: 98 STS Has DIC That Still Registers 100% Trans Fluid Life

08-09-04, 09:19 PM
I am concerned that the 98 STS my sister drives still registers 100% life after 6 years. Even the original battery still works perfectly. My father bought this car new in June 1998, and unfortunately died in November 1999. My sister inherited it, and has taken excellent care of it since then. It now has 83,000 miles on it, and I really expect the fluid to be somewhat worn at this point, although i he transmission still shifts normally.

Has anyone else had a malfunctioning DIC, or is the fluid in the transmission that good? The dealer doesn't recommend changing it until 150,000 miles, or it is starting to give trouble.


08-10-04, 02:17 AM
I believe in changing fluid BEFORE a problem. It won't fix anything after a problem happens.

I do my own so I change trans fluid fairly often. The 4L80 is a heavy duty trans so my own recommendation is by 100K. If she's planning to keep the car a long time it's cheap insurance.

Don't have a flush done. Have the pan dropped. There is a plug that allows more fluid to drain. Make sure the shop know where it is and drains the upper half. This is the only trans I know that has that.

08-10-04, 11:35 AM
Thanks for the info. I do all of my own labor anyway, so this will be a piece of cake. However, I am confused about this "bolt" you mention that drains the upper half of the transmission. Where is this located? I am used to pulling the pan after I pull the coolant line going to the radiator and running for a few seconds to drain the torque converter. I am very careful with this, and do not let it run too long. THEN I drop the pan, change the filter (or clean the screen in my Lexus), and reverse the procedure to fill the transmission and drive.

I wonder about that transmission sensor though. The 100 percent reading gives my sister false confidence.

What kind of transmission fluid do you use in the transmission? Is the stock fluid a synthetic? I assume it is. I may use AMSOIL Synthetic Fluid in place of the stock fluid, as it is great in everything else I use it in.

Just a few questions!


08-10-04, 01:17 PM
The 100% trans fluid life is quite normal. It will probably stay there unless you are towing or running the trans temps up very high.
I cannot discribe exactly where the drain plug is as I have not done mine yet but there is a hidden drain plug up in the trans that is accessable after the trans pan has been removed. Most of the oil is in the side cover.
Use what the owners manual recommends. I beleive it is Dexron III.

08-10-04, 03:52 PM
I believe it is on the drivers side, above the filter screen. After you drain the pan and remove the filter you should see a plug that will drain more of the trans fluid.

Anyone is free to correct me if I'm wrong.

08-10-04, 05:36 PM
I also have a '98 STS and the Tranny life says 99%. The car has over 93K miles on it. I'll probably change it at 100K miles. But at 93K how come it still reads 99%?? Seem like it will only be at 98% by the time I get to 100K. How accurate is the DIC???

08-10-04, 05:59 PM
I can see if the fluid is a synthetic, but Dexron III has never been good enough to last 100,000 miles. I am ready for AMSOIL synthetic transmission fluid in this car!