It is NOT an interference engine. If you are changing the belt at 90k interval, I think doing the hydraulic tensioner every other TB is reasonable. Personally, I use a 120k interval and do EVERYTHING, including the hydraulic tensioner.

I thought there was some distributor-ingrained thinking there. I can relate; I am still recovering from the first, last and only time I installed a dizzy 180° out of phase, and that was over 20 years ago. Not a mistake you make twice in the same lifetime.

I still work on one regularly as my 1966 International Farmall 140 tractor has a 4-cyl 123 CID distributor ignition engine (converted to electronic ignition but still mechanical distribution).

DOH. I didn't pay attention to what section I was in....

I can't speak for the aftermarket belts, but I can't recall ever seeing one of the factory belts breaking on a 3.4L. I'm sure it happens, but I only ever see the 5S 4 cylinder timing belts and the occasional 2UZ...which gets very expensive very quickly.

I agree--the only time they go is if something kills them: the WP leaks or seizes or an idler seizes or the hydraulic tensioner wimps out and it slips. The WP is more likely to die than the TB. That's why I let it go to 120k and then changed everything.

On the subject of WPs...

I was losing a lot of water from my water pump weep hole (I believe). Out of desperation and being 5 hours from home I used a cooling system “magic” stop leak. My idea was that I would fix it properly when I got back home. Well, the magic held up for a few months before I was forced to really fix my problem the correct way. Can I reverse the damage done from the “magic”? I plan to flush the system again.

I am one tooth off when I put my TB on per the line on the belt. The passenger side cam jumped so I had to realign it. I assume these marks on the TB are important?

Assuming TB means timing belt.

Yes they are important. That's why they are there and you need to have them all aligned or your valve timing will be off, just for starters.

Yes, TB (Timing Belt). I will have to figure out to make that work out in the morning. I just can’t seem to get all three TDC marks plus the marks on the belt itself to all be aligned.

Belt on backwards possibly?

Use something to clip the belt to both cams when they're lined up. Use some chip clips or something. Then you can use a wrench to shift the cams one way or the other however you need to to get them to a place where they won't try to jump and get the slack in the belt where you need it to get the mark aligned on the crank last.

Your belt might have some arrows on it somewhere in addition to those marks. If it does, make sure the arrows are pointing toward the front of the truck.

Once you get all three positioned, turn the cams inward toward one another to pull any slack from below out to keep it locked in place on the crank. While the slack is drooping at the top, you can put the top idler bearing back in. The final thing will be turning the left cam counter clockwise so that all of the slack is between the passenger side cam and the crank shaft so you can then pull the pin in the tensioner and it'll remove that slack. Before you put the covers back on, triple check that all of the marks are still lined up.

Nope. I've got the arrows pointing towards the front of the truck.

Copy. I have some big clips that I can use to get the lines "lined" up. I will take some pictures this morning.

I have been burned by that so many times. The best was when I tried to tell a 5th gen guy how to check his trans fluid on the dipstick...

Here is how I did it. Standard little black binding clips: