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2001 WJ TCC engine code and trans overtemp

8K views 11 replies 2 participants last post by  schupp77 
#1 ·
Hi,

this is my first post. Bought a 2001 GC Laredo at 121000 miles, rebuilt the engine. Love driving it, but has had a TCC solenoid code come one for a while. Did a filter and fluid change. The old fluid looked fine, no debris in the pan.

I've read that this shouldn't be a problem driving as it just means the converter isn't locked in. But recently went on a two hour drive ( have done this before with now problems) and had the trans overtemp light come on. Pulled over, fluid was definitely hot. waited a bit, then drove with OD off, no further problems. Coming back, same thing happened within 20 minutes, turned OD off, no further problems.

Previous diagnostics confirmed the TCC solenoid problem as well as a possible pressure sensor problem. changed the pressue sensor, TCC code still came on.

I'm wondering if this means I'm starting to lose the converter. My plan is to change out the solenoid pack first see if that fixes the lock up problem but If the overtemp is suggesting the converter is going, I'd just as soon change out the converter, as I'm planning on putting a cold air intake and power chip, and maybe a mild high performance converter would compliment those power adders. Thinking about adding a TransGo shift kit as well, If I'mgoing to have the valve body out.

Having a hard time finding what the stock converter stall speed should be. a Driveway test (brakes on, throttle up til close to engine stall) indicates about 2000RPM. Max torque of the 4.7 is supposed to be at 3200RPM. Any suggestion what stall speed I should target for a mild performance enhancement but still okay for street driving. don't mind firmer shifts.

Any thoughts on this? Thanks for any feedback.
 
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#2 ·
If the torque converter clutch is not activated, then the torque converter will continue transFer the torque of the engine, which will add heat to the fluid. If you drive long enough, it will cause the fluid to overheat. Which fault codes do you have and which part did you change?
No idea about which stall speed the original converter has.
 
#3 ·
I don't remember the fault code numbers, but it was definitely the torque converter clutch solenoid and line pressure sensor. I replaced the line pressure sensor. I suppose I could go back to oreillys and have the codes checked again to see if it's still the TCC code.

I read in another thread that if the clutches in the converter start to go, the lining could start to come off and start to circulate inside the trans. I've been on long drives before with the TCC error code on and not had the trans overheat, which is why I'm thinking the TC clutches are starting to go. Is this a reasonable assumption? thanks.
 
#4 · (Edited)
If the torque converter clutch solenoid doesn´t work, then the clutch will not be pressureized and no harm to the lining will be done. If the solenoid works, but the lining is at its wear limits, then the clutch is pressurized, but continues slipping. In that case lining pieces can come off, but should be catched in the inlet filter. (eventhough not a good situation).
So it is important to know which fault code is set, to know if the converter clutch lining is at its wear limit, or the problem is somewhere else. There is no special torque converter clutch solenoid, but its a combined LR/converter clutch solenoid. Its used for the LR clutch (low reverse clutch) or converter clutch, depending on the position of the hydraulically operated solenoid switch valve.
You said that with OD off the overheat didn´t occur, but in OD off the transmission goes until 3rd gear only, but still will apply the torque converter clutch. Maybe the bigger fluid flow due to the higher transmission input speed, could lower the fluid temperature more.
You could try the key dance and see if it will give you the code: ignition switch off/run three times and leave in run at the third time. The odometer will show "DONE" when no faults are stored, or any fault code(s).
 
#5 ·
Its a P0740 code, which, according to O'Reilly's OBD scan tool, is Torque Converter Clutch out of range error, potentially caused by a variety of things. Is there a relatively simple way to rule out the TC clutch starting to fail?

None of the wiring harnesses look frayed, connectors look clean but I'm going to spray them out with electronics cleaner this weekend. I'm also thinking about doing a fluid change with ATF+4 (currently has ATF+3), as I've read it's a better lubricant, may free up some sticky valves?

This jeep is pretty much my hobby so don't mind tinkering around as opposed to taking it to a shop, but I was hoping not to have to do a trans overhaul this soon after rebuilding the engine?

As an aside, what's your opinion of the Sonnax line pressure booster? seems like it would result in firmer shifts and holding power, maybe good for towing, but will it put more strain on the pump? Thanks for all the feedback.
 
