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Old 12-19-2013, 06:55 PM   #1
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Another Problem? (Transmission)

1991 Wrangler YJ 2.5L 5 speed (Pretty sure it's an AX5 tranny)
So the last few days I noticed that the shifter kind of "bounces" off of 2nd gear and makes a low pitched grinding noise. If I shift quickly it kind of jerks into gear and I feel it kind of grind/bounce into gear. (Not the signature grinding sound that's made when you try to pull a manual shifter into gear from idle without using the clutch pedal) If I pull it slowly, but constantly, into 2nd from 1st it will grind and not want to go into gear. But this is what confuses me the most.... If I pull it from 1st into N and kind of hesitate there for a second, then pull it into a 2nd it doesn't grind (while holding the clutch pedal down, not double clutching) Also, If i downshift from 3rd to 2nd it goes into gear like butter.

I'm thinking a worn synchronizer?
How would it fail in one day?
Let the vehicle warm up longer and shift slower?
There's no leaks.
I'm running Pennzoil synchromesh in it and I've heard it doesn't like cold weather, especially below zero.

I changed the transmission fluid about 3000 miles ago after I bought the Jeep. There were no gold flakes/specks in the oil anywhere, just a a little fine gray powder around the drain plug.

I plan on changing my fluid to Redline MT90 this spring anyway, I've heard great things about it.

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Old 12-19-2013, 09:40 PM   #2
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After rebuilding a few manual trannys, Id say your 2nd gear syncro is going bad, its the only thing that will cause that grinding while the shift fork tries to slide the sleeve over second gear. Putting it into neutral is probably allowing the gears to slow a bit, taking some work off of the syncro.

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Old 12-19-2013, 09:44 PM   #3
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From what little I've seen over the years, it's like the slicker the oil, the worse a transmission will shift, but then that is the job of the synchronizer to get that gear spinning so it will drop in. I would think thin synthetic oil or auto trans fluid would work best in cold weather.
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Old 12-20-2013, 05:27 AM   #4
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Gah! Guess I'll have the transmission rebuilt this summer. Doing a transmission rebuild myself is way out of my league and I'd probably completely mess it up. This is my daily driver and I don't want to risk anything. I'm guessing it's going to cost around $1000 to have a specialized transmission shop do it?
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Old 12-22-2013, 05:00 PM   #5
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Have some one look at it, it may be the clutch not disengaging, we can't tell for sure from here with out seeing it, may be just the master cylinder, buy passing internally and not turning the clutch lose.
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Old 12-22-2013, 10:48 PM   #6
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If the clutch didn't disengage the jeep wouldn't even start, let alone shift out of first.
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Old 12-23-2013, 08:15 PM   #7
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I'll have it looked at soon as I had the clutch system redone about 3 months ago. (New clutch disk, pressure plate, throw out bearing, hydraulic line, and flywheel resurfaced)

It only does the rough grind thing when I'm up shifting and accelerating, if I'm at a constant speed or standstill it shifts fine. Now it started doing it when shifting into 3rd also. It doesn't do it at all when I'm down shifting at regular speeds, or engine breaking.

I'll check the fluid level when I get home again. Maybe there's a leak I missed or didn't put enough in or something.
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Old 12-23-2013, 10:09 PM   #8
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Quote:
Originally Posted by KSmith37 View Post
If the clutch didn't disengage the jeep wouldn't even start, let alone shift out of first.
B.S.

Wow, I would like to know how a Big Rig shifts gears all day long with out pushing in on the clutch or a Rock Crawler fires there rigs up in gear so they don't slip and burn the clutch or why the Feds. made the Auto Mfg. add a safety switch in cars back in the late 60s or 70s so it would not start with out the peddle being pushed in.
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Old 12-23-2013, 11:32 PM   #9
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Pedal pushed in means clutch is disengaged, foot off the pedal engaged the clutch. Pushing in the pedal (disengaging the clutch) allows the transmission to shift because the load of the engine isn't on the trans via disengaged clutch. Foot off the pedal (engaging the clutch) puts the work from the engine into the trans. Therefore, a clutch that doesn't disengage won't start let alone shift out of first.
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Old 12-23-2013, 11:47 PM   #10
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The terms "disengage" and "engage" refer to the clutch itself, not the pedal as i assume you are referring to and the reason for this disagreement.
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Old 12-24-2013, 12:08 AM   #11
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Thanks for explaining how the system Should work, When there is no Problems, But the man has some problems.
Now if some one was to push the pedal down, and the system does not move the throw out bearing far enough to "dis engage the clutch disk" all the way, it would cause the same problems this man is having.

