Hello, I follow this thread with interest. I have a slight hesitation between 1 and 2 on my 2004 XK8 at 50,000 miles. It feels like a manual shift and slow engagement of a clutch. Should I change my ATF, and what type of fluid should I stock? Will I get into any trouble using Grant Francis' procedure that would mix the old with the new fluid? I have 4 post lift so no worries draining, just wondering about the filling. I also consider refreshing the power steering fluid, should I use the same juice? Thanks so much for these interesting replies.

 

Hi jagophile,

Your '04 XK8 uses the ZF 6HP26 six-speed transmission. See the link below for a fluid change DIY:

ZF 6HP26 Transmission Fluid Flush DIY

Also note that there are only three fluids currently known to be correct in the 6HP26: ZF Lifeguard 6 (the original fill, also available under the Jaguar brand), Ford Motorcraft Mercon SP (chemically identical except for the red dye), and Shell Spirax S4 ATF MSP (Shell is the manufacturer of ZF Lifeguard 6 and Motorcraft Mercon SP). These fluids have a very low viscosity of 26.8 mm2/s at 40 deg. C. These are the only fluids approved by ZF or Ford for use in your transmission, and based on our extensive research, they are the only fluids suitable. In the U.S., Motorcraft Mercon SP is usually the most affordable fluid.

Other fluids that claim to be compatible have proven to have higher viscosities, different base oils and additives, or other incompatibility issues, so do not use MaxLife, Castrol Transmax, Pentosin ATF 1, Liqui Moly, or any other fluid in your transmission. We've researched them all.

Cheers,

Don

 

Thank you Don, I have a case of Mercon SP on order $85, The link is most helpful and it seems most prefer a 3x fluid change to get as much fresh ATF into the system as possible. Here is a silly question, some advocate replacing the OEM torx t27 with larger T40 torx screws. Is there any reason not to reuse the original T27 screws? I turned the T27 just to check and none of them are hard to remove. I have yet to find the torque spec for these screws but I suspect it is not much.
Parker thanks, what fluid do you use in your power steering system?

At the risk of drifting this thread, while inspecting the pan I noticed the four U-joints on the independent rear axles have grease fittings. Of course I'm going to grease them, but where else on the XK8 are there zerk fittings? I may as well get them all at one time.

 

Hi jagophile,

I have moved your posts from the X300 forum to start your own thread in the X100 forum since your transmission questions are not relevant to the X300.

The transmission oil pan screws tend to corrode and the small T27 sockets in the screw heads tend to strip out when attempting to remove the screws. If all of your screws loosen easily, you can reuse them, but clean the threads well and run a tap up into the threaded holes in the transmission to clean away all of the residual aluminum oxide corrosion.

The torque specs for the screws depend on the type of pan you have. See the document at this link:

ZF 6HP26 Oil Fill Instructions

Cheers,

Don

 

I thought I'd share my experiences with changing the transmission fluid in my 2003 XKR convertible, with XF 6HP26 gearbox, 88,400 miles. Car lived in New York City her whole life until she retired to my home in Florida in 2021.

I first loosened the fill plug using an 8mm hex head 3/8" drive socket, with a 3/8" to 1/2" drive adapter, and a 1/2" drive 18 inch breaker bar to loosen the fill plug. Do not remove this plug at this time. I did, and got 48 oz of fluid out. I thought it was a good idea to loosen this first, so that if there were any problems, there was still fluid in the gearbox.


I then removed the drain plug and got another 64 oz of fluid out in about 10 minutes. I reinserted the drain plug and tried to remove the 21 Torx pan bolts. You MUST use a name-brand Torx bit for this (e.g., Craftsman, Husky, Snap-On). If you use a cheap Chinese Torx, it will just mess things up. The bit will strip, and possibly mess up some of the Torx head bolt. I had 4 bolts that the head stripped out on, which isn't surprising since the car came from New York, and they had some corrosion on the bolts at the front of the pan. I used a 3" cut-off wheel for three of them, and a Dremel tool with a cut-off wheel on the fourth, due to limited accessibility. I used the cut-off wheels to cut a slot in the bolt head.


