48RE Acting Up-Please Help!

[DaveHess]

Here is the Readers Digest version. The transmission (48RE) in my 2003 started hanging up in 2nd gear. Not shifting to 3rd unless I stopped and shut the engine off and restarted it. Then it would straighten out for awhile. I ordered a new GM Solenoid and housing for it along with a new transducer from my local dealership. Replaced both along with gasket, filter and fluid in April and it worked great. Fast forward to last week. We pulled our 2005 Jayco Eagle from Bismarck, ND to Hill City, SD via Rapid City. Our gross combined weight is 17,080 pounds. For those who have pulled through Rapid City, Hwy 16 through rapid on your way to Hill City is a long uphill pull that starts out with a lot of traffic lights in Rapid. The ambient temperature in the city that day was showing 91F on my overhead. The water temp was a tick over the 200F mark and the trans temp was showing about 195F (my probe is on the outbound fluid line) as we made our way into the city. By the time we started to climb, the trans temp was about 220F and within about 5 miles she skyrocketed to 280F. I was towing with the O/D off but could not get the converter to lock-up. Having nowhere to safely pull off we continued on up the grade at about 45 MPH. When things leveled out a bit, the converter locked up and the temp started back down. The rest of the pull was uneventful. Two days later (no trailer!) while on the Needles Hwy, the trans hung up in first but eventually shifted to second. I was again driving with the O/D off. This highway has some 400 turns and curves and ups and downs and eventually the trans temp began a steady march back into the red again. Eventually it settled down when the road settled down and trans was able to go to 3rd and lock up the converter. On Sunday we drove back to Bismarck and the trans performed flawlessly with temps never breaking 200F. Most of the time hanging between 180 and 200F. At this point I had decided I was going to do another fluid change when I got home just because of the two 280F readings. After placing the Jayco in storage and pulling the pickup away from the trailer, the trans again hung up in 1st gear. This time though the RPM went to about 2200 RPM and it felt like the transmission literally dropped itself into 2nd gear. It did the exact same thing shifting into 3rd and 4th. The converter locked up as normal. Nothing like the smooth shifts I normally experience. It did this same behavior at every stop light. Even downshifts were extremely pronounced. I have never experienced that before and I have owned this pickup since new (11 years). I took it straight to my shop and parked it. I pulled the stick and checked the fluid while it was running in neutral and it was right at the full line and although I know it is not an indicator like the old days, the color is still red on my skin. I did not state this above but I have read posts about bogging the engine so usually at 55 MPH (approx. 1600 RPM), I turn the O/D off when towing. Once I get the speed back up about 60 MPH, I will turn the O/D back on. I don't know if this practice is necessary with the 48RE or not but I read too much sometimes. Also, the check engine light never lit. Neither did the transmission overtemp light! Not a peep from the dash at all. BTW, the Smarty Jr is set on tow.

So, I am wondering what you all thought. Given the two overheat conditions I induced, I was wondering if the transducer is no longer functioning correctly and is causing my harsh shifting now? Any ideas would be very helpful right now before I start throwing money at this problem.

Thank you for your time. Sleepless in Bismarck.

 

[BDaugherty]

While I'm no trans expert, I sure would change the gov psi solenoid and transducer again and maybe check the bands while you're right there at it.

 

[p-Bar]

you need to install the mystery switch to lock up that torque converter. It's scary having that trans temp on the hot side of the cooler as I do too. wait for Cerb to comment he's pretty boned up on these though I think BD may be on to something.

 

[DaveHess]

My first thought on the road was a fluid change at a minimum and then after the shifting started acting up, my suspicion went to the solenoid and transducer. I find it interesting that the pickup towed excellent even in those hot conditions and then waited to have it's shift issues AFTER I parked the TT. And even then she didn't strand me. I had to limp it back to the shop about 7 miles away but she still didn't leave me on the side of the road. I know this makes me somewhat of a freak but I have been into cars and trucks since I was a toddler (old photos) and to me a vehicle like this pickup is not just a vehicle I own, I have a relationship with it. I take care of it and it will take care of me.

