Manual Transmission - Issues shifting into 1st & Reverse (Compilation thread)

[SadRobot]

I wanted to start a separate thread on this in case I ever solve it and it'll be easier for others to search it on the forums. I feel like most of this is spread out through a couple other threads about other stuff. So here we go:

Some basic info:

2019 Jeep JL Sport - 6MT
37" tires, 4.88 gears
ACT clutch

Timeline:

7/12/24 - ACT clutch installed by transmission shop. No issues after install.

11/15/24 - 1st gear starts to become sticky. Every 10thish shift it won't go right into gear. I now have just over 10,000 miles on the ACT clutch.

11/16-11/23 - Symptoms get worse. Now it's every time I shift into 1st and reverse the shifter feels like it's hitting something solid.

11/24/24 - Jeeps becomes unable to shift at Northwest OHV in Texas. Jeep gets stuck on an obstacle and can't shift into any gear. I have to get pulled back with a recovery rope to flat ground. Once on flat ground with a lot of effort I can get the Jeep into 1st again.

I get connected to a mechanic by a Jeep club out at Northwest OHV. Mechanic takes a look and says the slave cylinder has gone bad. We track down a new OEM slave and replace old slave. The process of replacing/bleeding takes 2 days.

11/26/24 - We never get all the air out and I drive the Jeep back to California with a low pedal.

11/27/24 - I drive it to the transmission shop that installed the ACT. They take a look and agree we did not get all the air out in Texas. They bleed the Jeep for 3 hours. After that I drive it home and it is back to normal. I think this issue is done and solved.

11/28/24 - On the way to Thanksgiving dinner the shifting into 1st is sticky again. I'm right back where I was on 11/15. Pedal feel and engagement has not changed. Just can't get into 1st and reverse easily.

12/2/24 - I drive Jeep back to transmission shop after the holiday and they test drive it and diagnose that the synchros have gone bad. $800 inspection fee before they replace anything. That sounds wrong to me plus they are out of loaner cars so I can't leave the Jeep anyway. I drove it home and shifting has gotten even worse. Jeep is now back to where it was on 11/24.

12/3/24 - I drop it a block away from my house to an auto shop. It has some good reviews and I can at least walk home from it. They have it for a day and say the issue is the master cylinder is leaking. I need a new one. They can't find one so they send me on my way and wish me luck.

12/4/24 - @roaniecowpony tracks down a master cylinder, picks it up and drives to my house. We install it, do a bleed and then test drive and Jeep is back to perfect again.

12/5/24 - I take the Jeep for a 40 mile drive. By the time I get back home the Jeep isn't shifting right again. Jeep is back where it was on 11/24. I check the master and see it's still leaking. It must be the line connection not the master. I track down a new line.

12/6/24 - I buy the new line and we replace the old one. After that we spend all day bleeding the hydraulics. We try vacuum bleeding, pressure bleeding. All of this with the back of the Jeep jacked up to get the slave cylinder bleed screw higher to release the trapped air. At first everything is back to normal again. Shifting is perfect. I drive home 40 miles. Once I get off the freeway and start getting to stoplights I have issues again in 1st and reverse. Jeep is back to where it was on 11/16. Pedal feel and engagement has not changed though. Still shifts in the same spot, the shifter just doesn't want to go in.

12/17 - The general consensus is that somehow there has to be air in the system. I talk about this with some mechanic friends of mine and they agree to help. We spend 8 hours bleeding the Jeep again. I start it up and immediately have issues getting into 1st and reverse. In the process of bleeding the replacement slave cylinder breaks a seal. It's toast.

12/18 - I admit defeat and have it towed to a dealer. I figure maybe they know how to bleed this thing better than me. Maybe have better tools. I don't know but I can't find a slave cylinder locally so nothing is going to happen for a week anyway

12/24 - I get a call from the dealer that the tech had a chance to get a new slave cylinder and will install it and bleed the system. They won't be able to test drive it until after the holiday and will report back on 12/27 if the bleed was sucessfull. If not the transmission tech is on vacation until 1/7. Next step would be to then pull back the tranmission and inspect clutch parts.

12/27 - whatever the tech tried to do didn't work. He then left for vacation. He told his assistant tech to buy some sort of $2 "hose" and that he'd work on it when he got back in 2 weeks. I have no idea what hose. The slave cylinder doesn't have a hose. Maybe they meant a hose to bleed it but that seems like something they'd have there already.

So in another holding pattern for the foreseeable future.

1/7 - had to tow the Jeep back from the dealer. The tech could not figure out how to bleed the hydraulics. He may have caused damage to the new master cylinder I just bought/installed. I'll be doing more troubleshooting tomorrow.

1/25 - Jeep is driving but issues are back with 1st and reverse. After bleeding it drove normal for a few days, then issues shifting into 1st like every 10th time. No issues shifting into 1st every time.

