I have been trying to decipher several threads about "Gearbox Fault" and other related shift selector problems like Transmission fault code P0706 . They seem to agree, but then something comes along and doesn't make sense.



This weekend I took a trio to Montrose, Silverton, and Ouray Colorado. For those not familiar with that area, it is called the Million dollar highway and has some wonderful twisties and long downhill descents. In order to not over heat brakes in the miles of 6% - 7% downhills, you use lower gears. I could use 4th, 3rd and in some of the 180' switchbacks even 2nd. But every time I would try to switch back to D, I'd get a "Gearbox Fault". If I pulled over and turned off the car, it would reset until the next up shift from 4 to D.


Here's my particular Symptoms:


Had Transmission work (Rebuild)


Park through Drive all work with minor exception that I have to move the lever a bit to the Park side of the detent to get Reverse to engage and "R" to light.


4 through 2 all work as should.


Moving from 4th to D causes "Gearbox fault"

What I've found:


1) The micro switch for Neutral is missing the metal lever that allows it to actuate in a range of locations (about +- 5/16" from detent) this means I can't start in neutral other than a very selective position. Annoying, but not the big problem. I can go Park to Drive and back all day (through Neutral) and never cause the fault.


2) Moving from D to 4 is fine...4 to D causes fault.

Question:
In replacing the transmission, could they have slightly stretched the cable or otherwise cause the alignment to change? If the Transmission Rotary Switch isn't in a position that the D-4 switch should be able to move, would it cause this fault? If so, would adjusting the cable (the opposing jam nuts in the shift lever assy) realign things or am I missing something? I think I read the you are supposed to move the lever on the transmission to neutral and then adjust those nuts until the indicator shows Neutral also. This is supposed to put the Transmission Rotary Switch and gear selector in agreement.


I read that there is no cable movement going from 4 to D, but the 4-D switch changes state. If d-4 switch changed state when the Transmission Rotary Switch wasn't properly positioned, it would generate an invalid binary state. Right?

 

You need the D4 micro switch or the TCM will log a DTC.

bob

 

I had that problem with mine and solved it with cable adjustment. Lever was not going all way into 4th and electronics thought I was going from 3rd to drive. With other symptoms you have I would look at cable adjustment

 

Went out this morning and verified all switches were working, so loosened jam-nuts holding the shift cable and adjusted it a bit in both directions.

As I adjusted it one way, the point that Reverse lit-up moved farther away from the "R" notch. I adjusted it the other way and it lit when the gearshift lever was in the notch when going from Park to Drive and Drive to Park. When it lit properly from both directions, I tried doing the 4th to Drive and Drive to 4th. NO "GEARBOX FAULT" !

Made a Neutral switch lever out of a springy piece of a hair clip and super glued it to the side of the switch and now it will start easily in Neutral.

Tightened everything and all's well.

Now taking it to the body shop to repair this weekends calling card a local deer left in the fender and door.

 

Glad you got it working

 

I have the very same problem. Do you have pictures of what you did? Thanks

 

DISCLAMER: Be sure to annotate how many threads are either sticking out the front or back past the jam nuts. That way if this doesn't help (or makes it worse) you can put everything bake where it was before you touched ANYTHING.


To identify if this adjustment may help you, do this first:
Watch the gear indicator lights as you slowly move from Park to Drive. Note when the "R" light come on. Then slowly move the lever from Drive to Park and note when the "R" lights. If it illuminates IN the notch going from "P" to "D" AND "D" to "P", STOP...this adjustment is NOT your problem.


If the "R" doesn't light evenly both directions and IN the notch, now we can start. ( My problem was that moving from "P" to "R" worked fine, but when I went from "D" to "R", I would have to go slightly past the notch to light the "R" and the gearbox engage reverse.)



Annotate exactly where the "R" light illuminates from both directions for future reference.


Remove the center console. This was simple for me because I've been working in there on radio stuff and it's not completely reinstalled. If you are not familiar with this, there are videos on YouTube. This one shows a guy removing his in about 5 min. Don't expect that fast the first time. Take your time and "enjoy"...read that remember!)
https://video.search.yahoo.com/search/video;_ylt=A0SO800.Zd1Y7oEALypXNyoA;_ylu=X3oDMTE0Y XRlM2ltBGNvbG8DZ3ExBHBvcwMxBHZ0aWQDQjM2MjRfMQRzZWM DcGl2cw--?p=youtube+XK8+console&fr2=piv-web&fr=yset_ff_syc_oracle#id=1&vid=fcef1d443f4cbab 38ca53df1ceef92f6&action=view


I don't currently have a picture available (It's in the shop fixing a $5000 calling card of a Mule Deer last weekend) but I have a picture that the adjustment location is identifiable in this earlier pic.






Once the console is out of your way, you'll be able to see the cable adjustment jam nuts (lower right in the above picture) To adjust, start by loosening the FRONT nut (sorry, I don't know the size...I used adjustable wrenched to save time.). You should be able to spin the nut a couple of threads to the front with your fingers. Then adjust the REAR nut forward until it is tight again. then check the position the "R" illuminates again.
If it is closer to the notch, continue until the "R" illuminates squarely in the notch from both directions. If it is farther away, loosen the REAR nut several threads and tighten the FRONT jam nut and repeat the check.




For the Neutral switch repair:
Start by removing the shifter knob and jam nut. Then 4 Phillips screws hold the J-gate cover on. You can just lift the cover up and off the shift lever to get the view in the picture. (You might have to set the hand brake and move the shift lever to "N" or "D" to facilitate lifting the cover off.


In the first picture you can see that the top micro switch has a metal lever that presses on the switch button when the shifter is in Park, but the lower one doesn't. That means the only place I could start it was park and the tiny spot where the gear shift lever actually touched the little white switch button.


These are pictures of the hairclip I used and the shape I bent it into. Sorry no installed pictures because I was in a hurry to reassemble. Will post the next time I'm in there for radio stuff.)






I clipped the outside leg of the hair clip and bent it into the shape on the left. I super glued it to the rear edge of the lower switch housing. I had to clean the switch quite well because there was white lithium grease everywhere in there and it didn't want to stick. DON"T try moving the shift lever for a while. Let the glue set. Also don't worry if it looks like the shift lever will snag the new lever. As long as you have a bit of an angle on the top end and it is mounted close to the rear body of the switch it will be fine when the j-gate cover is reinstalled. (The J-Gate keeps the shift lever from getting too close and hitting the end of the new switch lever.)


I realize this Neutral Switch Fix is probably temporary, but it will give me time to either find just the switch/lever combo and replace it, or find the entire assy on Craigslist or Ebay.


Hope everything works for you!
AC0FC

 

I'm not in town now. But when I get back I'll check what you said about the R light. Thanks so much for the explanation!