#6 · (Edited)
The P0740 code means that the TCM has seen a torque converter clutch (TCC) cirquit malfunction. It means in fact that after the TCC should be fully engaged, that there still is a certain speed difference between engine speed and transmission input speed. It could mean that the TCC is not engaging at all, due to a valve failure, or the clutch piston has pressure, but the clutch material is mostly worn away and will not hold the converter locked. This last case will produce more heat due to the friction and can cause friction material to break away and fall into the pan.
This problem can not be the TCC solenoid, since this same solenoid is used for 1st and reverse gear. There is however a hydraulically operated solenoid switch valve in the valve body, which could stick in the 1st/reverse gear position and prevent the TCC to be pressurized. There are three more mechanical valves in the TCC fluid cirquit, but they all sit in the transmission pump housing. (TC limit valve, TC regulator valve and TC switch valve. Doing anything to these valves requires the removal of the transmission, but experience shows that they hardly go wrong)
So there is a good change that the TCC lining is at its wear limits, which would mean a new (or overhauled) torque converter.
The Sonnax line pressure booster is nothing more then a resistor, which fools the TCM by modifying the line pressure signal from the line pressure sensor. It will finally let the pressure regulator solenoid in the solenoid pack, regulate to a higher (normally 15 psi) line pressure, which results in more holding power to all the clutches and a bit firmer shifts. It will however do nothing to the clutch overlap times. (this is the time, that one clutch from the actual gear is still pressurized, while an other clutch for the next gear, with different speed, starts to get pressurized as well. These overlap times cause most of the wear to the clutches and lots of heat buildup.)
By installing a Transgo shiftkit, you will also change springs from the accumulators in the valve body with stronger ones. This will result in much shorter clutch overlap times and firmer shifts, so reducing the wear and heat buildup. To be able to install the full Transgo kit, the transmission must be lowered, because some valve springs in the pump assy and a stronger clutch snap ring are part of the kit, however many do the parts which require lowering the pan and valve body only.
The pump has its own pressure regulator, which regulates to a pressure somewhat higher then the maximum required line pressure. The pressure solenoid then further reduces the pump pressure, to get the required line pressure. So adding the Sonnax booster will not put any more strain to the pump, but will increase the pressures on the clutches and internal seals.
The pump on the 5-45RFE is a real bullit proof gear type pump.
You still have ATF+3 in the transmission??? How long was it not changed? Fresh fluid has strong cleaning properties and can remove/dislodge dirt which can plug one of the small orifices which are in the valve body/solenoids.
 
#7 ·
I changed the fluid and filter maybe 10k miles ago, right after I rebuilt the engine. I thought I used ATF+3 as thats what was recommended in the owners manual, but now it looks like it's no longer available ( at least at the parts store I use for routine maintenance) so now I'm not sure.

I'm liking the idea of the shift kit and pressure booster, but if I have to lower the tranny, I'm wondering if I should just replace the converter anyway, given the likelyhood of it starting to go.

This gets me back to what stall speed to choose. Again, I plan on a CAI and power chip addition as well. I've read a slightly higher stall speed converter would complement these additions. Any ideas there? Again, thanks for all the feedback and info on the transmission operation.
 
#8 ·
so been a while since my last post. Two weeks into the Sonnax fluid pressure booster, I still get the engine code but it cycles on and off more frequently. I also seem to get more responsive downshifts into that alternate "3rd" gear going up mild grades.

So I'm thinking some sticky valves in the valve body or the TC still wearing out? haven't taken it on a longer drive up a hill yet, have one about half hour away may do that tomorrow morning.

different question, put a 2" lift kit on and put some bigger used tires on as didn't want to fork out the cash for new ones unless I liked the lift. Fronts are different from the rear, front tire circ is 98.25", rear is 97", so 1.3% difference in distance traveled between front and rear. I know it's not ideal but is that too much for the clutches in the transfer case to handle?

Thanks for all the input here.
 
#9 ·
Also not sure what the limit is between tire diameter front/rear. But the difference most probably will actuate the progressive coupler in the T-case and can prematurely wear the clutch pack.
The 5-45RFE has an alternate 2nd gear, not 3rd.
Most probably the torque converter clutch is worn, but with the higher line pressure it will let it hold a bit better.
 
#10 ·
Hello again,

My last post was in april. Since then the trans code has completely gone away but about 2 months ago I noticed that RPMs on the freeway would increase 100-200 rpm if I hit a bump while holding a steady speed. I don't think its the converter lockup completely disengaging as when I touch the brakes, rpms go up 300-400. I'm thinking the converter clutch is not holding well anymore, as was mentioned earlier but haven't replaced it as it seemed like the pressure booster was working due to the trouble codes disappearing. does this still sound like what is probably going on? I'm about a month away from having the time to drop the trans. Am I okay driving20 miles a day on the freeway or will clutch material start to clog ports? Once again, thanks for all the input.
 
#11 ·
Yes, it looks like the torque converter clutch starts to slip a bit, giving a few hundred rpms more. When the TCC releases completely, you get a 400-500 rpm increase.
Difficult to say if clutch material will start to clog ports. The inlet filter should take most of the debris, not sure about to which size it filters. If there would be a lot of debris, you would take a change of clogging the inlet filter.
Depending on how long you want to keep the jeep, you could also consider to change all clutches, while the transmission is off. If you already want to install the complete transgo shiftkit, you will have to take the pump unit out. Than it will be a bit more work to get all the clutches out. To remove the pump unit, you will have to remove the transmission front cover. This cover will need new seals for reassembly.
I did do the rebuild myself and bought the original mopar kit, but you could also go for better clutches like Alto Red, which seem to give better holding power.
 
#12 ·
thanks. This is my toy and the engine rebuild only has 20K on it so I'll probably opt for replacing the clutches with some stronger ones. I'm also looking to replace the TC with a slighter higher stall speed. I think stock is 1900-2300, I was thinking about going up to 2400. any recommendations for a particular brand. PATC carries red eagle and has a number of TC options available. thanks for all the feedback.
 
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