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Manual Transmission weird issue


drewvans

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Joined
Jan 9, 2022
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7
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Wisconsin
Hey All,

This is my first entry on this forum and I am pumped. I got my 98' TJ a few weeks ago and I couldn't be happier, however, I've run into a few speed bumps and I suspect something is up with my transmission (manual 5 speed)

First, I live in Wisconsin which, at the moment, reaches temps of about 0-5 degrees most mornings. When I start my jeep then go to shift, the shifter is usually VERY stiff. Usually only for 1st, 2nd, and reverse gear. After it warms up a bit, it improves. Second thing I've noticed is that, while I am sitting stationary, I can shift through the gears like butter, no issues at all. Then, when I am moving and I shift from 1st to 2nd (for example) it's noticeably more difficult. It has grinded once and sometimes it won't be in gear when I thought it was.

At first I thought it must be transmission oil that's too heavy for the cold weather. However, I am beginning to wonder if it's a bad clutch. The Jeep only has 33K miles on it so I'm leaning towards the oil but what do you guys think?

Thanks!
 

Jerry Bransford

TJ Guru Moderator
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Someone might have screwed up and filled your transmission with a conventional gear lube which is a terrible choice for cold conditions. Try changing the transmission lube to Redline MT-90 which is a full synthetic gear lube with the right specifications for your AX-15 transmission. Local auto parts stores won't carry it but Amazon has it at https://www.amazon.com/dp/B000CPCBEQ/?tag=wranglerorg-20

Your transmission holds 3.7 quarts. This is not guaranteed to help but it might. If it doesn't help your transmission needs work.
 
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SkylinesSuck

TJ Addict
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Mar 28, 2020
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2,680
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The stiff to move into gears part is your rubber lower shifter boot being super cold. You can replace it and see if new rubber helps, or just ignore it. They are cheap.

Does it grind after being warmed up?
 

derekmac

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Feb 10, 2016
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2,573
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NS, Canada
A few times when it's been colder out (-10 and colder), when I've started the Jeep to warm it up, I'd put the transfer case in neutral and the trans in gear, and it would be easier to shift when I'd get in it and go to leave.
 

aston4

Member
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May 1, 2020
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Location
Nm
the second gear grind issue when cold is a known issue with the AW 5 speed. when cold they all do it eventually. the problem is poor design and wear on the second gear syncro. the only realistic solution is change to Redline as pointed out above, which will help, and then shift very slowly and gently, doing best to rev match, until the transmission gets hot... which can take a long time in extremely cold weather.

Also the pilot bearing in the flywheel is probably needing replacement and isn't helping.
 

aston4

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May 1, 2020
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Location
Nm
... and when trying to get into reverse, touch second or third gear ( don't go fully into gear, just press gently toward the gear and then go immediately into reverse) which slows the shaft being spun by the crappy pilot bearing
 
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drewvans

drewvans

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Jan 9, 2022
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Wisconsin
Thank you all so much! She's in the shop right now for a quick look over and once I get it back I'll be putting in MT-90. I will report back, thanks again!
 
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drewvans

drewvans

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Jan 9, 2022
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Wisconsin
... and when trying to get into reverse, touch second or third gear ( don't go fully into gear, just press gently toward the gear and then go immediately into reverse) which slows the shaft being spun by the crappy pilot bearing
Gotcha, I've been hearing that too. With the AX-15, is there a way to change to better Syncros or even gear set to permanently fix the problem? Or would this require a transmission swap? For the most part I've heard the AX series are good transmissions...?
 

Mike Z

I love to drive…
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May 12, 2021
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71
Location
USA
Hey there,
I have a 97 TJ, 5 spd, 4.0 with 66,000. My transmission is stiff when cold. After driving for about 10 minutes, it shifts more smoothly. During the first 10 minutes, when it's cold, I go easy on it. I make sure that the clutch is fully engaged when I change gears and that my shifting is very purposeful and I go from one gear to the next fully. Like Jerry said, I switched to Redline MT-90 and did notice a positive difference,,,smoother shifting and no grinding. But, I do think some of your difficulty is just the nature of the beast.

Glad to hear that you are liking your rig. People either get 'em or they don't!
 

aston4

Member
Joined
May 1, 2020
Messages
39
Location
Nm
It’s an otherwise excellent transmission with the one problem of a lousy second gear synchro. DO NOT let anyone open it up and try to fix it. Manual transmissions are insanely difficult beasts to repair correctly, an order of magnitude more difficult to rebuild than an engine. The number of people in the US with the skills to do it properly is only a few dozen. Look at some rebuild vids on YouTube to get an idea. The few that can actually do it correctly charge thousands, build race transmissions, and don’t even bother with old junk like in our beloved Jeeps. Any random transmission shop staffed by monkeys will leave your transmission in far worse condition than it is in now, and your wallet will be a lot lighter too.

Just switch to redline and get used to the transmission. Replace the pilot bearing on the flywheel when it is time for a new clutch. After a few weeks of concentrating on shifting it correctly, you’ll find that your brain has figured out how to shift it without thinking and you won’t grind the gear any more.

Shift slowly and gently, always. Jeep TJ is an old fashioned little truck, not a race car.
 