If the clutch pedal was pushed in, and the clutch had a problem, and it Was Still Totally Engaged [still holding, as in not stopping the power transfer] the Jeep engine will start in gear and move the Jeep as it starts. Merry Christmas!
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Old 12-25-2013, 12:53 AM   #12
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I enjoy your sarcastic responses, i was just clarifying for the disagreement you initiated, but as I stated previously, i'd say that syncro is on its way out the door. Especially if that is the only gear you have issues with. A clutch problem would arise in all aspects including starting and shifting into all other gears.
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Old 12-25-2013, 11:10 AM   #13
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I'll keep you updated but I really think it's just Pennzoil synchromesh in this brutally cold weather. I just drove 200+ miles home for Christmas. Not a single grind. I granny shifted the first few miles through town and it felt a little rough but didn't grind. After it was warmed up I could pull the shifter as fast as I wanted and it wouldn't grind. This has been consistant, I'm not ruling out a bad synchro though, I'll have the tranny looked in the near future.

It's not the clutch, I put it in first and pull off quick , Jeep jerks forward and stalls as any manual would. If I do it slowly I can see the rpms drop and it "catches" and starts to roll forward. No noise, no scraping, nothing abnormal. When I gun the gas, it accelerates properly and doesn't slip. (Slowly, it's a 4 banger YJ after all )
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Old 12-25-2013, 03:51 PM   #14
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Definitely a possibiliity, atleast youre driving!
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Old 01-03-2014, 01:12 PM   #15
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Update: Have had no problems after it's all warmed up. Plus, look what I scored! $40 for a complete AX5, only catch is that it's in pieces and the original owner said he lost 3rd gear. I have a project this spring, I'm going to rebuild it and have a spare tranny just in case...



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Old 01-09-2014, 11:06 AM   #16
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Another update: So my master clutch cylinder blew a few days ago and I got stranded on the highway in -25 weather. My clutch pedal had been getting easier and easier to push down the past week and I forgot about it until it went to the floor one morning after work. Sucked, but I'm home safe without the Jeep for a while. Mechanic said it had been leaking for a while and it finally just gave out that day. Could this possibly explain the mild chattering noise I was getting when shifting? Because the clutch was having a difficult time engaging/disengaging? I guess I'll find out when I get it back. I'm really starting to think I got ripped off big time when I bought this Jeep. If it wasn't the clutch I'll just keep trying to rebuild that tranny I got!
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Old 01-10-2014, 04:07 PM   #17
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You didn't get ripped off. It's a 23 year old vehicle. It's going to have some problems. You can work through them. I'm in the same boat as you with my '95.

Yes, if the slave/master was leaking it very well could be the reason for the grinding/ hard shifts. I just went thru this exact problem with mine. I replaced the slave/master hoping to fix the issue with no luck. Turned out it was the T/O bearing. A new clutch, pressure plate, pilot bearing, throw out bearing, some fresh Synchromesh & it shifts like butta'.

See how it drives when you get it back & go from there.

NOW, I know this isn't what you want to hear, BUT: while I'm a huge supporter of the 2.5L, the AX5 that's bolted up to it is GARBAGE. No way would I spend the coin to rebuild an AX5 tranny. If it's shifting fine when you get it back, sell everything you just picked up for the AX5 & start gathering up needed parts for a AX15 swap. My AX5 is going strong as of right now, but who knows for how much longer. I'm slowly gathering up parts to do the AX15 swap. That way when the AX5 decides to crap out, I'll have a good start on the swap.

Just my two cents, hope this helps.

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