I have a 1990 f350 with a non-turbo 7.3L with a overdrive transmission. There is a switch on the dash to turn the overdrive on and off from direct drive and there is a switch on the transmission. Does anyone know what that switch is called and if you can pull in overdrive. The load will be a car trailer with a 1954 F100. I guess my main concern is can you tow in overdrive? Any info you can give would be greatly appreciated.

 

I've heard both sides, no not to tow in OD and others saying makes no difference.


If it was up to me, I'd see what are you RPM's depending on speed. If your pulling that trailer over 70mph then I see no problem towing in OD.

If your doing 55-60 I'd tow 'er in 3rd gear. Unless you have 4.10 gearing.

I'd want to keep the RPM's around 2000-2500.

 

I have heard both sides as well and I've discovered that the engine with be at higher rpms with overdrive off(E4OD).

 

If you're running at a speed where it will stay in od on you should be ok leaving it in od, but if you're driving at a little more conservative speed and its shifting in and out of od all the time, then turn od off. Its the constant shifting in and out of OD you want to avoid.

 

But if you two in overdrive it would be a good idea to install and auxilary trans cooler rated for the gcw you intend to be at because the trans will make more haet when in overdrive.

 

actually,the torque converter is locked up directly in OD.there is no slipping.at this point in time,it's as if your driving a manual trans.direct mechanical lock between trans and engine (engaged via electric.)
when i have to watch my trans gauge,is below the lockup,when it slips and multiplies torque.this builds heat quick if your not careful.that's why C6 trans really need some overkill trans coolers.
once locked up in 3rd or OD,she drops the heat right off.
i always use OD.if im on hilly terrain,and i know it will downshift up the hill,go back in OD,but another hill follows right after,i'll hit the OD button to just keep her in 3rd.
any other time,i let her do her thing.

 

I was always told that raitos other the 1:1 made heat. Is the overdrive on these built right into it or kind of a c6 with a lock up and an od glued to the back?
Edit: doesnt the tc lock up in 3rd then it shifts to overdrive?

 

when the torque converter slips/multiplies power to the rear wheels,it greatly generates heat.the C6's trans converter is always in this open state generating lots of heat.
the converter locks up in 3rd gear yes.it almost feels like another shift(but you can tell the difference easy) then it shifts in 4th(OD)
once this direct lock up takes place in 3rd gear,the trans cools right down.
the transmission is a solid unit yeah.4th gear is built right in.
its all mechanical just the the C6 unit.it's just controlled electronically.
some people don't like the feel of lockup in 3rd (they like what the toque converter is doing in the open state is why it's acting like rear gears multiplying the engines power to the wheels.) myself i like it,because i know it's saving fuel.
some do mods to keep the converter open,and lock it only when they like at higher speeds.
this uses extra fuel though.fuel economy seekers will do this mod,but use it just the opposite.so they can actually lock it up sooner than factory.but im getting off topic now lol.
i like this trans a lot.
edit,
actually i worded that wrong.its hydraulic like the C6,but with mechanical lockup (which is engaged electronically lol.sounds more confusing than it is.)

 

My trans friend still claims there is still a slight slip even when locked up like around 3%, grated its worlds better then my slushbox which can be well over 7%