Hi, my 05 XJR has just developed an intermittent problem in the transmission since yesterday. Every so often, it refuses to change to a lower gear when the car is driven off from a stopped position and remains in 2. I noticed this happens more frequently when the car is in the sports mode. It has no obvious relation (yet) to whether it's the first start of the day or later (but of course this has only occurred since yesterday.) Interestingly enough, the car does change to a lowerr gear when I flick the selector to the left, "manual" side, of the J-gate and then flick it back to D immediately. No error codes have been displayed over this entire period.

This staying in gear problem has happened about 3 times yesterday.

Today the car seems fine although there is a hint of the engine staying longer on the same gear in the sport mode, although it does change over ultimately..

I'd like to ask if anyone has any real idea what the problem is. Thanks

 

When NOT in sport mode, it should start in 2nd. If its on, you get the low gear. Your symptoms in reverse sounds like a gear selector problem or sport switch.

Always check linkage and cable first. then move to the more complicated stuff.

 

Same thing happened to me as I always suggest check the mass air flow sensor

 

Thanks. Will start there.

 

Thanks for the suggestion. Just for my better understanding, how does the mass air sensor link up to the transmission? I know the electronic links on this car are complex. When I had the dreaded throttle body problem, it also showed up as a transmission error message so I was stumped into figuring out the link, but of course this time there are no fault codes shown (yet).

 

Yeah that I never figured out lol but believe me when the air flow sensor is bad u feel it from your tranny

 

I do believe most cars get data from the MAS or MAP sensor on how to shift. The same was true to my girlfriend's 2000 Cav. The vacuum line came off the MAP and it was shifting hard. Also, the ZF starts in 1 no matter that mode it is in. I do know the older GM trans in the 95-97 XJR would start in 2nd unless you are in sport mode.

 

You mean the old Mercedes transmission?

 

Sorry, my mistake, maybe it does start up in 1 and not 2. Somehow I've always thought it starts in 2 like all my other previous automatic cars, which only start in 1 in the manual (semi-auto) mode, and not in the full auto mode (this is the problem with not having a gear display indicator in the dashboard, which my previous auto cars had). Bottom line though, it does still hang on gear intermittently, in the sport mode, with no warnings shown in the LCD display, but this hasn't been occurring in the normal mode.

 

I wish the car started in 2nd. All that torque with a low gear can make driving a little difficult off the line. The 95-97 XJR has an 4L80-E GM trans. All other XJ6's had a ZF 4HP 22 or 24E. Did Mercedes make it for GM? The way thinks work in the past 20 years..who knows who made the original of anything.

 

Sorry, the Mercedes tranny was in the supercharged V8 cars until the ZF took over.