42RLE Hold Gear

This is likely premature, but since @mrblaine is active, figured I’d throw it out. I’ve noticed on the new to me LJ that the Auto runs full coast even in 1. Is there a TC lockup workaround to this, even momentary? The crazy downhill benifits I’ve seen off road in the JL in western areas is huge.

I’d have no problem going manual but my wife would like to be able to drive it, and I don’t have the patience after 1st gear on road .

Tob said:

The NSG-370 is a manual transmission. Surely you must be confusing it with the automatic 42RLE.

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Yup, corrected

Steel City 06 said:

Assuming it is the 42RLE automatic you are referring to, I'm sure you could hotwire something to lock up the converter. That said, you may run into a stalling issue.

Be sure to use 4Low whenever needed. Even unlocked, the transmission and torque converter will provide significantly better engine braking in 4Low than in 4Hi.

If even that isn't enough, one common solution is the Rubicrawler, which is a secondary selectable gear reduction that can be added to the 42RLE. It functions sort of like an extra transfer case gear reduction and will make the engine braking significantly tighter than just 4Low alone.

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I definitely need to do some trial and error experimentation to see if I can get some actual engine braking out of it in 4 low.

While I'm planning on 5.38s, I'll be running big tires, and with the 3.73s and 33s this thing feels like a race car in low. A rubi swap (potentially JK?), RubiCrawler, and Atlas are options being explored.

I'm cautious about monkeying with the TCM (PCM?) circuitry with all the issues the module can create, but I'll at least start exploring a lockup switch option.

Circuit dump for now:
TCCS is a bad diagram per hear, removed.

TCC Solenoid seems to be missing from the trans diagram, although it seems it may be a function of the Low/Reverse solenoid circuit:



TORQUE CONVERTER CLUTCH (TCC)

Fig. 248 Torque Converter Clutch (TCC)
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The TCC (Fig. 248) was installed to improve the efficiency of the torque converter that is lost to the slippage of the fluid coupling. Although the fluid coupling provides smooth, shock-free power transfer, it is natural for all fluid couplings to slip. If the impeller (3) and turbine (5) were mechanically locked together, a zero slippage condition could be obtained. A hydraulic piston (6) with friction material (7) was added to the turbine assembly (5) to provide this mechanical lock-up.

In order to reduce heat build-up in the transmission and buffer the powertrain against torsional vibrations, the TCM can duty cycle the L/R-CC Solenoid to achieve a smooth application of the torque converter clutch. This function, referred to as Electronically Modulated Converter Clutch (EMCC) can occur at various times depending on the following variables:
- Shift lever position
- Current gear range
- Transmission fluid temperature
- Engine coolant temperature
- Input speed
- Throttle angle
- Engine speed

hear said:

View attachment 643222

For clarity, you pulled this connector image off an FSM for a 32RH-equipped TJ, not a 42RLE-equipped one?

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That's from Alldata, good to know it's a red herring. Makes sense since the circuit numbering doesn't match up.

mrblaine said:

Buddy did a fair bit of working trying to do this for the 32. I never explored it but at the end he related that the hydraulic circuits prevented TCC lock-up in 1st. I suspect that if you did manage to find a way to pull it off, in actual use you'd figure out after stalling it repeatedly that there is a reason they don't do it.

The rest of us just gear correctly and it works just fine.

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If the Jeep will engine brake in 4Low 1st, this is certainly a deletable thread.

Rickyd said:

That is your problem. First isn't very low geared.

With that transmission, 5.13-5.38s would be perfectly fine on the highway running 33s.

Low range will be your friend. Get those gears swapped ASAP before you cook that transmission. Speaking of cooking the trans look up the preferred cooler here and get a temp gauge too

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I assume the trans will make the less than 500 miles it'll see before the axle swap is complete.

Strizzo said:

i can confirm that my 05 with 42RLE will engine brake if i pull it down into 1, although it won't lock the converter.

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Thanks, I've got very limited seat time so far, just dropped it in first to try after hearing it mentioned in a JK on a podcast. I'll let everyone continue to blast me until I get a chance to try it out, LOL.