Keeping in second gear write up done.

There is nothing worse than when in low range going down a slope with the auto in second gear and having to slow up just a bit for a obstacle or corner and to have the auto change back to first throwing you forward in the seat. You then have to speed back up a bit and shift the gear lever back to third and then back to 1-2 position until the next time you slow up a bit. It's fine if the hill is steep enough for using first all the way as it will stay in first until the red line but you don't always want to be going that slow! Now this modification will allow you to leave it locked in second gear using a switch to hold it there.

See my how to section for the details!

Dang. Pre-1997. Has anyone figured out how to do this for 1997+ (OBDII) XJs?

Tim C.
90 XJ
01XJ

tacottle said:

Dang. Pre-1997. Has anyone figured out how to do this for 1997+ (OBDII) XJs?

Tim C.
90 XJ
01XJ

Click to expand...

The above thread is also an interset for me! Did anyone make an setup to keep the past 97 AW4 in second and not make it shifting down into fitst by itself?

I have the FSM for my 97. There are three solenoids for the 1-2 and 3-4, a 2-3 solenoid and an Lock-Up solenoid control.

Does this give you an idea how a setup like discribed in GOJEEP.com could be done?


Any Help is appreciated!
Simon Switzerland

The 97+ set up should be the same. I believe the difference is in the wire colors. If you have the FSM and wire diagrams should should be able to cross the colors from an earlier model to get the correct wires to switch.

Mike

I believe it is a bit harder than what is done on the earlier models. There is no more TCU. It is integrated into the ECU, and quoting B-loose:

... I think the problem is that there is an input sensor and a output sensor on the 97 and newer. The computer then can compare the input to the output and know what gear the Jeep is in. They may also be able to determine internal slip and gernerate a trouble code for it. Though it wouldn't be as easy as a switch like the older ones there should be a way to figure out the pulse ratio for each gear and feed it into the computer. I don't even know for sure this would work but I have thought about this for a while now.

Click to expand...

I believe the switch method will still work, but you will probably flip on the Malfunction Indicator Lamp, AKA check engine.

Hodge

There are no technical obstacles for a '97+ XJ. The problem is that the OBD II will sense an error and send the tranny into "limp mode" - it would be nice if the only issue was the check engine light, but that is not the case. In limp mode, the tranny will lock out overdrive among other things, the net result being a major heat buildup out on the highway. It typically reverts to a normal mode fairly quickly back on the highway, but if you've been wheeling for a few days straight it can stay in limp mode for several hours.

I ultimately removed my setup because of this problem. Better to deal with staying in 1st/low than a cooked tranny.

Nay

Thanks Nay and all

seems the whole thing would take some more engineering!? I try to deal with the factory down shifting and maybe there will be a solution in future?

I'll fit 30/9.5 tires soon and also change the speedogear to one with 33teeth. I guess I'll try factory and the new speedo gears on this problem. Maybe that could be one way, but I guess I can hardly imagine what all more comes with only changing tiresize and playing with speedogear-ratio.

Thank you all for your help so far!
Simon

Could you wire some sort of cutoff switch for the switch that locks 2nd gear, therefore elimiating the "problem" that the OBD II is detecting? Will the immediately return to "normal" mode if the problem isn't detected?

If so, you have the lock switch cutoff for normal driving, then active it when you want to be able to lock second.

You say in the article that if you leave it on overdrive will be off. Can you also just use thi for deactivating overdrive while at highway speeds.

basalt51 said:

Could you wire some sort of cutoff switch for the switch that locks 2nd gear, therefore elimiating the "problem" that the OBD II is detecting? Will the immediately return to "normal" mode if the problem isn't detected?

If so, you have the lock switch cutoff for normal driving, then active it when you want to be able to lock second.

Click to expand...

I don't know how you would bypass the OBD II detecting the failure of the transmission to properly downshift, which is what causes the check engine light to come on and ultimately the safety (limp) mode of the transmission. You'd have to convince the OBD II that the tranny is in first when it fact it is still in second.

What you are doing here is sending the transmission override instructions, and the OBD II doesn't like that. Cars have gotten too smart for a $5 override job.

Honestly, I found that I wanted that setup more onroad so it wouldn't drop into first on long, steep, hill climbs with hairpin curves (Colorado Rockies). Offroad, you are never with a group that all have a setup like this, and you'll always be going as slow as the slowest rig. I haven't missed the thing one bit, but it was a real PITA when I had it installed.

