LS430 External transmission cooler temperatures

[lexus430]

hi, i installed the external transmission oil cooler from LexusSparesDirect on eBay a few days ago and have taken it for a few test drives to see the temperature of the transmission oil using my OBD plug-in.

in normal driving with little stop start after about 15-20 minutes the temp is around 70c.

after 15 miles up the motorway (18c sunny ambient temps) i saw a steady 76c.

the 15 miles back (after a 3rd gear pull on the sliproad) i saw 81c, then it creeped back down to 79c by the time i came off again.

back through town with a bit more stop start it reached upwards of 90c

after a little pushing (50-75% throttle, 3-4k rpm upshifts) it reached 97c and stayed there until I reached my house (2 mins after) it was still 97c.


Does anyone know if these are normal temps or something I should be worried about - I didn't want to push it any more because that seems fairly high but it could be norma. it's a shame i didn't think to check on these before i installed the cooler.

 

edit: 2005 Lexus LS430 with 6 Speed Auto

[The-Acre]

24 minutes ago, lexus430 said:

hi, i installed the external transmission oil cooler from LexusSparesDirect on ebay a few days ago and have taken it for a few test drives to see the temperature of the transmission oil using my OBD plug-in.

in normal driving with little stop start after about 15-20 minutes the temp is around 70c.

after 15 miles up the motorway (18c sunny ambient temps) i saw a steady 76c.

the 15 miles back (after a 3rd gear pull on the sliproad) i saw 81c, then it creeped back down to 79c by the time i came off again.

back through town with a bit more stop start it reached upwards of 90c

after a little pushing (50-75% throttle, 3-4k rpm upshifts) it reached 97c and stayed there until I reached my house (2 mins after) it was still 97c.


Does anyone know if these are normal temps or something I should be worried about - I didn't want to push it any more because that seems fairly high but it could be norma. it's a shame i didn't think to check on these before i installed the cooler.

 

edit: 2005 Lexus LS430 with 6 Speed Auto

Bear in mind the coolant will be at those temperatures, and the fluid with the original setup runs through it. I found my external cooler got too hot to touch but it was fine. 

[BigBoomer]

The ideal temperature for ATF-WS is around 80C (175F) but you are good up to about 105C (220F).
Much above that for any length of time and your ATF will start to break down.
Most auto-boxes have thermostats and built in pumps that control the circulation of the ATF so it sounds like yours is operating normally.
ATF-WS can withstand a few minutes above 105C but sustained operation at those temperatures will cause problems.