Transmission overheating?

[dono]

Has anyone ever noticed if their shift plate and drink holder door becomes warm after normal driving? I have noticed that the shift rod itself gets hot, as it did on my C230K, but I just noticed that the shift pale and door are warm, and now I am a bit paranoid after reading jnenad's comments about transmission life and adequate cooling.

[Sulaco]

My shifter rod has always gotten pretty hot to the touch. And I don't even dare put a cold drink, candy, or frozen anything into that square cupholder/trashcan.

[dono]

That makes me feel better. I had my trans fluid and filter changed yesterday along with the rear differential fluid, and a cooling system flush. I just have to flush/change the brake fluid and power steering fluid in the next two weeks. and then if my TBA does not fail, I should be able to swing the long anticipated headliner change.

[benzfan]

Don't forget that in an automatic, the transmission cooler is part and parcel of the rad, so the coolest temperature you can get the fluid will be approx. similar to the temperature of your engine coolant (perhaps a bit cooler, give or take a bit). The transmission is designed to run at this temperature, so don't worry. This is also why there is a bulky insulation mat above the transmission in the tunnel. Even a manual transmission gets quite warm after a while. I have owned cars, most of them Italian, where the carpeting around the tunnel is quite warm to the touch after a good drive.

[Sulaco]

Is it much of a job to replace the transmission cooling? Expensive? I'm interested.

[benzfan]

I can't think why you would need to. It's integrated into the rad and won't go bad before the engine coolant side. You can, however, run the lines from the transmission to an auxiliary cooler, bypassing the rad completely. This would require some work to determine exactly where and how to mount it for best effect. If your car is a 97 or later, you would also then have the problem of trying to figure out how much additional fluid to put in, given that the tool used to measure level requires a transmission fluid temperature of 80 degrees Celsius. If your new cooler is really good, the fluid never reaches that temperature. So, one might interpret MBs engineering on these cars to conclude that the transmission fluid circulating in the integrated rad/transmission cooler is intended to be heated by the engine waste heat, not really cooled by the cooler in order to achieve the proper operating temperature. It's a solution in search of a problem to worry about supplemental transmission cooling on these cars. Check your lines periodically. Make sure that the cooler is flushed as part of the fluid change. Actually disconnect the lines to verify flow, change your fluid often, and don't cheap out on the type. It should live a long life with regular care.

[jnenad16]

as benzfan said, the trans works at around 200F, so the shifter and the center console will get warm after a while. but remember, its not only the trans that warms up the center console, its also the catalytics.

nenad

[Abuimad]

well thanks for the post it was a problem i always thought was associated with my car, and glad to hear its a standerd thing, cause in my other cars (pilot and civic) there is no heating in the interior

[benzfan]

That's because they're front wheel drive and the shifter is a cable shifter. So not only is the transmission not anywhere near you, but the shifter can't directly conduct heat. Plenty of people who have grown up on front wheel drive continually find things on rear wheel drive cars that bring questions to mind, as the design has quirks of its own. Don't worry. At least you won't be replacing CV joints annually on your Benz.

[Sulaco]

Yeah, but make sure you change those flex discs every 5 or 6 years. Don't want your drive shaft support and bearing to get chopped because of an old flex disc (like me) :(

On the bright side, the dealership itself only charged me $888 for 2 new flex discs, new drive shaft support with bearing.

Damnit.

[Abuimad]

whats a flex disk ??
and damn there expensive

[Sulaco]

If you buy them aftermarket, they are $70 each. +100 from the dealer I think.

Old cars have universal joints on the drive shaft. Our car has a rubber flex disc instead. It eventually dry-rots and comes apart. In my case it was at 150,000 miles.

But if it fails while driving, it can really throw off the balance of your drive shaft as it spins. The center of the drive shaft spins through this bearing that supports it and keeps it balanced (no vibrations). It also protects your undercarriage from being destroyed in the event of a failed flex disc. This bearing and housing are like $200 I believe.

Mine failed on the interstate not far from the dealership, and they were the only people who could fix it in the time slot I needed. So I had to shell out the cash.