5.9 trans. lock-up vs OD - JeepForum.com
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Unread 06-05-2013, 05:44 AM   #1
a70eliminator
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5.9 trans. lock-up vs OD

My hew to me 5.9 trans, can't determine if it's hunting between D and OD or between the OD and lock-up converter.
It's acts like this when cruising down the highway at around 2k 60mph.
The RPM will travel up to 2k then drop to about 1800 then back to 2000. It does this constantly while at cruise. When taking off it up-shifts fine and feels crisp. It's just under no load cruise that feels like it's sorta slipping in and out gear. Anything I can try to isolate problem if there even is one? The fluid is clean and full, did new filter when I bought it and the magnet was clean it all looked great, I've also installed a factory 5.2 trans cooler in factory location.

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Unread 06-05-2013, 06:02 AM   #2
wsigo
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When it jumps up to 2,000 rpm, lightly feather the throttle without completely closing it. If the engine speeds up slightly as you press the throttle- it's the lockup converter not locking.

I have a feeling that's what it is anyways, if it was kicking out of overdrive you'd be looking at something like 2,400 rpm or so on the high side.

Mine does the same thing now and then but usually only at speeds greater than 65. If you lift your foot completely off the throttle then get back on it, it tends to re-lock the converter.

I wish the damn thing would just stay locked even when my foot is off the skinny pedal.
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Unread 06-05-2013, 06:12 AM   #3
PolkaPower
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My 5.9 would slip in and out of gear when at WOT and hunt. It was the gov pressure sensor and solenoid.
On my 95 when the TPS was going bad it would totally bog down when I gave it gas and I would have to granny it to get it back in gear. Sometimes at a stop it would drop and raise RPM's and act like it was going to stall.
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Unread 06-05-2013, 07:16 AM   #4
a70eliminator
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Wsigo that sounds about right. I pushed the OD button and RPM's do jump to around 2400 with a crisp feel of a definate downshift and it stays there.
Then when I release the OD it goes back to what now I believe is the coverter lock-up (or no lock-up) syndrome. I don't want to overheat the trans and cause any undo wear by continuing this way unless it's in the nature of the beast, the lock-up converter.
My 5.2 ZJ trans. does not act this this way, but with BFG 31's maybe it never goes into lock up. The 5.9 it completely stock.
Polka, An ailing motor mount prevents me from "flogging" it although I have powered into it a little and it shifted crisp, I'll check the TV cable adjustment.
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Unread 06-05-2013, 07:25 AM   #5
PolkaPower
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Put a aux trans cooler on it or it will for sure fry the trans much sooner than it should. That was a big mistake from Chrysler that year.
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Unread 06-05-2013, 10:18 AM   #6
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Read thread starter.
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Unread 06-05-2013, 12:11 PM   #7
KJK
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Originally Posted by a70eliminator View Post
The RPM will travel up to 2k then drop to about 1800 then back to 2000.
When mine did this it was the throttle position sensor. I got one from Autozone and it's been great for several years now. Never threw any codes or anything either.
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Unread 06-05-2013, 12:42 PM   #8
a70eliminator
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Hmmm, ok thats something, i'll at least check the connections and clean it if I can. Hate just start switching parts without knowing for sure, especially OEM pieces for who know what crap you get at parts stores today. Was it an expensive part?
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Unread 06-05-2013, 01:14 PM   #9
Timo_90xj
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Quote:
Originally Posted by PolkaPower View Post
My 5.9 would slip in and out of gear when at WOT and hunt. It was the gov pressure sensor and solenoid.
I had that same thing happen, until I lost electric shift control of my tranny. Fault codes say governor pressure and speed sensor - of which both are fairly common issues with the 5.9/ 46RE on both ZJs and Dodge trucks. My tranny will stil shift 3 <-> OD and will lock-up, but to get it to shift into 1st I need to be rolling at less than 5mph, go to neutral and quickly shift to 1st. 2nd gear can be selected with the gear lever at any normal speeds.

Quote:
Originally Posted by PolkaPower View Post
Put a aux trans cooler on it or it will for sure fry the trans much sooner than it should. That was a big mistake from Chrysler that year.
As for the tranny aux cooler, you are 100% right. I'm at a point where I'm most likely in a need of a tranny rebuild because of a burnt transmission (also because of the other issues I'm getting). It's really weird Chrysler didn't include an aux tranny cooler for the 5.9 ZJs, the transmission gets VERY hot in normal city driving in 70*F or hotter weather. Now that I installed a temp sensor in the oil pan, I'm getting up to 230*F temps. It's WAY too hot, it should be around 160-175*F for long lifespan.

I don't even want to know how hot my tranny has been wheeling in deep snow.. Fluid was all brown and fairly sticky when I drained it, smelled really bad. With the old fluid I was getting fairly heavy 1-2 slippage.
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Unread 06-05-2013, 02:11 PM   #10
PolkaPower
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Quote:
Originally Posted by Timo_90xj View Post

I don't even want to know how hot my tranny has been wheeling in deep snow.. Fluid was all brown and fairly sticky when I drained it, smelled really bad. With the old fluid I was getting fairly heavy 1-2 slippage.
Mine got so hot it boiled out of the breather hole and smoked like Cheech and Chong This was also in the snow going up a mountain. Around 36* out. After it cooled off it was fine. I coasted down the road in N most of the way. That is when I became aware that the stock rad cooler was ****!
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Unread 06-05-2013, 07:36 PM   #11
ZeeJay1997
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Quote:
Originally Posted by a70eliminator View Post
can't determine if it's hunting between D and OD or between the OD and lock-up converter.
It's acts like this when cruising down the highway at around 2k 60mph.
The RPM will travel up to 2k then drop to about 1800 then back to 2000.
lockup should occur at 45-48 mph in OD.

when it is doing it, hold the accelerator steady and apply very light brake and see if it stops cycling. a common problem is that the brake switch is bad causing the tcc solenoid to activate and deactivate the tc.
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Unread 06-06-2013, 09:21 AM   #12
KJK
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Originally Posted by a70eliminator View Post
Hate just start switching parts without knowing for sure, especially OEM pieces for who know what crap you get at parts stores today. Was it an expensive part?
This is a pretty common problem with the TPS causing this issue (as well as the brake switch as talked about above).

The first one I bought was from the dealer and it was around $75. It was bad right out of the box. No returns on electrical parts meant that I had to eat that one no matter that it was defective. Once the box is opened it's game over.

So the next one was $35 from Autozone with a 2-year warranty. It's been great for 3 years.
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Unread 06-06-2013, 09:39 AM   #13
a70eliminator
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Well, last night I pulled the TPS just to get a look at it, ohm meter measured resistance from infinate to about 5.00 ohm and anywhere in between depending on it's position.
I don't know if it was maybe a bad plug connection or what but today driving to work it was all good again, I also did the brake test and your all right just barely touching the pedal raises the rpm 100-200 more or less but noticable, it's not doing it anymore thankfully.
I think now that it's not a critical tranny problem so thanks for the insight.
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