Hi, all....

Been full-time RVing for the past two years, hauling an 18K-pound fifth wheel. Just went over 72K miles, and the 48RE seems to be heading south. Overheats on even the flat roads when the ambient temps go over 80-degrees.. I usually bring her into 2d gear on the steep grades, and now it is in the habit of slipping out of gear, overspeeding the engine (3500 rpms) a few seconds before grabbing hold. A few scary times when I've taken an off-ramp, expecting when I selected 2d to have the engine slow me down, but much of the time, now, after a hard grade, I feel no change in the engine, as if I don't even have a second gear. Same when I select 1st. Have to use the brakes alone. And because the rpms are so low, the jake doesn't do much, either. Once off the highway, it's real slow to respond to the throttle, as if there is too much slip, the gears won't engage, and I have to rev it up real high to get it to move at all.

Took it to a dealer who found a loose band in the tranny. Tightened it, changed the filters and fluid and said I was good to go. But when I got back on the road again, the same problems occurred. Threw away about $500 there. The guy swore there wasn't a problem with the torque converter.

Here's what I don't understand. When we first got this thing, we'd routinely drive long days up and down steep grades with outside temps well over a hundred degrees and experience nary a problem. A real workhorse for more than two years. We were religious about changing the filters and fluids. What could have changed in this thing? Why would a tranny suddenly start overheating, even when we're traveling on straight, flat roads? And what about the slipping gears? Could this be a TC problem?

Thanks in advance for any ideas that might help me understand this, and, if possible, help me to ask the right questions when I take this in to a tranny place. Cheers.

 

Just a long shot idea but have you inspected the trany coolers to see if perhaps one of them is covered in dirt or debris and not cooling properly?

 

if the TC is slipping or lockup not engaging under heavy loads, the trans fluid temperature will skyrocket...

 

I have the exact same setup as you except for the jake. One thing I have been doing when accelerating is to let off the gas pedal at about 50 mph and let the converter lock up and then start accelerating again. Doing this I'm hoping to save wear and tear on the tranny and help on mileage. I do the same thing so it will shift into third and lock up sooner.

I'm figuring the sooner it locks up the cooler it will stay.

 

Okay, so three possibilities: dirty tranny cooler(s), the TC...and/or lockout not engaging...I'm heading to a tranny shop tomorrow, and I'd like to have some idea of what might be going on. Thanks... And I'll give the shifting routine a try as well. Many thanks.

 

Sounds like you have several internal problems that are contributing. A tear down and rebuild is your best option at this point.

As a guess, the direct clutch pack is probbaly toast plus there is excessive leakage on 1 or more seals causing the low pressures and the lack of engagement at times. More than likely slipping the TC with the low pressures and quite possibly warped the TC cover with the excessive heat.

With the weight you are towing there are 2 things you really need, a good multi-disk billet cover TC and a shift kit or custom VB to get the line pressures up and hold the power. A billet band strut and front servo cover will also help a lot to minimze leakage and other problems.

A good solid build with new thrust wahers and setting clearances is warranted also. A billet input shaft is your choice. Depends on how much you want to spend, but, a good rebuild with stock other than I listed would serve you quite well.

Good luck.

 

72K miles is good service life for a trans used hard like that.

I agree with 6.0 above, get that thing torn down and rebuilt if you can afford it. I'd go with a full build from a reputable builder. My priority would be to get a stronger flexplate at the same time, input shaft optional.

 

There should have been telltale indications when tech did service. Converter would leave a brown mess (clutch material or metal) in pan. Burnt low or direct clutch should have left a black mess in pan also. The band is shot if adjustment threads are inside locking nut, PERIOD...
Look at coolers/radiators for bugs and dirt blockage.
If the fluid (when changed yesterday) was a normal red and no significant material in pan or on filter, then unit needs the gov pres trnsducer and solenoid package. Replace the output shaft RPM sensor on extension hsg for good measure also.
I assume the speedo is not also messing up as you made no mention.

 

Do the input before the flex plate. If the input goes its taking a few other parts with it and requires the tranny to be cracked open. The flex plate is the easiest and cheapest part to replace.

 

Exactly, I would not even worry about the flex plate unless I wanted 600 hp and planned to do racing and/or pulling. The stock plate is plenty beefy and mated to billet cover converter they are even better as long the bolts stay tight.

Doing a VB the right way for towing with a triple disk TC will also impact your parts life. They don't need to slam shift to work well and last a long time. Way easier on shafts and flex plate if the shifts are firm not violent.

 

Okay. I've got the service info; they make no mention of anything burnt in the pan, and no unusual debris. Codes indicated a need for a forward band adjustment. And when I checked the fluid just now, it comes out on the stick a clear, reddish color, which I am interpreting as normal. Seems what dozer12216 is recommending might be most reasonable at this point (although the service doc indicates the solenoid is operating normally). But what I will do is print out all the great comments here and have a little sit-down with the tranny guy I'm seeing tomorrow and see what he says.

Again, many thanks for all the input.

 

My last trans service was done at 120K and one of the bands locknuts had backed off slightly cause what felt like a lot of slipping. Diesel tech stated they had started to see this quite a bit in the 48REs. Every time I have the trans serviced, I have them adjust the bands, replace filter, and flush trans. Been do that since new every 30K miles, no problems with trans at all.

 

I was having tranny issues on the F350 I just sold and it ended up being a clogged up tranny cooler. I pulled the lines and put compressed air in reverse flow direction thru both coolers(external and radiator) and blew a lot of particulate crap into an empty 2 liter bottle. Shot both full of brake cleaner and repeated several times and got more crap. Put back togather and tranny worked great. Low or no flow thru coolers=bad thing. Have been told by trans guys that this is a source of many trans problems and is often overlooked.

Bob