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Old 08-24-2014, 10:55 AM   #1
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Jeep Wrangler 1990 YJ Transmission Rebuild

I'm having some issues with my YJ and have been for a while.

I went mudding one day and when I got back on the road, it's grinds when trying to put in Reverse. Sometimes it'll work good, sometimes you can't put it into 2nd, 3rd, 4th, or 5th without it grinding. I'm afraid I'm gonna chip a tooth if I keep driving it like this and will cause the tranmission to be destroyed.

It must be the synchronizer not slowing down the gears.

I've rebuilt fourwheelers before, but nothing with transmissions.

However, I feel comfortable to try to rebuilt it. I have a budget of $500. I don't want to risk buying a broken transmission on craigslist.

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Old 08-24-2014, 02:52 PM   #2
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I also have a private shop out back with most of the tools.
However, I don't have the special "transmission jack". I also don't have a bearing press.

I have another vehicle to drive till I get this one back in good shape.

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Old 08-24-2014, 02:54 PM   #3
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I would start simple and drain and refill with fluid.. see if that helps before tearing into it.
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Old 08-24-2014, 03:04 PM   #4
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This mostly sounds like a clutch issue. If you're set on a rebuild, you'll have a hard time without a press. The synchronizer hubs are near impossible to remove without one. Also, measuring clearances with a feeler gauge is a skipped step that can result in a bad rebuild.
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Old 08-24-2014, 03:20 PM   #5
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Sounds like your clutch is not disengaging properly. Check your clutch master cylinder and see if the fluid is low.
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Old 08-25-2014, 11:43 PM   #6
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Originally Posted by 4Jeepn View Post
I would start simple and drain and refill with fluid.. see if that helps before tearing into it.
I haven't checked the fluid at all. I'm thinking its running low... oops


I'm gonna drain and refill with Penzoil.
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Old 08-26-2014, 12:50 PM   #7
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Each gear has its own synchronizer, except for 1st and reverse, neither of those gears have a synchronizer on their shaft.

You have described a clutch issue. Possibly the slave cylinder is bleeding off internally and causing the grinding that you are experiencing. If you are tearing it apart, plan on doing a full clutch rebuild. That is the only smart way to go.
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Old 08-26-2014, 01:36 PM   #8
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Each gear has its own synchronizer, except for 1st and reverse, neither of those gears have a synchronizer on their shaft.

You have described a clutch issue. Possibly the slave cylinder is bleeding off internally and causing the grinding that you are experiencing. If you are tearing it apart, plan on doing a full clutch rebuild. That is the only smart way to go.
1st has a synchronizer, only reverse doesn't.

And I agree with the clutch issue which is why that was my first bit of advice that seemed ignored in favor of a fluid change.....
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Old 08-27-2014, 01:48 PM   #9
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1st has a synchronizer, only reverse doesn't.

And I agree with the clutch issue which is why that was my first bit of advice that seemed ignored in favor of a fluid change.....
The oil needed a change. It was pretty dirty.
Fresh Oil, and now I'm going to bleed the system.

Correct me if I'm wrong, but I need to hold down the clutch then close the valve off?

Thanks in advance.
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Old 08-27-2014, 02:30 PM   #10
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The oil needed a change. It was pretty dirty.
Fresh Oil, and now I'm going to bleed the system.

Correct me if I'm wrong, but I need to hold down the clutch then close the valve off?

Thanks in advance.
Watch a YouTube video about clutch bleeding, it's a little difficult to explain
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Old 08-27-2014, 08:15 PM   #11
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I checked out the bleed line. (It's next to the one entering it. On my drivers side)
I cannot, for the love of god, figure out where the "bleeder screw" is. The end is a hole. There's a nut before that, then a coupling-like thing. PLEASE HELP. I plan on doing this in the morning.
The clutch pedal feels so easy to push now that I notice. I'm also pretty sure it's an internal. (I know I need to go from internal to external, but not right now..)
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Old 08-27-2014, 08:41 PM   #12
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The one with the black cap is my bleader. I have an internal slave

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Old 08-27-2014, 08:56 PM   #13
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The one with the black cap is my bleader. I have an internal slave

Attachment 1432193
How do you get it open? (Sorry, I know that should be easy, but...its not. )
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Old 08-27-2014, 10:05 PM   #14
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2 open end wrenches, 1 to hold the main nut, the other to open the bleeder valve. post a picture of yours so I can see how yours looks
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Old 08-27-2014, 10:18 PM   #15
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Pull the black cap off, hold the coupling and loosen the thing the black cap was on, while some one holds the brake down, then while they hold it on the floor tighten, not tight just snug the thing the black was on, repeat this while making sure the Master for the clutch stays full, do not let it run dry. Repeat till No air bubbles come out.

