Hi folks,

I was hauling water up a dirt road. Incline probably exceeded 20 degrees. And had 2000# of water in my f150 truck, so over design limits. If my sig doesn't show it, I'm driving a 2013 F150 stx 4x4 5L 6r80 trans dash activated 2h/4h/4l transfer case with a locking back axle. Everything has been working fine until today. I use 4h often and 4l almost once a month.
I'd almost reached my destination when the truck locked up on a straight section and wouldn't budge. i dumped the water.

I borrowed a 350 4x4, parked it uphill of my truck and chained them together. Tried to remove the driveshafts but they were tightly bolted and couldn't get them loose. Moved the 350 to below my truck and _slid_ mine down to a nearly level spot with a chain.
Unhooked chain. Started my truck and was able to back up in 2wd. Tried 2wd forward, heard 3 loud clunks then silence while fwd a few more feet.
I'm guessing my tfr case needs to be rebuilt as a minimum. Have not checked fluid level or condition. i think my mechanic changed the fluid 80k miles ago when i bought the used truck. (130k now)

Can anyone instruct me what probably needs doing?
Thanks in advance

 

It almost sounds like the chain is stretched in the case or possibly even broke and just wedged itself in to the gears and locked everything up.

 

2000 pounds is heavy for payload (suspension, axles, tires, body, frame), but not heavy for forward drive motion (transmission, engine, drive shafts, cooling system, transfer case). If the vehicle can *tow* 10k with properly configured WDH, the stress of hauling 2k worth of water shouldn't be the straw that broke a *healthy* camel's back. While I wouldn't suggest that weight was not a factor, there had to be other factors such as a defective part, long term abuse, or just really bad luck.

 

Its not bad to replace it yourself, you can pick up a used transfer case for a couple of hundred. After you add in all the single us bolts and the fluid maybe 4 bills depending on the deal you got on the transfer case. Yea they are used so your rolling the dice - but it will be better than yours is right now. Need normal set of tools and a floor trans jack will make it much easier. Rebuilding it get expensive and new ones are well - really expensive.
Here is the one I replaced. Just me and my son (no lift) and started with a crappy trans jack and junked it for a real one.

https://www.f150forum.com/f38/yet-an...-happy-568001/

 

It does appear that my truck had been used to haul stuff that damaged the bed. The back wheel wells were damaged and there was an imprint of something 3 or 4 ft wide that hit the top edge at the front of the bed. The dealer covered everything with a cheap plastic bed liner. I did notice the damage inside the wheel wells before purchasing.

So no telling what the truck had been through when I bought it. I've hauled quite a bit in the bed myself, on dirt roads at low speeds.

Thanks for your input. I've never had a transfer case go out before so you've been helpful.

 

Latest results:
I had it transported to a local gear and transmission shop. They wanted to rebuild the transfer case. I would have just asked for a reman replacement. My thinking was that a business that does only remans would be more efficient at rebuilding them.
Despite my thinking, I let them rebuild it.
I'm out of state today.(More about that in another post.) They called me and said there was nothing wrong with it except being a quart low. They wouldn't let me pay anything!

But I'm worried about this happening again. I was lucky where it happened because it was at a spot that let me maneuver a borrowed 4x4 f350 above it and below it. There is a 3,000 ft section of the dead end road i use where i would not be able get around it if the truck locked up there.

So not the result I hoped for, but it was good news as far as that goes.

 

It appears that I may have misread the situation.
My 6r80 transmission has given me some trouble. It may have been stuck in a high gear and the load was too great for such a steep incline.

Several times the speedometer has dropped to zero and the 6r80 gets stuck in a high gear. Sometimes pulling off the road and turning off the ignition, then turning it back on resets conditions somehow and the 6r80 resumes normal operation.

I am not certain what triggers this problem. I supposed that the wiring to the back axle sensor may have an intermittent connection. Thought about making a new pair of wires to see if it solves the problem.

But reading in the forum suggests other potential causes. (My mechanic said that the fluid is full and looked good.)

It seems some members have written that the speed sensor is in the leadframe. Others say to check and clean the electrical connections.

I have also had the truck after driving 20 miles at 60mph, then parking it and let it sit for 30 minutes. When attempting to drive it again the 6r80 was stuck in first gear. This and other issues was why I took it to my mechanic. I thought it might be low on fluid, but he says it isn't.

It has done the stuck in first gear routine twice. It also is doing the speedometer to zero and stuck in a high gear more frequently.

I'm disappointed that my truck no longer seems reliable.

Edit: my 2013 f150 5.0L 4x4 STX has 146,000 miles on it now.

 

@Dazing What you have just described is CLASSIC lead frame failure symptoms. The sensor in the top of your differential housing is for the E-locker. Not the speed sensor. The speed sensors are internal to the transmission and are part of the lead frame. Have the lead frame replaced. As well as the transmission bulkhead connector, get a new trans gasket and filter. While you're at it, research on the forum the "bulletproof trans cooler line mod" and do that as well. Or if the money allows, replace the trans cooler lines with OEM. If the cooler lines burst while driving it will pump out ALL of your trans fluid in a matter of a couple minutes at idle. a matter of seconds at speed. they are notorious for breaking with age at the quick connect in front of the rad support. Mine snapped within days of the lead frame replacement just because they got disturbed and bumped/moved around/etc while the other repairs were being made. I was lucky that mine broke in the parking lot at work. So refill with fluid and no major damage done to trans.

After these simple repairs, your truck will once again be just as reliable as it used to be.

 

@MPETE
Thank you for the very helpful response!

 

No problem. Glad to help. Hopefully you're back up and running soon.