XT6 2WD AT stays in 3rd gear regardeless of vehicle speed or gearshifter position.

[K9WAGON]

I have a 89 XT6 2WD automatic that I am working on for a friend . The transmission will not shift into any gears other than 3rd and reverse. You can put the shifter into 2nd and the light for 2nd does not not come on, nor does the 1 hold light come on when I depress the button. The car starts off in 3rd gear and stays there regardless of vehicle speed. I am trying to figure out how to diagnose this since i'm fairly certain its an electrical issue . Does the ecm control the tranny or is there a tranny control module ?

 

Any ideas would be greatly appreciated.

[operose]

I had an '88 xt6 2wd auto that would usually only use 2 and 3, but not 1... but on those days when 1st gear was working, you could smoke the tires!! honestly, I think these trannies are crap. it probably needs to be replaced, but a filter/fluid change might do the trick, you never know... there's also duty solenoids that control shifting I think.. might wanna get someone to scan the 4eat section of the FSM, although it's the most confusing crap I've ever waded through

[Turbone]

If its a 4EAT, its most likely the TCU.

[K9WAGON]

Where is the tcu located . What other cars have the same tcu ?

[idosubaru]

the TCU is located behind the drivers side rear seat side panel. swapping in another TCU is a good idea.

 

does the POWER light blink when you first start the car? sounds like it's in "limp" mode. your POWER light should (should when something is wrong) blink like 15 or 16 times when you start the car, this indicates there's a code in the TCU that may tell you something. pull these codes. if this isn't blinking and you're having these problems then i'd again suspect something fishy with the TCU.

 

a fluid and possibly a filter change could help. this will also allow you to inspect the trans fluid. check the fluid out and look for metallic particles or gooey stuff. sometimes a bad trans will have very fine metallic particles/shavings in the fluid. this will verify you need to replace the trans as this would indicate serious internal damage.

 

make sure the transmission oil pan isn't dented. a dented pan will obstruct the sump to the oil pump.

 

you can also install an aftermarket transmission cooler. you should have one anyway, good for the trans. this will also bypass the old trans cooler in the side of the radiator that could be clogged. as a VERY TEMPORARY test you can pull both trans fluid lines from the radiator and run them together, totally bypassing the terribly efficient radiator side trans cooler. if this is clogged, bypassing it may help.

[ruparts]

Hi, Glad someone else posted on this problem,(not glad you have them) I have the same on my 4x4auto xt6. I have done ALL the stuff recommended here, 3 different tcm were tried , one was my 2wd one that works perfectly, nada. Had the pan off, changed the fluid two different times, had the valve body off twice and checked all the valves for sticking, had ALL the solonoids off and checked electrically and for function on the bench, and flushed cleaned them both times with spray cleaner, nada. The solonoid pack is available only in aftermarket parts. I am still some what suspicous of the solonoids. My problem is that My car was like this when I got it so I had no prior information about how the symptoms developed , suddenly or little at a time.

If you get any real info that helps, please help me out too. PM me!!

I want to ask you a question , from a stopped position, put your shifter in 1st position (2), does the car act like its in two gears at once or like something is locked up, and will only move forward with moderate throttle??? My car does that as well as the symptoms you described.

You are the only one I've seen with these same problems.

I have a 89 XT6 2WD automatic that I am working on for a friend . The transmission will not shift into any gears other than 3rd and reverse. You can put the shifter into 2nd and the light for 2nd does not not come on, nor does the 1 hold light come on when I depress the button. The car starts off in 3rd gear and stays there regardless of vehicle speed. I am trying to figure out how to diagnose this since i'm fairly certain its an electrical issue . Does the ecm control the tranny or is there a tranny control module ?

 

Any ideas would be greatly appreciated.