AW-4 Shifter and Lock-up Torque Converter Tech

[TNT]

The following is Jeff A's wiring diagram to hold 2nd gear and disable the torque converter lock-up.

 

I used that had one wire hooked up differently somewhere diagram on my old '95 XJ. It always worked perfect for me thou... :nuts:

 

I plan on changing Jeff's design for my MJ. The design will hold 1st or second gear and unlock or lock the torque converter manually or work just like stock.. :brows:

I'll post a "how to" when it is done and tested.

 

 

Here is the following one Jeff made. :thumbsup:

 

:cheers:

 

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AW4 Auto Tranny Mods

By Jeff A.

 

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I am aware of a number of different methods to modify the AW4 Automatic Transmission in Jeep Cherokees. These range from a switch to cut power to the Transmission Control Unit, to a switch box to take the place of the TCU which allows full manual control of all gears and torque converter lockup. For my modifications, however, I came up with two criteria that had to be met. First, I wanted to be able to manually put the tranny in 2nd gear which is all but impossible in the stock configuration and I wanted to be able to shut the torque converter lockup clutch off when lugging up a gradual hill. This ability allows the engine to gain rpm's without downshifting to a lower gear. It can allow you to make the hill without downshifting. As for 2nd gear access, I mainly wanted that when in four-wheel drive low range. Sometimes 1st is too slow and 3rd is too fast. The transmission will automatically shift from 1st to 2nd with the shift lever in the 1/2 position at approximately 4500rpm and will down shift back to first quite violently without any warning as you slow down.

 

With these two criteria in mind, I examined the factory wiring manual, the factory service manual, and all the information I could find on the web. I came up with a relatively simple and safe method to accomplish my tasks. As for shifting, the tranny and TCU use a set of solenoids (Sol1 and Sol2) to shift between 1st, 2nd, 3rd & 4th gears. They are turned on and off in a binary manner to affect the shifts. 12V is applied to Sol1 for 1st gear, 12V is applied to Sol1 and Sol2 for 2nd gear, 12V is applied to Sol2 only for 3rd gear and 4th gear has no power applied to either solenoid.

 

My 2nd gear modification uses the fact that when the shift handle is in the 1/2 position, Sol1 is energized automatically and 12V is switched to the C8 input of the TCU. I am tapping off C8 for power to run Sol2 through a switch. In this manner, my switch will only have power running to it if the shift selector is in the 1/2 position. Therefore, if I am in 3 or D positions and accidentally operate the switch, Sol2 will not be energized and the tranny will not do any gear switching.

 

 

 

I have also included two diodes to provide protection to the TCU. One of these diodes will not allow power to be applied to the output of the TCU that runs Sol2 (C15). The other diode protects the TCU 1/2 input (C8) from seeing voltage when it shouldn't. The green LED and resistor are run off the other switch pole and provide illumination to indicate that the switch is on.

 

As for dropping out the torque converter lockup clutch, I used the brake input to the TCU (C10). In normal operation, the brake switch is engaged and this line is grounded. When the brakes are applied, this tie to ground is broken by the brake switch returning to its Normally Open position. I broke the line going to C10 and installed a switch. When this switch is operated, the TCU senses that the brakes have been applied and shuts off the torque converter lockup clutch.

 

 

Again, the Red LED and resistor provide illumination to indicate that the switch is activated. Just for your information, I tried simply breaking the drive for Sol3, which operates the lockup clutch, with a switch, but the TCU didn't like seeing no load and would operate erratically. I even tried to install a separate resistor load, but this didn't work. The brake switch is a better solution anyway. One thing to keep in mind is that the tranny will heat up quite rapidly with the lockup function turned off, so be prudent in the use of this switch.

 

 

The actual wiring changes were made at the input to the TCU and a harness with disconnect plugs was built to run to the console where the switches and indicators are located. As an update to this writing, I would suggest locating the indicator lights in a different position as they are frequently blocked by my hand or "stuff" in the console by the parking brake handle.

 

 

 

 

These modifications are working quite well for me and I recommend them wholeheartedly.

 

Parts List

 

I got all the parts for this modification from Mouser Electronics (800) 346-6873. Quantity Item Part No. Price Each

2 S1, S2: DPDT rocker switch 629-GRS402216 $1.21

1 LED 1: Green Cylindrical 604-L483GDT $0.18

1 LED 2: Red Cylindrical 604-L483IDT $0.21

2 LED holder 593-CLP126 $0.05

2 Solderless 2.2k ohm LED socket CNX310220 $0.77

2 D1, D2: Diode 583-1N4007 $0.05

 

Jeff A.

 

:cheers:

[deziped]

Your gonna like it. I did a similiar setup on mine a couple years back and haven't regretted it. I like the fact that off-road it makes 2nd gear, which is normally

useless when it shows up, useable/manageable in all RPM ranges with the flick of a switch. Running up long mountain passes I can hold it in 2nd & avoid constant power losing up & down shifting. Same for running down long descents for assisted braking. The switch on the TC makes it act like a manual in a sense or you've added gears. It's a worth-while easy & cheap modification. :D

[TNT]

Your gonna like it. I did a similiar setup on mine a couple years back and haven't regretted it. I like the fact that off-road it makes 2nd gear, which is normally

useless when it shows up, useable/manageable in all RPM ranges with the flick of a switch. Running up long mountain passes I can hold it in 2nd & avoid constant power losing up & down shifting. Same for running down long descents for assisted braking. The switch on the TC makes it act like a manual in a sense or you've added gears. It's a worth-while easy & cheap modification. :D

 

 

I did it to my '95 XJ back in '01 and loved it. I want the ability to keep it in 1st gear also.

 

I hate when the trans upshifts out of 1st then bogs the engine and shifts back down.

 

Locking the converter on steep descents in 1st will be nice.

[JeepcoMJ]

gah.

 

tim, I can't read all of that...my attention span isn't that long.

 

I'll call you this weekend. I am in iowa which is why I've been missing your calls...stupid phone.

 

-Pat