Truck stalls in reverse as soon as I switch from park to reverse well I'm holding down the brake.
In drive it bucks like crazy, wife almost couldn't stop when she braked and it happen the first time.
It happened out of no where!!! No slipping or anything prior to.
Thanks in advance for anyone who can help!!!

 

Low trans fluid will cause this.

 

If that isn't it, then your torque converter clutch must be staying locked due to either a electrical, mechanical. or hydraulic failure.

Steve

 

Yeah, it sounds like the torque converter needs to be replaced.

Darrin

 

Perhaps, but he would do well to determine WHY the TCC is staying locked, since that could be a problem in the valve body, wiring, PCM, etc...

Replacing the symptom without diagnosing the underlying concern is not a good idea.

Steve

 

Of course. Sometimes I don't have time to make a big long post and I forget that you guys don't know me very well here. Today I have time.

I always preach that you don't replace any major component relating to the transmission that has failed without going through the rest of it. If the converter failed then the transmission needs to be gone through and vice versa.

I think it's going to be found that it's the torque converter because otherwise there would have to be multiple failures to allow lockup in reverse or first in these transmissions. First, the valving in the valve body prohibits lockup. But lets say that failed and is stuck in position to allow it. Given that, then either valving to allow lockup would also have to have stuck in position to allow flow to the lockup piston, the TCC would have had to failed open, the computer failed providing constant signal to energize the TCC or there is a short in the wiring causing the TCC to energize.

On diagnosis. If there was a serious electronic failure like a short or problem in the PCM then there is likely going to be a code for the failure. If there isn't that then we can almost eliminate those things. Keep in mind that I said almost. But if that did happen then we would still need to have stuck valves. That is most often caused by debris and that would most likely show up in an inspection of the pan and fluid. Then of course, the TCC can fail. If that is the problem then we still have the stuck valving and need to look at the pan and fluid. Lets just say that it's stuck valving alone. Again to the pan and fluid. If there is either certain telltale stuff in the pan or the pan and fluid look good then it's likely the torque converter.

Again, to me, it sounds like the most likely thing is that the converter has failed and needs to be replaced. At that time, any respectable shop is going to examine the transmission and related systems to see what the root cause is. If you are a do-it-yourselfer, then start by looking at the pan and fluid.

Darrin

 

I have never seen a 4r70w converter hold lockup unless it was completely destroyed. If that is the case you will need a transmission as well. I vote pump or pressure regulator problem. Reverse uses the maximum line pressure. If the pump is worn out it will put a strain on the motor to try to make enough pressure. That could just be in the pressure regulator valve.
Alan

 

Thanks to everyone's feedback. Let me supply a little more info.
In park, engine runs perfect...I press the gas and the truck sounds good. There's no check engine light or any other warning light on!
I can go in reverse really quik, if I switch to Reverse and bearly touch the brake and let it go quickly. Not sure if that will change any of your feedbacks.

Tranny fluid looks good. I only checked via the dipstick so far.

I'm not a major DO-IT-YOURSELFER. I can take care of the basics and I don't mind getting into the intermediate level repairs or troubleshooting.
With that said Do you guys recommend me getting it towed to a Ford dealership or should I take it to a regular mechanic or do you think I'm capable of verifying or reparing it myself? I just bought the repair manual on CD last week. It should get here in a couple of days.

Once again, Thanks to everybodys feedback in advance. You guys are great!:

 

do it right the first time...get it towed to ford...if you try to do it yourself you will only mess around and screw somethin else up lol and if you take it to a mechanic...ohh believe me i know i am one...they will jack around and take weeks on it...im not sayin ford wont take a while on it...but its your choice.....ill never take my truck back to the ford place here..once my tranny was startin to mess up and i took it to them...know what they said?!???!?? we cant find the problem we recommend a brand new transmission...i was like psh! so i took it to a tranny mechanic and told him i NEEDED it to be fixed today..he hoped in drove it for a couple miles came back told me what the problem was and fixed it in a few hours

 

Ok, I would love to hear how a worn out pump puts more strain on the engine trying to make more pressure.

