Hello, I spend 99% of my time in the X308 forum but my wife drives a 2004 XJ8 (x350) and I could use a little feedback on an issue she is having.

When accelerating, the drive-line will "slip" a little and then there is a whining sound as the car gets "back into sync". It does not seem like the transmission, but I could be wrong. I did a full fluid/filter/electrical sleeve service on her transmission last Summer and it shifts great. I changed the differential fluid last Summer as well.

I tried searches using several descriptive words trying to find someone with the same issue, but no luck. Is there a driveshaft issue that would cause these symptoms?

It used to only do it on hard acceleration and then very infrequently, but she says it's getting more common and occurring at varying speeds.

Thanks.

 

Could be some issue with the driveshaft, either the rubber donuts at either end or perhaps the center carrier bearing. Although it does sound more like a transmission issue. Also check your transmission mount. The transmission might be rocking upon acceleration, causing an imbalance with the driveshaft.

 

Perhaps it is the transmission, it just seems so flawless otherwise. I have been doing some general research on that transmission and a few members describe a similar issue. One member completely cured it by adding Lucas stop slip.

I know the previous owner sold the car to us with a leaking transmission pan gasket. That's why I immediately dropped the pan when we purchased the car. Maybe she did some damage before we bought it? That was over 12,000 flawless driving miles ago though...

 

One little tip.....when I search this forum I use google.

 

My first suspicion would be low transmission fluid. Even though it's a pain to check, it would be worth checking just to rule it out.

Cheers,

Don

 

Very timely post, Don. I just got out from under the car. lol

I suspect I overfilled it a little a few months ago. It was exhibiting a little roughness about 6 months ago so I added a little fluid and it smoothed out. But today as soon as I took the plug out I started getting overflow and the temp was only at 23 C. It was not a stream, but very steady drops. I let it drip up until it hit 35 C and put the cap back in. I let it drain into a towel so it's hard to discern how much came out, but I would estimate 100 to 200 ML.

The fluid that came out looked like it just came out of a ZF bottle. Clear and clean.

Do you think this was the problem? If so, did my overfilling do irreparable damage?

 

I took it for a test drive and it still has the slipping issue. My wife was with me and she said it's better than it was, but definitely still there. It makes a whining sound, too.

A ZF transmission is not something I am willing to throw parts at until it's fixed. There are things I will do that with (suspension for example) but not the transmission. I could spend a couple grand on valve bodies and fluid yet still accomplish nothing.

I made an appointment to drop it off at a high end independent shop that specializes in BMW and Jaguar. They are very familiar with the 6hp26. They recently did the alignment on my XJR. I loathe to have anyone else work on one of my cars, but feel an exception is warranted in this case. For $95 they said I will KNOW what the problem is, and if necessary they have the software to re-flash it and the know-how to complete the proper driving adaptation procedure.

Don't think less of me for taking it to a mechanic, please. Haha

It takes a man to admit when he is out of his depth, right?

 

A torque converter lockup clutch failing will feel like a universal joint failure. You will feel it at lockup under acceleration at 55mph or so.

 

The shop says they suspect the adapter seal? I think they are referring to this:

Mechatronic Seal Adapter 6HP26 & 6HP28 & 6HP32

He said as it gets worse the transmission has trouble maintaining pressure in gears and "slips" out for a few seconds. They can't rule out valve body damage, but said they could replace that seal for a couple of hours labor and if that doesn't fix the problem then the valve body may need to be replaced.

I could probably replace this seal myself, but honestly I don't want to right now. If they will do it for a reasonable price I will let them. If it turns out the valve body is bad I'll work on a game plan from there. I suspect I would just do it myself because if they do it I feel it would be cost prohibitive. He's working up all the quotes now.

Any advice?

 

Ok, update. They want over $1,000.00 to replace the adapter seal. They are quoting 4 hours of labor and VERY high prices for new pan and fluid (which is already new) and computer re-flash with adaptive driving.

I told him I was on my way to get the car.

 

Ok, I could use a little encouragement and/or discouragement here.

After researching everything it appears dropping the valve body to replace the adapter seal is not that difficult. Is there any aspect of this procedure that is risky for a DIYer? I removed the front portion of the valve body on my 2001 XJ8 (5hp24 ZF) to install an updated main pressure valve. Would this be more or less difficult than that?

I can get the seal for less than $20 and I already have enough fluid (7 liters on hand). The pan/filter assembly was installed new last Summer, so I don't see any reason to replace it.

I found a local transmission shop owned by a guy from my church. He says if I give him the fluid he will replace the seal for 4 hours labor at $85/hr. Should I pay him $400 or do it myself

One last question. The guys at the high end place insisted that a computer re-flash would be necessary after replacing the seal. Is that true?

