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Weakest link in Jimny drivetrain?
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Author:  paynebrody [ Mon Dec 07, 2015 10:03 am ]
Post subject:  Weakest link in Jimny drivetrain?
Hi guys.

I have a 2010 Jimny (manual) with a slightly stretched trans box chain (suspected..). Lash between transmission and trans box seems ok (when in gear), likewise between rear diff and trans box seems within reason. In neutral the backlash between the transmission and the transfer box seems excessive indicating (in my mind) a stretched chain.

My question is thus, what is the consequence of leaving this unattended? I'm used to chain backlash on my dirt bikes so the 'feel' doesn't bother me. I assume the weakest links in the drive line are the various uv joints scattered throughout. Is it safe to treat these as a fuse? Or am i likely to inflict damage to the diff or transmission by shock loading the system?


Thanks,
Brody
Author:  got_bar_work [ Mon Dec 07, 2015 10:26 am ]
Post subject:  Re: Weakest link in Jimny drivetrain?
The chain would probly die before anything else. My coily one did. I just used it as a reason to get a geared wt case
Author:  fordem [ Mon Dec 07, 2015 10:45 am ]
Post subject:  Sorry I can't answer your question, but ...
Unless I'm very much mistaken, all the chain does is drive the front output shaft - so unless what you're looking at is backlash between the front & rear shafts, with the case in 4WD, I would think you're looking in the wrong place.

That out of the way, let me ask you this - why would any internal part of the transfer case change the backlash BETWEEN the transmission & transfer case - isn't that "linkage" completely external to the transfer case? It seems to me that the only thing that could cause backlash between the two is the jackshaft linking the two, and I fail to see how either the transfer case or the transmission being in neutral would/could have an impact on the backlash.
Author:  Jezza86 [ Mon Dec 07, 2015 11:06 am ]
Post subject:  Re: Weakest link in Jimny drivetrain?
Chain drives front and rear with dog clutch engagement between rear output and front output.
If the chain stretches too far it will chatter and jump teeth well before it snaps.
Author:  Jezza86 [ Mon Dec 07, 2015 11:08 am ]
Post subject:  Re: Weakest link in Jimny drivetrain?
I assume he is talking aboout the backlash between the input and output flanges on the transfer.
Author:  tanshi [ Mon Dec 07, 2015 11:10 am ]
Post subject:  Re: Weakest link in Jimny drivetrain?
front diffs and front axles are usually the first thing to go.
Author:  Gwagensteve [ Mon Dec 07, 2015 11:45 am ]
Post subject:  Re: Weakest link in Jimny drivetrain?
I'd generally agree with that, but we do have a club member who runs small tyres and open diffs who has done a transfer chain. Car has covered something like 30k.
Author:  greyghost [ Mon Dec 07, 2015 12:51 pm ]
Post subject:  Re: Weakest link in Jimny drivetrain?
i'd agree with Steve, on this
I broke everything in the driveline except the transfer chain, my case was geared though.
Jimny's are made of GLASS
Author:  paynebrody [ Mon Dec 07, 2015 2:38 pm ]
Post subject:  Re: Weakest link in Jimny drivetrain?
Jezza86 wrote:
I assume he is talking aboout the backlash between the input and output flanges on the transfer.


Jezza, correct. lash between input and output (rear). I'll clarify my test: Car on level ground, in 2wd, handbrake on. No (well minimal) backlash between rear diff and transfer case. As not in 4wd, I'm able to spin front prop shaft freely. When car is in gear, the input shaft has minimal backlash. When I'm in neutral, I get a lot more lash in the input shaft. Feels suspiciously like the rear wheel of a dirt bike with a loose chain. I imagine the 'no lash when in gear' scenario can be attributed to the transmission essentially 'locking' the input shaft. Likewise the rear diff in effect 'locks' the rear prop shaft. With the rear prop 'locked' and the input shaft free to rotate (in neutral) the only thing I can see allowing lash in the input shaft is a loose chain.

Gwagensteve wrote:
I'd generally agree with that, but we do have a club member who runs small tyres and open diffs who has done a transfer chain. Car has covered something like 30k.


