About a year ago I had a problem with the cruise control mysteriously disengaging. I eventually noticed that I could lightly tap the shifter just right and repeat the problem. I also noticed that the gear indicator light on the dash would flicker at the same time.
After some research I concluded that the AT mode switch was out of adjustment. The mode switch is activated by the gear shift lever. When the lever is moved it moves a mechanical linkage that is attached to the side of mode switch. Inside the mode switch are a series of electical contacts. As far as I can tell these contacts then interpret what gear the gear shift lever is in. In turn the mode switch tells the AT which gear to shift into. Any misalignment and the mode switch will incorrectly signal what gear the AT is in. In my case a slight jostle and the gear shift would move just enough to make the mode switch think it was time to change gears. In turn that would cause the cruise control to cut out.
My cure was to adjust the mode switch. It is held in place by two 10mm bolts. To be set properly, per the manual you loosen these bolts and then rotate the unit while checking the connector for proper resistance. It seemed a pain to get to the connector. I figured the unit had either worn itself out of adjustment clockwise or counterclockwise. I guessed clockwise so I loosened the bolts and rotated the switch maybe 3 degrees (the manual gives a 5 degree range). I took if for a test drive and all was fine.
That cure has worked fine for over a year.
Part two of the saga - A couple of months ago the AT shifted rough from 1 to 2 and 2 to 3. The 3 to 4 shift was fine. ASAP I checked the fluid level and condition. Both were fine. I couldn't find any battery or alternator problems. The problem went away with an engine start and stop. A couple of weeks ago the rough shifting happened again. It has now happened a total of about 5 times.
I started thinking mode switch again and also remembered these posts -
http://www.4x4wire.com/forums/showf...;oldertype=&bodyprev=#Post407075http://www.4x4wire.com/forums/showf...B68&Number=341938&Forum=,,c15,,&Words=transmission%20%2Brange%20%2Bswitch&Searchpage=2&Limit=25&Main=341921&Search=true&where=bodysub&Name=&daterange=1&newerval=1&newertype=y&olderval=&oldertype=&bodyprev=#Post341938
This from the second post caught my attention - "Mode switch: the Isuzu 4L30 transmission has a history of mode swithc faliures. due to the grease inside the mode switch degrading from heat (proximity to exhaust pipe???)."
Last night I took apart the mode switch and indeed the grease inside was a mess. Way too much looked to have been originally installed and it had became more of a paste. I cleaned it up and so far this repair has solved the harsh shifting. Of course only time will tell if indeed this was the problem.
For those with similar problems be warned that getting at the switch to clean it is not a cakewalk primarily due to clearance issues. FWIW here are the major headsup points-
You will be touching the exhaust often. Therefore only work on a cool vehicle.
Be prepared to fight the 14mm bolt holding on the shifter linkage. Mine was on so tight I had to use an extra long wrench for leverage.
Getting at the 10mm bolts can be a little tricky. I used a socket with a short extension to get the upper one. A gearwrench made it much easier to remove the lower one.
It is just plain annoying to get your hands up in there to unhook and rehook the wire connector.
Getting the unit apart could also be a problem if you don't have star or torx bits.
Adjusting the unit could be a problem. However if you pay attention during disassembly you should be fine. There is an alignment notch in the switch. Put that back the way you find it. If not you will likely be checking the connector terminals for proper resistance (assuming of course you have a manual to know which ones) while you rotate it. Alternatively you can do a series of trial and error runs with the switch rotated into various positions to see where the gear indicator on the dash lines up the best. Again this is not all that hard but it is not a simple plug and play either. You have to be prepared to fine tune the switch re-installation.
I hope this helps someone else who has similar issues.
