only wobbles when they are rotating check half shafts and front prop. Hope you can visualize what I am try to say.

Something is miss aligned. This could be a bent axle or tracking. Not sure how to check this, but assume tracking check would highlight issues.

If it's a bent item then a second hand unit is going to be the best option in my opinion.

Swapping the axle, prop shaft, half shafts etc is not complex. If you can do kingpin bearings you can do the rest if you have the time and tools.

Just trying to help.

Mike
Last edit: 13 Jun 2019 22:53 by Scimike.

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14 Jun 2019 04:13 #209929 by Lambert
Replied by Lambert on topic Front diff remove/repair
As suggested if it is running properly in 2wd the front drive line shouldn't be rotating and is therefore not going to make a vibration even if it is bent. It's much more likely something is happening to the wheels as they rotate causing them to not run true. So something like a buckled rim, an egged tyre, or damaged hub/bearing assembly.

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14 Jun 2019 08:12 #209930 by 2013gary
Replied by 2013gary on topic Front diff remove/repair
Thanks both for the excellent replies. I have manual hubs fitted and the wobble occurs in both 4x4 and 4x2 modes on those. That said, I haven't checked to see if the hubs are disengaging when I switch modes. They both make a reassuring clunk when I turn them though so I just assumed they were working correctly. Silly question time: to disconnect manual hubs is it just a case of taking them off?

Also I've swapped front and back wheels and the wobble remains on the front axle, so I'm thinking that the wheels are fine.

When changing the king pin bearings I removed the half shafts and these didn't appear bent or damaged either.

I haven't actually replaced the front wheel bearing (only the king pin bearings). Would a wheel bearing that's had a big knock cause a wobble like this? I assumed the wheel bearing was okay because it's been through an MOT with this damage, so I assumed that if there was significant play then this would have been highlighted.

So would it now be sensible to assume it's either a damaged manual hub, bent prop shaft or wrecked wheel bearing?

Gary
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14 Jun 2019 08:41 #209932 by Lambert
Replied by Lambert on topic Front diff remove/repair
Not necessarily. It could be possible though unlikely that the wheel mounting flange is bent. Effectively any part that isn't fixed when the wheel rotates needs to be examined as do any bracket locations that can affect the relative position of the axle to the thrust line of the car. As in if the axle is not either straight in itself or mounted square to the car could result in weird oscillations. It is also possible that the front prop is remaining engaged at the transfer box end some how and is spinning when it shouldn't, if it is bent that could be a problem.

When you smashed the rock did you stop against it or continue over it before coming to rest? I'm just wondering if you managed to catch the rear prop because that would give you the constant oscillation if it were bent. A mechanic ought to have spotted that though, oh yeah kwik fit, probably not.

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14 Jun 2019 09:10 #209934 by 2013gary
Replied by 2013gary on topic Front diff remove/repair
Right okay, looks like it could be a number of things so need to strip it all down.

I actually hit two rocks and continued over them. For context I was driving down a narrow lane that I wasn't familiar with, and as another car approached in the opposite direction I darted into a makeshift passing place not noticing the big rocks. It was quite a bang and I nearly tipped over. Its quite possible I hit the rear prop, but the wobble is definitely coming from the front as it shakes the entire front axle. To be honest I haven't even looked at the rear end for this reason.

I had a mechanic/friend take a look a while back they couldn't see anything wrong. I feel the same way about kwik fit but I only used them as they were the nearest garage that would do a wheel alignment check and hopefully spot anything else that could potentially be causing it.

Gary

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14 Jun 2019 09:27 #209935 by Lambert
Replied by Lambert on topic Front diff remove/repair
Ok. So multiple impacts along the length of the car. Could be a lot of things. Have you examined the transfer box and its mounting points? A Jimny is a very short car and vibration travels easily especially when it is severe. Also check all the control arm bushes thoroughly, they should need a lever to obtain movement and be firm to the hand. Also check the main gearbox rear mount, if it is running the central prop out of line that might be enough. It could also be something as simple as knocking off the rear prop balance weight. You are going to have to be thorough and check everything closely.

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14 Jun 2019 09:33 #209936 by Lambert
Replied by Lambert on topic Front diff remove/repair
It would be prudent if you can safely lift all 4 wheels off the ground and switch it on with an assistant engage drive and look and feel what is wrong. Be very careful with doing this as the spinning bits of the car will show you no mercy as they try to kill you.

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14 Jun 2019 13:43 #209940 by Basketcase
Replied by Basketcase on topic Front diff remove/repair
Have you tried driving it with the front prop removed to try and eliminate any distortion in the front prop? Take the front hubs off too so the shafts in front axle also don’t turn and see if it still vibrates

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17 Jun 2019 07:32 #210046 by kirkynut
Replied by kirkynut on topic Front diff remove/repair
Where are you based Gary?

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18 Jun 2019 09:37 #210077 by 2013gary
Replied by 2013gary on topic Front diff remove/repair
Thanks again for helpful replies.
@Lambert I have a transfer box guard which appears undamaged. Nevertheless I've removed it and had a look and everything looks okay. I tested all of the control arms by trying to move them by hand and I didn't notice any movement at all. I've had a good look underneath and everything *looks* straight and undamaged, although I only have limited experience when it comes to the running gear. I didn't notice anything that looked like a balance weight on the rear prop - is it an obvious thing to see?As for putting it completely in the air and driving it I'm not sure I have the cahonies!

@basketcase thanks for the suggestion I will try this next. Another silly question, is removing the front prop as simple as undoing all the bolts? Or are there other things that I should be aware of?

@Kirkynut I'm based in Tonbridge, Kent. If you know of or can recommend anyone around here that knows Jimny's well then I'd be very grateful!

Gary

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