I may have reved my truck to hard because it slipped out of first and it now is making a weird ticking noise on the top of the engine. what could that be?

You mention a "ticking" sound,,is this from the top or bottom of engine..?

Does the ticking go on acceleration or increase with engine speed..?

A ticking noise from the top usually indicates camshaft/valve noise..

Run your engine until at normal temperature, then turn off and leave for 5 minutes for oil to settle..

Make sure your car is on level ground and check your oil level..wipe dipstick and check it again, make sure you push the dipstick all the way in an re check oil level. Top up if necessary.

The best thing to do is remove old oil filter. Drop the old oil and fit a new filter, top up with new oil, run the car and check oil level again, top up if necessary.

Low oil and old oil can wear thin and cause ticking noise from top of engine, and will also NOT PROTECT your engine...oil is the blood of your car, check levels weekly at most and change every 12 months or as recommended by your car booklet.. Use the BEST oil you can afford.

Could be valve problems get a garage to check it out or to make sure get a two foot length of wood and hold it to the top of the engine against your ear while somebody is reving it up

A slipping belt makes a loud squeaking noise when the engine is running. The belt needs to be changed if it is cracked or fraying on the side, or if it begins to slip.

sometimes pieces from inside your catalitic converter break loose and make a ticking noise and would be hard to spot without the engine running

Before you change lifters try this trick. Drain 2 quarts of oil from the engine and top it off with auto trans fluid. Let the truck idle for 45 minutes or until quite , then change the oil and filter. I have made many lifters get quiet this way and it will not damage engine.

After it's warmed up to operating temp, if it makes the noise at idle but goes away reving the engine, I would guess that a lifter has gone bad. Rod bearings as a rule knock all the time. It's hard to diagnose these things over the internet, because there are so many variables when it comes to noises.

You need to warm the car up and then while it is running, open the hood and try to pinpoint the source. lifter noise will sound like a "tick" and come from somewhere near the top. Rod bearings will sound like a 'knock" and will come from the bottom of the engine.

could be a cracked flexplate (flywheel)

Noise out of the engine. Noisy valves? Low oil level? Is the sound like tick, tick, tick, tick......that's how bad valves sound. I don't know if you have solid lifters those have to be adjusted after some mileage. Hydraulic ones are self adjusting. Only a good mechanic can tell for sure.

Suspect transmission has failed. Recommend further diagnosis as transmission rebuilds are very spendy.

Starter drive not engaging fully . Sticky or worn, but don't think changing thermostat had anything to do with it. Try having starter drive inspected & lubed if possible , but you may end up with new starter.