On a recent trip to Baja I foolishly drove my truck (2001 f350 4X4 auto. with 3000lb slide in camper) into some loose sand and promptly got stuck in about 6 in. of sand. I tried to back out but the wheels would not turn no matter which combination of gears I tried (2 wheel, 4x4 high or 4x4low, hubs manually locked). Although I had the gas pedal to the floor the wheels simply would not turn. The tachometer maxed out at about 2000 rpm when I did this.

I eventually managed to back out in short distance increments by repeatedly digging out around the wheels and laying carpetting behind the rear wheels, only to get stuck again each time the wheels drove off the carpet.

I was surprised that flooring the gas pedal did not create enough torque to spin the wheels and am suspicious that the transmission may have been slipping. Has anyone had a similar experience or know of a way of checking for transmission slip? For instance, should the vehicle move when the brakes are firmly applied and the gas pedal is gradually pushed to the floor?

 

The wheels were not spinning, traction control must have been on!
I would think that if the Tranny were slippin, you could have gotten more than 2000 rpm out of it. Maybe Mark K will be along to help out more with the tranny issue, but I think more must be involved.

Matt

2002, F250 SD, SC, 8' Bed, V10, 3.73 LS, Arizona Beige, ICI Stainless Step Bars, Truxedo Tonneau, Prodigy Brake Control, Flowmaster 40

 

The key to your situation was the camper. With that much wieght on the tires, the force it takes to turn those tires in sand is tremendous. You're lucky you didn't snap a driveline, and your tranny probably took the brunt of it. You should have your fluid checked in the tranny for burned fluid.

Are you sure it went into 4 LO? Most forget to be stopped, foot on brake, in nuetral, then turn into 4LO. My buddy did the same as you THINKING he was in 4LO, but actually was in 4HI. He complained how the truck wouldn't spin the tires (without a camper)in 4LO. I showed him 4 LO and the truck will about turn itself inside out in 4LO. Now he's happy

Just a thought.

 

Thanks for the insight into this problem. I guess I am lucky that the transmission slipped rather than snap the driveshaft. I haven't checked the transmission fluid for burning but will do so now.

I did follow the correct procedure for shifting into 4x4lo and assume that it must have engaged.

 

With the pedal floored, 2000 RPM, and the tires not spinning you do not have a slipping transmission. That is the torque converter stall speed. If the engine speed went over 200 RPM the transmission was slipping and is now toast.

If you held that position for more than 10 seconds you probably have some internal damage. At the very least the fluid is destroyed.

 

>With the pedal floored, 2000 RPM, and the tires not spinning
>you do not have a slipping transmission. That is the torque
>converter stall speed. If the engine speed went over 200 RPM
>the transmission was slipping and is now toast.
>
>If you held that position for more than 10 seconds you
>probably have some internal damage. At the very least the
>fluid is destroyed.




Exactly.

Better get on that trans fluid immediately.

 

I just checked the transmission fluid. It was clear with no burnt smell. The 2000 rpm speed was held only momentarily.

I am still confused about exactly what was happening. Was the transmission/torquue converter intended to behave that way because of the high force holding wheels or was it because of some malfunction in my drive train? Please explain.

 

Think of it this way...Your torque converter is what allows you to sit still at a stoplight without stalling.
Without this "fluid coupling",the clutches in your trans.would fry in short order if the necessary slippage was accomplished through them.

 

[updated:LAST EDITED ON 29-Dec-02 AT 11:44 PM (EST)]It was working as designed.

If you only held it at 2000 RPM for a couple seconds you should be fine as is.

If you want to learn more about an automatic transmission and torque converter head over to www.howstuffworks.com They have a very good explanation complete with drawings and animations. It's very good.