When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
New to the forum, and new to my '05 C2S (49k miles, 6-speed). I picked the car up about a month ago and aside from the typical clicks and creaks on the interior, there is one issue that has me perplexed. I've done a ton of digging to try and find people with similar issues, but most of the threads went dark long ago. This didn't come up on the PPI, and the local indy shop said it seemed "normal" and that some cars do it more than others. But it's driving me insane so I'm searching for any additional insight. Due to the roads I initially drove the car on, my lack of familiarity with the stiffness of the suspension, and just the general excitement of getting my first Porsche, I just didn't notice the thud. Now that I've had a chance to put some miles in, I've isolated the when/where of the thud. So here's my best description:
I'm experiencing a thud/thunk feeling when shifting from 2nd to 3rd. Normal shifting, not shifting hard/fast. Engine speed or wheel speed doesn't seem to matter. Shifting slowly (or double clutching) does seem to help a bit, but that feels like a weird 'hack' that I shouldn't have to figure out in order to avoid the thud. During normal driving it feels/sounds similar to hitting a small bump in the road. Nothing metallic, or crunchy.
The issue presents itself in a few different ways. From a stop, if I depress the clutch and quickly move the shifter into 3rd, I get a thud. If I keep the clutch fully depressed and row through the gears from third, no issues, sounds, feelings. Nothing. Feels smooth. If I release the clutch, I can repeat the same issue every time.
The clutch was replaced at 39k miles, so I would hope it has nothing to do with that? IMS was also replaced at this time. The gear oil was replaced at 48k, so that shouldn't be an issue either. I've read a few threads mentioning motor and trans mounts, but no one seemed to follow up with a real resolution.
Any thoughts? I'm going to shop it around for a second opinion when I have the chance, but in the meantime maybe someone out there has an idea!
On a 14 year old car with your symptoms.. my first guess would be just that.. motor mounts and transmission mounts. Motor mounts are a super easy job. Would take care of those first and then see if any improvement happens. If not, then transmission mount would be next on the list.
Maybe you can try recording a video of the "thud" happening.
I hate to say, but sometimes the local indy has not seen nearly the numbers of cars or has the amount of experienced techs as your most popular Porsche dealer may have. For a symptom that has been hard to pinpoint and also stumped your local indy, I may consider taking it to the "stealer" for a diagnoses. I know they are way more expensive, but with the volume of cars they see compared to a local indy it may sometimes be beneficial to get their take on the situation. It does not mean you have to have the work done at the stealer, but paying and getting a second opinion from them may not be a bad idea.
I think I’ll give the motor mount route a try. Before I pull the trigger on buying the parts, I’m going to see if I can get an appointment at the dealer. I agree that it seems worth a few bucks to get a second opinion.
Am I doing any harm to things continuing to drive it like this? I’d hate for it to turn into a bigger trans problem before I have a chance to address the mounts.
I think I’ll give the motor mount route a try. Before I pull the trigger on buying the parts, I’m going to see if I can get an appointment at the dealer. I agree that it seems worth a few bucks to get a second opinion.
Am I doing any harm to things continuing to drive it like this? I’d hate for it to turn into a bigger trans problem before I have a chance to address the mounts.
I also have a thud sound, from first to second, second to third, and all gears really. Hard to hear as you go faster, too much other noise. Ive replaced mounts all and no change. I run the recommended trans fluid from porsche and no change. I think its internal in the transmission honestly. Clutch was new for me too with my 4.0 build by Raby. It was there before too. Also happens when letting out clutch in neutral after coming to a stop. After doing clutch in and out once it does not happen again, until i drive off.
I also have a thud sound, from first to second, second to third, and all gears really. Hard to hear as you go faster, too much other noise. Ive replaced mounts all and no change. I run the recommended trans fluid from porsche and no change. I think its internal in the transmission honestly. Clutch was new for me too with my 4.0 build by Raby. It was there before too. Also happens when letting out clutch in neutral after coming to a stop. After doing clutch in and out once it does not happen again, until i drive off.
Finally, someone with the same issue! Lol
So you haven’t found anyone who could give a real diagnosis either? My biggest concern is damaging something due to whatever is causing the thud. If it is truly a “that’s just how it is thing”, I can learn to live with it. Though I really wish it wasn’t there haha
I have a thud at random times with my MT. I suspect that is what your are experiencing... maybe. Hard for me to describe as I just attribute it to gear engagement. Sometime when I put the car into gear it may crunch a bit as it sometimes does, then almost immediately I get a clunk as if everything just tightened up. This may happen with or without a crunch engagement and again is only sometimes. It has been with me for 120+ K miles so I don't pay it much mind. Honestly, I don't pay much attention to it.... but I suspect.... wracking my brain here.... that when I let the clutch out when in neutral, then press the clutch down... maybe touch the gas and rev.... and engage the gear quickly, I get the clunk..... Anywho, I think I am spinning up something... double clutching without moving. I know I did the last night and then very quickly slammed it into reverse and actually got a grind before popping in... and I had the clutch fully depressed.
The way I understand the synchros/dog gears to work, is that the tips of the dog rings slide along the shaft and into the receiving ring, the shaft is conical shaped and acts as a clutch to spin up the other side to match the dog teeth. (The teeth are somewhat pointed and or sloped sides.) Sitting still, and having a shaft or whatever spinning quickly, like in double clutching and throttle blipping can sometime lead to a crunch or clunk when shifting. So I understand.
If you are experiencing what I occasionally experience, I don't think it is anything to be worried about... or it would have broke already with mine.
Peace
Bruce in Philly
Not from a Porsche, but you can see the dogs and the conical cone clutches that spin up the other side to match the male and female dog teeth. The crunching (or thunking may) comes from the dog teeth coming together. The big drive gears are always engaged, it is the dogs that are the real engagement. If the difference in rotation is great... say from blipping... and you shift fast, you could, in theory, not allow the cone clutches to spin up the other side fast enough and you will get a grind or crunch or thunk.
UPDATE: Took the car into the dealer this morning to see if they can help get to the bottom of the issue. I sat with the lead tech in the car and we walked through the symptoms. He was definitely a little puzzled as well but they came back with a few recommendations including:
- Replacing the cables (I know, I've read a lot about this and it may or may not have anything to do with the issue. But, it also can't hurt as a relatively inexpensive place to start)
- Replace the clutch fork, throwout bearing, bearing sleeve, slave cylinder due to visible wear on the fork pivot (This suggestion came with they eye watering price of ~$2,200 so I'm going to get an estimate at my indy before going any further) This seems logical to me, but the price hurts. Hopefully I can get that down to about half that cost. Anybody have thoughts on the mechanics of this suggestion?
Look like my water pump needs to be replaced too (car has about 50k miles so no surprise there), but again, going to get an estimate on that repair elsewhere.
I've found a few threads on this issue but no one has posted a fix. So, if I end up with a fix I'll keep updating the thread!
Had the water pump, thermostat, plugs and coils replaced, as needed. So the car is running well but the transmission issue persists.
My indie shop didn’t think that the (admittedly, guess) suggestions from the dealer were going to def fix the trans issue, and for the cost, didn’t advise on trying it. They checked motor and trans mounts, seemed ok. So... no solution yet. The most frustrating thing is that I can’t find any credible info on any forum to corroborate the issue, or more importantly: a solution. Many of the know issues and common repairs for these cars are so well documented, but not this one!
As much as I enjoy driving the car, I have to admit that this issue is ruining the whole experience for me. Hoping some more warm weather miles bring me some more enjoyment.
11-15-2019, 12:16 AM
997 Transmission Thud - 3rd Gear
