Hello Everyone and Happy New Year!
As the post title says, I have been experiencing a problem with my transmission shifting - it is a ZF4HP24 as I have a 2000 RR Vogue with the 4.6 Engine.(Bosch)
This has been an intermittent problem that has been haunting me the last three months, but now it has become constant. What the problem is, is that from a standing start, the transmission will shift sweet as you please, but as you accelerate and go through the gears, it appears to 'hang' on third gear and is very reluctant to shift to fourth. Previously, as I accelerated, i would see a shift between gears at 60kph and 2100RPM, but now I have to continue accelerating so as it appears that the Tachometer and Speedo are synchronized but I do see a very short shift when in the 70-80kph range and the RPM settle to where they normally would be. By short shift, I mean it goes through two gear changes in rapid succession. I am down to my last few ideas, but none are really practical without draining the transmission and inspecting the valve body/galleries for gunk or blockages.
By reading this forum and conducting many searches, here is what I have checked so far:
-'SPORT' Button - this is not depressed and I have nothing to indicate it engaged - when I do press it, the information displayed indicates that I am now in SPORT mode and the 'hang' up is still evident.
-MAF Sensor - this has been thoughrally cleaned with CRC MAF cleaner and is now spotless.
-Transmission Fluid Level - I have checked the records I have and DexIII was used to fill the transmission. I have checked the fluid level per the guideline provided in RAVE and workshop manual - what fluid did drip from the plug was clean with no odd smell.
-Throttle Position Sensor - this was a long shot, but the potentiometer as a smooth resistance curve when tested with my multimeter.
-EAT ECU volatile memory - this was suggested by a mate and as it cost nothing, I tried disconnecting the battery per procedure and reconnecting an hour or so later. No change.
-I have inspected all of the plugs located on the transmission and could not find anything amiss, I gave them all a squirt of electrical contact cleaner anyway on the off chance that there was a bad contact.
-The transfer case change to Low Range works perfectly with no errors observed and same in Manual mode. The shifter cable does not appear to have any undue slack and all changes to gear are reflected in the Binnacle information display.
So guys - where do I go from here? I am thinking my next course of action is to drain the tranny and drop the valve block to check the shift solenoids and clean the galleries of the valve block. This is really the last option in my mind and I am game to try anything that you could suggest. Lets hear those ideas!