peirek wrote:
path1 wrote:
I want the fluids (transmission and coolant) to circulate faster than in overdrive mode.
This! It will make a difference in your Tranny fluid temps.
:R
Total B. S.tuff.
The fluids pumped around via transmission are NOT going to "circulate faster" whether in OD or not in OD.
What you MIGHT see though since the engine will be TURNING HIGHER RPMs is the engine COOLANT will get circulated faster to a certain extent.
The engine fan will also be running faster but at speed will not have much over all effect.
Folks tend to put WAY TO MUCH time and energy in worrying about engine coolant and transmission oil temps.
Folks, please understand the STANDARD configuration of modern day vehicles from the time automatic transmissions were invented the transmission fluid is plumbed into the radiator via a short loop internally in the radiator.
This loop is placed at the BOTTOM of the radiator tank where the engine coolant is the LOWEST temperature possible. This loop will keep the transmission fluid near engine coolant temps (that IS the way it is designed).
Additionally with vehicles which are factory setup for towing they will have a SECONDARY transmission cooler plumbed in AFTER the radiator loop.
99.9999% of the time this is plenty sufficient to keep the transmission temps well within the factory specs.
With that said, the OP should FOLLOW the FACTORY RECOMMENDATIONS OUTLINED IN THE MANUAL as to whether or not to lock out overdrive.
I myself HAVE NEVER locked out overdrive UNLESS the transmission continually "HUNTS" gears (down shift then up shift in a quick repeating pattern).
I towed with a 97 and 2003 truck with 4 speed automatic overdrives and I can only think of once or twice I locked out over drive and that was only for that particular grade.
Newer vehicles with Tow/haul mode is completely different, the T/H mode DOES NOT LOCK OUT OD.
I would say if the manual does not tell you to lockout OD while towing then try driving with OD and if transmission downshifts and upshifts too much (up/down quick pattern) then lock it out. The continual shifting is actually where damage can come from, not the fluid temps.