Valve chatter under load

[Kawboy]

I have a 95 XLT 2.3. When towing my jon boat at highway speed, when placed under a load such as going up an incline or when it down shift's I get a loud chatter that I suspect is from the valve train. A friend recommended putting premium fuel in it. It seems to work! Does using 91 octane harm an engine designed for 87 octane?

At 65-70 MPH, I'm about 1,500 away from redline on the tach with overdrive off when towing. Not sure what my trans or rearend gearing is (to old and disabled to crawl under there.) Would it hurt to turn the OD back on when towing a boat that weigh's about 1,000 lbs total when the terrain level's out? Does it hurt the trans turning OD on and off while driving? Love my little truck and just don't want to cause needless preventable damage if I can help it.

 

[shadetree]

Overdrive is for fuel economy, not power. Normally, if the truck is under that much load, it will downshift automatically. However, it does not harm the trans to take it in and out of overdrive while moving.

Using premium can do harm to the engine in the long run.

"Valve clatter" is actually detonation (pinging), and has nothing to do with the valves. These engines have a natural tendency to ping, especially under load, but if the pinging is excessive there is a problem, and can be caused by several things. If the truck runs fine out of overdrive when pulling a load, and runs ok the rest of the time, I wouldn't worry about it.shady

 

[pedal2themetal45]

Just a thought
the timing belt may be going south..
tim