4L80E T/C lock up

clutch_dust · February 27, 2002

with a name like clutchdust, you should know i have no clue about auto trannies. i use my '94 1 ton to tow (when the wiring isn't on fire!) but i'm told that i shouldn't tow in overdrive because it can burn up my tranny.

i've been told that is because the tranny is switching in and out of lock up but if i can hotwire the T/C to lock up, i could tow that way.

i really don't want to burn up this truck (yet) but don't want to tow at 45mph either. the truck must have really low gears cause it only runs 70mph @ 3000 rpm (diesel) so towing in drive would put my cruising speed around 45-55mph. that makes for some long trips!

what's the scoop on manual T/C lock up?

bassdog · February 27, 2002

Welcome cluth_dust,

I have a 94 1/2ton that I use to tow. I have no problem towing my bassboat at 70mph

A suggestion would be to install a tranny cooler, that'll save the tranny life alot. I have not installed one yet, but planning to when I have some $$$.

I do not tow in OD for the same reasons. I run close to what you are running @ 70, I have 3.42 gears.

Hope some of this helps.

Shaners · February 27, 2002

The new trucks that have the tow/haul button say (in the manual) to tow in OD. I have the 4L80E in my HD and I tow a '32 travel trailer (8000 lbs). I have the factory tranny cooler, and I have never seen over 195* on the tranny temp gauge.

I suggest putting on a tranny cooler, if you don't already have one.

I would try to tow in OD and see how often the tranny unlocks the torque converter. If it isn't unlocking all the time, then you should be OK in OD.

How heavy is the trailer you tow???

jd hauler · February 27, 2002

I have a 99 2500 with 3:73's and the 6.0. I will be towing at the 8000 lb mark also, so I gather from the previous post that you can tow in o.d. as long as your using the tow/haul mode, is this correct? I have never towed heavy with an auto before. Is there anything to be concerned about? Do you really have to mash it on the long hills? also I ran third the other day to work and this was the most I have ever seen the tranny temp guage come up .

clutch_dust · February 28, 2002

trailer and car is ~4500# (truck weight is about 7500#). how do you know when the T/C locks up? i can't feel it so how do you know?

truck already has tranny cooler but since it's a diesel 70 is about my top speed even when i'm not towing. if i have to tow without OD, my towing speed would be engine limited to about 45-55mph. i definitely don't want to be towing a couple hundred miles at 55!

truck is a '94 so i don't have a tow/haul button.