Yep Steve mine is bone stock, 50k on the odometer.

greyghost wrote:
i'd agree with Steve, on this
I broke everything in the driveline except the transfer chain, my case was geared though.
Jimny's are made of GLASS


greyghost, this is reassuring...

I guess worst case (excuse the pun?) then chain stretches some more and I get chatter or a total failure of the chain. Either way I'm up for a new chain and/or box depending on damage incurred if the chain lets go (read, either way I'm up for a second hand complete box as chains are expensive apparently). Sound like a fair appraisal?


Thanks for your help.
Brody
Author:  pete_79 [ Mon Dec 07, 2015 7:42 pm ]
Post subject:  Re: Weakest link in Jimny drivetrain?
So do you have any chatter in the transfer?
If the chain is loose it will be slapping around everywhere in the case, there's not a lot of clearance in there.

If you're asking for the weakest point, I agree with Tanshi.
Front diffs/axles are the weakest link.
Author:  Mike57 [ Tue Dec 08, 2015 9:19 pm ]
Post subject:  Re: Weakest link in Jimny drivetrain?
Jezza is spot on and Steve might be referring to me with the stretched chain. I had a stretched chain in the first transfer that came with the car which I got as a demo with 3,000 km on it. It was noisy from the start and always seemed to have an issue. Eventually it started to jump when under full load at about 20,000 km. As Steve sates I only have 215 tyres. My replacement box which was second hand was stripped and checked this year as it also became noisy but the chain was only slightly stretched and did not need replacing and it was the bearings on the front output shaft that were noisy. That was at 40,000 km.

I also have a whine in my manual transmission and have replaced both rear wheel bearings but no other issues so far. In my opinion if you stay with standard tyre sizes then the transfer is most likely the weakest link before the axles and diff or CV's. Once you go to oversized tyres then it all changes. It might depend upon how and where you drive. I have done a lot of outback km on rough roads carrying a full load.

The chain is unlikely to break though just jump and also rattle against the housing when stretched. I suspect that the chain in my first box had suffered from someone trying to drop the clutch and spin the wheels. That sort of shock loading will certainly cause some damage to the chain.
Author:  alien [ Tue Dec 08, 2015 10:49 pm ]
Post subject:  Re: Weakest link in Jimny drivetrain?
Weakest link in a Jimny - the driver =P
Author:  Seth2013 [ Wed Dec 09, 2015 12:46 pm ]
Post subject:  Re: Weakest link in Jimny drivetrain?
paynebrody wrote:
Jezza86 wrote:
I assume he is talking aboout the backlash between the input and output flanges on the transfer.


Jezza, correct. lash between input and output (rear). I'll clarify my test: Car on level ground, in 2wd, handbrake on. No (well minimal) backlash between rear diff and transfer case. As not in 4wd, I'm able to spin front prop shaft freely. When car is in gear, the input shaft has minimal backlash. When I'm in neutral, I get a lot more lash in the input shaft. Feels suspiciously like the rear wheel of a dirt bike with a loose chain. I imagine the 'no lash when in gear' scenario can be attributed to the transmission essentially 'locking' the input shaft. Likewise the rear diff in effect 'locks' the rear prop shaft. With the rear prop 'locked' and the input shaft free to rotate (in neutral) the only thing I can see allowing lash in the input shaft is a loose chain.



could be wear on the main output shaft,

Image

the movement in my sierra case is pretty bad because of this.
I've only ever bent a rear drive shaft in my jimny, but I'm pretty tame with my use of it I think. too scared of rolling it still.
Author:  paynebrody [ Tue Feb 02, 2016 7:23 pm ]
Post subject:  Re: Weakest link in Jimny drivetrain?
Just to follow up on this, I kind of just lived with it waiting for serious chatter or chain jumping etc etc. The other day I was under the car and thought I should check radius arm bolt torques. All of them were loose! Like well under spec. The 'backlash' I was referring to has been seriously reduced. Will put a few more kms on the clock before putting it to bed but so far so good. Should have bloody checked to begin with....
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