I've got 355/70/17 tires on my truck. They measure out to a true dimension of about 35.75" tall. The Stock tires were 265/70/17 I think? Maybe 245...its a 2wd.

Anyways everybody on forums will tell you your driving your truck to death row with 35"+ tires and stock 3.55 but I have ran my truck like this for years and aside from a few issues when I had a "line pressure booster" i haven't had a single tranny issue.

Now I find myself pulling a small horse trailer every now and again weighing maybe 3500 loaded. I don't go on the major highways 80km (55mph) roads in tow/haul mode and she just hums along at 2000rpm. The fluid isn't burning up and the truck engine temp gauge sits a tad below half (normal operating temp on my truck).

Any opinions?

 

The issue is because your effective gear ratio is much lower than 3.55 with 35+ inch tires you're RPMs are not up into the powerband of the engine. This makes the transmission run harder and search for the proper gearing more.

You won't see the difference in engine operating temp, but where you will see it is in the temperature of the transmission fluid.

Now 3500# isn't a lot of weight for your truck, so the tranny will probably be fine for years. Much over 5000# though and I'd seriously consider re-gearing to at least 3.92s or preferably 4.10s...

 

what is the running temp for the transmission on a 96 ram 2500 automatic with the 5.9 magnum?