I then used a handheld impact driver to loosen one of the bolts. I only mention this in case you don't have an air compressor and impact gun. Not sure if these are still available, but I'd bet so. I used this method on one bolt, but decided to pull out the air gun for the other three bolts.


I could then lower the pan, and got another 28 oz from the pan. Due to my schedule, and I also arranged it this way, the car sat on the lift for 20 hours until I could work on it again. In that time, an additional 19 oz of fluid came out, for a total of 159 oz (5 qts). The fluid was like black water, but luckily did not smell burnt. That is my highly calibrated measurement system, made from a 1/2 gallon juice jug. Sorry the picture is sideways. I know that others have said that they got 6 qts out, but I had to deal with what I had taken out, and face the possibility that my gearbox was initially 1 qt low.


Since i knew I was going to run some fluid through the gearbox, I cleaned the old pan/filter out and reinstalled it. Before installing it, I sprayed penetrating fluid into each hole, and chased the threads with a 6mm x 1 mm tap, just to clean up any corrosion that might have been in there. I purchased a box of 50 units 6mm x 1mm x 30 mm hex head bolts from Ace Hardware for $12, and already had 5/32" ID x 3/4" OD fender washers on hand, to replace the Tork head bolts.

A little aside here: A buddy from high school (class of 1979) worked for General Motors. He told me that they used Torx bolts on the assembly line because they were quicker than regular hex head bolts and washers, and the tool was less likely to slip out and cause damage. If you look up the Torx wiki page, you will also see that you can apply more torque on them than regular Allen head bolts. Interesting discussion there that I won't repeat here. So, yes, it took me slightly longer to install the hex head bolts, and I'll lose a point at my next concours (not likely). My solution works. These bolts were installed without anti-seize. If you insist on using anti-seize, reduce the installation torque from 88 inch-lb to maybe 75 in-lbs. The 88 inch-lbs is for dry threads.

Another aside: I thought I saw that someone else had several of their Torx bolts strip out. They just cut the heads off, and removed the remaining bolt with locking pliers. Not an ideal way to do this, and I would suggest my method first. If the head gets twisted off, you would have no choice but to use this approach. If you do have to use that approach, and the bolt is sheared off at surface level, that person said to drill the bolt out and use an easy-out screw extractor. That isn't recommended either, as there is a better way. There is a tool called a Rescue Bit (only available on Amazon as far as I know) that goes into a Dremel tool. It allows you to grind that bolt out in little tiny dust. I've done this with a water pump bolt that broke off in the aluminum block of my Lotus Esprit. There were still threads left, but not enough to hold a bolt. Your next step is to use a Time-Sert (also only available on Amazon, as far as I know). It's the same concept as a helicoil, but helicoils are crap. The Time-Sert is basically a solid bolt, with external and internal threads. You drill the case out bigger, tap it, and install a Time-Sert with a special tool, then your bolt just screws into that. I HIGHLY recommend that approach. I've talked with a machinist that would basically do the same approach, using a bolt, but once the bolt was installed, he would cut the bolt off and drill it out, but if the drill bit slipped, the housing (e.g. engine block, transmission) was trashed. He was working on his fancy-*** drill press, and you want to do it using a hand-held drill? HIGHLY recommended that you look into these two tools. They are a lifesaver.

Back to our main story: Old pan was clean and reinstalled, and I added 5 qts of fluid back in through the upper cooler line, using a Slippery Pete fluid pump (also on Amazon). I liked this one because it had a barb on the end to hold it in place when filling the gearbox through the side hole (coming up). I had thought about using a funnel, but the hose opening was so small, it was just better to pump the fluid in. Remove the upper hose at the cooler, with a paper towel under it, as there is a bit of fluid that comes out.


I covered the area with a towel, and held the pipe/hose in place with locking pliers loosely holding the pipe, while I pumped 5 qt of fluid in.


