Taxi Driver Online

So as my tx2 passes the 300k mile mark its running better than ever Its actually running quite well apart from this issue that has suddenly occurred

When trying to reverse the cab off the drive which is uphill first thing in the morning it really struggles. It slips in reverse really badly and you really have to put your foot down and rev the bollocks off it to actually get it to move and other times it just wont move at all. Drives absolutely lovely in the forward gears but reversing is a nightmare. Once the box has warmed up and up to temp it'll reverse a bit better but i get this awful judder when reversing constantly. I've also had it before where it feels like it struggles to build up pressure. What it does is there'll be no drive in reverse and then it'll bang into gear and suddenly shoot off because i've got the pedal depressed quite far which is a real issue when parallel parking nearly hit the car behind me a couple of times because of this . I did change the oil and filter in the box about a year ago but it has only done about 800 miles since as it only gets used occasionally. I checked the level and its up to the max with a warm box. The only thing i've noticed is the fluid has gone brown even though its only done 800 miles not sure if thats the old fluid thats mixed with the new fluid.

Any ideas on what this could be. I suspect that it might need a box rebuild or new box but anything i can do or check?

So took the taxi for it's mot today. Haven't really used it since this issue started. I seem to of completely lost reverse gear. Sometimes it will go when you absolutely rev the bollocks off it and then once moving its alright. I also had it where its stuck in first gear, switching to 2nd then drive would rectify this. Thinking maybe it might need a box rebuild. Any ideas?