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Transfer Case Fluid Change Leads to O/D flashing


Active Member
April 7, 2015
Reaction score
City, State
Montauk NY
Year, Model & Trim Level
1998 Ford Explorer XLT
I changed my transfer case fluid today and replaced with motorcraft transfer case fluid because I've never addressed the t-case and wanted to make sure it was filled properly with good fluid. To my surprise the old stuff looked surprising healthy.

The change was simple and seamless. Afterwards I got in the truck, started it, and switched from "Auto" to "4x4 High" to "Low".

The light on the dash indicated that I was changing to high 4x4 then low pretty easily. But when I tried to switched back to high from low the light on the dash continued to illuminate "low". I switched back to low then back to high then auto. Eventually the light indicated i was no longer in 4x4 and I assumed I was back into auto.

Later i came to the car and heard a small clicking from the 4x4 switch a few times. taking it for a drive felt very much like 4x4 drive was still engaged even though the light didn't illuminate on the dash indicating so. Getting up to 30 MPH the car wouldn't come out of 2nd gear. I then noticed the o/d light flashing.

I pressed the od button and it seemed to stick.

I drove home right away. I turned the car off and on and in and out of 4x4 high. The dash light was quick to respond to my switch but the car felt the same (4x4 engaged).

Then my heart really sank. I turned the car on again, put it in gear but none of the drive gears engaged ! No forward or reverse, and when I tried to put it back in park t made a sort of grinding noise !!! Ahh !

I turned the car off in neutral and back on and the gears began to engage again and I was able to get it in park without the grinding noise.

Then I ran straight to my computer to write the story here. What the hell did I do ?!

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After all that it seems to be back to normal. Its driving like usual (doesn't feel like 4wd is engaged) and its shifting properly. What a scare. But I'd still like to hear some input from everyone...Did I do something wrong ? As far as the transfer case goes, all I did was drain, replace drain screw, and refill, replace fill screw.

I can't see how changing the transfer case fluid would effect the transmission unless you bumped something or disturbed a wiring harness. There is no 'shift' at all from auto to high. All it does is engage the clutch in the transfer case.

If it's getting stuck with the front wheels driving it must think a wheel is slipping and it's trying to use its auto 4wd function. Likely a speed sensor if this is the case.

There's a 'brown wire mod' which is a band aid fix, but would guarantee you aren't stuck in 4wd. It would also disable 4wd auto when switched and give you 2wd.

Ditto, that sounds like the TC not switching between functions properly. The shift motor is a weak link with age, but it only really does one thing, move the TC from one position(4wd hi) to 4wd low. The rest is all done electrically by engaging the internal clutch to "grab" the front output shaft. The BWM disconnects that signal from reaching the TC internal clutch.

If that happens again, be sire it's not in 4WD by turning the front wheels quite a bit. Binding will tell you that the front shaft is driving. You can tell it's in 4wd low by the rpm's, that is really obvious.

Thanks guys. Doing a bit of research I discovered that a few people have had issues of being stuck in 4wd low. It was so strange that the dash "4x4 low" light wasn't on, and that's why I thought I had finally gotten myself out of it, but discovered as soon as I put it in gear and drove a little that it was still stuck. Thankfully I got it out of 4x4 low and it feels normal again. But I'm still cringing at the sound of the grinding noise that occurred after I brought the truck home and tried to get it out of low.

In 4WD there is a lot more gear noise and stresses going on, which you always feel on the street etc. Off road you might not feel much odd in 4WD, but where you had it on the street that was a normal result. Just keep an eye on it and don't stick it in 4WD accidentally.

Thank you for your diligence, Don.