1/30 - My clutch was removed and after everything the underlying issue was the grease used by the install shop. More details here.


Bleed Methods:

- disconnecting the line to the reservoir and vacuum bleeding from there
- vacuum bleeding from the slave cylinder
- pumping the clutch then opening the bleed valve to get air out (repeat a gazillion times)
- pressure bleed from the reservoir
- remove slave and point it vertical. Depress rod by hand, open bleed screw to let out air, close bleed screw, let rod come back out (repeat a gazillion times).

Parts Replaced:

- slave cylinder x2
- master cylinder
- hydraulic line

Other maybe relevant info:
- When Jeep is off I can shift through all the gears smoothly.
- Through out all of this my gears never grind. Just feel like hitting a brick wall when shifting. Also issues getting out of 1st and reverse. You really have to pull sometimes to get it out of gear. Pedal engagement remains normal.
- About 3 weeks before issue started I got a croaking sound when I depressed the clutch pedal.
- I can not 100% say when the leak in the hydraulics started. The Jeep was out of my hands at several points after the initial issues started. It went through 2 mechanics before it was noticed so it's possible it didn't show up until later.

Current plan:

- See if the bleed the dealer tech did worked. If not then I can rule out air in the system.
- The pressure plate is not lifting completely from the clutch disc so now have to move on to find out why.
- I got a possible idea from a few others yesterday. Their problem ending up being burrs on both the input shaft splines and splines on the clutch. They did a sand/file and then the pressure plate was able to flow freely. Both people who had this problem though were right after install
- The transmission shop that did the install says they used the grease that came with the ACT kit.
- About a week ago the clutch developed the infamous Chewbacca groan. This has never happened prior to last week.


I will update the thread if I make any progress. As it has been pointed out a few times on this forum this Jeep is my only vehicle. I'm determined to get it fixed. I have no plans on buying a brand new Jeep. Things just don't fail for no reason. There is a reason it's not shifting into 1st and reverse I just haven't found that reason yet.

Other threads about experience with ACT:

https://www.jlwranglerforums.com/forum/threads/slave-cylinder-upgrade-recommendations.137696/

https://www.jlwranglerforums.com/forum/threads/help-issues-after-act-clutch-install.116092/

https://www.jlwranglerforums.com/fo...testing-by-advanced-clutch-technology.111416/

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[Kracka]

Ahh the joy of heavy ACT clutches... Reminds me of my DSM/EVO days dealing with constant master & slave cylinder failures.

I hate to say it, but the problem is your clutch. Go back to OEM or an aftermarket alternative with similar pressure plate clamping force and watch your issues disappear. Otherwise, you're just going to keep chasing your tail with leaking/blown master+slave cylinder seals.

 

[Jeremynolan94]

I hate to say it, but the problem is your clutch. Go back to OEM or an aftermarket alternative with similar pressure plate clamping force and watch your issues disappear. Otherwise, you're just going to keep chasing your tail with leaking/blown master+slave cylinder seals.

If this is the case, ACT needs to chime in and explain their claim that the stock JL hydraulics are sufficient for their clutches. I have the same clutch as OP and have developed the same groaning sound, but no issues with shifting. I replaced my slave once but it didn't fix the issue. Seems that someone needs to develop an external slave and master that can handle their clutches. Just my two cents.

 

[58Willys]

It may be the stock OEM hydraulic system, master/slave cylinder, is just not sufficient for a stronger clutch. I believe in the 19A recall, there was some language that it was a "design specification error", that caused the clutch issues. So if a 250 ft/lb pressure plate was the spec given to the clutch manufacturer originally, and the hydraulics were designed for that, then the revised spec of say 340 ft/lbs; the stock hydraulics are just not designed for the increased clamping force. Numbers are not actual values, just for illustration purposes.

 

[fspalt]

Both Centerforce and McLeod now have internal replacement slave cylinders. I wonder how many now have those installed? Those seem to be better designed and easier to bleed than the oem slave. I am having similar issue to OP but haven’t done the clutch recall yet. I’m debating on getting the recall done and going back to stock as who knows if the others will also have their own issues.

It may be the stock OEM hydraulic system, master/slave cylinder, is just not sufficient for a stronger clutch. I believe in the 19A recall, there was some language that it was a "design specification error", that caused the clutch issues. So if a 250 ft/lb pressure plate was the spec given to the clutch manufacturer originally, and the hydraulics were designed for that, then the revised spec of say 340 ft/lbs; the stock hydraulics are just not designed for the increased clamping force. Numbers are not actual values, just for illustration purposes.

 

[SadRobot]

Both Centerforce and McLeod now have internal replacement slave cylinders. I wonder how many now have those installed? Those seem to be better designed and easier to bleed than the oem slave. I am having similar issue to OP but haven’t done the clutch recall yet. I’m debating on getting the recall done and going back to stock as who knows if the others will also have their own issues.

