I recently purchased a Dodge 2004.5, 2500, single cab, 48RE auto, 4x4 pickup, in great condition with 172,000mi. Young truck considering my 1st gen 1992 had 378,000mi. The 48RE trans seems to shift a bit odd when it's at operating temperature. Shift gears 1-3 fine, holds 3rd from 40-50mph, then while winding 2200 rpm it will very briefly shift to 4th and immediately into lockup OD. I don't detect any slippage from gear to gear. Engine RPM's don't flare if I really step on the diesel pedal. The local Dodge dealer scanned for trouble codes and found nothing, but confirmed the odd shifting. The dealer told me the transmission is junk, and $3500 to repair/refurbish. Took the truck to a transmission shop for 2nd opinion. The boys at the trans shop test drove it, confirmed the odd shifting. Stated it an internal problem with the trans and $2200 to tear down/repair. Here's something else odd, When the trans is cold, all the gears shift at normal points. Again, I cannot detect any tell tale signs of slippage.

I'm just wondering if anyone else had trouble like this.

Thanks, Nick.

 

If it were mine, I'd drop the pan and clean the valve body real good, you know. Take pictures so everything goes back in the way it came out and use solvent (mineral spirits) and a good clean work area. Wash and scrub everywhere and blow off with compressed air and reassemble. Sounds like some sticky spool valves. Mine did the same thing, seemed fine just shifted weird. If you don't have a decent load against it mine will shift into 4th at 45 every time and then almost immediately you feel the lockup. Mine also shifts quick on a easy take off. usually into 3rd by 25-35 mph. If I'm hooked up to the three axle enclosed trailer (heavy!) it shifts pretty normal.
The fact that your issue is temperature sensitive tells me it isn't a major issue.
Just thermal expansion oriented. Rebuild? Replace? Hardly what I would agree with.

 

That shift\lock strategy is perfectly normal on the 48RE's, thats the way they were designed. In fact, you will find people thta swear they shift locked-to-locked on the 3-4 shift. On the 3-4 shift the lockup is just pulsed off instead of a full unlock so it seems like a locked shift. Since the 48RE contains heavier parts the lockup strategy was chnaged to keep it in lockup which is where you want it.

Its fine, drive and enjoy.

 

x2!