Transmission mystery

[ettiennet]

My RR is a 2000 4.6 , very good mechanical condition (now it is), 155k km's .

In "D", when driving at any speed in highest gear, and I take my foot off accelerator pedal, it goes into neutral with engine idling, which gives me no engine braking, unless I force a downshift to 3 using the gear lever . When cruising at higher speeds (say over 90km/h), it will go to neutral as described before, but when I want to accelerate again, she bangs it back into gear with quite an uncomfortable jerk. It's always done this, since I've had it, about 18 months. No faults have ever come up when this happens...

Not one of my usual P38 fixers no what to do about this, and they say they don't know of another car that does this (go into neutral with selector in "D"). The Transmission oil and filter was changed, made no diffrence here.

Did Land Rover/ZF have different software for different models, or does mine have a bug ? Anyone out there have this? Any help would be appreciated.

(I posted this on Rangerovers.net, had over 100 hits, but nobody came back to say they have seen or heard about this).

[Pedro_The_Swift]

The smaller Zf's in the Disco's will go to idle under a certain speed, when approaching traffic lights etc,, I dont much like the loud bang bit-- how hard are you hitting the go pedal to achieve this bang?

[ettiennet]

Hi Pedro, thanks for your reply.

Because I'm expecting the bang, I try to just touch the pedal gently, but depending on the speed I'm doing, the jerk increases with speed, ie, the higher the RPM it ends up at. When I pull the selector back to "3", then it engages the gear very gently, as usual.

[PaulP38a]

I would be removing the xyz switch and giving it a good clean. Alternatively, see if you can borrow one from a well behaved P38 and see if it makes a difference.

[ettiennet]

Thanks Paul, I will do that, seems easy enough. I don't have any issues selecting gear though, the lights are always following the lever correctly, etc.

[PeterH]

Just out of interest, what atf are you using?
I remember reading not to use a fully synthetic atf in P38 transmissions as it can cause problems with the adhesives that bond the bands.
Don't know if there is any truth to that, has anyone else heard this?

[PhilipA]

Not True.
ZF list of recommended ATF for 4HP22 and later includes Transmax Z.
I have used it for about 8 years in my 92 RRC with no ill effects and good changes at 220KK.
Regards Philip A

[PeterH]

Thanks PhillipA, good to know that's not the case.
I read that on a Range Rover forum somewhere, good to remember the internet is like the drunk guy down at the pub...some truths mixed in with all sorts of rubbish!

[Pedro_The_Swift]

and the best thing about transmax z is you can use it in the Auto, PAS and ACE in the D2;)

[peter38]

I had a slip from 3rd to 4th in mine and after having it fully rebuilt ie new clutches gaskets new valve block and solinoids it still did it and all the gurus could not get humpty together again, so of to Davis L/R and they put a good HP24 from a HSE in it and its good, However the ecu has been told its a 4.6 europe I would guess so it communicates with the now 4.6 controller but when towing after a couple of hundred Ks the MAF goes of the air and idle runs at 2k she has run like a dog but then I hook up the Nanocom evo 11 and reset adaptives ,remove faults and away she goes like new again. I cannot alter the engine designation back to 4lt Aus it keeps defaulting back so I think the Becm may have been unlocked and altered as well, I dont know I will have to persist in questioning Davis L/R.

However back to your trouble I would have it read "diagnostic" poss trouble with controller/ecu or maybe adjustment on selector if to fine it can cause problems.

I