What's a transmission "donut"?

My daughter who lives in rural PA and far from me has asked her old dad for advice, so I’m writing for any help I can get. She owns an 87 Corolla with 147k miles. About 2 months ago, her boyfriend drove the car over a concrete highway median. Except for burning lots of oil, she’s never had a major problem with the car. A couple of weeks later, she took it in for repair. One wheel was replaced along with the oil pan and a crossbeam member under the car. The front end was aligned and new brakes on the front were put in. The mechanic put in what he called a “donut” that was to stop fluid from leaking out the exhaust wehn the car shifted into high gear. Since the repair work was done, the transmission slips between 2nd and 3rd when she accelerates and sometimes when she starts off from a dead stop. The transmission fluid is not low. She does plan to take it to another mechanic, one at Star Auto Service, that was recommended by a friend. What should she tell the new mechanic to look for? What could the “donut” be, and would putting it in have anything to do with the transmission slipping? Any information or advice will be appreciated.

Good question. I have no idea what a transmission “donut” is, unless maybe it’s a transmission mount, but that would have nothing to do with fluid leaking.

I think that something has been lost in the translation, so to speak.

I am referring to “a “donut” that was to stop fluid from leaking out the exhaust wehn the car shifted into high gear”. Fluid leaking out of the exhaust when the transmission shifts?

Please call her back and try to get the information from her again, as something in her description is very much wrong. I am unable to answer your question, but if the question contains more accurate information, someone (perhaps Transman) may be able to identify that part.

The “Donut” they were referring to is a round gasket which goes between the exhaust manifold and the exhaust pipe where it connects to the manifold. It has nothing to do with the transmission.

Here it is:


I think an exhaust donut isused as a gasket between exhaust components. Perhaps it was an exhaust leak that was repaired and the transmission is a separate issue.


Thanks for responding. I need to get more information from her. I’ll do that and post again. Another repsonse says that the “donut” is likely a round gasket between the exhaust manifold and the exhaust pipe. The fluid leak out the exhaust problem is really bothersome. I’m wondering if it could be the oil she says the car has burned liberally all the time she’s owned the car. In any case, I will get more specific information about the oil problem and the transmission issues. Thanks again.

Thank you for the information. I’ll talk to her again soon and get more specific details about the fluid leak out the exhaust, the oil leak problem, and the transmission slipping. When I have more details, I’ll post again. The donut would have nothing to do with the transmission, so the oil leak and the slipping gears seem to be two different problems. Thanks again.

Where I’m from the common term for the asbestos gasket that goes between the flanged joints of the cat converter (or muffler) and the exhaust pipes is the “doughnut”. Transman has kindly posted a picture.

Either terminology is different in your neck of the woods or the tranny issue is unrelated. The “fluid leaking” and the “slipping when it shifts into high” make me wonder if perhaps there is in fact a tranny problem and perhaps the “leaking” was not out of the exhaust but rather something like a cooling line or…perhaps…even…a hydraulic part that controls the torque converter lockup. I’m not a tranny guy, but Transman is. Perhaps he’d join us again with these thoughts in mind.

Thanks for your response. I intend to get more specific information from her right away, and when I do, I’ll post again. I believe there is a transmission problem, and your idea that the fluid leak is hydraulic fluid of some kind is a good one. I’ll recommend that she tell the next mechanic to check for that type of leak. That will give her a good place to start the conversation, and given the car’s age,it’s a good idea if the mechanic checks the hydraulic lines and the torque converter lockup anyway. Thanks alot.

Trying to help a child log distance has it’s frustrations. A trip over the concrete median? Sounds like a good “story” there and perhaps you’re not getting the whole story! My guess is that this was a rough trip and the exhaust system was moved around and caused the need for the “donut”. A cross member and oil pan means a pretty heavy hit.

The transmission shifting could be fluid leaking somewhere from the tranny that is causing the shift problems. There are lots of places for a leak and the bouncing around may have damaged a line, or coupling and is leaking.

Leak from the exhaust, what is that about? Exhaust don’t leak fluid, other than some water from condensation. Perhaps some fluid, maybe trans fluid is leaking onto hot exhaust pipes and causing a smell and some smoke when the car is warmed up.

She should tell the mechanic that the car took an unscheduled trip off road and some damage was repaired but there are still issues. Let the mechanic drive the car and assess the situation. You have to actually see the car to sort this all out.

Thank you for the information. You have summed up what I’ve concluded from my daughter’s somewhat cryptic description of the problems. It’s quite likely there was transmisson damage done from driving over the median. Her boy friend from Los Angles had been visiting her in PA. She had taken a short trip to visit her mother and step father in Illiois. He was driving to the airport in Philadelphia to pick her up and got caught in a snow storm. The road was snow packed and slick, and he slid into and over the median. Thankfully, he did not go over the median and into oncoming traffic. Although she says the gear slippage only started after she had work done on the car, I think the association is coincidental and that the problem already existed. I’ve been dubious about the fluid leak out the exhaust from the beginning, but I told her I would describe the problems just as she did to me. I will certainly remind her to tell the new mechanic about the encounter with the median and that there are still problems.
Thanks again for responding.

This car at 20+ years old and burning oil already is teetering on a leap into the scrap heap. Hopefully a simply solution can be figured out. I would not put much money into this car that has lived well past its average life. I hope for the best.

I’m afraid your assessment is correct! I’m hoping for a simple solution, but either way, I’ve encouraged my daughter to begin serious thinking on getting another car. Thanks for your response.