Bongo Fury

Hi All,
Back after a few years and needing some help pretty quickly.
Can anyone help me pinpoint why, when driving uphill and under load, the autochange is fine for 1st, 2nd, 3rd (I think) and then seems to rev up past 4000rpm then reluctantly "tries to change to 4th". If I back off the throttle, it does drop in gear, though when revving again, it is comparible to a "slipping clutch-free revving" of a manual car, with no discernable power output or acceleration. Also,
if I am going downhill and put my foot down at about 60mph, the same thing happens-free revving.

There are no noises, bangs or anything else-the van also seems perfectly fine at lower/around town speeds and driving conditions. Been told "AT oil is low/old (it is old I admit), pressure seal gone, higher range clutch (?) gone etc etc" I just want the guys that know Bongos best-you, to advise before I put it in the garage.

Any help really appreciated.
Thanks in advance,
Tim (S Wales)

If it's old you should change the ATF - it will make a world of difference
Your problem sounds like I had when my fuel filter was blocked. I know that sounds funny, but a new filter fixed it completely - I think it's something to do with the restricted fuel flow making you push the accelerator more, thus fooling the throttle position sensor and the gearbox (something like that anyway )

I'm sorry to say that this sounds like the start of failure of the high clutch to me. If I am correct you are looking at a transmission rebuild to sort it reliably. By all means try changing the oil & clean the filter but I feel you may be wasting your time & money.

Thanks guys, sadly a full recon was needed.
One garage wanted £1250+VAT! shopped around and would recommend Cwmbran Gearbox Centre (South Wales). Great service-sampled oil, tested and drove it (rather than the usual 5 min test drive and prognosis!).
Cost was £895+VAT (£1074 all in). Realise the box was on way for while now, as the new one actually feels "tight" and positive on shifting.
Thanks for the replies.
Tim