I talked to Jeff at Goerend Transmission yesterday and he sent me a wiring diagram for the mystery switch. Being that I have never used one before, I asked about the proper time to use and not use it, basically how to use it. The answer was very vague and did not give me a warm fuzzy. I need to understand how to use the switch controlled lockup before I will attempt the mod. In the situation I was in on the grade in SD, I understand that I could have locked the converter with the 48RE in second gear and I would not have had the temperature issue. But in my mind, I am not clear as to what actions I would take to accomplish this. In other words, do I manually place the shifter in "2", then engage the mystery switch? Do I leave the shifter in "D", O/D turned off and then engage the mystery switch? And if I do this, and the transmission is in second gear when I activate the mystery switch, what will happen if the transmission feels it is time to shift to third with the mystery switch engaged? Below is what Jeff sent me:

"Hi Dave, some folks like to lock the converter when towing especially up a grade. You would be able to lock the torque converter manually in 2nd gear once you are moving if you are pulling up a grade. The valve body would have to be set up for this however. I hope this helps. Thank you"

My valve body is stock. It is on my Christmas list but life keeps getting in the way. I am hoping Cerb will jump in here with thoughts and recommendations.

Dave

 

[cerberusiam]

You have a 48RE, don't need to modify the VB to get lockup in any gear. Manually shift the trans into 1st or 2nd and flip the switch and TC lockup should engage. The TH button should not matter what position it is in when you manually downshift as that will lock OD. With no VB mods the mystery shift will allow lockup at any time in 1 and 2 and hold that gear. In D with OD off it will hold D (I think). In D with OD on it will lock the TC and immediately shift to OD. On a stock VB the TC lockup solenoid applied vents full gov pressure to the circuit and it will shift to the highest gear available so it is bets used to hold a manual gear or hold OD on a grade or dyno. One thing to remember is the shifts with a manual lockup switch are locked to locked, it never unlocks the TC like it should so under load and power the input shaft is in danger.

Something is not right as the trans should have gone into lockup mode with the OD off unless you had it floored. The lockup on an 03 is less aggressive than the later turcks but once you are up to speed you should be able to back off the throttle and get it locked then roll into the throttle and maintain speed. The GM style solenoid USUALLY fixes the solenoid problems of not reading right and setting incorrectly but the transducers are a total POS. Even the delaer stock has benn known to be bad out of the box or shortly after. To verify that takes a scan tool and gauges to match demanded against read against actual pressure so most times it is a lot easier just to chnage the transducer again.

What it is doing NOW sounds like either the TV pressure is maxxed out or the gov pressure is just not reading correctly to the ECU so it runs it to the limit and hard shifts it. When you have to shut the truck off to get fintionality back usually means there is some type of short or cross feed in the harness somewhere. The VB harnesses are good for that after time and then it starts eating transducers. I would get a new transdcuer and the VB harness and swap them both again just to get rid of that possibility.

The other thing you want to do is check the TV cable and make sure it is not jammed wide open. Disconnect at the trans and make the cable moves freely in the housing and make sure the lever on the trans moves freely cold and up to operating temp. The TV pressure valve in these VB's can go bad and cause all manner of problems if they stick, chiefly hang shifts and hard shifts when they do. If you feel ANY tight spot in the TV lever manually moving forward and back you need to get the Sonnax repair kit for the TV.

Some things to look at and check. Problems like this can be hard to track down so you have to work it from several angles to find the problems. Good luck with it.

 

[DaveHess]

I took it out last night for the first time since Sunday. Ran and shifted perfect. I am going to act on your advice Cerb and replace the transducer and harness. The transducer I have done. Is the harness difficult for a guy laying on his back on a concrete floor.....?

 

[cerberusiam]

My guess is you have a transducer that is flaky or a harness that is problematic when the truck warms up.

You have to drop the VB to do the harness as the connector is thru the case for the trans control harness. It is not the worst job to do on your back, a creeper helps a lot.

 

[DaveHess]

Thanks Cerb. I appreciate your time and assistance!

 

[DaveHess]

My local dealer's parts department could not figure out the part number for the wiring harness. I am going to completely empty the fluid and change the transducer. Here's to holding my breath.......

 

[cerberusiam]

Here you go. http://www.electricaladvantage.net/48re.aspx

 

[DaveHess]

Cerb... You are THE man! Thank you!