FJ62 A440f AT oil temp light - Rodney response (1 Viewer)

[85lc]

I mentioned a problem in another thread but thought I'd repost it here with the response I received from Rodney so that everyone can see:



Problem: driving the cruiser to work after installing the Extreme Valve Body from Rodney @ Wholesale Automatics, and so after driving for almost an hour, I was nearing my destination and slowed down from 70 to 35 as I made my exit and lo and behold the AT Oil Temp light comes on. F@@&@!!! See my many previous posts about this. So I realized that this only happens when I slow down after cruising for some time. My lines have been triple checked and the flow rate is fine. I have a new external trans cooler in front of the radiator (I used Georg's recommended brand). The radiator was replaced OEM last year. I also just had a new torque converter installed with the valve body. I am at a loss. Could the trans cooler in the radiator be not working? As I said, the flow rate is fine. I'm running synthetic fluid. Rodney's valve body came with a new screen and the old screen looked fine but I replaced it anyway. I'm thinking of installing an aux fan in front of the aux cooler. I am running stock 4.11 gears on 33" tires. I have 4.88's but they are not installed yet as I am wavering on those versus 4.56. I have no plans to ever go bigger on the tires so 4.88 might be overkill. Thoughts??

so I sent this same note to Rodney and his response was great so I thought I'd share it with everyone here:

Hi James its Rodney from Wholesale Automatics,


This is in fact normal, When the torque convertor lock-up comes on it stops the oil flow through the torque convertor and because the convertor is basically stuck between a hot engine and a hot oil pump the oil in the torque convertor over a very long time normally more than 45 minutes will get quite hot even though the oil temp light and oil temp gauge if you have one says that all is still normal. But when you slow down and either stop or come into a town the lock-up will release and the super-hot oil will then go past the temp senders and this is what you are seeing. Only 2 ways to fix, 1/ put one of our Heavy Duty Billet torque convertor in that allows for the flow to continue while the lock-up is on “or” every now and then when on a long trip slow down to under lock-up speed for a few minutes to flush the hot oil out and then continue. Took me 2 years to find this problem and find the cure.

I have a stock 1990 FJ62 with 160k miles. At the end of the last two highway trips (~80 miles, partially in GA hilly country, trip lasting 1 1/2 hrs), the AT Temp light comes on when I slow down and stays on until the truck is stopped. A few minutes later, restarting the engine and the AT Temp light is off. The trips were late afternoon trips and the outside temperature is fairly warm. This issue just started last week.

These trips will be routine trips. I guess I could break these trip up in say 2 or 3 stops or slowdowns but that doesn't make sense

I am not a mechanic. Is this something a regular transmission shop should be able to resolve?

 

[SteveH]

I would not take it to a shop, and the best way to cool a hot automatic transmission is to leave the engine running and put the truck in N or Park. This lets the fluid pump through the cooler.

Generally, what causes high fluid temps is lots of time in 2nd or 3rd where the TC is not locking up. If you're on flat ground in 4th gear, it rarely runs hot. So, hilly country on a hot day will do this.

I would install an (approx. 11"x11") cooler (documented many places here on Mud). Mine dropped the temps around 25-30F.