Hard to get into 1st gear from a stop

racecar825

racecar825

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Recently bought a 1998 TJ Sahara with 163000 miles. Sometimes it is hard to get into first from a stop. It it takes a firm pressure to get it in, 2nd gear is a bit notchy but fine otherwise, 3rd to 5th are as smooth as butter. It's still driveable, but sometimes i worry i won't be able to get it into gear at a red light. I changed the transmission fluid to Redline MT-90 about 100 miles ago and it feels like it got slightly better, but the problem is still there.

Symptoms:
  1. Seems like it happens after driving a bit and the Jeep warms up.
  2. If I put it into 1st while rolling at ~2-3 mph, it slides right in without any problem.
  3. sometimes it grinds into reverse when at a stop
  4. I can go through all the gears with the engine stopped, no problem

This leads me to believe that the clutch isn't fully disengaging and keeping the the input shaft of the tranny slightly spinning, but i could be wrong.

After reading a lot about this issue, some people say the synchros on the AX-15 are known to go bad. Some people have replaced the slave/master cylinder and the problem goes away. I just ordered the LUK pre-filled master/slave assembly. Hopefully that fixes the problem. Has anyone else had this problem?
 
Before doing anything drastic try letting the new fluid do its thing. What did the old fluid look like? Any metal shavings? Any gold colored flakes in it? Was it basically an amber color or was it dark? Any clumps come out? H2o contamination? These will help find out what is going on inside the gearbox.
Be certain to always carefully inspect any fluid you drain from the Jeep.
 
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Yeah I have the same problem on my NV3550. The grinding in reverse you experience is normal because the reverse gear on your AX-15 is not synchronized. But I sometimes have problems getting into first as swell. Usually shifting into 4th or 2nd and then into 1st solves the problem. The pressure plate could be on its way out, but I just think it's the synchros getting tired. One day I'll put a new unit in, but these old transmission can go a long time even with failing synchros.
 
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With that mileage and the symptoms you describe, I agree with your diagnosis that the clutch is probably not fully disengaging.

Not sure if this works on a TJ but try pumping the clutch pedal a few times before going into 1st like you might pump the brakes if your brake master cylinder was failing.

If that helps, I would replace your master/slave cylinders as that is probably where the problem is. Otherwise, maybe time for a new clutch.
 
If you're in neutral at the light (stopped), the light turns green and you immediately depress the clutch and try to shift into first, it will struggle until the clutch disc and input shaft have a chance to slow down. I just depress the clutch and wait a couple of seconds then engage first gear. At least this works for me.
 
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When I changed the fluid, i remember it not being too dirty, just a bit dark, but I did notice some golden flakes at the bottom. I think I still have the old fluid in a bottle somewhere. I will check that today.

I'll run it a bit more to let the fluid work before swapping anything. How long does it usually take for the fluid to take effect? I'll also try what everyone suggested to see if anything else helps.
 
Might just be the syncros are worn. Expensive to fix but easy to live with. Treat it like a crash box with no synchros, press in the clutch immediately before shifting. Don't sit with the clutch in.
 
Getting the AX-15/5 or NV3550 into 1st gear from a stop has been an issue across the board since forever. I had the same problem with my AX-15. I'm not so sure there has ever been a definitive fix for this issue. I only stopped having that issue after converting it to an automatic lol.
 
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So the old fluid looks darker than I remembered.

IMG_3159.JPG

IMG_3157.JPG
 
Pretty well documented problem, had this issue with an AX-5, then once in gear it was fine. I ended up just replacing the trans and it went away, after trying tons of different fluids, recommendations, etc.
 
racecar825 said:
Symptoms:
  1. Seems like it happens after driving a bit and the Jeep warms up.
  2. If I put it into 1st while rolling at ~2-3 mph, it slides right in without any problem
Click to expand...
It could be the clutch disc not disengaging, it also could be that the gears are just not meshing. Try this, after you are stopped for awhile very gently try to push it into first, similar to the 2-3mph shift but let the clutch out a bit to spin the gears. If it slides in then the problem isn't the clutch. My Ford requires this technique sometimes, with no syncros if the gears aren't aligned they wont engage. No matter what you do unless the car moves or you let out the clutch to spin the gears it wont go into gear.
 
This is normal, especially if you're sitting with the clutch in long enough that the transmission stops spinning. Both my NV3550's have had this happen. The reason it goes in butter smooth at 2-3 MPH is because the transmission is spinning and the gears can mesh (IE the synchros can do their job). If you sit a long time with the clutch in, just bump it out to get things spinning again and try to go into 1st. It is better to just sit in neutral without touching the clutch pedal so the input shaft never stops spinning.
 
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You are correct about thinking the clutch is not fully disengaging. I Believe that is what it is also. It very well could be the original clutch from 98. 22 years ago......:p

With that mileage I would bet your synchro's are worn also. But, Try your slave kit and see. Also keep giving the new oil a chance as mentioned. But I would bet the pilot bearing is dry and hanging on to the input shaft bearing surface and not slowing down enough for smooth engagement.
 
