So I have a 300+ 39" wire fence to stretch. I started with an H brace properly built. I have got a combo of wood posts and t-posts. There is some uneven ground. Some ups and downs. Nothing radical. I use a fence stretcher attached to a come a long anchored to my deere tractor. For some reason I can pull it really tight. Use proper staples hammered into the wood posts. T-post clips attached. Take the tension off and it loosen's up enough to not be satisfactory. I am wondering wth I am doing wrong????

Fence posts either not deep enough or strong enough. Put a really strong one in to anchor the first section, then continue off of that.

I do not think the posts are the issue. They are not moving and are good sized and rock solid.

What kind of wire fence? Chain link? If chain link, are you using tension bars.

No, it is like Redbrand field fence. Mine is H&H brand I believe. Quality fencing built in OK. USA.

We used two fence pullers on the tension bar, one on top and one on the bottom. That's all I got from memory. We used it for horses,

ETA: we did a whole length at one time, not in sections.

Is your Tractor strait inline with the section of fence or off to one side a couple of degrees? i found when we ran our fence if i was off a couple degrees going away from the posts I was attaching it to that the section wouldn't be as tight as I liked. After the first section I made sure i was off a couple degrees in the direction I would be stapling the fence to the post.

As for the ups and downs, I had some interesting grades to cover. anything past about 10* and I found it easier to put a braced post at that point and after 25* an H post was necessary.

If less than 10*, I stretched real tight, like probably tighter than I needed. Then I installed the t-posts prior to tacking and releasing tension.