Hello, So my 1999 XJR with the 722.6 trans has decided to start dying when I put it in drive or reverse. I just did a trans fluid change, filter and contact plate. I left the old solenoids in. I'm wondering if I bought a bad contact plate? When leaving the shop after the oil change everything was fine, when I came back out to start the car again after an hour the engine stalls when put into drive. The car will start and idle but has a rattling sound now? Any insight would be very a[ppreciated.

 

I'm not sure what the exact issue with your XJR might be but when I started looking into these trannies when my 99 started delaying going into drive from reverse a few years back decided I should replace the conductor plate.
I watched a few videos, mostly for mercedes related (same trans) issues. Mine had also declared an output speed fault and gone into limp home twice.
I got a cheap (not sure of the source) conductor plate and connector body off ebay and decided to change the fluid (only) as the more videos I watched people mentioned getting the real mercedes conductor plate and connector kit.
I only got 4 qt's to drain so I did the drain, refill, filter change dance twice and things have been quiet on the trans scene in my driveway. If the issues do return however I think I'll source the real mercedes parts.
You don't say where you sourced your parts but this may be the issue.
The other thing I did see (dodge owner video on you-tube) was related to trans fluid making it all the way up the cable to the trans control module because of bad seals in the connector body.
If fluid was making it past your connector at the trans this might be something to check.

 

I bought the contact plate off of ebay.
My issues started with getting stuck in 2nd or 3rd gear after a hard acceleration. If I pulled over and turned off the car and restarted it everything went back to normal. Also when i got the car back it shifted perfect and started up again after around an hour. It was up to operating temp when I took it from the mechanic shop and when I went back to it after it cooled off it wouldn't go. Is this a symptom of a bad TCM? Also, I need to repair my BCM, would this have any effect on the trans operation?
Is it possible that the tranny is overfilled?

 

if the issues you describe started after the plate was replaced I'd say they're related. People mention getting the mercedes part and I wasn't sure if that was because they'd tried the cheaper parts or just the typical "buy it from the dealer" sort of response people will toss out. It sounds as if this is one of those parts that we want to get with a mercedes logo on the box.
You don't say whether the connector body & seals were replaced going from the trans to the TCM. That should be checked as well since that's another well known problem area. I would guess given the issue with the ebay conductor plate these parts should be mercedes parts as well.
On the dodge related video I watched the repairer decided to replace the TCM because it had been damaged due to the fluid that had wicked all the way up there. You might have to check how far fluid might have traveled along the harness.
Personally I'd suggest sourcing the mercedes conductor plate and connector body & seals and start there, checking the trans harness at the connector for fluid wicking.
Although I'm sure I'm not aware of every possible control scenario on the XJR I'd be surprised if the BCM & TCM would have too many interactions so I'd guess the BCM is not what's behind your current trans/ shifting issues.
I guess (also) that I should pitch my ebay parts and source the mercedes parts myself as I've been babying my big cat and could just be one hard shift away from limping home myself!
Good luck.

 

"Personally I'd suggest sourcing the mercedes conductor plate and connector body & seals and start there, checking the trans harness at the connector for fluid wicking."

I changed the plug, filter and pan gasket when I changed the conductor plate, is that what you are talking about?

Could it be overfilled?

I checked the fluid last night and(cold) it was at the top line. I bought my flexy dipstick on ebay as well. Maybe ill look up the length of the Mercedes part and check it against mine.

 

"Personally I'd suggest sourcing the mercedes conductor plate and connector body & seals and start there, checking the trans harness at the connector for fluid wicking."

I changed the plug, filter and pan gasket when I changed the conductor plate, is that what you are talking about?

Could it be overfilled?

I checked the fluid last night and(cold) it was at the top line. I bought my flexy dipstick on ebay as well. Maybe ill look up the length of the Mercedes part and check it against mine.

 

I'm not sure what symptoms I'd expect for overfilling but it would be good to correct.
I got my dipstick from an ebay seller as well but the length checked out vs a tech bulletin posted here somewhere. Mine doesn't go all the way down to the handle touching the top of the fill tube.
You need to check the level with the trans warm and the car sitting level. If you find the tech bulletin it tells you what temp to check fluid at.
I have the file for this at home and can look for it later but again, it's here somewhere.
I've seen kits on ebay that had genuine mercedes conductor plates, connector & seals, pan gasket, and filter. Some even came with mercedes fluid which I believe (IMHO) is unnecessary as one thing I would bet on is mercedes is sourcing that.
As for the other parts (conductor plate & connector) I'm not sure who else would make them other than the original supplier to mercedes, it doesn't seem like a high profit margin set of parts (limited audience clamoring for these) but your experience and the warnings of others I found researching this issue makes me wonder about that. It's certainly not a fun enough job to do twice because of substandard parts, dropping the pan to change the fluid and filter was a huge mess, dropping the valve body to get to the conductor plate looks noticeably worse...

 

How did you check the level when cold, did you run the engine at idle?

You may have overfilled the gearbox. The manual states that it MUST NOT be overfilled. One difficulty wen using the dipstick is that it tends to hit a bit of a resistance a couple of inches before hitting the bottom of the sump. If your dipstick was not fully in when checking the level during filling, the gearbox was overfilled. The overall length of the dipstick does not matter as it does not work like usual dipsticks. It needs to be inserted until it hits the bottom of the sump, then pull it out and take the reading (quite a bit of the dipstick will still stick out of the tube when it hits the bottom). To verify that you have inserted the dipstick all the way, measure 704 mm from the plastic tip of the dipstick and up and make a paint (or tape) mark on the dipstick flexible shaft. When the dipstick is fully inserted, the mark should align with the top edge of the tube. When taking the level reading, use the appropriate marks on the plastic section of the dipstick for cold or hot.

 

Years after you posted this, the 704 mm length let me know I hadn't been getting the measuring tool all the way to the bottom. Saved me from over-filling the gearbox.