Wide open throttle when put in Drive

[HHhuntitall]

Then I have some great news for you, a 47\48RE is nothing but a beefed up 727 with an OD on the back.



The OD is dead simple in how it works all the way thru. Follow the same procedures as you would with a 727 and you will good to go. The ATSG manuals will get you up to speed on the differences quickly.



The governor solenoid\transducer and the lokcup\OD solenoids are the only electrical parts in the trans and they are dead simple in operation. Their operation is completely controlled by the TCM. Keep things clean and its good. Shift kits are a little different but most of them detail the changes well.



In this case it probably doesn't need a rebuild if the pan looks clean. The sprag will a lot of times lock and not spit any fragments out. Swap the TC and good to go.

Aww, heck!! I've never really looked at the service manual..... I'll be... I see tools I don't have, though. Lots of tools I don't have... ...



I thought the newer trucks had a much different transmission. I've never pulled one apart. I've looked at a few, but never pulled it apart. With the overdrive units I know the springs make it "difficult" to service.....



On the transmission I got called on, it seems the clutch is locked up, in my opinion. Shifted to neutral, it acts fine, drives fine on the highway... put it on stands, engage the transmission and the speedo goes to 45 in just a second.....



Sounds like you've had your's apart a few times...

 

[cerberusiam]

Aww, heck!! I've never really looked at the service manual..... I'll be... I see tools I don't have, though. Lots of tools I don't have... ...

If you have the basic tools to do a 727 you pretty much have all you need to do a 48RE. A lot is just attention to detail and getting the clutches aligned in the packs, as usual.



The OD direct unit comes out of the OD case in 1 piece so its not a big deal to disassemble the bulk of the trans. Take the assembly and put it in a shop press to relieve the spring and get it apart. You could use a big arbor press if your careful. As long as you have the leverage to compress 800 psi and hold the unit your good.

On the transmission I got called on, it seems the clutch is locked up, in my opinion. Shifted to neutral, it acts fine, drives fine on the highway... put it on stands, engage the transmission and the speedo goes to 45 in just a second.....

If the clutch was locked via the lockup solenoid it would kill the engine NOW when put in gear. Once the solenoid engages it forces the trans to shift to drive and stay there. At an idle it bumps the rpms a couple hundred then dies. Ask me how I know this.



Typical problem with the stock TC is the weak parts internally and the failure of the sprag just gets more common the older they get. If its a reman TC from Dodge its even mor elikely to happen because they changed something in there and these faulres got more common.

 

[Mhannink]

It's only going to full load, the rpms are not spiking. It does it in forward and reverse, and is not throwing any codes. A short would throw SOMETHING, as it would eventually overheat and short the PCM or TIPM. I have seen quite a few failures in the TC and valvebody, especially after 60-100k miles. Stamped or cheap parts are typically the problem I've seen. I don't work on the auto's very often, mostly because the cost of the scanners, tools, and the vast and endless possibilities... ... That, and lack of experience with the newer autos. If it was an old 727... . no problem!! I'd have it torn out, overhauled, and put back in two days!! But the newer trannies have grown in complexity to the point you almost have to have a designated shop to tear into them. I can't keep all the new tools, along with all the new tools for the engines I have to buy, scanners, programs, parts, payroll... . "The Everest... ... the Everest never ends!!" (the Grinch)



With little description, Cerebrusiam has nailed it's characteristics. It works fine once you get down the highway, just stopping can be difficult. N works great.



I've been over it front to back last night; I can't find any bad connectors, frayed/rubbed wire loom, and I threw every sensor code there was unplugging and starting, trying to figure it out. I didn't dissconnect the APPS input wire, as the connector was difficult to seperate, and appeared "iffy" to take apart... .

ok i misread the original post i was under the imperssion it was going to full rpm and reading full load. but just reading full load yeah the tc makes sense.

 

[cerberusiam]

also if it does use the apps which it could its going to look at the voltage thats how it knows the postion and if the voltage is false aka short to power then it will rev the engine up and read engine load with out a code. hook up a scanner and in neutral hammer the throttle. it will say engine load is 75 plus percent if not 100. as for the computer voltage and apperage throw codes. thats how it knows if voltage or amperage is high or low it throws a code. however if you have a short to power it might not throw a code as long as voltage is correct it wont trip the comp.

Electronics don't work that way. Too many fail safes built into to make sure its does NOT run away at any time.



