XH II XR8

A couple of questions, on a 1998 XH XR8 what controls the kick down? driving at 100kmph cruising with light throttle the trans will kick back to 3rd gear by its self, by pushing you foot to the floor will make it change back up again at high revs to top gear. at times jumps straight back to third but comes right for 50-100km or so then with no issue. a 200km trip could see it do it 3-4 times. trans shifts smooth, functions normally other than this kicking down by its self. any thoughts people? cable? solenoids? sensor of some sort?

got rough shifts real quick and wouldn't change higher than 2nd from memory, warranty paid just on $5K to rebuild and that was probably 5 years ago or more. was the family car but now just parked in my shed for odd cruise days.

no heat shield not on it. problem was very intermittent, could drive for an hour and it does it once then was fine. hot of cold. 5 minutes in or a hour. nothing constant about the fault. the gasket/ trans has two bolts on one side and one on the other, under the actual bolts there is no loop or gasket just a gap where a gasket should be. surprised it still sealing. yes my GT-P also has one (4 speed) going to swap it for a 6 speed auto or manual once i get time. 4 speed has gone once but was rebuild under a aftermarket warranty. standard cooler not big enough was the issue in they say. (the 500hp the car is may have also played a part...lol)

Thanks Dave good to know, i will check that as well. (I was working of what the service tech said on a previous car i owned (EF XR8 SVO)) I have solved the changing issue, I have only owned it for 4 days and this frustrated the crap out of me. the previous owner drove it for a year like it was (not every day.) The plugs on the inhibitor switch on the trans were dirty and with a clean with some electrical cleaner the trans now works perfectly. Will now shift manually as well and hold in a lower gear if selected. interesting enough when i was under it checking i see some muppet that has serviced the trans at some stage has put the pan gasket in backwards. will be put right when i service it at a later date.

that was on my mind how ever on a XH its a sealed trans so i cant check, dealer needs to. looks nice and dry with no leaks. how ever i did notice today that when i select 1 gear and drive off it still changes right up to top gear. this is normally the inhibitor switch on the trans so will chuck one of those at it tomorrow hopefully if i can get one.

maybe its 2nd it drops to?.. it sits on about 2000rpm at 100kmph and when it changes its self down it slips around to about 4500rpm. a stab on the gas to accelerate slightly faster speed seems to get it to drop back to the higher gear then doing maybe 2700ish rpm then again shortly after back normal 2000rpm for the 100kmph (ish) not always exactly at 100 either could be 95-105 trouble is to get it to do it i could drive 50-100km down the road before it does it once. its not like it does it every time it hits 100kmph from a standing start it changes up smooth and up perfectly. up and down shifts.

yeah im sure it changed to 3rd as once it changed back after flooring it it changes to top then the lock up clicks in soon after.