Switching from Synthetic ATF to Natural?

There is no problems and only benefits to running synthetic in the 700! If you really don't want to put synthetic in when you do filter changes or when it gets flushed, then don't. There is nothing special that needs to be done. Synthetics and petrol based ATF are fully compatible with each other. Synthetic is much cleaner and will be much better for your trans in the short AND long term, but its your Truck, your call.

Well cost wasn't really my concern. I thought that I would be better to run natural in the 700r4. It would probably cost me $36 for natural, and $60 for synth -- I can afford the $30.

The first reason why I considered switching back was if it were doing harm or being less effective in the 700r4. The second reason is that I noticed that at high RPMs on the highway it will run at (for example) 3500 rpm. After 10 seconds, the rpms drop down by 400-500 rpm and you feel the truck pick up a little bit -- like the trans just clamped down a bit harder on the clutch plates. I thought that the synth was too thin and that it was taking longer to build up pressure on those plates. There is a small drip coming from where the control level runs in through the case -- nothing so much that there is ever a spot on the ground, but enough that I notice it's a little wet around there. That may -- over time cause my trans level to be low. I'll check it again tomorrow and see if that's the case.

What size tire, what gear ratio, and is that in 4th?

for real, that sounds like alot of rpm to be cruising around

Adair

Seriously though, 29" tires 3.73 in 1:1 (not OD) would be 81MPH at 3,500RPM

GMC Gremlin

Use 4th!!!

Well that's not cruising -- I was trying to see if it was slipping/not engaging.