Hello; I have a 99 xk8 with 84,000 miles it has run without any problems since I bought it over a year ago until the other day. I was coming off the interstate onto a sharp exit ramp and I shifted to manual mode in the J gate to 4th gear then to 3rd at around 45 mph to slow down rather than just using the brakes when I shifted to 3rd the car started bucking for lack of a better phrase so I shifted back to 4th and and the bucking stopped I then wen over to drive. At the next traffic light the car shifts smooth through to 3rd as always but the 3 to 4 th shift is rough not like a bang into 4th but clunking ( or lagging) into 4th once in 4th the shift to 5 is normal and the car drives normal in all gears it just has the rough shift 3 to 4 .... any help on what to do , cause of problem and recomended repair. also what model trans are in this year?
thanks
ward Moore

Retired USA
Yorktown Va

 

Get the car into a tranny shop as soon as you can, would be my recommendation.

 

The Rotary Switch is a common source of problems for these older transmissions, and using the manual shift function in the J-gate will usually bring the problem to the forefront. This switch is located on the side of the gearbox and sometimes gets wonky when the "manual" side of the J-gate shifter is used.

The Rotary Switch occurred to me because you say the problem started as you went to the "manual" side of your shifter.

So, how does your car behave when you're only using the P R N D side of the shifter, and NOT using the "manual" side?

Are you able to read the diagnostic codes?

My 1997 has a ZF 5HP24 gearbox. Not sure if that exact model is used in a 99.

 

The same model ZF is in the '99.

 

JGate is not recommended for downshifting manually, and you wouldn't be the first to hurt the tranny by doing so. I'm with cohi on this one, let a transmission shop or dealer diagnose it. The TCM can provide lots of feedback to diagnose individual gear problems like solenoid activity, but you would need AutoEnginuity scanner or dealer software to communicate with the tranny. I'm normally optimistic, but not getting a warm fuzzy on this one.

 

The Transmission has the rough 3rd to 4th while being operated in std mode ie: D it does not seem to make any difference if you are in "S" mode or not. I have not tried the manual side since this started. There has been no fault codes or reduced performance indications either.
Thanks

 

H20 I hear ya on the "not recomended" on the down shift using the J gate, that's the first thing my wife said to me and I would hate it if she were right( it's her car) I'm use to my BMW's, have had several and using the manual side has never been a problem and this just happened with out much thought on my part. I will take it to the local dealer and let him run the diagnostics.
Thanks

 

Hi Matt Whats the ins and out about using the J gate? Is it bad to go across from D to 4 then to 3 and use the power with more control of the squirt?

Thanks Al

 

Where's the recommendation not to downshift manually? That's exactly what the Driver's Handbook does recommend:

(This is from the six speed 4.2 handbook, but the earlier 5 speed follows similar text)

'When driving in gear position D with sixth gear engaged, the gear selector can be shifted horizontally across the gate to 5. Provided the vehicle's speed is not too great, the transmission will shift down to fifth.'

'To achieve appropriate levels of engine braking on roads with long downhill gradients, position 3 or 2 may be selected depending on road or traffic conditions.

When the gear selector is moved from D, 5, 4 or 3 down to 2, downshift to second gear will only take place at appropriate road speeds'

And for those who really like to abuse transmissions:

'selecting reverse is inhibited when moving forward above 5 mph.'

Is there a dealer only circulated publication that expands, revises or contradicts this advice?

 

I agree, downshifting with the j gate should be fine. The tranny is programmed to not destruct when shifting in any bad way. If you try downshifting to 2nd at 130, it just will not do it until the speed drops. The tranny just needs to be looked at, it's the tranny, not the shifting that did it. On that note, I would not commonly use an automatic to slow down unless I planned to do a burnout in a lower gear after the slowdown. This kind of driving is fun, but hard on equipment. Harder driving will explore any weaknesses in the equipment and hasten its failure. I will also add that the mileage on the cars tellls me that it neesds a fluid and filter change. Hard driving on dirty old fluid with worn out friction modifiers is risky. Fluid needs to be changed at 60K without fail.

 

I would guess that the 4th gear micro-switch in the selector lever illumination module is not operating properly. It could be faulty, disconnected, missing or the plastic 'disc' is broken or missing.

You need to remove the illumination module to inspect the disc/switch for correct operation.

bob gauff