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R72 Gearbox Output Shaft Bearing Removal

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25 Mar 2018 11:34 #190846 by ZukracerV6
Hi,

I am well underway on rebuilding the gearbox but I have one question and want to clarify the Bigjimny wiki article on the rebuild. I have replaced all the bearings but the ones on the output shaft.



The screen print from the wiki page shows the shaft and bearing in question. If I have it right the top bearing (already removed in picture), gear and bottom bearing all come of the top of the shaft one after another?

Just want to double check as its not very obvious looking at the shaft.

Thanks Sam

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25 Mar 2018 13:35 #190849 by OlaGB
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27 Mar 2018 21:49 - 27 Mar 2018 21:50 #190942 by ZukracerV6
Thanks, your help is appreciated!

All of the bearings have now been replaced and the gearbox is now being put back together. Rebuilding the box was far easier than taking the engine/gearbox out! All this because of one knackered bearing.

Will post some photos on my build thread.

Sam

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Last edit: 27 Mar 2018 21:50 by ZukracerV6.

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28 Mar 2018 05:31 - 28 Mar 2018 09:17 #190948 by Max Headroom
Sorry to jump in on this thread but...

Does anyone know why the R72 box was prone to these bearings breaking up?

And does rebuilding with new and presumably different bearings necessarily mean that the bearings wont fail again?

Again, not meaning to hijack Zukracer's thread, but I thought that while on the subject it might be worth asking... :whistle:


IF IT AINT BROKE, KEEP FIXING IT UNTIL IT IS
Last edit: 28 Mar 2018 09:17 by Max Headroom.

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28 Mar 2018 11:09 #190961 by OlaGB
Not 100% sure why they dont last, but i found 2 bearings with some noise/grinding in them when i did mine, both where on the countershaft. Maybe oil level related, or maybe directional force problems, i dont know. I just bought the car , with the issue allready.

The new bearings where all sealed, except for one..
Not sure if thats a good thing either, but the bearing kit seller sure ment it was better than stock.

If the new bearings lasts another 90k km, im good for 8-10 years or so.. Ive never owned a car for more than 4.

Max Headroom wrote: Sorry to jump in on this thread but...

Does anyone know why the R72 box was prone to these bearings breaking up?

And does rebuilding with new and presumably different bearings necessarily mean that the bearings wont fail again?

Again, not meaning to hijack Zukracer's thread, but I thought that while on the subject it might be worth asking... :whistle:

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05 Apr 2018 07:51 - 05 Apr 2018 07:53 #191310 by yakuza

Max Headroom wrote: Sorry to jump in on this thread but...

Does anyone know why the R72 box was prone to these bearings breaking up?

And does rebuilding with new and presumably different bearings necessarily mean that the bearings wont fail again?

Again, not meaning to hijack Zukracer's thread, but I thought that while on the subject it might be worth asking... :whistle:


One reason is that more of the torque is being transfered in the gearbox in the R72 compared to older models with different gearing. More or less the difference in the torque and thus the load is the same as the difference in the gearing. This is also the reason why the 2005 and more recent jimnys do not have the problem with the transfer box as the load on it is less. Of course there is also the wider chain in the transfer cases from 2005 and up.
If you cannot change the bearing size to wider or bigger bearings there is not much you can do to make it any stronger.
Better lubrication, better cooling will help, using the correct oil viscosity as well. Higher revs will lower the torque, but higher revs could make it hotter and make lubrication worse.
Not sure how smart it is to change the bearings to closed ones though, but this has also been done to the SJ413/samurai gearbox on older Suzukis...

2005 Jimny M16A VVT, 235 BFG MT, 2" Trailmaster, 17%/87% high/low gears.
Last edit: 05 Apr 2018 07:53 by yakuza.

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05 Apr 2018 08:31 - 05 Apr 2018 08:37 #191311 by Max Headroom
Thanks OlaGB & Yakuza.

I guess I'm still non the wiser about whether new bearings will fix the problem ;) Keeping it topped up properly with fresh oil seems to be all one can do.

I had my g'box drained down and refilled (but not flushed) There were metal particles present, but I dont know how much or how big they were as unfortunately I wasn't shown. (In aviation, we have magnetic plugs on engines or g'boxes and any particles go off for spectral analysis to determine where in the component the metal is coming from which helps determine the remaining life and functionality of that component, and avoids future component failure while in use)

At the moment I have no perceptible bad noises coming from the g'box, but then the car is that damned loud (soft top Jimny) I cant hear much anyway! :laugh:

My only worry is that I sometimes feel a bit of difficulty getting it into first or reverse gear; it just doesn't feel very positive; then when I lift my foot on the clutch I think "yep I didn't think that was fully engaged :dry: " but this may be a separate issue

Is the g'box plug magnetic? if not, I will attach a very strong earth-magnet to it to keep any metallic debris in one place


IF IT AINT BROKE, KEEP FIXING IT UNTIL IT IS
Last edit: 05 Apr 2018 08:37 by Max Headroom.

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05 Apr 2018 12:06 #191317 by Busta
I believe the issue is entirely due to lubrication, hence the replacement bearings often being a sealed type. I'd be very surprised if it was related to the load on the bearings. Many people are running bigger engines with these gearboxes and we see no evidence of this accelerating the wear or causing premature failure.
Also the problem does not seem to be present in the more recent Jimnys (I believe Suzuki fixed the problem around 2008/9?), even though they are still using the same gearbox.
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05 Apr 2018 12:28 #191318 by ZukracerV6
Yes the drain plug is magnetic. Mine was covered in fine mettalic swarf and parts of the bearing cage.

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05 Apr 2018 18:10 #191338 by Riccy
Some people attribute the problem to a leak from the intermediate prop on early VVT models. This was the cause of my R72 failure initially

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05 Apr 2018 18:20 #191339 by Max Headroom
Thank you Zukracer, Busta & Riccy :)

My Jimny knowledge is ever being increased!

Although debris was found in my g'box and its making no nasty noises (that I can tell) , at least not yet at any rate, what would be the best thing to do bearing in mind that this is my daily drive to work...
Should I hold tight and hope that no bad noises start and if they do, deal with it then?
Or should I find a convenient moment to get the g'box stripped down and the offending bearings replaced before they fail? I am assuming that they are going to fail at some point; unfortunately I dont have much history with this car other than service stamps in the book mostly from some Ford dealer.


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05 Apr 2018 18:35 #191343 by Riccy
Run it and keep checking everything for leaks! The prop leak is from a bad glue seal on the gearbox end connection cap.

Redline MTL oil is commonly used to try and make shifting easier. Its normal to sometimes need a second go on the clutch pedal to get going. The clutch cable could be worn/out of adjustment, worth checking maybe?. its easy to adjust. plastic cover on the side of the gearbox with a plastic nut on the outside where it goes in. cover just pulls off.

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R7me gbox & 5.16 Rocklobster, 33" Toyo MT, 2x ARB Locker diffs, 7" lift, Recaro's, etc

SL06 ULS ULYSSES M18 VVT
Pickup/tipper, R7me gbox & 4.3 Rocklobster, 31" Cooper STT pro, 2x ARB Locker diffs, 4" lift, OMP seats, Poly bushd', Caged, etc

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