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Transmission issue
This has happened twice, once today and once about a year ago. Both times the weather was around 100 degrees. The transmission acts like it doesn’t want to shift any higher than third gear during in-town driving. It will downshift if I step on the gas, and eventually after running a few seconds at higher rpm, it will shift into fourth and eventually fifth. But when I slow down, and it downshifts, the problem repeats. The engine temp gauge appeared to increase today as this was happening, so I parked and shut it off. The cooling fans ran for about a minute then shut off, and all seemed fine. I did a hard reset by touching the negative cable to the positive, and that seemed to make the problem go away. A year ago I pretty much did the same thing with the hard reset. The problem did not recur until today. I was 200 miles from home today, but after the reset, it worked fine. The odometer shows 175k miles. I don’t know much about the history other than what I’ve done to the car since I bought it 3 years ago. I’ve never done anything to the transmission. I’m suspecting something computer related because the hard reset fixed it for about a year last time, and seemed to fix it again today. I assume the computer tells it when to shift. No error codes, no fault indicators, no error messages at all. Any ideas or suggestions? Thank you. |
I think it's time for a fluid/filter change first. Not necessarily a flush, but 2-3 fluid changes to get most of the original out.
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My 99 XJR was going into limp home (won't shift up) occasionally and displaying a transmission fault message on the dash so a little different from your symptoms. Limp home seemed to resolve itself with a key on/ off cycle (and some time to rest while I was at work). It finally started not shifting into drive from reverse without a several second delay. I changed the fluid and filter and cleaned the pan and that has cleared up this behavior for a while now. Mine has ~90k miles and the fluid I got out was pretty brown. I was able to get 4 qts out by pulling the pan and I think the trans takes 8 qts for a total refill. I'm planning on doing the procedure again in the next few days and will also look at the connector for the trans to trans control module which apparently can leak and allow fluid to be pumped up the harness causing all sorts of confusing symptoms. I agree with RJ237, a couple of changes should clean things up pretty well and I've seen enough regarding the connector on the internet to suspect that part is worth looking at anytime you have flaky trans issues on these big cats...
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I have ordered a filter, pan gasket, and fluid for a Saturday project. I plan to replace the filter and as much fluid as I can, drive it for a week or two, and drain the fluid again, filling it with new. I might even do it a third time. No need to change the filter each time, is there?
The fluid is kind of brown on the dipstick I bought. It also appears that the transmission is over-filled quite a bit, which may be causing the issue. The issue has only occurred twice, both times on very long trips on very hot days. I will report back with my findings. Thanks for the suggestions. |
Originally Posted by aquifer
(Post 1927215)
I have ordered a filter, pan gasket, and fluid for a Saturday project. I plan to replace the filter and as much fluid as I can, drive it for a week or two, and drain the fluid again, filling it with new. I might even do it a third time. No need to change the filter each time, is there?
The fluid is kind of brown on the dipstick I bought. It also appears that the transmission is over-filled quite a bit, which may be causing the issue. The issue has only occurred twice, both times on very long trips on very hot days. I will report back with my findings. Thanks for the suggestions. And if you are going to change the oil several times to get as much of the old oil out, then yes, change the filter on the last cycle of fluid change. Also, the level of oil is dependent on the temperature of the gearbox, so I would also buy an IR thermometer. Keep in mind that there is a procedure for checking the transmission oil. |
[Duplicate post]
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[QUOTE=aquifer;1927215It also appears that the transmission is over-filled quite a bit, which may be causing the issue. The issue has only occurred twice, both times on very long trips on very hot days.[/QUOTE]
This transmission should NOT be overfilled. The Workshop Manual warns that "excess fluid MUST be removed". |
Originally Posted by AZjag1999
(Post 1929060)
I would also recommend changing the connector adapter. They tend to leak fluid. I bought this kit when I service my transmission: https://www.ebay.com/itm/OEM-Mercede...gAAOSw-u1Zd9tW. It works great and everything fits, but you need to buy the ATF separately. Shell ATF 134 will work just fine.
And if you are going to change the oil several times to get as much of the old oil out, then yes, change the filter on the last cycle of fluid change. Also, the level of oil is dependent on the temperature of the gearbox, so I would also buy an IR thermometer. Keep in mind that there is a procedure for checking the transmission oil. Also, I’m hearing a noticeable clunk sound as I come to a stop after a long drive. More of a tunk than a clunk. Shifting to reverse when hot...tunk. As the car is stopping....tunk. Shifting from reverse to drive....tunk. The U joints seem fine. I changed the fluid and was careful not to overfill. Seems to shift fine other than this sound. Ideas are welcome. Thanks. |
Check the propshaft front and rear rubber couplings ("giubos") and the centre bearing.
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Originally Posted by aquifer
(Post 1929544)
When you say the connector adapter leaks fluid, is it internal or external? There are no external leaks, does that indicate mine is ok, or....? Also, is this something that can be replaced with just the pan off, or is it more complicated? Also, I’m hearing a noticeable clunk sound as I come to a stop after a long drive. More of a tunk than a clunk. Shifting to reverse when hot...tunk. As the car is stopping....tunk. Shifting from reverse to drive....tunk. The U joints seem fine. I changed the fluid and was careful not to overfill. Seems to shift fine other than this sound. Ideas are welcome. Thanks. |
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