mightyorion

Hello everyone,
I'm about to embark on the road trip of road trips traveling from seattle, wa to jacksonville, fl. I plan on towing a 5x8 uhaul loaded total to about 1500lbs. I have a 1998 Z71 5.7L ext cab with 6ft bed and auto. I am beginning to wonder if my max speed really will be 55-60mph with the tranny in 3 and not OD. I'm at around 2200 rpm @ 60. My question is will running at that rpm be safe for such a long period and if not what's your suggestion?

old dog

i think you would be ok in overdrive on the down grade's and flat terrain,that should limit the higher rpm's to the hill's where you will need 3rd . but probably need a trans cooler if it doesn't have one .

lukemoore646

second the cooler, most people burn their autos out by pulling in OD, it is ok on long flats and downhill grades but the shifting in and out of OD and the added heat of OD just makes a recipe for disaster

mightyorion

I do have a towing package on the truck as well as a tranny cooler that appears to be about maybe 1ft by 1ft mounted in front of the radiator on the passenger side. I figure on the upward slopes and acceleration periods I will avoid OD and once i'm on the highway flat or desending grade i'll go ahead and hit 70mph and go to OD. I consider myself to pretty understanding of certain mechanical systems and I would Imagine that i would immediately be able to spot this "in and out of OD" by simply paying attention to the RPM as well as being able to audibly and physically sense this occuring. I suppose I'll give it a shot. Would possibly entertaining the thought of an aftermarket tranny temp gauge be wise, and if so what kinds of temps am i looking at for a "safe range" Thanks for all your help so far.

bad2006z71

nothing over 200deg for your trans temp for any length of time. 170 is the best temp

also its ok to tow in OD as long as the truck is not hunting for gears.

lukemoore646

DEFINATELY on the temp guage, they should all have one, just dont confuse torque converter lock up with OD shifts, i agree the less hunting the better, hunting makes unwanted heat, remember an auto is just as good as a stick if properly taken care of

wffokker

Hauling 1500 Pounds is peanuts though, that truck should have no problem at all unless that u haul is U shaped on the front and 14ft tall lol,

mightyorion

Okay, so a few more questions, lol. I feel like one of my new guys that reports to the command and has no idea whats going on, but I don't really wanna mess the truck up. So upon second inspection while giving the radiator fins a good old rinse, I discovered that what I mistook earlier to be an A/T cooler is actually the condenser.. the tranny lines just go through the radiator. I looked up an aftermarket tranny temp kit to discover that the fitting is supposed to go into a replacement drain plug that allows for easy installation of the thermocouple, my transmission has no drain plug. Has anyone done this before on a like setup, and if so how did you do it? Finally, torque converter lockup v/s gear hunting -- i understand and see the shifts, so what am i looking for to discern the TC lockup vs. OD back and forth? Thanks again for all of your inputs, I certainly do appreciate it.

lukemoore646

if you are in overdrive say, going 70 and start up an incline and you feel and see what resembles a downshift it is probably going out of lock-up. the torque converter is never in a 1:1 ratio with the tranny until it gets into lock-up, its like having another gear

bad2006z71

correct. ive you are driving and you count 4 gear changes then what appears to be a fifth gear change thats the converter locking up. same as reverse, the converter will unlock then if more is needed it will downshift.

i would suggest the tru cool 40K transmission cooler. i just installed one, and my temps have not gotten past 160deg yet. thats with a little light towing and ac on full blast in 80-90deg temps. might be overkill but heat is what usually kills transmissions.

here is a link to my install:

https://chevroletforum.com/forum/silverado-sierra-fullsize-pick-ups-21/tru-cool-40k-trans-cooler-upgrade-24487/