This one is stumping the transmission shop! My 97 already has 110,000 on it if that helps, and it's an auto tranny with full time 4x4.

First symptom was grinding when shifting into reverse. I immediately shifted back to drive, then tried again, no problem. Did that a few times over a 2 week period. Then, going about 70mph, I hear a grinding noise that kind of builds up to speed. It's not a sudden grind but seems to be in sync with the wheel speed, not engine speed. Pulled to shoulder in neutral, stopped, put it back in drive and continued (now towards a shop!), grinding reappeared within a few minutes. On surface streets (0-40mph), I found that if the grinding started, I could goose the pedal and it seemed to drop back into sync (no grinding, gone for a few more minutes). Made it to shop in this manner, and discovered that reverse was no longer possible...nasty grinding on each try.

First suspect was tranny, but after tearing down the tranny they found it to be very clean and in good mechanical shape. Moving on to transfer case. The shifter fork that engages gears for 4x4 H and L appears to be lifting out of 4H just enough to lose engagement and grind. It's essentially a neutral condition. The mechanic pulled the electric shift motor and the problem seemed to go away (on the lift anyway). They put on a motor from another old transfer case and the grinding happened again.

So it seems both the electric motor assemblies are bad (this includes the two sensors that are wired into the motor wiring harness). OR, the computer conroller that tells the motor what to do is freaking out.

Has anybody out there experienced these symptoms, or have a good idea as how to pinpoint the cause? I could change the motor assembly, throw in a new transfer case, or both, or can the signals from the computer be checked?

Thanks for any of your thoughts!

 

Hi Tyrus,
It seems you have a problem with your Explorer's tranfer case that mirrors a problem with the larger transfer case(BW 1356) that is used in late '80's and up F-150 to F-350 & Bronco. After discussing this problem with my mechanic, he informed me that the problem lies within the planetary gear set & shift hub,sun gear/shift fork assembly. As you use your vehicle day to day, in and out of forward and reverse, especially vehicles with over 100,000 miles clearances open up between the shift hub & sun gear that hold the transfer case in gear (2 Hi,4 Hi, N or 4 Lo). As these clearances open up more and more, the transfer case starts to slip out of gear, mutilates the shift fork's nylon wear pads, bends or breaks the shift fork, as well as ruins the planetary gears then the whole assembly will have to be replaced.
If you have your transfer case serviced see if the above has happened, newer rebuild kits for the BW 1356 use thrust washers (as found in C6 trans kits) between the shift fork-sun gear-planetary gear set to alleviate the problem, hopefully your transfer case can be rebuilt or repaired with the same type of fix. I hope this helps in any way.

Todd
BB79RANCH