We picked up my wife's 2005 XJ8L with 120k miles , which had a lot of deferred maintenance from the second owner, but had previously been well maintained by a reputable dealer in Portland, OR with the first owner. We brought it up to speed maintenance-wise and it has been just fine to the current 146k miles. The trans has worked without issue, aside from Reverse taking about 3-4 seconds to kick in.

I decided that a fluid change with pan/filter/mechatronic seals would be ok to do at this time. Funny thing, as I was gathering all of the necessary parts and equipment for the weekend job, the car starting having trans issues the Wednesday while driving home, and threw the warning lights. My wife was on the phone telling me this, so I had her immediately pull into a parking lot and shut it down. I joined her (brought my ultra-reliable 97 XJ on my way home), and had a quick look. There was a little bit of fluid leaking on the ground from the belly pan, but not the trans itself. I figured we had a leak problem and hoped it had enough left to get home, since this was the first time of an issue. We restarted and made it home another 8 miles without much issue, and oddly no warning light.

Come Saturday, the trans light came on immediately when I went to move the car into the garage, and I barely got it in. As I was removing the belly pan, I noticed a LOT more fluid coming out of the nose. A quick check showed the cooler connection (luckily nicely at the very top) was totally loose, almost ready to fall out entirely. Why?? So I tightened it up and carried on with the messy business, knowing at least the only known issue was VERY low trans fluid.

Turned out that it wasn't too bad of a job, and the mechatronics unit was easy enough to remove/reinstall. The biggest waste of time issue I had was the little sensor (not sure what it is...vibration, inertia??) that was mounted on the tail under the electrical connection has a little plastic tab held down by an 8mm bolt. I accidentally broke it off of course, and had to rig some other way of holding down the sensor (or whatever it is). Once I got that done, the rest was easy enough.

So I ended up getting about 2 quarts total of old brown, fairly thick fluid out, and about 6.5 quarts (about 6 litres) of Mercon SP back in. I had no means of resetting or updating the firmware, so I will leave it to itself to sort things out.

It ended up being successful all said and done, and the wife says the car feels like it was given new life. Shifts great (except Reverse still takes 3-4 seconds to engage), and has given her no issues.

LESSONS LEARNED:
1) If you suspect a trans fluid leak, you're probably right. Don't forget the cooler lines!
2) Have a little stub of 8mm hex key for the side fill plug. There is no access for a socket wrench! I used an 8mm crescent on a 1-1/2 inch stub of high-strength hex I actually extracted from a socket.
3) Expect to strip a few of the original 27T pan bolt heads. It is just too weak to handle the removal torque. Luckily vise-grips save the day easily enough.
4) Expect to break a pan bolt or two from the replacement kit if you get the cheaper Chinese ones. The new bolts are T40 luckily, but the bolt grade itself is low. BE CAREFUL tightening, and might even go 5 ft-lb on torque wrench.
5) The fluid temp can rise a lot quicker than you think. BE READY to put the plug back in.
6) Finally, if the temp runs away from you and goes above 50 C, DON'T PANIC and turn the engine off! It makes a big mess in a hurry. Just put the drain plug back in quickly.
7) Don't be afraid to check your fluid level. It sounds intimidating with the temp sensing and such, but the hardest part is getting it jacked up level and safe (both directions).
8) Don't be afraid to change your fluid even if it is high miles and no known change has occurred before. Flush might not be a good idea, but at least a pan/filter change and new fluid is prudent.

 

Hi Erik,

Good post! Thank you for sharing your experience!

I personally have no reservations about flushing the fluid in high-mileage 6HP26s and have flushed numerous ones that had done over 120,000 to 150,000 miles. Recently I serviced an S-Type that had just turned over 200,000 miles that, as far as we could tell, had never had the fluid changed. The 6HP26 transmission had been shifting harshly for a long time, then developed a leak and began slipping. The owner was convinced the transmission was toast and that he would have to salvage the car.

The owner had already purchased a pan/filter and connector sleeve, but before I replaced those I wanted to be sure the gearbox didn't have any significant internal damage. So I added fluid to set the correct level (it took more than 3 liters) and took a test drive. The trans behaved much better, so I was hopeful that all was not lost. I proceeded to change the pan/filter, flush the remaining fluid and set the proper level. Then I cleared the adaptations and updated the firmware. The transmission now behaves as new and the owner is thrilled.

Your 2005 XJ would probably benefit from the firmware update if you can find an independent shop or a nearby forum member who has SDD with the necessary calibration files.

