Whenever I ask my horse for a lead change through a diagonal he will only switch his front but not his hind. When I'm jumping, he will normally land on the correct lead but if he doesn't he usually switches it himself. I was hoping I could get some advice on how to help my horse get a full change. Any advice would be awesome!
First I would check soundness issues. Some horses don't want to change behind because of hock problems. Once you rule that out.. I will describe how I ask and get the hind change.
Going across the diagonal, make sure your horse is moving foward not behind your leg..... lets say on the left lead; use your right leg and start a leg yield to the left keeping the horse straight; use your right rein, supporting w/ your left rein; so you get to see the inside (right eye) but don't allow the left shoulder to drop out (that is what your left rein is for) at at the same time as the rein work; soften w/ your right leg keeping it and the girth supporting that side of the horse use your left leg and drop it back a bit behind the girth (as if you are pushing the hind end to the right (new inside) do all this to ask for the change. Make sure you are stitting upright; don't lean inside or outside. You can shift a bit of your weight to the left allowing the horse to free up the right shoulder for the change.
When my horse was originally learning changes at one point I used a small Tom Thumb type spur and used it (as I described the above change from left lead to right lead) I would tap left spur just behind the girth for the back leg change.
Make sure you don't over use this because you don't wanting them to get all keyed up. Depending on the horse.
Working on Dressage movements on the flat like leg yields shoulder in etc. REALLY helps....
Live in the sunshine.
Swim in the sea.
Drink the wild air.
I like to do counter canter and spirals to help build up strength behind, balance, and responsiveness to the leg. If you have it available hill work can also develop hind end strength.
Also, I sometimes find that they change in front first because they are rushing and anticipating the change so lots of simple changes to make sure they are listening and also to get them working off the hind end. If they are ready for a flying change they should be able to do a good simple changes with minimal trot steps. I also work on canter transitions, first trot-canter and then walk-canter. In order to do a clean flying change, they need first to be able to execute a good walk-canter transition.
If they are just being lazy behind, sometimes the crop behind the leg will be enough to remind them, but for the nervous ones it can make them too anxious. I have one that if he gives me a late change behind a little reminder with the crop and he's perfect. Another one I tried that with and we nearly jumped out of the arena.
I would need to see you asking for the change, but there are a few things that tend to lead to front lead only change.
Caveat....before you can really ask for a lead change you and your horse need to know all the aids, and have a good understanding of the basics, shoulder-in/out, haunches-in/out, half-halts etc.
First thing, make sure your horse is on its hind-end, if your horse is on its front-end you will never get the change. Try to reinforce the idea of the horse being on his hind-end by asking for a half-halt before you ask for the change.
Second thing, ask for haunches-in. Remember the change is all about the engine behind, you need to be able to change that gear behind or you will only get the change up front.
Third thing, rhythm, a horse can only change its lead a one instance during a canter stride, you need to ask at the right time for it, or you may end up asking for a front change only. You need to feel when it is possible for your horse to swap, when the desired lead hind leg is not under your horse, for your horse to be capable of it.