AW4 Shifting Question

[99XJLove]

Ok, My friend just bought a 95 country. It has the AW4 trans in it. It is having problems shifting. It won't go through the gears if you put it in drive. If you shift it manually it skips second. It also won't downshift on it's own. We are sure that it has something to do with TCU or something related to that. He is on his 2nd TCU with no luck. I have searched and found some info but it is for the RENIX era stuff and I don't think that it pertains to this situation. We also tried unplugging the TCU and it still acted the same way. No 2nd gear.

 

[recycledxj]

Try looking at your TPS, had the same problem once... I put a new one in and the problem went away.

 

[Ecomike]

lawsoncl is the best guy I know here on the newer AW4 issues. There a number of threads here on this sort of issue, but you need to use google search for search words less than 4 letters, like AW4.
There is a speed sensor involved, 3 electric solenoids do the shifting in D, and the TCU, ECU< and TPS get involved. Even the NSS is involved in the tranny wiring, but not with your current problem.

The no 2nd, in 1st to 2nd manual shift sounds like an internal problem. Might trying draining and replacing 3-4 quarts of T fluid 3 times to see if goes back to working. Be sure and use only Dextron III, Dex III.

If all gears worked in manual mode, and not in D, then it would electric solenoids or their wires causing the problem. Easy to access, right above the drain pan.

 

[Slip Kid]

If your shifting manually, it will always skip 2nd, that's not a problem - 2nd gear can only be accessed electronically, when the #2 solenoid is powered, by the TCU or otherwise. With the TCU unhooked, you won't be able to get to 2nd without powering the solenoid by other means. With everything hooked up and working properly, with the shifter in the 1-2 position, it will not shift to 2nd until somewhere between 4-5k RPM.
It sounds like this one is doing no electronic shifting at all. Check that the TCU is indeed getting power. The trans itself should be the same throughout the years, mechanically and electronically. The TCU changed as far as the connector goes, and wire colors, but I'm not sure how its functioning changed. Make sure its getting power, if it is, try replacing the TPS and adjusting the kickdown. If it's still broke, ask someone else

 

[99XJLove]

The fluid has already been changed with reccomended spec fluid DexronIII. It made no difference. Like I said the trans acts the same way weather the TCU is connected or not. Manually shifting it shouldn't cause it to skip second. That's why the 1-2 gears are on the same level on the shifter. It should automatically go to second then you move to 3rd and so on. What voltages should be going on at the TPS? And at the TCU? Which Wires on the TCU? Any schematics? Like I said this is not my vehicle, I have the AX-15 in my 99 so I'm not famillar with any of this. My freind could do all of the research himself but he gets frustrated with the internet. So I'm just trying to be a good friend and help him out the best I can.

 

[bigalpha]

It is absolutely incorrect to say that the AW4 will "skip" 2nd gear if you shift it manually into 1-2. The trans will only shift into 2nd gear at something like 4-5k RPM regardless if the TCU is working or not.

Follow the troubleshooting steps in this document and come back:
http://www.transonline.com/transdigest/magazines/1997-10/Shift%20Pointers/index.html

I had a similar problem, where the trans would default to 4th gear. Turns out all 3 shifting solenoids were bad. Replaced them and now it shifts.

OP: when you put it in drive, does it start out in 1st or does it start out in a higher gear and just barely creeps forward?

 

[99XJLove]

I'll have to ask him. I actually just found the link that you posted by searching on Google. Thanks for the info. I think it will work in first but just stay there. I'll ask. It deffinately doesn't downshift on it's own.

 

[bigalpha]

One of the key elements is going to be .. does it start in 1 and upshift through the gears? If it just doesn't downshift, I'd lean TPS.

