I have not driven a heavy automatic in a lot of years, so here is my question.

On a steep twisty uphill 32 deg C (90 F), running about 60KPH in 3rd gear so 2800ish RPM is an engine temp climb up to around 203 from 188 normal. If the hill is long enough the fan clutch bites and the temps drop rapidly to 185 - 186.
I am not concerned about the engine temp,13 degrees is not that bad, so much as transmission temp.

The transmission temp light did not trigger

I know automatics do not like be to really hot.

The Disco handles the hill without issue, but here in BC long winding uphills are pretty normal, often off road that can be second gear and slow.

And how tight should that filler bolt be, I can not seem to budge mine ?

 

clean the area with a wire brush and spray it with your favorite penetrating oil for a few days in advance. Should come loose.

There is a trans-cooler built in and should be keeping the trans temp under control.

 

Most automatic transmissions can handle 300F without alarm. Our vehicles at work here have temp gauges and in the "red" is 320F. But, when temps rise to the 270/280F degrees...you start to see some heat transfer from the charge air coming off the trans cooler in front of the radiator.

So, picture the radiator trying to cool the engine under normal conditions, 90 degrees out, everything working like it should, engine temp is 186 degrees...so, the heat exchange differences are 96 degrees. Meaning the 186 degree temps are being brought down by the 90 degree temps being blown/force past radiator.

Now, if the trans cooler, mounted directly in front of the radiator, is seeing temps around 190+...you have no where to go... but higher...especially in climbing conditions...where you may be punishing the trans and speeds are low (less air flow). That's why l mentioned in our other discussion about pulling it down into 3rd on a long up hill climb...to get the engine turning faster, which in turn, turns the torque convertor faster, which in turn moves more fluid through the transmission to the cooler. Lugging the transmission is the number one cause of failure and heat build up...so, avoid this at all cost...even if it means slowing down to drop into a lower gear.

I believe the slight increase you are seeing is acceptable, totally. However, if you see anything above 215 degrees and the hill has no end in sight...l'd be looking for a place to rest the old girl.

Brian.

 

Now, the plug...that thing must be put in by some super strength human with no sense of humor...because it breaks loose hard. Just make sure the allen headed wrench or tool you are using is firmly planted into the plug. Usually, l use an allen wrench and slip a box end wrench over the end for more leverage. Note to self, don't drain the fluid until you get the filler plug out...or you may be in trouble...if it strips out...and you have no way to refill immediately.

Brian.

 

Provided the hill isn't too long or steep the autobox should run all day with no problems. Just ensure you have sufficient ATF in the autobox. Also check the ATF level and replace the autobox filter and ATF if necessary. The ATF should be blood red, if it is brownish and smells then replace it PDQ.

Check in RAVE for the torque setting. If you have a socket set with Allen key sockets and a good ratchet use that or a T bar. Ensure the Allen key is well located in the plug as you don't want to round it out. I seem to recollect it was an 8mm Allen key.

 

There is something up with mine for sure, 7mm fits 8mm does not #50 Torex fits.

I had thought about trying an allen key and big wrench, I will give that go after a few days of penetrating oil.

I had the transmission serviced the spring, got to wonder if they used threadlock, I am ordering a new filler bolt just in case.

Once again thanks for all the advice, I tend to be a little OCD about maintenance, so far i have not had to walk out of the bush I don't want to start now for lack of a few minutes work.