transmission problems?????

[ropinfool2]

Howdy all, Finally had a chance to load up the truck and put it to work. I hauled my 5th wheel, (11,500 gvwr, not weighing anywhere near that) a couple hundred miles round trip camping. Hit some pretty good hills and don't think the transmission is shifting right, but you tell me. Pulling a hill in OD, foot buried, speed holding at 65, ok, speed starting to drop, 60, transmission downshifts, ok that's what it's supposed to do, speed drops to 55 and transmission UPSHIFTS!!! Went from 2500 rpm to 1800 rpm. truck falls on face. My foot is buried. Pull my foot off and jam it back down and truck downshifts, ok, holding speed, after 45 seconds or so, upshifts again!!! WTF???? Reach the top of hill, ****** off now. Hit cruise and watch what it does, pulls the next two hills just fine but the 3rd hill doing the same thing, speed drops to 45 and it still won't downshift!!!! Was just getting ready to pull it into second manually when I see brakelights. Border Patrol checkpoint. This really has me stumped. I've never seen this before but have never pulled a load like this before. Is this what you guys are seeing????? Oh and I avg. around 9 mpg on the computer so it's closer to 7. I'll fill up tomorrow and avg it out. No SES light, haven't checked for codes using the key thing yet. Thanks in advance. John

 

[WoodChuck]

Are you sure it's upshifting and not just going into 3rd lockup?

 

[Bertram65]

The downshifting sounds normal, if I am running less than 2000RPM towing in OD or even sometimes above 2000RPM with a long steep grade it is very common for my truck to slow down on the hills even with my foot to the floor. I usually let off a little and take it out of OD manually, then at the top of the hill put it back in. Not sure what gears you have, I have the 4. 10s, 70 is a little fast which is 2150 RPM so I usually run slower, and have to take it out of OD on most long hills, 3rd is ok, I can still run 55 MPH, that's about as fast as I like to run in 3rd.

 

[ropinfool2]

First, no codes set and I avg. 10. 5. I guess that's not too bad compared to the 5 or 6 I would've gotten with the 460 I used to have. No I'm not sure what's going on, it could be the converter locking or unlocking, don't know. All I know is I've been towing for many years with quite a few different trucks and none of them ever shifted like this. This is the longest trip I've towed with this truck, and this is a two week old trailer that we just got. Didn't feel right to me. I have the 3. 73 gears. I tried locking out OD but didn't see much difference there either. I know I'm going to use this as an excuse to bomb it, I only hope that I can make it up the hills afterwards. I only tow around 65 mph (55 is the limit here) so I don't need much. I didn't see any smoke whatsoever, I figured to see some when I was really loaded up. Anyway thanks for the responses, I guess I'm looking to hear how your auto acts when you're pulling a long or steep hill. I know mine never shifted into 2nd. Thanks again. John

 

[Bertram65]

At 65MPH you are running right around 1800RPM, my truck is pretty gutless at anything below 2000RPM. I would imagine you will have to go to 3rd on anything but flat ground with the 3. 73s running at that speed.

 

[ropinfool2]

Ok, I can see needing to stay over 2000 rpm, the point I'm trying to make is I couldn't keep it over 2000 for very long. It kept shifting (don't know if it was actually shifting gears or locking/unlocking the TQ) and dropping my rpms out of the power band. Even with the overdrive locked out. I would have to take my foot out and put it back in to get it to "shift" and then that only lasted 45 seconds or so until it "shifted" again. I didn't see what difference the overdrive button did, seems pretty worthless. Thanks for the reply. John

 

[ropinfool2]

Ok, talked to the local Dodge transmission guy and this is what he told me. If you leave the OD engaged while pulling a hill and it downshifts to drive, it monitors transmission temp, if that raises more than a set amount (not enough to set the transmission temp idiot light) it will shift back into OD and lock the converter in order to cool the fluid?? I guess it sounds feasible. I will start turning the od off the first time it shifts down and see what happens. John

 

[TCDiesel]

Ok, talked to the local Dodge transmission guy and this is what he told me. If you leave the OD engaged while pulling a hill and it downshifts to drive, it monitors transmission temp, if that raises more than a set amount (not enough to set the transmission temp idiot light) it will shift back into OD and lock the converter in order to cool the fluid?? I guess it sounds feasible. I will start turning the od off the first time it shifts down and see what happens. John

If This Happens and RPM"s Drop ,EGT"s Will skyrocket,The Stock lockup Clutches Will not hold,Also the engine will fall flat on it face,Try to keep RPM"s Above 2000 ,RPM"s Are more important than speed,No lower than 2000 and no higher than 2400( unless you want to race up the Hill) In OD ,drop to 3rd around 2000. This will Put you around 45/52 MPH TC will stay lockup and engine should pull out and speed should gain, When safe and RPM"s around 24/2500 return to OD.



If 3:73 + 10,000 LBS + Hills = flat on face.

 

[WoodChuck]

If This Happens and RPM"s Drop ,EGT"s Will skyrocket,The Stock lockup Clutches Will not hold,[/QUOTE



On a bone stock truck? I would hope not.

 

[Bertram65]

Ok, talked to the local Dodge transmission guy and this is what he told me. If you leave the OD engaged while pulling a hill and it downshifts to drive, it monitors transmission temp, if that raises more than a set amount (not enough to set the transmission temp idiot light) it will shift back into OD and lock the converter in order to cool the fluid?? I guess it sounds feasible. I will start turning the od off the first time it shifts down and see what happens. John

That would make sense for the older Dodge automatic but not for the 48re. The 48re has 3rd gear lockup so there is no more heat being produced when it is in 3rd with the TC locked up then when in OD.