First of all, there is no feedback device from the transmission to the computer to show line pressure and the pump hasn't got it's own processor to know that it needs to make more pressure. Nothing is there to tell the pump to work "harder". Next, a worn pump that is working against less pressure will turn easier than a good pump that is working against the proper pressure. Finally, and you should at least know this one, the pump is splined directly to the converter hub. Therefore it can't "work harder" at all on it's own. It can only do what it can for the rpm that it is provided. It can't turn faster or "harder" than the engine under any circumstance.

Now, if the pump was all beat to heck and not able to turn then that would be a whole different story. But saying that a worn pump that can't make enough pressure and will cause the engine to stall is just flat backwards. A worn pump will let the engine turn more freely if anything.

And, so what on full line pressure? Do you have any idea how many shift kits max out the line pressure at all times and don't have that problem? Also, do you know what the computer does in 'limp home' mode?

Maybe you should get out that book you have laying next to your computer that you use to help people answer their questions and read it cover to cover to learn what actually goes on to make these transmissions operate.

Darrin

 

If I had a book beside me I would put it down. I'm actually in the air conditioned house and the books are in the shop.
Line pressure is in part controlled by the pressure regulator valve and the epc solenoid. If the pump is worn it will produce less pressure. This will make the pressure regulator valve attempt to increase that pressure. More pressure being generated by any pump will require more load on the part that drives that pump. Not 4r70w specific, merely basic hydraulics. Despite the fact, go cut open a 4r70w converter that is causing full lockup all the time. Unl;ess the converter is completely destroyed it cannot do this. The single plate design doesn't work that way. A 4r100 triple plate is a different story. Besides the fact that the flow to the converter when unlocked comes in through the input shaft forcing the lockup piston into the off position. If the lockup piston was truely jammed there would be little or no flow. That is another thought however. A restricted cooler could cause this problem. That would be signs of severly damaged transmission and converter.
Alan

 

But you didn't answer my questons.

How about the kits that max out the line pressure not having this problem and what does the computer do to line pressure in limp home?

Wouldn't those conditions cause this problem if what you are saying is the case?

I don't know what it is long distance, but I can darn sure guarantee you that it isn't simply a worn pump and it isn't the pressure regulator valve telling the EPC to give more pressure.

You obviously don't know what the pressure regulator valve does and how it works. Back to the book with you. If you don't have it in there with you then you might want to go get it and start reading. I see that you did because you got the names of the parts right.

You didn't get the operational basics though. The pressure regulator valve cannot call for more pressure or attempt to regulate a low pressure condition. All it does is bypass fluid back to the pump to control max pressure. It's like a blowoff valve.

The computer is what controls line pressure by opening and closing the EPC and the programming directs that. There is nothing to measure line pressure in these transmissions to feed back to the computer and the computer is the only thing that can tell the EPC what to do. Therefore, neither a low or high line pressure scenario will cause a fault and the EPC won't be directed to do anything to correct it because the computer has no idea that it exists.

Anyone working on these transmissions should know at least that much.

Darrin

 

Hello All, thanks again for all your feedback.
I had the truck towed to Ford dealership last week. They stated that they dropped the pan and found metal shavings. Per Ford, my two options were a rebuilt tranny for $2600 or for them to begin troubleshooting the repair of my existing tranny would be $800. Luckily, I spoke to a buddy and he mentioned to me that an acquaintance of ours had a transmission shop.

I paid Ford their $88.00 for the inspection and had it towed to the Tranny Shop. Mechanic broke it open and didn't find any shavings...maybe Ford cleaned them out I don't know. Anyway what he did find was that the torque converter was so worn out that a piece of it broke off and it damaged other items in the tranny. Therefore, I had him rebuilt the entire tranny per his recommendation. He charged me $1400, everyone said that it was a good price.

Per the mechanic, after the rebuilt he was still interested in why this occured on a truck with ONLY 65,000 original miles. He stated that he went through two sensor solenoids at the tail end of the rebuilt. His theory is that the computer is bad causing the solenoid to over heat, in which caused the torque convertor to work overtime. He's going to look for a salvaged computer tomorrow and replace it.

My question to you Experts is, "Does this all sound legit??"

He's a good guy and I trust him. I would just like a second, third or fourth opinion.

Once again thanks for all your advice and feedback in advance. :o