I drove around 220 miles today and while creeping along in a traffic jam my transmission light came on. I stopped and checked the fluid and all was well except it was overfilled about a pint. My fault, as I added too much a few day ago. Will being overfilled cause this. My thought it could have foamed the fluid by being too full. When I started it up after about 5 minutes all was well.
Any opinions?
Thanks, RagJag

 

I am very late finding this thread...but here goes.
My 92 FHC 4L with automatic is also exhibiting the same thing. I also checked the fluid level in the Spring, saw that it seemed low, so added Dexron. Then (occasionally) I have noted that it will surge at highway speed, revs increase, seems to kick down a gear, immediately recovers itself and continues along EXCEPT that the tranny light is now on. If I turn the engine off, either while stopped or coasting, and immediately start up again - all is well.
I checked the tranny fluid level and it was over-filled. I am in the process of syringing out the excess.
When the issue first arose, I though that perhaps I was causing the issue by invoking the "sport" mode on the tranny selector, but soon realised that that was not the case.
There is lots of info out there suggesting that overfilling can be harmful.
There is no evidence on the dipstick of foaming.
One more thing:- when the tranny light is on as per above, I notice that when setting off from stop, the tranny is in what I would almost describe as "limp" mode, because it sets off in 2nd. Once the light is turned off (again, as above) this "limp" mode stops.
Just my two cents worth Canadian, which is not worth much these days !! LOL

Gerry T.

 

I have been working on replacing the fuel pump. During a few test spins to see if the fuel system was working, my trans light appeared. When this happened a few months ago I was told to clean the contacts on the transmission rely. I did and the problem went away.

Today I took the car on a long long long drive in the heat of the day and ended up in a traffic jam. It ran fine, but near the end of my adventure, the trans light came on. I got home without any problem and did the shut down restart. The light went off.

Did you figure the cause???

Tony

 

There is no real pattern to the tranny problems I experience as far as I can tell. However, I seem to experience the issue more often if I do not let the car (and tranny) warm up thoroughly before getting on the highway at 65mph. If I take it easy around city streets and then hit the highway, the problem happens less often.


I have thought about draining a pint or so of the tranny fluid and replacing it with the Lucas Oil transmission oil. This product seems to be available for trannies, engines and diffs and is highly regarded. I have not yet done this, because the last few times out on the road, the Jag has behaved. As said, there is no pattern to it all !!!


Perhaps I should have a look at the transmission relay as you suggest.