Hello,

I been doing some reading on the Disco 1 ZF 4HP22 transmission and on forums for the other cars that use the same tranny there are lots of people saying you shouldn't rev the engine in park or neutral. There were apparently a couple of TSBs from Volvo and others stating the same thing (because engines would be revved for 30sec at 1800rpm in park or neutral for emissions checks). Has anybody here encountered similar issues with Discos? I'm asking because I've revved in park/N on numerous occasions. The TSBs state that this issue occurs when shifting to P/N from D. Apparently if you shift to park, turn off the engine for 1min then restart in P you're ok since oil pressure drops. I'm still not certain what problem this is supposed to cause.


RM

 

Not sure if this pertains but, are they talking about doing a stall test, 10 seconds in drive and the rpms shouldnt climb above 2200, then letting the torque converter cool for an hour before doing the test again.

 

Never heard of this as a problem for the ZF that is being used in your trucks.

 

The only problem I can see is if you are revving the engine and then drop it into drive.

 

Thanks for the responses. I get the part about shifting into drive while revving. I'm just curious about this whole thing because on the volvo, BMW and some range rover forums for cars that share the Disco ZF 4HP22 transmission they make a big deal about it. The thought seems to be that if you shift from Drive to P or N, the pump doesn't turn off, causing clutch damage to the point that there were TSBs saying to turn car off for 1min to depressurize, then restart in P for revving. I'm not trying to make a big deal of this or anything, just expanding my knowledge.