Well I drove a 2005 today ,had the 3.73 rear end. This is what I found, STRICK and VERNOME were right . In tow mode 4th gear is locked OUT PERMANENTLY.What you get on a easy takeoff emty is a 1-2 shift at 15 mph, a 2-3 shift at around 30 mph ,and a 3rd gear lockup just a hair latter. this is as high as it shifted in tow mode , I fed the throttle on easely and speed climed to70 mph at 3000 rpm 75 at redline. you could hold a steady speed at redline (75 mph) trans stayed in 3rd gear lockup . no more upshift. At 75 mph I let off throttle and trans stayed in 3rd lockup , which gave downhill motor brakeing ,down too 2000 rpm at which time it went out of lockup, at that point I fed a little throttle and manually pulled shift lever into 2nd, and trans shifted into 2nd LOCKUP and I had downhill motor brakeing untill 1800 rpm at which time trans came out of 2nd gear lockup. Now one couldnt ask for a better setup then that. With tow mode off , with easy takeoff I got 1-2 shift at about 3 mph, 2-3 shift at 15 mph 3-4 shift at 43 mph and 4th gear lockup at 50 mph. This is with a 3.73 rear end ,a 4.11 will shift at lower speeds I would assume. I have driven the newest allisons. The allison has a 5 speed instead of a 4 speed. This is a matter of personall choise. My opinion is the Cummins doesnt need a 5 speed, The allison also has a tow mode that raises the shift points in all 5 gears. But the allison also has a feature, that if you hit the tow mode button twice, the fist push increases the shift points the second push locks out 5th,or overdrive.
At present I rum a 98.5 with the 47re. Tow a 12000 lb trailer. 102,000 mi with no trans problem to date. But I drive the trans , try to avoid lockup shift while under power , thats what takes out the torque converters. Get that puppy into lockup then poor it on. And my trans has NO lockup for brakeing. My opinion is that short of the extra gear this 48re in the 2005 funtions as good as any allison I'v driven.

 

MY BIG MISTAKE!!!! In my previous reply, just ahead of this one, I stated my opinion of the 2005 48re. Well I was wrong!!!!!!! I'v sence found out that the truck was a 2004.5 The trans DID react as discribed which was GOOD,GOOD,GOOD!! But it was a 2004.5
Today I drove a 2005, The trans DONT ,I repeat DONT lock out the overdrive . I couldnt believe Dodge would be so stupid as to make that change for the worst. Of course the salesman didnt know didly doo about it. or even understand the need to be able to lock overdrive out. But after talking to him we decided just maybe the truck I drove wasn't right so he gave me a 2nd one to try. The 2nd one DIDN"T lock out eather. So I dont know ,maybe a commputer reflash could give this feature back, I dont know . But I do know that if you cant lock out overdrive, this trans is going to hunt constantly between 3rd and 4th in hilly country, regardless of the tow mode.
So most of the guys giveing replys here are correct . The 2004.5 owners say it lock out overdrive and there right . But the 2005 owners are complaining as there trans are hunting gears, NOT GOOD AT ALL. As stated trans works great on empty truck, but for towing??? And of course we all buy these trucks for running around empty. Where in h--- does Dodge get these engineers.????
One starts to wonder how come these aftermarket Co. can build a needed trans and Dodge cant??? And why would Dodge discontinue the lockout feature after already haveing it in there. Obviously they have NO conseption of whats needed here. It amases me they know enough to keep the Cummins
Well there'll be no 2005 in my future.

 

Maybe it was in response to fuel economy complaints and/or federal mandates . . . or maybe it was a stop-gap attempt at competing with the more "advanced" auto trannies from the competition . . . who knows?

Mine's an 04.5 and I can confirm that T/H locks out OD with or without a load. I think it also locks up in 2nd and 3rd differently - but I'm not as sure about that.

Neil

 

Well murvin your lucky you got yours last year! The 2004.5 I drove couldnt have worked better. Downhill brakeing in 2nd ,3rd and 4th and you could controle all gears. Not so on the 2005s. Went to another dealer today ,told there trans man you couldnt lock out 4th in the 2005s he dissagreed, said he'd check it out. I drove a third 2005 and it wouldnt lock out. Went back in shop and the trans man said he brought it up on the commputer and you can lock it out . He saved it for me to read . Sure as shooting it said for 2005 push the tow mode button and it raises the shift points and locks out overdrive. I told him the computers wrong or I'm not doing something right. But if you do what the computer says to do it DONT lock out 4th. He said well I can check that in a second by putting the scanner on the truck, So he did And sure as heck he couldnt lock out 4th. So he drove the truck and no way can you lock out 4th. When theres NOLOAD in third gear she upshifts into 4th no matter where the tow mode is. So heres the first man I ran into that recignises the folly of this setup. He said he was going to check with STAR and see whats going on. He also said he was going to see if a simple thing like a reflash might correct this. After all the 2004s got it.

 

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I have the 05' with 48re. I know the tow/haul (in the 05') will still allow 4th gear (overdrive) but I thought that 3rd and 4th both had the convertor locked with no slippage. I thought this IS supposed to be an improvement. Helps the tranny/convertor not get so hot and not frag itself. Am I right in thinking the convertor remains locked thru this process????