Nay

Seems the write up isn't done on the past '97 AW4?

I also had some thoughts about what kingfish mentioned. Does anybodyelse have experiences like Nay had?

"...There are no technical obstacles for a '97+ XJ. The problem is that the OBD II will sense an error and send the tranny into "limp mode" - it would be nice if the only issue was the check engine light, but that is not the case. In limp mode, the tranny will lock out overdrive among other things, the net result being a major heat buildup out on the highway. It typically reverts to a normal mode fairly quickly back on the highway, but if you've been wheeling for a few days straight it can stay in limp mode for several hours.

I ultimately removed my setup because of this problem. Better to deal with staying in 1st/low than a cooked tranny. ...."

Having the switch only on for maybe a few minutes while going down a pass, or let me say Alproad. I have to brake sometimes and maybe can also speed up onto third and don't have the tranny pulling. The car will get pushed by gravity and the AW4 shall work as a break. Sure it might heat up, but I guess it's not the same as driving up hill for a long time?

Hi Nay

I figured out a major difference in the idea for using this setup:

Your use was going uphill with a group. My thought was using this system for going down, wanting to keep rev's low and saving brake-pads.

Did you have any good experience using your setup going down??

Would appreciate any infos to where you found the ECU or TCU and if you also connected the white wire (1-2 and 3-4 solenoid control) with the darkblue/White wire (positive current from fuse in "junction block")?

I checked under the dash in my car, but have to do some more research on how the unit should look like and where it is mounted...

Have a good one
Simon

HodgePodge said:

I believe it is a bit harder than what is done on the earlier models. There is no more TCU. It is integrated into the ECU

Hodge

Click to expand...

The TCM is still present on all AW4 equipped XJs. The wiring is similar and the trans and TCM didn"t change with OBDII. The only difference is that the PCM is more sensitive to the signals coming from the TCM and will set a code if they can't communicate over the bus. I have a OBDII 96 XJ and I have wanted to do this mod too. Maybe I will do some checking on my own for this mod. I will keep you updated if I find anything out.

Bryan

Bryan C. said:

The TCM is still present on all AW4 equipped XJs. The wiring is similar and the trans and TCM didn"t change with OBDII. The only difference is that the PCM is more sensitive to the signals coming from the TCM and will set a code if they can't communicate over the bus. I have a OBDII 96 XJ and I have wanted to do this mod too. Maybe I will do some checking on my own for this mod. I will keep you updated if I find anything out.

Bryan

Click to expand...

OK, the TCM is definately different. 32 pins for the 95 vs 26 for the 97+

Still looking into this.


Bryan

OK, so I checked and found my 96 is the same as the previous years and the same as pictured Go-Jeeps write-up. My 96 is a OBDII vehicle and I just hooked up the wires per the mod write up. No codes were set, and the check engine light never came on. I am not sure about how the 97+ models will react to this mod, but I was able to find the info to perform the mod.

Here is a picture of the TCM connector for the 97+ models.


The TCM is located under the drivers footwell, to the right of the steering column, mounted near the AC/heater box. According to the schematics I found, and referencing Go-Jeeps write up. I found the wires were different, but the trans and TCM still operated the same. You need to jump pin 26(darkblue wire with white tracer=Ignition run/start) to pin 12(white wire= trans solenoid A). The rest of the write up instructions are the same. After checking into what was done for the mod, I doubt highly any code will be set, and no other systems will be affected. This is just my opinion on what will happen, but I need someone to try the mod and see what happens. I seriously doubt any damage will occur to the trans, as this is the same process done on the previous years trans/TCMs.

I hope this was helpful. I found Go-Jeeps write up as the most clear and simple explanation of this mod. Thanks again for such a great website and for all the information you provide.

Bryan

Thanks mate for the comments
I have not heard any problems with this mod on a 96 so you should be fine. It is not just the OBDII that makes it throw the code in 97+ as they must have made other changes to the TCM/ECU from that year on as mentioned above.

so there are '96s with OBDII? when was the actual cutoff?

mad maXJ said:

so there are '96s with OBDII? when was the actual cutoff?

Click to expand...

96 was the first year of OBDII. There were a few exeptions, basically any new model from the 94 model year on was required to be OBDII compliant. In 1996 all new motor vehicles sold had to be OBDII compliant.

Bryan

Back from the dead......
So, anyone running this on a 97+?
I really want to lock it into 2nd rear......
Shawn

In the very first post it said for details look at the how to section,don't see a how to section,where is it ?