If some one can tell this better, Please do so, Thanks.
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Old 08-27-2014, 10:21 PM   #16
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If some one can tell this better, Please do so, Thanks.
That's why I suggested a YouTube video haha
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Old 08-28-2014, 07:01 AM   #17
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2 open end wrenches, 1 to hold the main nut, the other to open the bleeder valve. post a picture of yours so I can see how yours looks
It looks the exact same as yours. Except there's no black cap.
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Old 08-28-2014, 08:48 AM   #18
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I bled it twice. (The 2nd guy had work today) Already, it's easier to put it in reverse. There's still a grinding, but it's a ton slower. I think bleeding it some more will get the clutch to fully come out.
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Old 08-28-2014, 01:39 PM   #19
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I bled it twice. (The 2nd guy had work today) Already, it's easier to put it in reverse. There's still a grinding, but it's a ton slower. I think bleeding it some more will get the clutch to fully come out.
It could also be time for a new clutch, but you'll figure that out after you completely bleed the system
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Old 08-28-2014, 03:59 PM   #20
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It could also be time for a new clutch, but you'll figure that out after you completely bleed the system
I'll report back what happens!
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Old 08-28-2014, 07:16 PM   #21
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I bled it like 10 times and theres no stream of liquid flowing out, just a tiny bit that rolls down the wrench. It was a lot better, but it still grinds in 4th when the clutch is in. I guess it's time for a clutch replacement.
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Old 08-28-2014, 07:42 PM   #22
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I bled it like 10 times and theres no stream of liquid flowing out, just a tiny bit that rolls down the wrench. It was a lot better, but it still grinds in 4th when the clutch is in. I guess it's time for a clutch replacement.
That or the synchronizer is bad. Tough call
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Old 08-28-2014, 08:45 PM   #23
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That or the synchronizer is bad. Tough call
Well, it grinds in reverse, 4th, and 3rd. Sometimes in 2nd when I'm shifting.
If you keep it there, (I only did this one) it doesn't slow down.
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Old 08-28-2014, 08:50 PM   #24
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I guess I'm gonna take it to a professional and get a estimate on how to get the transmission working smoothly again. I'm trying to get it in great shape for the Sheriffs-JeepFest
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Old 08-28-2014, 11:51 PM   #25
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Well, it grinds in reverse, 4th, and 3rd. Sometimes in 2nd when I'm shifting.
If you keep it there, (I only did this one) it doesn't slow down.
If it's grinding in reverse, it's most likely a clutch issue. Just get a good clutch kit and replace everything
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Old 08-29-2014, 01:50 PM   #26
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If it's grinding in reverse, it's most likely a clutch issue. Just get a good clutch kit and replace everything
Okay, Is this a good one? (Keep in mind I need it here fast, but cheap)
Jeep Cherokee COMANCHE J10 Wrangler 1989 1991 Clutch Kit Sachs K1675 23 | eBay

I found a completely rebuilt AX15 for 720 and it comes with a 1 year or 12,000 mile warranty on Ebay. (They have a 100% Positive Rating with 737 Reviews)

What do you recommend I do? Should I just replace the transmission because it had a lot of Metal Shavings and maybe the syncs are on their way out?

I've replaced the timing chain, and the ignition thingy. It cranks up perfectly and runs smooth. Transmission is just pissing me off.

Also, anything else I should probably check while I'm working on the jeep before I take it 98 miles over to the Sheriffs-Jeepfest??
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Old 08-29-2014, 02:10 PM   #27
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Okay, Is this a good one? (Keep in mind I need it here fast, but cheap)
Jeep Cherokee COMANCHE J10 Wrangler 1989 1991 Clutch Kit Sachs K1675 23 | eBay

I found a completely rebuilt AX15 for 720 and it comes with a 1 year or 12,000 mile warranty on Ebay. (They have a 100% Positive Rating with 737 Reviews)

What do you recommend I do? Should I just replace the transmission because it had a lot of Metal Shavings and maybe the syncs are on their way out?

I've replaced the timing chain, and the ignition thingy. It cranks up perfectly and runs smooth. Transmission is just pissing me off.

Also, anything else I should probably check while I'm working on the jeep before I take it 98 miles over to the Sheriffs-Jeepfest??
I'd start with the clutch before swapping out transmissions. Metal shavings are pretty regular in fluid changes for trannys, if there were actual brass or steel chunks, then you'd need to worry. I've only had good luck with luk clutch kits for jeeps: http://pages.ebay.com/motors/link/?n...769910&alt=web
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Old 08-29-2014, 02:19 PM   #28
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I'd start with the clutch before swapping out transmissions. Metal shavings are pretty regular in fluid changes for trannys, if there were actual brass or steel chunks, then you'd need to worry. I've only had good luck with luk clutch kits for jeeps: http://pages.ebay.com/motors/link/?n...769910&alt=web
Okay, I'll do one day shipping and replace the clutch. Hopefully, That's all I'll have to do.
Do I need any special tools or advice?
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Old 08-29-2014, 02:45 PM   #29
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Okay, I'll do one day shipping and replace the clutch. Hopefully, That's all I'll have to do.
Do I need any special tools or advice?
To remove the transmission there are 2 e12 reverse torx bolts on the top of the bellhousing. You can use a 12 point socket if you have one. Other than that there's not really any special tools, just metric and sae sockets. When installing the pressure plate to flywheel, I suggest you use blue threadlocker, and torque the bolts to 40 lbs torque. The pilot bearing can be difficult to remove so use a slide hammer if you have one, if not pack in grease, wet toilet paper or whatever to pound it out with a metal dowell, plenty of videos on YouTube to get a feel of how to do that.
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Old 08-29-2014, 02:50 PM   #30
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To remove the transmission there are 2 e12 reverse torx bolts on the top of the bellhousing. You can use a 12 point socket if you have one. Other than that there's not really any special tools, just metric and sae sockets. When installing the pressure plate to flywheel, I suggest you use blue threadlocker, and torque the bolts to 40 lbs torque. The pilot bearing can be difficult to remove so use a slide hammer if you have one, if not pack in grease, wet toilet paper or whatever to pound it out with a metal dowell, plenty of videos on YouTube to get a feel of how to do that.
Alrighty! I really appreciate all of your help!

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