I just put a fresh motor and trans in my car. I have 2 large tranny coolers on my car. We had it running inside a shop for about 20 minutes then took it for a test drive. My temps NEVER went above 119-120 even when I put it in drive to bring the rpms up to try to warm it up. Sitting in traffic it would only get to about 115. I verified this by scanning with hp tuners and my trans temp guage. Reason I ask is my lockup on the highway isnt working it will half *** work when accelerating up to 70. Is the fluid too thick at those temps? Also the temp outside was about 35 degrees. I only drove it on the highway for about 5 minutes and about 10 in the city then took it back fearing somthign was wrong.

 

it takes a long time for it to warm up especially at those temps.

 

Those temperatures are not a concern. What might be an issue is how restrictive the coolers are and what they will do in temperatures around 0 degrees.

 

The trans temp itself should not affect lockup as its determined by engine temperature,
The dual cooler however could be a little restrictive depending on how they are set up, With large twin coolers its preferred IMO that the be run in para ell rather than series this will reduce any restriction, The lock uo issue may be tuning related if its intermittent

 

i have seen lock-up with tranny temps under 100 degrees. fluid temp does not seem to effect the trans shifting when driving around town.