I know exactly how you feel about it going into lockup too quick while towing. I have started using OD lockout somtimes when I get aggrivated with it.

Its kinda funny I dont tow so I get upset when mine shifts to 4th unlocked when just slightly accelerating.

The S.E controls line pressure rise, not line pressure. It takes the function of the TV in the older trucks. If the S.E. is not programmed right it will not work as it should. I will send you a PM.

Richard

PM recieved.. Thankyou

I have exactly that problem too,mine is shifting in to 4 th gear and locks at the same time ,not always ,but with partial throttle ,it does it sometimes ,it doesn,t bother me ,but you can really feel the tranny is loading the engine hard ,and you can feel the compressors slowing down in airflow

Perfect description.. Do you tow much?

I believe it's doing just what it should. If your towing heavy, just lock out OD till higher speed. I would really not want tranny unlocked for long time with a heavy load: too much heat.

I've driven the earlier 47RE's that had unlocked and locked OD. It drove me nuts... unlocking anytime you add a little throttle.
Problem is 4th gear is a bit tall (.69). But the Cummims can run all day at 2500+ rpm. Just takes a while to get use to a different engine noise.
Works for me, anyway.

RJ

The Tow/Haul really doesn't lock out 4th while engaged. It just helps the tranny stay in gear a little longer. I think my best bet would be to go to the dealer and have the tow/haul dissabled and turned back into the old O/D switch. I'm fairly sure its a TSB.

I know the shifting isn't really hurting anything it just annoying.

My mistake. I thought 48RE had both Tow/Haul and OD lock out!

RJ

Not really much,but this happens also when not towing.
If I have my 9000 pounds boat behind the truck ,I drive with o/d unlocked ,I know its producing heat ,but where I live ( Europe ) we can ,t drive faster than 50 mph with a trailer behind.... and thats just the speed where there,s not enough turbo pressure to let things go like it should,the truck is shuddering and begging for more throttle so there,s pressure build up.
If I drive 55-58 mph in 4 th locked with the boat on the trailer ,there is no problem at all.
Before I went with the twins ,and with the stock tranny ,this was no issue at all.

A.J

2004 has od lockout
2005 has tow/haul but it can be flashed to OD lockout.
2006 has od lockout and tow/haul.
On my 2004.5 shifts about 45 into 4th and T/C locks at 50 mph. I added a led light and lockup switch for the T/c. The light tell me when the TC is locked. I used the switch to lock T/C when towing about 45 in traffic. The switch also helps when slowing in the mountains.

If you are towing with a 2005 in tow/haul where the shift points change then 4th gear would happen about the same time as lockup.

Note: If you flash a 2005 to OD lockout and then install a Smarty then the Smarty will change the lockout back to tow/haul. If you uninstall the Smarty you do NOT get od lockout back.

Sounds like my best option is to get the O/D lock out option TSB from the dealer. I wonder what they'll say about all the mods on the truck. Then again who cares I'm way out of waranty. Wonder what the cost is?

After Flashing the DRBIII must be plugin and the feature o/d off enabled.

https://www.dieseltruckresource.com/...hlight=lockout