Of the 2 options I've read the internal on the CFII is better. I know one person who has already snapped the rod of the external CFII slave. The metal tip popped off into the bell housing. Not something that sounds super fun to deal with.

 

[WJ43]

I have similar issues with my ACT although I am almost always able to get it in gear.... Eventually

In another thread I red that Act recommends bleeding with the slave disconnected and the rear in the air.

My problem gets worse as I drive longer distances and is fine once it cools.

I also feel I have air in the system still, and like you mine got worse after driving it for about 6 wks.

Mine is going to a transmission shop in January I will update if they find anything.

Good luck

 

[SadRobot]

I have similar issues with my ACT although I am almost always able to get it in gear.... Eventually

In another thread I red that Act recommends bleeding with the slave disconnected and the rear in the air.

My problem gets worse as I drive longer distances and is fine once it cools.

I also feel I have air in the system still, and like you mine got worse after driving it for about 6 wks.

Mine is going to a transmission shop in January I will update if they find anything.

Good luck

I bled mine with the Jeep jacked up in the rear. When that wasn't solving anything I did this method below.

I got every single bubble out. So unless there's a black hole somewhere inside the hydraulic system trapping in air I don't know where else it could be.

My last ditch effort was to have the dealer bleed it. Maybe the tech knows something I don't. I'll know tomorrow if that was successful. If it was not then the clutch has to come apart and the troubleshooting will continue.

 

[m3reno]

I had my recall done in June of this year. Prior to the dealership changing the clutch, it was getting difficult to get into 1st gear at a stop, if I'm rolling it goes in smooth. They did the update with the factory clutch and all was fine for about 10,000 miles. Now I'm having difficulty going into first from a stop and, as of late I could here a little bit of grinding going into other gears while I'm driving and shifting. Not going into first gear in consistent and the other issue of grinding happens every 10 shifts.

 

[SadRobot]

I had my recall done in June of this year. Prior to the dealership changing the clutch, it was getting difficult to get into 1st gear at a stop, if I'm rolling it goes in smooth. They did the update with the factory clutch and all was fine for about 10,000 miles. Now I'm having difficulty going into first from a stop and, as of late I could here a little bit of grinding going into other gears while I'm driving and shifting. Not going into first gear in consistent and the other issue of grinding happens every 10 shifts.

These JLs are like the piñata of cars. Once you open them up you're never gonna get it back to the way it was...

 

[fspalt]

I called my dealer yesterday and they said they can have parts and can do the recall on my Jeep on 1/6. I feel this is the only way I won’t end up eventually stranded like Sadrobot. If I’m still having issues after that, time to part out and go to carmax.

 

[SadRobot]

I called my dealer yesterday and they said they can have parts and can do the recall on my Jeep on 1/6. I feel this is the only way I won’t end up eventually stranded like Sadrobot. If I’m still having issues after that, time to part out and go to carmax.

Just be prepared with JSCAN if you have larger than stock tires and new gears. My bigger fear is I do the recall and get stuck in limp mode out on the trail.

 

[Fatfreewilly]

So basically what I'm seeing here is that, the stock JL Clutch and Flywheel are crap and prone to exploding and feel weak, but if you upgrade to a Centerforce or ACT heavy 'normal' flywheel, the slave cylinder needs to be upgraded to some sort of heavy-duty one?

And you have to roll it in a ditch to get the correct bleeding angle on it?

Jeep. Why couldn't you make a normal manual for the JL.

 

[SadRobot]

So basically what I'm seeing here is that, the stock JL Clutch and Flywheel are crap and prone to exploding and feel weak, but if you upgrade to a Centerforce or ACT heavy 'normal' flywheel, the slave cylinder needs to be upgraded to some sort of heavy-duty one?

And you have to roll it in a ditch to get the correct bleeding angle on it?

Jeep. Why couldn't you make a normal manual for the JL.

And don't forget that the brakes and the clutch share the same fluid reservoir just with a plastic divider inside. So forget trying to remove it and bench bleed.

 

[azwjowner]

So basically what I'm seeing here is that, the stock JL Clutch and Flywheel are crap and prone to exploding and feel weak, but if you upgrade to a Centerforce or ACT heavy 'normal' flywheel, the slave cylinder needs to be upgraded to some sort of heavy-duty one?

And you have to roll it in a ditch to get the correct bleeding angle on it?

Jeep. Why couldn't you make a normal manual for the JL.

I'm not sure, given we also have reports of the same issue with the stock clutch after recall replacement. It seems to be more like "don't touch the clutch unless you absolutely have to."

That said, I'm curious if anyone ordered the ACT "street-mass" flywheel (the one that is a normal JK flywheel weight, which is still significantly more than the JL's light flywheel) rather than the heavier "pro-mass" and is having a similar issue.

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