 

[xj_punk]

same problem with my buddies 98. shift into drive and it goes straight to 4th i assume. if shifted manually it works fine and hits all the gears. i had the same problem with my 93 when i was installing my 1st and 2nd gear switches i shorted something out and i found a fuse labeled transmission in the engine bay fuse box and it was blown so i replaced it and all was well again.

so does that transonline write-up that was linked earlier in the thread apply to all years xj? it mentions an inline fuse for the tcu and if that is the problem it would certainly make my job of fixing it for my buddy a whole lot easier.

also, are there any differences in the tcu in different years? just wondering if i have to find the same exact year in the junkyard or a 95+ or 97+ etc.

thanks guys

 

[jeepman121]

How do the solenoids look? Mine have been acting up similar to yours (especially in moist weather) I've just been to busy to change them out.

 

[bigalpha]

Yes, that document pretty much covers all years with a few small exceptions ... the inline fuse being one of them.

Do you want to know what they look like, or if they look different when they go bad?

 

[xj_punk]

is it a tube style in line or a mini fuse in a holder? i will just trace the wire and find it regardless. if it looks fishy at all i will replace it

 

[bigalpha]

Should be a fuse holder ... i believe it's yellow; but I don't think your 98 has an inline fuse.

 

[99XJLove]

I think after 89 they got rid of the inline fuse. I am unable to find one on my friends. There is no starting in 1st if you are in D It will downshift to 3rd but that is all. Any suggestions?

 

[Slip Kid]

It is absolutely incorrect to say that the AW4 will "skip" 2nd gear if you shift it manually into 1-2. The trans will only shift into 2nd gear at something like 4-5k RPM regardless if the TCU is working or not.

Follow the troubleshooting steps in this document and come back:
http://www.transonline.com/transdigest/magazines/1997-10/Shift Pointers/index.html

I had a similar problem, where the trans would default to 4th gear. Turns out all 3 shifting solenoids were bad. Replaced them and now it shifts.

OP: when you put it in drive, does it start out in 1st or does it start out in a higher gear and just barely creeps forward?

How will it know to shift into 2nd without the TCU?

 

[bigalpha]

Without the guidance of the TCM (when you unplug the TCM to test the trans and see if it shifts manually), the solenoids don't fire ... yet it will still shift into 2nd if you put it into '1-2'.

 

[Ecomike]

In 1-2 (No TCU power), it stays in 1 unless you reach about 4500 rpm, then it shifts to 2 hydraulically. In 3 it shifts to 3, in D it shifts to OD. If you get up to about 30 mph (stock) in second and drop it into 1-2, it will shift from 3 to 2.

You have one of 4 problems, all solenoids are bad, or, the TCU is bad, or the TCU has no power (check wiring and fuses), or the TCU to tranny wiring is trashed or disconnected.

 

[lawsoncl]

I'm betting the trans computer has no power, since he already tried replacing the TCU.

The article at http://www.transonline.com/transdigest/magazines/1997-10/Shift Pointers/index.html was written for the Renix era Jeeps, but it still works fine as a guide for testing for the later models up through 97. The pinouts on the connector are the same. Minor changes are the TPS voltages for D2 will run opposite (0->5 volts), no power/comfort switch, no inline fuse, and some of the wire colors may be different.

In particular, check for voltage on D14 and D16, a good ground on D7, and the solenoid resistances. And yes, the tranny will upshift into 2nd near the redline regardless of the TCU.

 

[lawsoncl]

deleted duplicate post.

 

[xj_punk]

so that article won't work for a 98? that sucks

I'm betting the trans computer has no power, since he already tried replacing the TCU.

The article at http://www.transonline.com/transdigest/magazines/1997-10/Shift Pointers/index.html was written for the Renix era Jeeps, but it still works fine as a guide for testing for the later models up through 97. The pinouts on the connector are the same. Minor changes are the TPS voltages for D2 will run opposite (0->5 volts), no power/comfort switch, no inline fuse, and some of the wire colors may be different.

In particular, check for voltage on D14 and D16, a good ground on D7, and the solenoid resistances. And yes, the tranny will upshift into 2nd near the redline regardless of the TCU.