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Agree with @Jerry Bransford that there is no definitive fix that anyone can spit out to empirically solve the issue. All that has been recommended are pointing to possible resolutions for the issue you are having.

The issue is that the input shaft to the tranny is not slowing down. This could be a clutch disk that won't release, a bad pilot bearing or a host of other issues.

After replacing my tranny fluid and then replacing my clutch master and slave, my issue wasn't resolved. Next step was cto replace the clutch, pilot, throw out bearing.
Meaning. It was time to pull the tranny.

Turns out none of those things were my actual problem. My AX15 input shaft seal was leaking and the fluid was running down the front bearing cover tube and being sling onto the clutch.

Replaced the front bearing seal and clutch components and I am now up and running with no shifting issues
 
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Thanks for all the advice everybody. I'll swap out the slave/master first. If that doesn't work, I'll start looking into clutch issues. How much does a cluch job usually run if i go to a shop? Dropping the tranny might be too much for me.
 
If that old fluid is showing all that is gold, then you have some serious syncro wear. If what I see is air bubbles then the old fluid isn't terrible.
 
racecar825 said:
Recently bought a 1998 TJ Sahara with 163000 miles. Sometimes it is hard to get into first from a stop. It it takes a firm pressure to get it in, 2nd gear is a bit notchy but fine otherwise, 3rd to 5th are as smooth as butter. It's still driveable, but sometimes i worry i won't be able to get it into gear at a red light. I changed the transmission fluid to Redline MT-90 about 100 miles ago and it feels like it got slightly better, but the problem is still there.

Symptoms:
  1. Seems like it happens after driving a bit and the Jeep warms up.
  2. If I put it into 1st while rolling at ~2-3 mph, it slides right in without any problem.
  3. sometimes it grinds into reverse when at a stop
  4. I can go through all the gears with the engine stopped, no problem

This leads me to believe that the clutch isn't fully disengaging and keeping the the input shaft of the tranny slightly spinning, but i could be wrong.

After reading a lot about this issue, some people say the synchros on the AX-15 are known to go bad. Some people have replaced the slave/master cylinder and the problem goes away. I just ordered the LUK pre-filled master/slave assembly. Hopefully that fixes the problem. Has anyone else had this problem?
Click to expand...

I have a similar issue. I just ordered a pre-filled master/slave assembly, as well. Let me know how yours goes. I watched several YouTube video’s for install. Wish me luck. I enjoy working on my Jeep with my kids. Good bonding.
 
If it grinds, then there is something wrong like worn synchros or a clutch not disengaging. When my synchros went out in my first gearbox, I used to float every gear (not use the clutch) because my synchros were so gone that it didn't matter if I used the clutch or not. The clutch not disengaging theory doesn't make much sense to me. It would have to be extremely slight for you not to notice. I've had it happen before and I immediately noticed when shifting through every gear and the Jeep would shake at stoplights in gear.

If it isn't grinding, then you just have a normal Jeep transmission. Don't waste time and money on it. Reverse is grinding because you don't have a synchro for the reverse gear. You have to wait for the transmission to spin down to shift into it.
 
racecar825 said:
Recently bought a 1998 TJ Sahara with 163000 miles. Sometimes it is hard to get into first from a stop. It it takes a firm pressure to get it in, 2nd gear is a bit notchy but fine otherwise, 3rd to 5th are as smooth as butter. It's still driveable, but sometimes i worry i won't be able to get it into gear at a red light. I changed the transmission fluid to Redline MT-90 about 100 miles ago and it feels like it got slightly better, but the problem is still there.

Symptoms:
  1. Seems like it happens after driving a bit and the Jeep warms up.
  2. If I put it into 1st while rolling at ~2-3 mph, it slides right in without any problem.
  3. sometimes it grinds into reverse when at a stop
  4. I can go through all the gears with the engine stopped, no problem

This leads me to believe that the clutch isn't fully disengaging and keeping the the input shaft of the tranny slightly spinning, but i could be wrong.

After reading a lot about this issue, some people say the synchros on the AX-15 are known to go bad. Some people have replaced the slave/master cylinder and the problem goes away. I just ordered the LUK pre-filled master/slave assembly. Hopefully that fixes the problem. Has anyone else had this problem?
Click to expand...

I had a similar issue with with my 2001 that has the nv3350 with a transfer case drop installed. I found that the stock shift boot is made of thick rubber and binds up going especially when cold. I pulled it off and now shifts like butter.
 
Ive got a brand new AX-15 in my TJ. It’s maybe 3 years old this June. Hasn’t even hit 20k miles. Since new, it‘s been randomly picky going into first, but notchy into second. Yet it shifts smoothly just about all of time and never grinds.

Reverse, I absolutely put into first, first. Then, into reverse. It’s simple an action that I do without even thinking. Works every time. Used to do the same w my NV3550. like others have mentioned: no synchro for reverse?

End of the day, the TJ is a different shift feel than any car or modern manual vehicle Ive ever driven.
 
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