No Engine Braking in 4x4 Low 1998 Explorer

[tinkering]

1998 Explorer 4x4 4L

The drive train freewheels when going down hill in 4x4 Low, and 1st gear. Shouldn't the engine be braking the vehicle when in 4x4 Low, and in 1st gear? It is free wheeling which is very hard on the brakes; I had to ride the brakes the whole 2 miles down (a lot 45 degree grade).

[shorod]

How fast were you going when you tried to shift to 1st gear and 4x4 low!?! That combination sounds like it would top out at like 5mph! If you leave the truck and Auto or 2WD and shift to 2nd or 1st does the engine apply some braking?

-Rod

[tinkering]

Originally Posted by shorod

How fast were you going when you tried to shift to 1st gear and 4x4 low!?! That combination sounds like it would top out at like 5mph! If you leave the truck and Auto or 2WD and shift to 2nd or 1st does the engine apply some braking?

-Rod

I started out in 4x4 Low but had the gear shift in D. I then switched to low gear on the move but was no more than 5 mph. 5 mph is about all you want to do on this jagged goat trail of a mountain road.
I will try some of the other combinations that you mentioned above, to see if there is any engine braking taking place there.

[shorod]

You mention you started out (presumably from a stop) in 4x4 low. Here's what the service manual says for engaging 4Low:

"When shifting into or out of LOW range, the GEM requires that the vehicle speed is less than 5 km/h (3 mph), the brake is applied, and the transmission is in NEUTRAL."

Are all of those conditions being met? I didn't find anything in the service manual suggesting what could cause the truck to freewheel unless the 4Low is not actually being engaged due to a transfer case selection motor or transfer case issue or issue with one of the inputs needed to engage 4Low (neutral safety switch, brake pedal position switch). Are you pretty sure that 4Low is engaging as would be confirmed by a very low gear ratio?

-Rod

[tinkering]

Originally Posted by shorod

You mention you started out (presumably from a stop) in 4x4 low. Here's what the service manual says for engaging 4Low:

"When shifting into or out of LOW range, the GEM requires that the vehicle speed is less than 5 km/h (3 mph), the brake is applied, and the transmission is in NEUTRAL."

Are all of those conditions being met? I didn't find anything in the service manual suggesting what could cause the truck to freewheel unless the 4Low is not actually being engaged due to a transfer case selection motor or transfer case issue or issue with one of the inputs needed to engage 4Low (neutral safety switch, brake pedal position switch). Are you pretty sure that 4Low is engaging as would be confirmed by a very low gear ratio?

-Rod

Thanks, I will really focus on that stuff on a road test rather than when in the midst of transporting someone down the mountain, as was the case last time.
I will focus as you say, on whether 4Low is actually engaging.
I will post my findings.

[tinkering]

Originally Posted by shorod

You mention you started out (presumably from a stop) in 4x4 low. Here's what the service manual says for engaging 4Low:

"When shifting into or out of LOW range, the GEM requires that the vehicle speed is less than 5 km/h (3 mph), the brake is applied, and the transmission is in NEUTRAL."

Are all of those conditions being met? I didn't find anything in the service manual suggesting what could cause the truck to freewheel unless the 4Low is not actually being engaged due to a transfer case selection motor or transfer case issue or issue with one of the inputs needed to engage 4Low (neutral safety switch, brake pedal position switch). Are you pretty sure that 4Low is engaging as would be confirmed by a very low gear ratio?

-Rod

When stopped, I hold the brake on, transmission in neutral, I turn the control to 4x4Low. I can feel and hear the slight clunking noise of it switching to 4x4Low; the 4x4 Low indicator light on the dash comes on.
I also turned the overdrive off (just in case that was the problem) by pushing the button on the end of the gear shift lever.
I selected 1st/Low gear; I can feel the engine braking going down the mountain (it just doesn't brake as much as my Chevy 3/4 Ton 4x4 when it is in bull low). We tried it in 2nd gear too while in 4x4Low and it was noticeably less engine braking.

I think my problem initially was: not stopping or <3 mph, not holding the brake on while in neutral, before switching to 4x4Low
So we have engine braking in 4x4 Low but not as much as our Chevy 4x4. We still have to use the brake pedal quite a bit more than with the Chevy. Does this sound normal?

What should the engine idle be at? Maybe my engine idle is too high (I am currently having problems with the Idle Air Control valve)? I might start another thread about that.

[shorod]

Honestly all the Mountaineers and Aviator that I have experience with have been AWD, no option for 4 Low. It does sound suspicious that you are not getting much engine braking at all when in 2nd gear. I wouldn't expect an overspeed condition to cause the transfer case to override the 4 Low selection.

Engine idle should be somewhere between 650 and 750 rpm I would expect, but I don't have the specification in front of me.

-Rod

[tinkering]

This is a late follow up but better late than never. The whole problem was attributed to the PCM and fusebox that these Expeditions etc. and F150s right up to the current years are experiencing. Water gets through the wind shield seal and into the PCM and the fusebox behind the dash. I changed them out and all of the meriad of electrical glitches were no more. I also replaced the burned out dash lights. NICE. Even the intermittent problem with the key and the security system went away.
I took it into a glass shop who knew how to seal everything up properly. VOILA!
I also applied sealer to those channels that travel along the length of ths roof. The factory sealer cracks and water seeps in there too. Ford isn't all better ideas.
The main thing though was the transfer case began to shift properly into and out of low, with the dash 'low' indicator light smiling back at me for the first time since owning it!

[shorod]

Thank you for following up with good details on what you found the issue to be! I'm glad to hear you got it resolved.

-Rod

[tinkering]

Originally Posted by shorod

Thank you for following up with good details on what you found the issue to be! I'm glad to hear you got it resolved.

-Rod

Thanks shorod. I always try to follow up. It's the finishing touch to the whole forum process. I like to contribute too. Automotive forums has been a lot of help over the years. Excellent.