With 5 qts of clean fluid in, I basically had replaced 50% of the 10.6 qts (for easy math). I reattached the hose at the cooler, and took the car for a 5 mile drive. I noticed an immediate improvement in the shifting characteristics. When I initially shifted into reverse or drive, it was much quicker. Under hard acceleration, it was also quicker. I drove with the Sport button engaged, and drove it harder than I normally would, my thinking being that this would provide slightly higher pressures and help clean out the old dirty fluid from some crevices.

Round 2: Went to drain the fluid out, but I guess I had tightened the drain plug too much the first time, and it stripped out. It's also possible that it wasn't designed for multiple insertions. Not a big deal. I removed the pan to drain it, and got 4.4 qts out this time, without letting it sit for a long period. Pan back in, refill with 4.4 qts of fluid. By my calculations, I was at approximately 25% old fluid, 75% new fluid.

Round 3: Repeat of round 2. Went to approximately 12.5% old fluid, 87.5% new fluid. For many/most people that might be sufficient, but my fluid was so nasty looking went it first came out, and also when it came out for round 3, I decided to go one more round.

Round 4: Drained the fluid out, and let it sit overnight, getting a total of 139 oz (4.4 qts) out. I installed the new pan and filter (Amazon, $70 for the correct ZF pan). Before putting fluid back in, I removed the fill plug on the side of the transmission and practiced inserting it wearing gloves. I found that a 3/8" universal joint and long extension worked best. I put the plug back in, and added 4.4 qts of fluid in, then installed a new O-ring in the transmission cooler line.

I started the car, shifted through the gears, then raised the car back up and opened the drain plug. I pumped <1.5 qts back in (I spilled an ounce or two) before it started flowing back out, and it took about 10 minutes to get up to the correct 30 deg C. I put the plug back in, and even though I had practiced that, it was still a pain, and I dropped the plug and it rested in a place where i needed a long screwdriver and magnetic pickup to get it out, so I suggest that you have these tools nearby.

Fluid: If you look carefully at my photos, you can see that I used Valvoline Max Life ATF. That was the fluid that I used for the flushes. It was $5.63 on Amazon, also at Walmart. However, before my final fill, I was doing some reading. That fluid is acceptable for the 5HP24 transmission, but is not listed for the 6HP26 transmission. So, I have some 'not great' fluid in there, but I used the Ford Motorcraft Mercon SP fluid for the final fill. O'Reillys Auto Parts had it for the lowest price locally or online that I found, at $12.99 a quart. I bought 8 quarts, and I'll be taking 2 quarts back. I didn't want to have to repeat the warming process if I didn't have enough fluid.

Optional: You might consider disconnecting the battery for 10-15 minutes to reset the transmission ECU so that it will relearn your driving patterns. I did, although not required.

Conclusion: Long job, at least on my calendar, but well worth the effort. Cost was about $200. The car shifts a lot better, and I'm sure that this will lengthen its life. I expect to only put about 3,000 miles a year on my car, so this should last a long time. I would HIGHLY recommend changing fluid at 50,000 miles, and even more frequently if you expect to drive a lot of miles. My Pontiac Grand Prix GXP wants fluid change every 20,000 miles. If you were to have the dealer do this, you are looking at around $800 for a simple drain, new pan, and new fluid. Will they actually do that, and will they fill it using the proper method? You have no way of knowing, and if your gearbox explodes in the future, it is your problem to deal with. So, if you can, do it yourself and you like your car and want it to last longer, change the transmission fluid.

Another aside: While I was under there, I also removed the grounding strap that runs form the frame to the engine/transmission. It was impossible to get to the location on the engine, but on the frame, I removed it, cleaned it up with a bit of sandpaper and reinstalled. My car won't see the salt from the NY roads, will live in a garage, and will rarely see wet roads. Even before I bought my car, I read about electrical issues that certainly sounded like a grounding problem. The PO had previously replaced the grounding strap at the battery, so I cleaned up this strap, just in case.




I'm getting paid by the word here, right?