Cheers,

Don

 

One extra item I believe in was mentioned as a no-no. Do not be too concerned with fluid temperature on fill up. Then shift into park and turn the engine off. Dump a few more liters of diluted fluid. Then refill again and waiting for 50 degrees and install plug.
I like being OCD on maintenance. I feel this partial dump maybe removes one more liter of old fluid. Peace of mind.

 

I rarely recommend a simple drain and refill anymore because it's easy enough to flush the fluid via the cooler lines with inexpensive materials available at many home and hardware stores:

ZF 6HP26 Transmission Fluid Flush DIY

Cheers,

Don

 

The older now retired guy that ran the parts dept at the local Ford dealership told me, that these are modified truck transmissions.

 

The older now retired guy that ran the parts dept at the local Ford dealership told me, that these are modified truck transmissions.
Thats why their so strong with normal use, & care.

 

I don't know if that is true about being a modified truck transmission, but nearly all the vehicles the 6HP gearboxes were used in were passenger cars with the exception of a few SUVs like Range Rovers and the Ford Expedition/Lincoln Navigator:

https://en.wikipedia.org/wiki/ZF_6HP_transmission

 

Excellent info, thanks! I had read your great comprehensive post on the DIY flush. I had one question about that: Upon removing the lines at the transmission, how much fluid will drain from them? It sounds potentially messy at that moment.

There is a good foreign shop here that knows Jags well ( Henry's Auto ? Foreign Auto Service and Sales near Medford, Oregon ), so I will check with them concerning the SDD firmware update. Any idea what to expect for the fee?

 

When i asked for the XP fluid we got to talking when he found out what it was going into.
Said that not many vehicles other than trucks, or thats what the XP was designed for.
Made sense to me as when i was young, truck clutches & many other drive train parts were truck parts.
After market types that hopped up their cars to make them stronger.

 

An hour of shop time would be fair because they will need to connect a battery voltage maintainer, scan for stored Diagnostic Trouble Codes and clear them, clear the Mechatronic adaptations, update the firmware, and test drive the vehicle to confirm proper operation. If you want them to complete the adaptations drive cycle, that alone can take more than an hour, but if you just drive the vehicle normally all the adaptations will eventually reset.

 

That's an intriguing story, so I just did a little research to see if there is any evidence that the ZF 6HP26 evolved from a Ford truck transmission. I couldn't find anything that suggests this is the case. The ZF press materials from the introduction in 2000 suggested the 6HP26 was evolved and improved from ZF's own 5-speed transmissions, such as the 5HP24 used in the Jaguar X100s and X308s.

According to Wikipedia, for what it's worth, Ford used Mercon SP in the 5R110W 5-speed transmissions in the F-Series Super Duty trucks beginning in 2003.5, and they used Mercon SP in their versions of the 6HP26 (6SHP26, 6R60, 6R75 & 6R80) from 2005 to 2008 in vehicles like the F-Series Super Duty trucks, Ford Expedition and Lincoln Navigator.

https://en.wikipedia.org/wiki/List_o..._transmissions

Since it appears the 6HP26 was introduced prior to Ford's introduction of the 5R110W, it doesn't look as though there is any merit to the idea that the ZF evolved from the Ford. I haven't found evidence that Mercon SP was used in any other transmissions, but I would be curious if you come across any.

Cheers,

Don

 

Like i said thats what i was told, this was a modified truck transmission..

No way to verify, or to prove false, seemed possible but who knows?

 

Well, after working perfectly for 3 days, on the fourth day drive home, it started slipping and throwing fault light. After coasting into a gas station parking lot and sitting for a few minutes, it managed to drive another 5 miles to home, where it then threw fault light and slipped so badly it would not move any further. At least it got the wife home.

I went through the whole routine again to verify the connector was good and replaced fluid again. NO JOY. Off to the shop to determine least expensive route forward. :-(

 

The issue sounds expensive. There are several import car parts resellers here. Salvage yards. They have x350’s. Not sure what a transmission costs. I have seen several junkers that had engines and transmissions intact.
I might go that route if a transmission was needed. The ZF transmission is tough. The low fluid level most likely caused your issues.
Running x350 show up on eBay for 2 -3k. Hopefully a transmission is 4 - 500.00 from a salvage yard.

 

Looks like quality used trans with 60 day warranty run around $700-1000 . Mine is super clean other than the issue, so hopefully it can be repaired for similar cost. Hoping to keep it under $2500, but likely will run up closer to $3000 to get her back on the road. Though the values are dropping, the car is too nice to let die from this!