Question about overheating, 86 Yoda Pickup

Hi, I have an 86 toyo pickup with an 84 engine in it. 22R. For a while now, it heats up. Not enough to have to stop the vehicle but it does get worrysome.
My truck is automatic with overdrive. When I climb a gradual grade as I do every morning on the way to work it heats up. Its about a 5 mile gradual climb.

I notice if I run the truck with the overdrive off causing the engine to RPM much more it stays much cooler but if I am in Overdrive it heats up. Same thing going down hill after the 5 mile climb. I turn off the overdrive to keep me slower going down the hill and the temp gauge drops.
Would you think my waterpump is causing this problem. Thanks, Eric

when engine is cold start it up take ratiator cap off and see if it is circulating good if not water pump or partially clogged ratiator or could be heater core clogged.....good luck...

thanks, I have an idea it is the water pump. I do notice no movement in the water when first started, even when it runs for a while, no movement in the coolant. The belt is tight. I would guess the pump because when I run in out of overdrive I am thinking it is making the pump work alot harder therefore cooling down the temp.

If your water pump wasn't working it would overheat right away.

If your truck is overheating on a long steep hill, so is your tranny.

You should not be in OD on a long steep hill, you're making the engine and tranny work harder than they should.

If your water pump wasn't working it would overheat right away.

If your truck is overheating on a long steep hill, so is your tranny.

You should not be in OD on a long steep hill, you're making the engine and tranny work harder than they should.

Hey fourwd1, thanks for the tip. At what speed would one shift the automatic overdrive off when climbing a gradual hill? I figured running it with overdrive turned off would be hard on the engine. The hill I climb daily is a gradual slope and about 4 or 5 miles with some level areas.

No, running steep uphill w/OD on is hard on the engine (and tranny). It makes it lug (bog down) and overheat. The engine isn't operating in it's power band.

There's no specific speed/steepness/RPMs/etc to turn it off,. Every vehicle/situation would be different. You should be able to "feel" it. Shifting to a lower gear could even be needed.

Yes, fourwd1, Driving 4 or 5 speed manual trans is quite easy cause its easy to notice by the sound of the engine and feel of the drive when to shift up or down. I really prefer manual over automatic but thats what came with the 86 I got. Anyway, I changed the thermostat today and it seems much better.

Parts on the other hand are something else. Last week we did the idler arm and link pins. Link pins were too long, had to return them. Today I got a new thermostat and when I changed that, I just got a plain gasket instead of the rubber "o"ring that is needed to fit in the housing groove on my truck.

Got the parts from our local small town autoparts dealer here. 2 orders and 2 mistakes. Think I am going to be getting my parts elsewhere from now on.