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Jerry Bransford

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Reverse is not synchronized on many manual transmissions including your AX-15 and my old VW bug. The technique used to shift into Reverse without grinding is to momentarily shift into any forward gear like 1st then move the shifter into Reverse. Voila, no grinding!
 

aston4

Member
Joined
May 1, 2020
Messages
39
Location
Nm
A few times when it's been colder out (-10 and colder), when I've started the Jeep to warm it up, I'd put the transfer case in neutral and the trans in gear, and it would be easier to shift when I'd get in it and go to leave.
I just finally got around to actually comprehend what is written here. This is BRILLIANT! It warms the gears without having to move the vehicle. Absolute genius. Damn.
 
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drewvans

drewvans

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Jan 9, 2022
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Wisconsin
Hey there,
I have a 97 TJ, 5 spd, 4.0 with 66,000. My transmission is stiff when cold. After driving for about 10 minutes, it shifts more smoothly. During the first 10 minutes, when it's cold, I go easy on it. I make sure that the clutch is fully engaged when I change gears and that my shifting is very purposeful and I go from one gear to the next fully. Like Jerry said, I switched to Redline MT-90 and did notice a positive difference,,,smoother shifting and no grinding. But, I do think some of your difficulty is just the nature of the beast.

Glad to hear that you are liking your rig. People either get 'em or they don't!
Good stuff man, I appreciate the insight. Can't wait to get to work, thanks!
 
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drewvans

drewvans

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Joined
Jan 9, 2022
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7
Location
Wisconsin
A few times when it's been colder out (-10 and colder), when I've started the Jeep to warm it up, I'd put the transfer case in neutral and the trans in gear, and it would be easier to shift when I'd get in it and go to leave.
Woah! Sorry, I am a total novice so would you mind unpacking that a bit for me? How would I put my transfer case in neutral?
 
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drewvans

drewvans

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Jan 9, 2022
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7
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Wisconsin
Reverse is not synchronized on many manual transmissions including your AX-15 and my old VW bug. The technique used to shift into Reverse without grinding is to momentarily shift into any forward gear like 1st then move the shifter into Reverse. Voila, no grinding!
Thanks for that tip! Reverse honestly doesn't ever grind, just 2nd gear. I will keep that in mind though for the future, appreciate it (y)
 

aston4

Member
Joined
May 1, 2020
Messages
39
Location
Nm
Reverse is not synchronized on many manual transmissions including your AX-15 and my old VW bug. The technique used to shift into Reverse without grinding is to momentarily shift into any forward gear like 1st then move the shifter into Reverse. Voila, no grinding!
I’ll just add to this, that if the gear teeth aren’t line up right after touching a forward gear to stop the reverse idler shaft from spinning, and the gear lever feels stuck, letting the clutch out just the teensiest scoochie will move the reverse gear enough to let everything mesh.

Weird how this was just common knowledge back in the old days. I guess it’s still common knowledge in the rest of the world that’s still mostly manual, though not for much longer…
 

aston4

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Nm
Woah! Sorry, I am a total novice so would you mind unpacking that a bit for me? How would I put my transfer case in neutral?
The big lever that switches from 2WD to 4WD. There’s an N in he middle. In that position it disengages the transmission from the drivetrain. So the transmission can be in gear with all the spinny bits spinnin, but Jeep doesn’t move. Spinny bits spinning (because the transmission is in gear with running engine) makes heat through friction.
 
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drewvans

drewvans

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Jan 9, 2022
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Wisconsin
The big lever that switches from 2WD to 4WD. There’s an N in he middle. In that position it disengages the transmission from the drivetrain. So the transmission can be in gear with all the spinny bits spinnin, but Jeep doesn’t move. Spinny bits spinning (because the transmission is in gear with running engine) makes heat through friction.
Aha! Got it. I will update!
 
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BobbyA1

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Sep 18, 2021
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35
Location
Virginia
Thanks for that tip! Reverse honestly doesn't ever grind, just 2nd gear. I will keep that in mind though for the future, appreciate it (y)
My 2nd gear grinds all the time - if - I try to shift at speeds above 15mph (up or down) otherwise it works just fine. I read somewhere online that with the TJ and perhaps many other vehicles, that 2nd Gear is always the first one to go bad, the 2nd gear synchro might be worn out?

I've changed both the Transmission and Transfer Case fluids and it did produce noticeable results, smoother shifting but it still grinds at shifts above 15mph in 2nd. If you haven't already, it might not be a bad place to start, changing those fluids out, see if it gets any better. I used Redline MTL in the transmission and Valvoline ATF-4 in the transfer case.
 
Joined
Nov 15, 2021
Messages
55
Location
Ga
Someone might have screwed up and filled your transmission with a conventional gear lube which is a terrible choice for cold conditions. Try changing the transmission lube to Redline MT-90 which is a full synthetic gear lube with the right specifications for your AX-15 transmission. Local auto parts stores won't carry it but Amazon has it at https://www.amazon.com/dp/B000CPCBEQ/?tag=wranglerorg-20

Your transmission holds 3.7 quarts. This is not guaranteed to help but it might. If it doesn't help your transmission needs work.
Jerry, I plan on switching to red line in my tranny (nsg 370) what weight do you recommend for my specifications? thanks