 

Well done. The only suggestion I have is that this job goes much better if you have two people doing it - one underneath the car doing the fresh ATF pumping, and one in the drivers seat running through the gears as the last quart or two of ATF is being pumped in with the engine running. I know from experience that an even better way is to involve THREE people in the job - one underneath the car pumping in the fresh ATF, another one underneath the car holding the fill tube firmly in the fill hole to ensure that the fill tube does not fly out during ATF pumping, and one in the drivers seat handling the gearshifts....

Happy motoring....

 

Hi 73MustangBill,

Thank you for sharing your experience changing your transmission fluid. I know what's involved doing this job and all the extra time it takes to photograph certain steps and then post them here with well-written descriptions of your work. We're grateful for your efforts.

One comment I would make is that I do not trust Valvoline Maxlife Multi-Vehicle ATF in any of my vehicles for the simple fact that Valvoline claims it meets the specifications for an implausibly wide range of transmissions. For example, Valvoline claims its MaxLife Import Multi-Vehicle Transmission Fluid is suitable for use in ZF 3-speed, 4-speed, 5-speed, 6-speed, 8-speed and 9-speed transmissions. Yet ZF insists that the 3-/4-, 5-, 6-, and 8-/9-speed boxes require four different fluids, and if you check the Material Data Safety Sheets for those fluids, you'll find that their chemical properties are quite different from one another. The only way Valvoline can make such claims is by compromising their fluid's properties so it is "close enough" to function in gearboxes that call for fluds with very different viscosities, friction and slippage characteristics, seal compatabilities, anti-corrosion requirements, etc. A fluid "good enough" for use in so many gearboxes can't possibly be optimal for use in any of them.

Here's a link to the product info sheet in which Valvoline makes its implausible claims:

Valvoline MaxLife Import Multi-Vehicle Transmission Fluid Product Sheet

If you watch eBay, you can generally find a case of Motorcraft Mercon SP for less than $130 - $140, or about $10 - $11 per quart.

Another comment I'll offer is that Time-Serts are a perfectly fine solution for stripped threads, but I've serviced over a dozen ZF 6HP26 transmissions and have thus far always been able to preserve the original threads in the transmission case when the head of a screw stripped or snapped off by cutting off the stripped head, dropping the pan, then twisting out the screw shaft with Vise Grips, or when necessary, center-drilling the broken screw and using an extractor. Obviously, this work is done with care, but so far I've never had much trouble getting the old screw out while preserving the original threads. So I'd recommend trying these methods before going to the effort and risk of installing a Time-Sert. The skill and care required to install a Time-Sert are at least as high as to drill out and extract a broken screw.

I'm not sure why you would need or want to use a Rescue Bit just to remove a broken screw. Rescue Bits are very hard and designed to remove broken screw extractors or broken screws that are so hard they are difficult to drill. Controlling a Rescue Bit is a fairly high skill operation. Much easier to drill a broken screw and use an extractor. Worst case, you can drill a progressively larger hole through the broken screw, then use a tap to re-form the threads.

I like your idea of cutting a slot in the stripped head of a stripped screw, but the thought of using an impact driver concerns me due to the risk of actually damaging the soft aluminum threads in the transmission case. When the impact driver is struck, the steel screw threads would be forced against the aluminum case threads, potentially weaking them or even shearing them off.

For others who may be looking for additional information and methods for servicing the 6HP26, check the "How To /DIY Repair & Maintenance" thread in the stickies in the X350 forum.

The great news is that there are often multiple ways to successfully accomplish a service or repair. I appreciate your creativity and willingness to share your procedures, and you've given others some good ideas that may be helpful when they're performing the same service.

Thanks again.

Cheers,

Don

 

Don,

That's a fair assessment. I did not have troubles with a broken bolt, but if it is possible to remove them with locking pliers, great.

Bill

 

I'll chime in and shut up. All the above is good info so I'll keep it simple stupid (I'm not calling you stupid). Mercon SP, I see you found reasonable price. Also available at Ford dealers if need be. Replace the filter, just do it. If your screws are ok you can reuse otherwise go with the bigger headed ones, drive a couple hundred miles and change fluid again. Butter is the word I use. Like Butta!!! 4 post lift !! So nice. TM