O/D Off Button/ 4th gear question - JeepForum.com
 
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post #1 of 8 Old 05-22-2020, 11:28 PM Thread Starter
LateGreatZ28
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O/D Off Button/ 4th gear question

Quick background on the Jeep, it’s a 94 ZJ (4.0 w/ 42re) that I bought from my friend’s dad for $100. Needless to say, at that price it came with every Jeep problem in the book. Fuel pump, compete ignition system, CPS, PCM capacitors, Governor Pressure Sensor/Solenoid, and a hundred other parts later, it seems like the only problem left is 4th gear on the trans.

It drives fine for the most part, but as soon as it shifts into 4th gear, the Jeep starts vibrating violently. Now narrowing this down is a whole different story, but in the meanwhile I want to disable overdrive so I can keep driving the Jeep while minimizing the risk of FUBAR’ing the transmission.

That being said, I think the O/D button doesn’t work. From what I’ve seen online, pressing it should turn on a light on the instrument cluster to let you know O/D is disabled, but I’ve never seen this light on, much less while pressing the button.

So my main question is: Is there a way to test this O/D circuit, or even something as stupid as making sure the bulb isn’t burnt? I know on some cars pressing the trip button while turning the key to on lights up the dash, but I don’t know if a 94 ZJ has some similar function.

Also bonus question: Referring back to my 4th gear vibrations, is there a common thing to look for? Torque converter? TCC solenoid? Just rebuild the O/D?

Thanks for reading and I hope someone helps!

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post #2 of 8 Old 05-23-2020, 08:28 AM
jeepjeepster
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Here is what a quick search turned up. Maybe you have a code, but even if you dont, the light should flash 55. Turn the key on and off 3 times, ending with the key on. The check engine light will also flash codes. One guy said he had to have the tranny in D, another said he didnt.

Tranny codes for 1994 OD button LED

11 Engine RPM input
12 Output shaft sensor input
13 Vehicle speed input
14 Governor pressure sensor input
15 Throttle position sensor input
16 Transmission fluid temperature input
17 Overdrive override (control) switch input
18 System voltage
19 Internal fault in module
21 Governor pressure solenoid output
22 Overdrive solenoid output
23 Converter clutch solenoid output
24 Overdrive override (control switch) lamp output
25 Internal fault in module
26 Governor pressure sensor offset drift
55 End of code transmission

Have you dropped the pan yet? A popular problem is the O/D snap ring breaking into pieces, not sure if that could cause the issue or not. I've always read that once it pops off, you just lose O/D.

Does pressing the O/D off make it kick out of O/D? Should be a surefire way of knowing if its doing anything.

1994 ZJ-I6 w/270,000 mi
1998 ZJ 5.9 w/66,000 mi Slate Black
2004 KJ w/108,000 mi
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post #3 of 8 Old 05-23-2020, 08:55 AM Thread Starter
LateGreatZ28
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Quote:
Originally Posted by jeepjeepster View Post
Here is what a quick search turned up. Maybe you have a code, but even if you dont, the light should flash 55. Turn the key on and off 3 times, ending with the key on. The check engine light will also flash codes. One guy said he had to have the tranny in D, another said he didnt.

Tranny codes for 1994 OD button LED

11 Engine RPM input
12 Output shaft sensor input
13 Vehicle speed input
14 Governor pressure sensor input
15 Throttle position sensor input
16 Transmission fluid temperature input
17 Overdrive override (control) switch input
18 System voltage
19 Internal fault in module
21 Governor pressure solenoid output
22 Overdrive solenoid output
23 Converter clutch solenoid output
24 Overdrive override (control switch) lamp output
25 Internal fault in module
26 Governor pressure sensor offset drift
55 End of code transmission

Have you dropped the pan yet? A popular problem is the O/D snap ring breaking into pieces, not sure if that could cause the issue or not. I've always read that once it pops off, you just lose O/D.

Does pressing the O/D off make it kick out of O/D? Should be a surefire way of knowing if its doing anything.
I’ll double check the codes, but when i checked it about a week ago, it only had the code for disconnecting PCM power and no trans codes.

I dropped the pan to change out the governor pressure sensor/solenoid and I don’t remember seeing any broken snap rings, although I could be mistaken. Is that something visible with just the pan off and not the valve body?

