4405 no low when hot

[joe canuck]

97 X with rebuilt transfer case, shifts good when cold or after short drive, however when hot wont shift into 4 low, sometimes lite will come on (4low) but wont shift, when switch moved back to auto the 4 low stays on and of course if you drive it will bring on the flashing OD lite, only way to reset is to disconnect battery. had this problem before trans was over hauled (different reason) ? is there any likelyhood the controler, or a relay is to fault in this situation?.
I pulled the shift motor apart and found no wear, or faults in there. prvious ownr had never used 4 low)
anyone have any suggestions? I couldn't find any similar problems on forum search

any input appreciated

regards

 

[IZwack]

How are you engaging 4LO? Are you stopping and putting the vehicle in Neutral?

 

[joe canuck]

Yes the usuall drill, neutral, dead stop, brake applied and then turn switch
if it goes in, get the click in dash within 2 seconds than slight clunk at TC when it goes in.
If it won't go in there is no click in dash, have waited as long as 15 seconds, lite will go on but no click-clunk no low engagement

 

[IZwack]

Well its intermittent so its going to be hard to diagnose the problem.

But typically, first you have to verify that the shift motor has indeed made it to 4LO by removing it from the transfer case but leaving it connected (electrically) to the rest of the vehicle and then rotating the switch to 4LO. If the motor moves, then everything "upstream" of the motor is fine (including all electricals). Then the problem is probably mechanical.

When the vehicle fails to engage 4LO, is it then in neutral even when you move the transmission to Drive? I ask because in order for the transfer case to go to 4LO from 4HI, the shift motor must rotate through the Neutral zone of the transfer case. If the shift fork is slightly bent, or the shift fork's white plastic/rubber bushings are worn out or missing, then the transfer case is probably not making it all the way into 4LO and is mechanically in Neutral.

Below is what the shift fork looks like along with the gear it operates. At the end of the forks are the little white plastic/rubber bushings. These bushings are known to wear out or are just missing.

 

[joe canuck]

when it won't engage it is still in 2high, the resetting by disconnecting batt is just to get OD lite off, there are no noises etc like it may be partially engaged

shift fork, gear, shaft and inserts have less than 1000km on them

 

[IZwack]

Next time it wont engage, I would remove the shift motor. Its held in by I think three 10-mm bolts so it should only take a few minutes. Check if the triangular shift rod thing is pointing to the 4LO position.

 

[joe canuck]

will try that to rule out mechanical problems, then if warranted, move backward up threw electrical.

thanks for input