how often should tranmission fluid be changed?

Transmission fluid should be changed every 30,000 to 60,000 miles. If under heavy use it should be changed every 15,000 miles.

Reasons you could be shifting hard, throttle linkage damage, wrong type of transmission fluid, low transmission fluid, engine malfunction, etc.

Lucas Transmission fix, say stops slip, and its not like the old or cheap stop slip products that ruin the trans, It helps lower temps and rough shifting, and hesitation, and seal leaks too, works in most if not all trans including light duty manuals.

Also Lucas Oil 10441 Automatic Transmission Fluid Conditioner is great too.

Or lubegard

Lucas transmission fix is thick goo that changes the viscosity of the fluid. I would not use it.

Lubegard is best (except for Type F or CVT for which you do not use it for.) The Lucus does not stay thick when mixed in rest of fluid, as with any trans fluid add it when warm and while running in park and never over fill. If you have any seal leaks, use it first, and let it work for a while, then use lubegard to fill back up to fill line or drain or syphon out enough to get the proper amount of it in(1oz per quart). The lucas seal condition is good and will not do any harm to trans otherwise, it works and the lubegard is better for everything else. If you have no or few seal leaks go straight for the lubegard and there is many to choose from for specific use as-well as the universal which is good on its own. The lucas does not turn the fluid to sludge. The lubegard has friction additives that work so much that if your scared to do a filter & fluid change you do not have to worry about it with standard pan removal filter & fluid changes and then add it back it with new fluid unless its already slipping bad.

Of course if your fluid is not nice clean red then change your filter & fluid before adding any additives.

If your trans is slipping and will not drive, No additive will cure this. They will however help to prolong the life of a trans if it still works. Also if your trans fluid is very dirty but still works plan on doing trans filter & fluid changes way more often preferably until it stays red without a power flush to get it there as this removes the friction additive off the clutches and will start slipping on older clutches.

If the ATF turns brown and smells burnt you waited way too long. The Lucas stuff can make your transmission last a while longer if you are having problems but I would not use it on a transmission in good shape.