'06 XK8--
I was coasting until a traffic light changed. I tried a accelerate but instead heard and felt an substantial *BANG*.

The car still moves, but crazy shifting and some squeaking noises on the right side render the vehicle in need of repair.

Any insight on what to check will be appreciated.

PS- How much does a rebuilt tranny cost (ouch)?

 

Definitely check that right side. The transmission relies on the input of the ABS module for road speed. A failed bearing or ABS reluctor ring will confuse the TCM. After that, I'd say have the TCM diagnostics code read for more specifics. These later transmissions are not particularly prone to internal failures (disks, clutches), but sometimes need a rebuilt valve body. Of course, failed sensors can make small problems sound big.

Best of luck, keep us posted.

 

Thanks! I'll report on repairs.

 

Just to give you some data: a rebuilt valve body and Transmission Control Module will run about $1800....if you can find one. Add another $150 for fluid & filter, mechatronic sleeve, Then if a shop is doing the work....probably 4 hrs shop time.....have no idea what shop time costs these days.

 

Sorry to hear about your transmission problems. Good luck. This forum is a great source of information. Comparable repair costs on a 5 speed? Mine has 75k. From what I read in here,
it's only a matter of time. Fluid swap (using Mercon) and install of a Transgo (to reduce possible A drum failure) are planned.

 

Luckily, the problem turned out to be garbled communications. Coils #2 & #4 corrupted the network resulting in multiple drivabilty concerns.

All is well. Repair cost $725.

 

Two ignition coils caused all that trouble?

 

?????

Curious. Did you get any codes? If so what were they?

Very Strange.

 

Speaking of trans problems, I've noticed lately that my 04 XK8 convertible (111K miles) is making a sound at the same spot in the road frequently and I'm perplexed. It is a place where I am accelerating somewhat rapidly to reach traffic speed of 60 MPH and the road begins to go uphill around the time that my 5 speed trans shifts into an upper gear. The sound is best described as a "hoot" noise. Then yesterday it made the sound and fell flat on it's face momentarily. I instinctively let off the gas immediately and re applied and the car went on down the road. Could this be a failing torque converter? Anybody had this symptom? I'm an experienced mechanic and have rebuilt several automatics in my career and am also curious if I could rebuild the trans myself. I'd love to hear some input.

 

You likely have a case of the infamous ZF "squawk". Plenty of posts on here (and other car forums such as BMW that use the same ZF 6HP26 transmission). The friction modifiers in our ATF gradually break down with time and heat cycles, and the clutch packs can begin to grab. That is what causes the noise (but no harm, ZF tech support assures me). Doing a fresh ATF drain-and-fill with the proper fluid usually cures it. Quite a few of us having been using Mercon SP ATF for years now....

 

Thanks for the reply Jon89. I searched quite a bit but didn't know the name of the official diagnosis. I'll try using the term "ZF squawk". But I'm confused about the 5 speed vs 6 speed trans. My shifter shows only 5 speeds so I assumed that is what it is. Does the 5 speed share the same malady?

 

If it says 5 on the left hand side ont he selector you ahve 6 gears. The 5 speeds say 4 instad. The J-Gate just prevents you from selecting 6th gear because you would just move it to D for drive instead for that and back into automatic.

 

The 4.2 cars (2003 to 2006 model years) all have the ZF 6HP26 transmission that is typically called the 6-speed....

 

I see said the blind man. I'm getting older so I'm more easily confused apparently. Thanks, gentlemen for the enlightenment. A fluid and filter change is definitely in my future. If I keep going I hope to get this car to reach 1000 miles between problems someday. My record thus far is about 400. But damn it's fun to drive and pretty as anything. I appreciate the help guys.

 

For some reason I never get problems until I drive long distance and then it's just gearbox fault and restricted performance. If I give the car a rest it works just fine for a bit and then bugs out again. When I get home I give it a few days off and then never happens for a year until I go on holiday again. I replaced the thermostat this time so maybe that was the problem because it was stuck open. And the intercooler pump isn't working so I need to replace that, that could also be a problem. Gearbox oil is to be changed this next service so I hope when I go on a long drive up to Scotland next year it will work perfectly.