I find that my trany will not lockup in third unless I am already in OD and it down shifts on a hill then it will drop to 3rd then lockup but on the normal upshifting it will not lockup until it is in OD. I have read that the trany has to relearn to lockup in 3rd. I have tried this by driving at around 30 mph for a while but it has not worked. Can I remove the battery terminals for an hour lets say and will that put the trany back to ground zero instead of driving 100 miles at 30mph? It is a pain when going through town or taking off up a grade with a load on and I can not get up enough speed to get into OD.

 

Third gear lockup will be @ 50-55mph. You can get 2nd gear TQ lockup in the 35mph range.

 

Tow haul mode will make it lock up in 3rd consistently, as will running with the exhaust brake on if you got one, as will running in OD lockout

 

Forgot to mention I have a 04.5 3500 and the Tow/Haul button does little more than lockout OD.

 

add a t/c lockup switch. I added a light that tells me when the t/c is locked and then the addition of the switch is easy.

If interested do a search for t/c lockup.

https://www.dieseltruckresource.com/...t=t%2Fc+lockup