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Saturn Transmission Thumping

I have a 2002 Saturn SL2 (automatic). A few days ago it abruptly started thumping pretty heavily when shifting gears, especially going into reverse and 4th (or possibly 5th) gear. A couple mechanics told me the transmission is going, and that it would need to be replaced (but it would cost more than the car is worth. One said that we could try replacing the computer that controls the transmission, but it would cost ~$300, and might not do any good. Another said to try Lucas Transmission Fix. I’ve seen mixed reviews of it online, so I’m wary. Is it a good product, or does it just briefly mask the problem? Also, I looked under the hood, and cannot tell where I would even put it. Thoughts? Thanks so much,


Don’t put the Lucas in it, and for gosh sakes don’t just go throwing a computer at it.

What do you mean by “thumping”? Are you just saying that it shifts really hard?

How many miles are on it? How often and by what method(s) has the transmission been serviced?

Is it safe to assume that the fluid has been checked? Level, color, odor?

When it comes to “mechanics” the only person who should be giving you any transmission advice is an actual transmission expert. General automotive shops usually know little of transmissions. Take it to a local, independent, transmission specialist.

But if it is a high mileage transmission and has not been serviced regularly then assume the worst.

Thanks for responding so quickly, and on a Sunday evening, no less. I think my responses are going to be a little inadequate, but I’ll answer each question as best I can.

Shifting hard is probably a better way of putting it. Sometimes it feels like it is slamming into gear.
It has 163,000 miles on it.
I take it regularly (every 3000-4000 miles) to get it serviced, but I think they generally just change the oil. When it got to 100,000 miles, I had it fully serviced at Meineke, which included a transmission check. Also, at about 150,000 miles I asked the mechanic (a local guy) to do a full check up on it, and I think that included a transmission check, but I’m not positive.
The first place I took it when the problems started was a general mechanic, and the second was a transmission specialist (local and independent). I don’t know for sure if either checked the transmission fluid, but I really hope so, since they both said they thought that the transmission was going. I do know the second guy ran diagnostics tests on it, and they came up negative. I am a little frustrated that both mechanics just kind of said, “Your transmission is probably going out,” but couldn’t really tell me for sure. Neither one tried to sell me on replacing it, though, so I don’t think they were trying to cheat me.
Sorry I can’t give you better answers; I’m a med student, and really don’t know a lot about transmissions, or engines in general, to be honest. Thanks again, and I’d really appreciate any further advice.

Could be a faulty EPC Solenoid (or connection). Electronic Pressure Control is used to control the transmission line pressure depending on load and throttle position.

It could be a sign of the pinion shaft in the differential has slid out of position and is thumping the side of the transmission case. The pinion shaft is press-fit with no other retainers. A very bad design. With the automatic, I don’t know if it can be repaired on-vehicle without removing the transmission.

Do yourself a favor and get a definitive line on the transmission fluid. Pull out the owner’s manual and follow the procedure there to check it yourself. A typical procedure is to have the car at full operating temperature (e.g. after a long drive), running at idle, run the gear selector through each shift position, end in park and with the car running check the level on the dipstick. You should be at whatever the mark is for Full-hot. For some cars the transmission has to be in neutral which is why you should check your owners manual.

Note the level, color, and smell and report back. Based on your maintenance report I’d imagine that you are just headed for the end of the line - its best to have an automatic serviced every 30K, including a new filter. That’s probably not what the manufactuer’s maintenance schedule says, but they don’t really care what kind of shape your trans is in by the time it hits this mileage.

Thank you all for your input. I just got home from school a little while ago (after 9 PM), and have not had a chance to check the transmission fluid. There is an old Saturn dealership on my way to school, and I spoke to one of their mechanics, who has a lot of experience with Saturns, and he said it may be a problem with one or more of the solenoids. I’m going to take it over there tomorrow. If there is any resolution, I’ll let you know about it. Thanks again,


Turns out it was the solenoids, so those are going to be replaced tomorrow. Thanks the help, everyone.

Well, when that doesn’t work (b/c there’s a good chance it won’t) feel free to report back.

I hope you are wrong… Why do you think it won’t work? The mechanic seemed pretty confident that it would work, and I thought he seemed to be honest and knowledgable. This is what I get for not knowing anything about engines…

You’ll have to forgive me for being cynical. You basically have a transmission with over 160K miles on it that wasn’t really serviced as well as it should have been (if at all - that’s still ambiguous) over its lifetime. I have no idea what the basis of the solenoid diagnosis is (or even what solenoid or solenoids are involved), but I can tell you that these kinds of things are not no-brainer diagnoses and the shop gets paid whether it makes a difference or not. If you have any actual details (e.g. error codes, tests, which solenoid(s) is(are) being replaced you can post that for comment.

These boards are full of people dumping money at problems that don’t get solved. You may have been given the impression that a computer diagnosis was involved, but computers are not really as smart as people think - in fact they are only as useful as their human operators.

However, in agreement with you - I also hope that I am wrong. If it works I want you to feel relieved and justified and thrilled that you didn’t have to go the big $$ route. If it doesn’t work I suppose I’m just trying to help soften the blow.

Of course, a hard shifting transmission can also stay on the road a really long time. It is a sign of issues, but not a sure sign of immanent death.

So far, so good. No rough shifting at all today, but I guess time will tell. I thought you made a good point about computers only being as good as their human operators. Part of the reason I felt hopeful was that the mechanic at the dealership really seemed to know what he was doing, and did not seem to just be relying on a computer. Like I said, time will tell, though. Thanks again,


I’m still hoping I’m wrong about being skeptical. Some people do actually know what they’re doing. They’re just hard to find. Best of luck with it.