Thanks,

 

I'm enjoying my own little thread here, haha. So I sourced all ZF parts including all new upgraded t-40 pan bolts for a total of $187, which includes the price of the ZF fluid I had already purchased. I have researched the replacement and it looks very straight forward. I always say to myself "if you replaced all the timing gear on a V-8 Jaguar, certainly you can do THIS...."

The shop quoted a respectable labor charge, but the parts mark-up is where I was really disappointed. Excellent service and reasonable labor rates (considering the brands they work on) but the parts mark-up was the deal breaker.

Since I am only replacing a seal it seems the car should "re-learn" whatever it needs to as my wife drives it. If that turns out not to be true I will happily pay them to re-flash the TCM and perform the adaptive driving.

 

While your in there there are also 4 rubber seals to also change out. While you have the valve body down do it as well as even more preventative maintenance.

Check out attached...

If you want PM me I have a PDF I can share as well on the valve body take down/install procedure.

 

I just ordered them, thanks for the tip. I would very much like the PDF. Sending PM..

Thanks

 

Well, I got the fluid drained, pan dropped and valve body removed (after removing the electrical sleeve of course).

The adapter seal is a loose fit, old one and new one, but the new one is in place. I don't see any visible damage to the old seal, but it is very rigid. The sealing edges though are still fairly pliable and intact. I guess it could be cracked in such a way that I don't see it; I hope so because that means the new seal will correct the problem.

The little sealing sleaves are pushed into their respective places. Based on their length there really wasn't much ambiguity as to which one went where; I just matched sizes and switched them out. The new sleaves are just a "hair" longer than the ones that came out. Perhaps the old ones shrank? In any event, the sleeves were fairly flush with the metal surface when I removed them, but the new ones protrude out a little (see picture). I don't want to force them in farther unless I know they are supposed to be flush. Does anyone know if they should be forced in flush, or are they supposed to protrude to make a seal.

Thanks

 

New ones will protrude a little. They are fine. All is well.

 

Everything went back together pretty well. The electrical sleeve is always hard to "set", but I'm pretty sure I got it.

There was a lot of spillage, especially while removing the valve body, but I think around 6 liters came out, maybe more. I have put about 6 liters back in but still can't confirm she's full.

The car is still up on jack stands as I wait for it to cool (2nd time today). It heats up so fast I miss my window to verify the level. When I added fluid it was kind of strange. If I pumped it in fairly fast it would flow back out, but when I stopped pumping it would not flow. So I kept adding and adding, slowly, and it would only flow out if I pumped a bit faster, but stop as soon as I stopped pumping fluid in. It was at 49 C when I put the cap back on last time, and it still wasn't flowing when I removed the siphon hose.

I have done this about 5 or 6 times, on 5hp24 and 6hp26, so I am fairly familiar with how filling it is supposed to work. The shop that gave me the adapter seal diagnosis said the fluid level was good, so I must have done it right last time.

When I shift through the gears it's smooth and there are no fault codes, so I'm anxious to drive it and see if the "slip" has been improved or eliminated. My wife has driven it a couple of hundred miles over the past weekend and said it never slipped once, BUT she drove it like a grandma. She is usually a very aggressive driver so it's been tough for her, haha.

I am rambling, but I'm just waiting for it to cool so I can test it again. I really want to get a test drive tonight. I put a box fan blowing on the transmission and left the garage door open. Soon I hope.

 

The fluid temperature finally dropped to about 33 C so I cranked it up again, ran it through the gears and started adding fluid. At 45 C it started streaming out! It took almost 7 liters. I capped it off, dried everything and put the undercarriage panel back in place.

Test drive: I went about 10 miles, high speed interstate, curvy back roads, stop and go in-town traffic etc. I gave it everything I had, floored it at every speed, zoomed up to 90 mph on interstate (by accident, honestly officer). I did hard braking followed by vigorous acceleration and the car didn't blink. Smooth and fast.

Finally I took it onto the stretch of road where it slipped so bad last time. The surest way to get it to slip in the past was to cruise at 50 mph and hit the accelerator followed by coasting and then the accelerator again. It used to slip badly EVERY time I did that. Well, I could NOT make it slip tonight. I would hit the gas and coast, then floor it, then coast etc... In fact, the car seems faster and takes off from a stop more smoothly than before.

Ok ok, it's only 10 miles. I'm not going to raise the victory flag just yet. BUT, the results so far are pretty encouraging!

I spent less than $200 on parts and fluid. I just pray it STAYS fixed.

Edit: I forgot I spent $25 on the little tube shaped seals that abonano recommended, so I did go a little over $200.

 

Excellent, good news so far and hope it stays that way.
Thanks for sharing and look forward to hearing it's resolved

Best
Jim

 

Methinks you have done it!

When you asked about the seal protruding I am guessing that

it needs to protrude since it is sealing against the valve body.

Well done and I have learnt something too!