transmission overheating on hills

hello everyone, first time posting here and have got a serious issue. the AT/oil light is coming on at the top of long steep uphill grades with a load of only a couple of passengers and the camper shell. the yota is a 2002 double cab TRD with 200,000 miles and i just got the transmission rebuilt last july after the torque converter continued to malfunction and eventually seized. because of the amount of metal debris in the old tranny fluid, the shop warranty required a new tranny cooler. my mechanic decided to save me replacing the radiator/oil cooler by adding an aftermarket tranny cooler and bypassing the original oil cooler inside the radiator. any ideas of to cure the problem of my tranny overheating and why this might be happening? even in 40-50*F temps this is happening, and not going over 55mph. thanks for listening any advice appreciated

 

Any pictures of how the aftermarket tranny cooler is installed? If the cooler is too small / too restrictive / doesn't get enough airflow, then it won't perform as well as the OEM radiator.

 

Are you in over drive? Running in drive only, circulates a lot more oil thus giving you more cooling.

I'm still thinking you don't have enough cooling oil. Aftermarket coolers work better when they are plumbed along with your original radiator tranny cooler.

Before you start throwing a shit load of money, spend $110 bucks and get a new radiator. 200k on the clock means that your original is ready for replacement. Radiators are so cheap on the internet, it is a no brainer. They are easy to change too.

KO

 

I cannot confirm this, only restate what I have read, that is, the light is set to go off above 250 degrees F.

My personal experience is from monitoring with a scangauge. I have never tripped the light but my temps have maxed out at 235*. I have since learned that turning off the overdrive in those situations helps a lot to reduce temps, sometimes as much as 30*.

Are you still stock, gears and tire size? Larger tires without regearing will compound the problem, making your trans work all the harder, thus more heat.

 

ok thanks you guys for all the info, here is my reply to the questions asked: no picture yet of tranny cooler, will post soon if possible or needed. one time was in overdrive off when light came on but most times have been IN overdrive, now that i know it circulates more oil to have it off i will do that, as well as replace the radiator soon, good idea right?! and about the tires they are 285/75 so much larger than stock, and can sombody point me to some info about re-gearing and cost/time involved?

 

Regearing is expensive but is the best mod I have done to my truck.

Are you a 4x4 or a 2WD? Can't tell from your info.

 

4x4 TRD with ARB bumper no winch yet and snug top is only extra weight

 

If you regear, you have to do the front also. Will double the cost basically.

If you have the ability, tools and the space to do it, check out these guys. Very good reputation on this forum.

http://eastcoastgearsupply.com/c-62270-assembled-3rds-clamshells.html

If you don't have the above or the inclination, you can do what I did. Find someone to do the gear setup and install for you. I used these guys because of their reputation and their proximity. Regearing front and rear will cost you about $2,000.

http://www.justdifferentials.com/

 

right on good to know, with that cost i will be waiting on that upgrade but i bet its well worth it. any advice on new radiator and where to buy? should i get a new thermostat as well and any other parts while I'm replacing the radiator? thanks again

 

I have no personal experience with swapping the radiator. Mine is still the original one at 130K. Not sure about the t-stat but I would think new hoses are called for.

 

Which motor? I found a couple on ebay for $80. I've had good luck using radiators from ebay sellers. My 1998 has had 4 radiators, getting pretty quick at changing them. Lots of deer collisions around here.

 

It should not overheat in OD on any terrain unless it is towing or hauling a heavy load.

The mechanic probably bought a cheapie Aux trans cooler and it's just not up to doing the job.
If the entire stock cooler is being bypassed and replaced with an external, it needs one probably 3x the size of the one that comes with the towing package.

 

3.4 liter v6 , any advice on brand of radiator? before the next deer collision you should consider arb bull bar, and save the radiator. tons of deer around here too thats why i just installed my bumper after the first deer collision. thanks again

 

i see, well that would explain the overheating if that is true, i know that the tranny cooler cost about $80 so that might be cheap. so when going uphill better to have overdrive off or on?

 

If you've got the light coming on, that is SERIOUSLY overheated and it needs to be fixed immediately.
Don't take it back to that mechanic for anything... he's an idiot and hopefully your new transmission has not been damaged by the overheated fluid.

Correct the cooling configuration and change the fluid THIS WEEKEND.

 

wow, yes this is serious and thank you for the advice. so correcting the cooling configuration would be : new radiator to AUX tranny cooler and then back to tranny right? any advice on synthetic atf fluid?

 

I usually use my O/D on long flats or freeways, if going uphill w/long grade, turn off O/D, push the ECT button if you hjave one & most certainly an aftermarket cooler thats got the plumbing squeezed down is going to create or at least magnify cooling issues & the A340-F DOES NOT DO WELL WITH HEAT, if you wait to flush/change fluids, its probably going to fail.. if you start getting some hard upshifts, its a ticking time bomb, already been thru it...

 

All ATF is primarily synthetic.

I'm not sure what your year trans requires, check the dipstick or the manual. If it calls for Dex-II or Dex-III, then Mobil-1 is good.
If it calls for T-IV, that comes from the Toyota dealer.
Amsoil claims compatibility with T-IV... I don't trust them with my trans.

 

Only time I come out of OD is if the trans starts "hunting" between gears... same goes for the 2-3... I'll pull it down to the lower of the 2 gears it's hunting for.

Heat in the automatic trans comes from two sources... slippage on the plates, which only happens (in a healthy transmission) during shifts, and from the TC when it is not locked.
Even on hills, if the TC is locked, and the trans is not hunting between 3-4, there is no need to drop it out of OD.

 

so does replacing the radiator also replace the original tranny oil cooler? if so thats the next step along with changing the fluid.