The ECU sees no amperage, it can't handle it. Everything the ECU monitors on is on the back side of the circuit behind the load. Its looking for voltage in certain ranges and most of all constantly check resistance. If there is a short resistance immediately goes low and the ECU shuts the circuit down.



Generally anything under 5 ohms causes a no run\start or limp mode. Anything over 100 ohms cause a CEL and depending on what circuit limp mode. Low resistance is a short, high resistance is a break or bad component. Wait til you get a dead one and find that unplugging the fan will restore functionality.



The ECU will shut down communications on the bus and go into safe mode with most shorts on components. Its protecting itself from the amperage. In this case everything is good until the trans is put into gear. Nothing wrong elsewhere and no codes. As soon as gear is engage the load starts and with no wheel speed the ECU knows no better, it can't sense what the trans is actually doing.



If I were doing this for a living, I would be at every electronics and engine control school they had because darn few have figured out how to troubleshoot these things consistently yet.

 

[HHhuntitall]

So, with the broken sprag, it doesn't lock up the TC clutch, it's just locking the stator in the impeller?

 

[cerberusiam]

So, with the broken sprag, it doesn't lock up the TC clutch, it's just locking the stator in the impeller?

Its locking the stator so it is trying to turn as fast as the impeller, result is no flash stall now.



The sprag release below a certain rpm of the TC to give it slip at a stop. As the rpms come up the sprag engages the stator to start the fluid coupling working.

 

[rscurtis]

You may want to revisit that statement. The stator is locked whenever there is a significant speed difference between the pump and the turbine- it is locked when the truck is idling in gear. It has no mechanical connection to the pump or turbine, its only connection is to the stationary stator support on the nose of the transmission. As the load on the converter is reduced and the flow between the pump and turbine slows down, the stator begins to rotate with them through the sprag clutch. Unlocking the stator at idle (even if you could) would have no effect, as the turbine element is also sitting stationary at that time. The only way the stator is going to lock up the converter is if it completely fails and the pieces get lodged between the pump and turbine elements.



Page 21-439 in the 2003 service manual explains its operation.

 

[Bob4x4]

Ck the torque convertor. If it wants to lock up and drop rpm below idle the computor will try to keep it from stalling

Wow 2 pages and still the same :-laf

This is not that rare,if you had access I am sure if you did a search in the star archives you would see a few of these cases. I have seen a half dozen or so myself first hand

 

[HHhuntitall]

... or the sprag clutch fails and locks up. I don't have much experience with lockup TCs. The old TCI "Conservator" convertors had a similar design, with a lower rpm lockup, but they functioned with a regular 727 transmission. But, now, if the stator or sprag gear were to break, could a piece be lodged between the piston and the thrust washer assemble, or perhaps between there and the impeller?



And let me ask this... . if the transmission were higher mileage, say 178k miles, and the pump was weak, and the clutches in the TC worn, could it be that the TC is trying to lock up and not killing the engine? I haven't had the truck back to check transmission fluid temp or fluid pressure test. Are the pressure ports 1/4in Pipe thread? O-ring?



As I said, I don't work on auto trannies very often. This is the first I've had that was doing this. I've seen the E4ODs that have done it on gas rigs, but that was a valving situation, and wouldn't do it in reverse. And they didn't make the truck go to full load when put into drive... ...

 

[cerberusiam]

You may want to revisit that statement.

Technically, your right the description is likely incorrect. Functionally its close enough to demonstrate what the sprag does and the results when it locks. Been too long since I looked at the function and the correct part names.



Could be a thrust washer\bearing failure and something, sprag or other piece, is jammed. The sprag failure is much more common but washer\bearing failures happen also.



The lockup finction is completely under control of the ECU and initiated out of the VB. I would hazard a guess anything that would cause it to try to lock at an idle would also exhibit other strange behaviuor, and, it will never activate at 0 wheel speed.



Test ports are 1/8 NPT, IIRC. #3 is going to give you line pressure. #2 is the gov pressure which are the 2 that will be pertinent at that point.



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[HHhuntitall]

Right, I got the locations and pressures out of the service manual, I was wanting to know the thread size to see if I could do it with what I have around here. If it's NPT, I can do it. I've got several guages that go up to 3kpsi for hydraulic operation, though I know 300psi is the spec on these. I've called the guy twice now, but no return call, so now the subject may be null, except for my educational purpose and curiosity. Thanks for the time. I do have one '06 "slush-o-matic" (as my grandfather always called it!) in the fleet, so knowledge is power, I guess. I also happen to have stumbled across an another '04 that needs a transmission at the moment..... might could end up with it reasonably priced.....