Why is the transmission still giving problems after a second replacement?

Hello, Dave here, contributing to RepairPal and providing expert advice since 2010. My first thought is, has this vehicle been in some sort of accident which has caused frame damage or unresolvable alignment issues? Secondly, are all the tires exactly the same size, brand and worn evenly? Tires that are dissimilar can cause drivetrain issues. I question if the folks testing your vehicle are mindful of your concerns and trying to drill down to the cause -- it would seem to me something is not being found here. The replacement transmissions - if not of high quality - could also be suspect of course. As far as fumes and leaks and engine performance issues - this all needs competent troubleshooting. From my computer keyboard it is difficult to offer much advice without being able to evaluate your vehicle -- so my best suggestion is to get someone trustworthy and skilled near you who can thoroughly do that. Reach out to a shop near you -- https://repairpal.com/auto-repair-near-me Click the link or call us at 877-913-1554. We'll gladly find you a certified RepairPal shop in your area.