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Old 20th January 2009, 23:41   #1
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Default 4x4 gearbox crisis

I recently purchased an old CJ500 equipped with a 4-forward, 1-reverse speed g'box. It's a 4x4 and the transfer case houses a LOW and a HIGH gear and the counter gears. Its the later version of gearbox from Mahindra in which just one separate lever (instead of 2 levers) is provided to engage and disengage the 4x4 gear.
There's no problem in engaging the 4x4 mode, both HIGH n LOW operate well. But its tough getting to the neutral position. The lever comes to the neutral postion but when i engage any gear by the regular lever n release clutch, there's a driveline snatch. Its the peculiar sound of incomplete meshing of the gear teeth. If i try to move forward irrespective of the snatch, the vehihcle does not move an inch.
We checked for excessive clearances in gears. They are assembled correctly to our knowledge but the problem of getting in neutral (complete disengagement of 4x4 mode) still persists.
help....
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Old 21st January 2009, 00:26   #2
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Quote:
Originally Posted by unmesh View Post
I recently purchased an old CJ500 equipped with a 4-forward, 1-reverse speed g'box. It's a 4x4 and the transfer case houses a LOW and a HIGH gear and the counter gears. Its the later version of gearbox from Mahindra in which just one separate lever (instead of 2 levers) is provided to engage and disengage the 4x4 gear.
There's no problem in engaging the 4x4 mode, both HIGH n LOW operate well. But its tough getting to the neutral position. The lever comes to the neutral postion but when i engage any gear by the regular lever n release clutch, there's a driveline snatch. Its the peculiar sound of incomplete meshing of the gear teeth. If i try to move forward irrespective of the snatch, the vehihcle does not move an inch.
We checked for excessive clearances in gears. They are assembled correctly to our knowledge but the problem of getting in neutral (complete disengagement of 4x4 mode) still persists.
help....
Just try adjusting/tightening the bolt which is shown in the pic. the shift rod for high-low range selector is being pushed back which puts you into neutral. the bolt is adjusted to restrict the easy movement of the shift rod. and this mechanism is same for a single lever operated transfer case.
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Old 21st January 2009, 06:50   #3
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Quote:
Originally Posted by unmesh View Post
We checked for excessive clearances in gears. They are assembled correctly to our knowledge but the problem of getting in neutral (complete disengagement of 4x4 mode) still persists.
I do not know what your problem is. Maybe tightening the bolt per above will solve it, dunno. If not, how gears fit together is called "gear lash". For each application, for differentials, transmissions or transfer cases the tolerances differ. It is not just a case of adjusting to get a tight fit. Some applications require a looser fit. You may need to get an expert to look at it and replace washers, gears etc as needed and to set the proper gear lash TO SPECIFICATION.
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Old 21st January 2009, 13:32   #4
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Originally Posted by DirtyDan View Post
I do not know what your problem is. Maybe tightening the bolt per above will solve it, dunno. If not, how gears fit together is called "gear lash". For each application, for differentials, transmissions or transfer cases the tolerances differ. It is not just a case of adjusting to get a tight fit. Some applications require a looser fit. You may need to get an expert to look at it and replace washers, gears etc as needed and to set the proper gear lash TO SPECIFICATION.
with DD. unmesh, what i suggested is a temporary solution to keep the shift rod not to put you in neutral. there could be other problem, may be with shift fork.
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Old 22nd January 2009, 00:20   #5
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Originally Posted by unmesh View Post
so could u help me with some more technical data jus like the diagram you posted earlier? that would really help.
unmesh, this diagram was posted somewhere in this forum by Arka. but dont know in which thread. anyways i am posting it here again. i hope it will be helpful for you.
the two shift rods you see in which one is for changing 2wd-4wd and vice-versa and the other is for low-neutral-high. the L-N-H is very similar to 1-N-2 or 3-N-4 mechanism as in normal gearboxes. your problem is gear slipping into neutral. as i showed you the location of the bolt, you should find the bolt on either sides. just remove the bolts on either side and check it. inside you should find a spring and a ball on both sides. if the spring or a ball is missing, then i think it must be the culprit.

The single lever concept is very similar to normal gear lever we use for normal driving. the single lever is enough to shift those two rods instead of using two seperate levers for each shift rod. if you observe the flow in single lever lever i.e 2H-4H-N-4L and its same with two levers. you cant change the flow with two lever.
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4x4 gearbox crisis-t18-partsbreakdown02a.jpg  


Last edited by star_aqua : 22nd January 2009 at 00:29.
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Old 22nd January 2009, 09:01   #6
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Originally Posted by unmesh View Post
The exploded view of the transfer case assembly is really very helpful. Thanks for that.
Do u have any such drawings of the detailed assembly of the entire gearbox alongwith the transfer case?
@Unmesh & Vijay: The diagram's posted above are from the CJ3B Page. Since most model of Jeeps available in India have inherited a lot from the CJ3B, you'll be able to find a lot of relevant technical information on transmission, differentials etc on the CJ3B page here .

Quote:
Originally Posted by unmesh View Post
(My gearbox has ONE lever for dealing with 4x4)
Not sure how different the internals of your gearbox are in comparison to the CJ3B's gearbox. Experts, please advise.

Last edited by S@~+#0$# : 22nd January 2009 at 09:08.
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Old 22nd January 2009, 16:43   #7
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Not sure how different the internals of your gearbox are in comparison to the CJ3B's gearbox. Experts, please advise.
yes Santosh, gearbox could be different. but here its the transfercase and it will be usually T18 spicer what most of us have.
I have sketched the shift rod mechanism in which you can know how the shift takes place.
Name:  shift rod mechanism.jpg
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@unmesh: make sure you have all the parts i.e. Poppet spring, Poppet ball and interlock in right place as per my drawing.
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Old 22nd January 2009, 23:16   #8
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@ star aqua - Man you have some nice sketching skill. What profession are you in apart from Jeeping.

cheers
vishwas
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Old 23rd January 2009, 09:31   #9
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@ star aqua - Man you have some nice sketching skill. What profession are you in apart from Jeeping.

cheers
vishwas
Thanks Vishwas! i used to sketch teachers in my schooling days and thats how i got this skill . BTW am basically a SE and the Software i develop is for Engine Management System(Engine ECU) .
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