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Discussion Starter #1
I haul a large truck camper 24x7. It is around 4k pounds. The truck is a 2001 Lariat LE, DRW, 4x4, 7.3L with a build date of 02/01.

Within the past couple of months, I noticed that when I am on a hill and try to back up, sometimes the truck would roll forward, and I would have to hit the brakes and give it diesel to get it to go backwards up the incline.

Recently, it not only behaves as mentioned above, but it is now slipping(?) out of reverse regardless of the incline. Its like its getting pulses of fuel as it goes backwards and in order to get it to move at all, I have to press the pedal pretty far down. The truck has a hard time going backwards.

A week ago, I was driving on some hilly terrain and my O/D light started flashing. I stopped, turned off the engine and checked the fluid level. When I started it again the light was off. It did seem to choke a little going from first to second the fist time after I started it, but that is the only time I have ever noticed any tranny problems other than reverse.

I went to a shop and had the codes read. P0781: 1-2 shift error and a turbo pressure error. I expected the turbo because I have fuel/oil in my valley.

Now, my plan of action is to service the transmission and see if there are any metal bits and how dirty the fluid is. Is this a waste of time with this error? It hasn't been serviced in at least 20k miles. I would also say that about 1/3 of my driving is on dirt roads. Someone mentioned a possibility of dirt holding one of the valves open....

Next problem: The tranny was replaced by the previous owner. How can I tell which tranny I have? The dipstick saws to use mercon, but all of the write ups say to use mercon V in a 4r100. Which is what I imagine I have.
 

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Discussion Starter #2
By service, I mean drain the pan, pull the pan, change the filter, clean the pan, put in a new gasket, and possibly flush the system using the method described in the FAQ. I say possibly because the whole idea of draining the tranny with the engine running freaks me out a little. I am unable to locate a new drain plug for the torque converter, so I am going to skip it.
 

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So I serviced the tranny and the fluid wasn't pretty. I wont ever let it get like that again! I am going to change it again in a few 100 miles. Also, there wasn't a great deal of metal on the magnet which is good. Reverse is still acting weak. I am going to try the 2000 mile trek to the states. Wish me luck!

Oh, btw this is a remanufactured ('03) tranny that was rebuilt in '07.
 

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Discussion Starter #4
I made it out of Alaska and have been driving for a couple of months without any catastrophic problems. I still have trouble with reverse slipping(?.. no power/movement) when trying to back up an incline.

I now have a chance to get a tranny out of a wrecked 01. I am going to go talk to the guy and check it out tomorrow.

Before I do, I was wondering what else I should do to diagnose the issues. So far, I have only changed the tranny filter and changed its juice. Are there any sensors, cables, harnesses, etc that I should look at?
 

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Make sure the fluid level is about 1/4 to 1/2 -_______above the full mark.
Draining the tranny with the eng running?????? I think you misundertstood someones insructions.
You don't need a new drain plug for the tc if it has one in it. It's a 1/8 pipe plug, just tighten it up good when you reinstall it.
mercon...mercon V...or the new sp which is synthetic, all are ok. I wouldn't put the sp in it if you're haveing a problem, would b e a waste of money.
 

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Discussion Starter #6
Thanks for your reply. My tranny fluid was full before and after I changed the filter.

Step 5 and 6 on this page says that you run the engine.

I used mercon V.

I wont be getting the tranny out of that wreck. It turns out the truck is older than they thought.

Any more clues on trouble shooting vehicle that has a week reverse? Thanks!
 

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I really doubt it's going to be pretty... I never even checked the codes before I started my rebuild, didn't have to (or know that I could). When something like that is happening something is giving up the ghost inside your transmission. Mine was doing the same thing only in forward. Low and reverse use the same components, when I got into my transmission, and got down to where low and reverse are at (in the back) I could easily turn the transmission in the forward direction (direction it was slipping) but in reverse it was very stiff. I got into it further and had two ugly thrust bearings and some worn out clutches.

it is possible that your transmission has something caught in a valve ball, But after this much time it would be either embedded in the ball permanently or would have worked it's way out.

I've got a thread up I just started called

" noob transmission rebuild... for the poor man "

It's not that bad, and if yours is still running then when you get where you're going you might want to give it a try. Worst thing you can do is break it, and it sounds like it's already broken...
 

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Discussion Starter #9 (Edited)
I am finally getting my transmission replaced. I should have it back today... I hope. Thanks for all of the insight. I would have loved to have tried the rebuild myself, but I don't have anywhere to do it. It's killing me knowing that my baby is in there with all of those men who are doing who knows what. Is your rebuild still going strong?
 
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