You could rightly accuse me of being an old fuss-budget, but I find the six-speed in my 2014 Unlimited to be seriously clunky (like an old, non-synchro truck from 40 years ago). I know it's not designed as a smooth-shifting sports car, but grinding from 1-2, 5-6, and into reverse seems over the top. Is this a synchronizer problem, or a shifter problem? Does anyone have any successful experience with overhauling a perfectly functional transmission, merely to improve shifting? Or is there a well-known shifter kit I've overlooked that would significantly improve things?
Improve shift feel on JK six-speed?
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It could be a problem with the clutch not disengaging fully, either by user error or by mechanical problem. Considering your experience with manuals, I'd place my bet on a mechanical problem. You might consider synthetic fluid in the gearbox as a possible improvement.
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Mine is clickie, doesn't grind. First thing I would do is a fluid change... If you haven't ever done it, I would run, not walk to a get at least 2 QT of MS-9224 spec lube and change it out. I recommend Redline MTL. Drive it a little while and then see if that helps. It won't be an immediate improvement, it takes a bit to mellow out the tranny. But it will.
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837 Posts
Not recommended but I can make those shifts with no clutch and no grinds. This is the best trans uve driven tbh.
Only issue is the jump to 5th/6th. The gates a bit wide.
Only issue is the jump to 5th/6th. The gates a bit wide.
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Yep i can too.
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Honestly the 6 speed in the JK really isn't that bad and 100 times better than the older non synchro ones. I'm putting an SM465 in my fj40 which has a non synchro granny gear and there is a night and day difference. I wonder if people have forgotten what older transmissions are like. The jog between 5th and 6th did take a little getting used to but still...
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I wouldn't say "issues" but it is a pretty far jog over to the right to get it into 6th gear. Just took a little bit of getting used to, but after that not issues at all.
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Exactly. It is way off to the right its not a natural shift and definitely not the same width or spread as 1-2 to 3-4. Its a like H pattern design the a { added for 5-6. Just feels way off.
One test can eliminate clutch as the problem by slogging along in 4th and let off the throttle put it into neutral then give slight pressure into 5th. You need to be quick but not too quick and not too firm. It takes practice but if you have exp. driving an old dump truck you will be good. Even motorcycle expierience is good as you have the idea of clutchleess up shifts already. Same idea but with a slight pause and at a low rpm.
If it goes in with no issue then your synchro's are fine and gears etc but if theres just no way in hell to make a shift without the clutch then you have gearbox issues.
Now that I think about it it may be easier to try the 3-4th shift. I can do this easily. You have to be kind of totally putzing along for it to work but it will go right into the next gear.
More than likely you have a worn clutch not fully disengaging or something related to that from your description.
This is my first jeep jk and definitely first NEW vehicle but I have had mostly 70s muscle cars with T-5 trans and even a brand new t-5z will not shift as well as this jk gearbox. Its really good for a truck.
The only issue you should have that is normal is trying to shift near redline too quickly. If the rpms dont drop enough it does resist. I just double clutch when im hammering on it and its all good.
Hopefully some of that rambling on helps you
^i got my jk brand new had 27 miles on it.the shifter itself has a long throw and isn't like a gated shifter where you have a slotted pattern to push it into so you can sometimes get into the wrong gear(or try to)and its gonna grind.i put a barton shifter on my challenger because of the slop in a brand new oem,,pricey but worth it
I appreciate all the feedback. I did try the fluid change (to full synthetic). No difference at all. I've been driving sticks for 55 years, so I know this thing has lots of company, and is better than many trucks--and even some muscle cares--of the 50's through 70's. And, of course, I've learned to adapt: always multiple movements before shifting into reverse; always count 1-2-3 for the 1-2 shift; always be very careful on the 5-6 shift (which, as Mr. Poop says, is not "natural"). It's entirely manageable, just not a pleasure (as so much else is, on this rig). I'd be ready to pay whatever it took to turn it into a modern 6-speed feel. Thanks again, guys.
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Not sure if this issue has been fixed on the line yet, but '12 and '13 owners were finding their transmissions underfilled.
The trans in my '13 was seriously notchy when new, but wasn't grinding. At about 1000 miles, I drained the factory oil and went to Redline synthetic oil (Pennzoil Synchromesh is a more readily available compatible synthetic).
It helped, but didn't totally alleviate the issue. By about 3000 miles, it was shifting much better. I'm still under 10k since my Jeep isn't a daily driver, but no complaints.
Edit: Sorry mtrout, I was posting my info as you were updating yours about the steps you've already taken.
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^ This.
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118 Posts
Worth starting with simplest and cheapest option -- change transmission fluid.
I'm doing that this weekend and going with Amsoil based on all of the reviews from others on this thread.
This would not cause the grinding but the inner shift boot will definitely make shifting tougher if it has come unseated, which seems to be a common issue. Mine was slopping around inside and pretty mangled up. It would sometimes violently pop out of first.
I'm doing that this weekend and going with Amsoil based on all of the reviews from others on this thread.
This would not cause the grinding but the inner shift boot will definitely make shifting tougher if it has come unseated, which seems to be a common issue. Mine was slopping around inside and pretty mangled up. It would sometimes violently pop out of first.
kinda clunky, marbly sounding, and wants to jog from #1...but no grinding
clutchless shifts fine 2k -2.5k rpm1-2, 2-3, 3-4 but to 4-5 is hit or miss (more practice for me I guess)
that combo 1-2, 5-6) does sound like the inner shift boot interference like mentioned
clutchless shifts fine 2k -2.5k rpm1-2, 2-3, 3-4 but to 4-5 is hit or miss (more practice for me I guess)
that combo 1-2, 5-6) does sound like the inner shift boot interference like mentioned
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Likely shift boot, especially if most of the issues are with 1-3-5. Those are the gears where the inner boot is being squeezed.
It's also easy to test by removing both the outer and inner shift boots. I removed mine and drove around for a few days like that to confirm it was the inner boot.
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As long as your shifting properly and fully engaging the clutch there should be no "grinding". If there is, take it in under warranty. It can feel "clunky" at times depending upon the rpm's you're shifting at. That's pretty much normal, but "grinding" isn't.
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