I guess I never really thought about taking it to 4th and then pressing the button lol, the vibrations make me want to slow down as soon as it happens. I’ll try it out though.

In the off chance that it doesn’t do anything, I wonder if it could be something simple like the button being bad. Hopefully it’s something that dumb, but I never have had luck with this Jeep lol
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post #4 of 8 Old 05-23-2020, 09:20 AM
wingless
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Welcome to the forum.

Good luck w/ your ZJ.

This is THE place to locate every bit of information on your vehicle.

Start w/ the correct Factory Service Manual (FSM) for your vehicle. The FSM has an excellent transmission section.

When the 46RH in my ZJ failed, the symptoms were violent shaking, as the warped frictions and steels were only partially disengaged, causing two different gears to partially operate at the same time.

My 46RH rebuild topic might be useful for the problems on your vehicle.


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post #5 of 8 Old 05-23-2020, 02:50 PM Thread Starter
LateGreatZ28
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Quote:
Originally Posted by wingless View Post
Welcome to the forum.

Good luck w/ your ZJ.

This is THE place to locate every bit of information on your vehicle.

Start w/ the correct Factory Service Manual (FSM) for your vehicle. The FSM has an excellent transmission section.

When the 46RH in my ZJ failed, the symptoms were violent shaking, as the warped frictions and steels were only partially disengaged, causing two different gears to partially operate at the same time.

My 46RH rebuild topic might be useful for the problems on your vehicle.
I’ll check it out, thanks. Do you think that’s what is causing the vibrations , 3rd and 4th trying to engage at the same time?

I read from a couple of sources that OD problems would either be from the torque converter or TCC solenoid related, but I guess the solenoid would throw a code?
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post #6 of 8 Old 05-23-2020, 03:05 PM
wingless
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Quote:
Originally Posted by LateGreatZ28 View Post
Iíll check it out, thanks.
You're welcome.
Quote:
Originally Posted by LateGreatZ28 View Post
Do you think thatís what is causing the vibrations , 3rd and 4th trying to engage at the same time?
Don't know. Follow the FSM. There are excellent and comprehensive tests defined. Mine also had violent vibrations and in my case those were caused by warped frictions and steels.
Quote:
Originally Posted by LateGreatZ28 View Post
I read from a couple of sources that OD problems would either be from the torque converter or TCC solenoid related, but I guess the solenoid would throw a code?
The solenoid failure is common, with a replacement coil pack a common solution. It is not clear to me how a solenoid failure would cause the vehicle to shake.


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post #7 of 8 Old 05-26-2020, 12:15 AM
AlamoJeeper
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Welcome to the forum. It sounds as though you are getting quite an education about things ZJ.

On my 1995, the "O/D OFF" button is a press momentarily and release to disable/prevent the OD/4th gear. And then press momentarily and release to permit OD/4th gear. And repeat as desired. Basically, push OFF/push On.

On my 1995, when the button is pushed to disable OD/4th gear, there is a small LED immediately above the button which illuminates to show that OD disable has been selected/activated. It is hard to see in daylight.

On my 1995, when I turn the ignition ON, the light illuminates for about 1-2 seconds.

When I leave my subdivision I have a short straight with a 55 MPH speed limit and then a hill to climb. To save some wear and tear on the engine and transmission, I activate OD disable before turning out of my subdivision to keep the transmission in third gear and do about 45 mph until I top the hill. Then I accelerate to 55 and shift into OD/fourth by momentarily pressing the button to deactivate the OD disable.

For broken snap rings, there would probably be pieces of the snap ring in the pan.
.
Attached Thumbnails
OD_Disable_Switch.jpg  

AlamoJeeper
- 1995 4.0L NP249 - mostly stock
- Link to rehabbing my 1995 ZJ.
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post #8 of 8 Old 05-26-2020, 07:27 AM
LordHobbit
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I was having similar issues with the button and had to replace the switch in the o/d off module behind the panel. It's a real easy job (if you know how to solder) once you get that module out of the dash, not a real easy job.

https://www.jeepforum.com/forum/f13/...utton-4257737/ And thanks to Wingless for his photos. You'll see the small momentary push button in the photos. That is what I replaced and it's been working great since.

93 red ZJ 196k 4.0. Spent more money than I should have ...
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