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Great info, thanks Petza. If I buy with FF transmission mounts, will that address the deteriorated foam pieces? Is there any other part that’s needed to address that? I will try this out. Thanks!
Originally Posted by Petza914
I had that same thumping in my 997.1 C2S when releasing the clutch at slow speed in traffic. I already had the RSS semi solid mounts, so knew it wasn't motor mounts, but what I did find is the the foam isolators that are part of the transmission mounts just disintegrated in my hand. The primary transmisison mount was still in good shape without any tears in the rubber, so while I had my car on the lift for the engine work I was doing over multiple months, I installed the Function First Transmission Mount inserts. I went with the orange soft ones as stiff transmission mounts can transmit a lot of gear whine and vibration to the cabin and chassis and with the solid mounts in my 928 because of the Corvertte Z06 6-speed I have in that, knew I didn't want that in my 997.
Close up of the OEM transmission mount bushing. If there are cracks connecting the designed gaps, you need to replace the mount bushing before installing the FF inserts. Mine were fine. Note how the side foam pads are completely gone.
Another pic with the mounting bracket out of the way - cleaned up and ready for install off the FF inserts
With a 4-post lift and high-lift transmission jack, the job is really easy
FF Inserts Installed. Note the side isolators - the OEM mount had soft foam versions here, but even at 60k miles, mine were completely shot.
I used a silicone grease to lubricate the FF inserts so they would mate well with the OEM bushing when installed.
As far as I can tell, this seems to have addressed the thumping noise. I still have a noise back there, but it's different and think it's a worn suspension top mount, so my next repair will to install Tarret Momoball top mounts back there like I have in the front, which will remove the last bits of rubber bushings from my suspension.
Anyway, the FF inserts are great - they mate with the original mount bushing to give it extra support and stiffness and control any motion back there.
My car has the OEM SSK and fresh PTX in it. I get the stiff 1 > 2 shift in the morning, but just do it slowly and deliberately as you do and it's because 1st and 2nd have different synchro ring material, like you mention. Once warmed up, it's not a problem at all. I hardly ever have a problem going straight to 1st at a light, and if I feel any resistance, like Carreralicious does, I pop down into 2nd to stop the trans shafts from spinning and then it goes right into 1st. If you don't have a SSK, I'd recommend you install one as it really tightens up the shifting - the Numeric is probably the one to get, but my OEM one works great too, so not worth the time to swap it for something else. I will install numeric cables that I already have in the parts cabinet should I ever have a cable failure. The other thing that might help is the OEM cables can pop out of their mounts underneath the car. Make sure yours are snapped it and then wire tie them into that position. When they pop out, they create just enough slop as the move and flex where the shifting gets just sloppy enough to notice it doesn't feel precise.
I don't have a thump - that I have noticed when shifting between gears while driving, but I HAVE noticed a thump when letting out the clutch pedal while stopped and in neutral. I've always thought it was odd. It's a very subtle thump, and I notice the engine RPMs dip down a bit. When you let the clutch out in neutral, the input shaft on the transmission with all the gears on it go from standing still to spinning at the same speed as the engine, and one could assume that this will create some amount of load, including the load of churning the transmission fluid and squeezing the excess between the gears as they turn and mesh, but I haven't noticed that load in any other manual transmission except the 911 so it has always struck me as odd.
As for shifting, I had an actual grind sometimes when going into second when cold. Replacing my shifter and cables with the full Numeric setup fixed the grind, but cold notchyness is still there. My theory is that the synchros are kicking back a little bit on that 1-2 shift and all the rubber in the stock setup cushions that kick-back and doesn't allow the synchro to keep moving until full engagement which then results in the grind. The main cause is the use of steel synchros I believe. But you already knew that.
At least these transmissions are bullet proof - if not without character. I would very much rather have a Getrag for sure. But I'm glad we don't have breaking transmissions as an item to keep high on our rainy day fund list. I haven't even ever heard of one breaking. Same is not true for WRX transmissions (which is what I came from previously).
Good to know that the 997.2 base has a self adjusting clutch thanks. Yeah I was thinking of changing the engine mounts to see if that makes any difference on the thumping. I have 2 years of CPO warranty so I’m just going to see how it goes. I’m getting used to matching revs to avoid the thump so it doesn’t bother me as much anymore. When I’m accelerating hard to redline, it doesn’t thump as much because the revs are matched well, I think.
whether or not your base 997.2 has the self adjusting clutch , depends on the model year. Up until the 2011 model year, the self adjusting clutch was exclusive to the “S”, but according to the brochure, all models received the self adjusting clutch in 2011. At that point, Porsche added other S items to the base model, including the Sport steering wheel. In fact, Porsche reduced the price of some option packages for 2011 models.
I've got that occasional dull thump, too, in my '11 C2S with 32k miles when I use the clutch. Offhand, I can't say whether it's during engaging or disengaging it and, like I wrote, it's not there all the time. Since I've only had the car for about 2 months, I wasn't sure if this was normal or not. The previous owner did replace the transmission mounts not too long before I bought it.
You know what this might be.... do the 997s use a sprung hub clutch for engagement smoothness? If so, could be the springs in the hub loading up. Mine does it during engagement only, which would support that hypothesis.
After driving my 997.2 base manual for a few months, I have the following thoughts. For context, I’ve been driving manuals for over 20 years, previously owning a 02 WRX, e46 3 series, and R55 John Cooper Works Mini. Out of these, I loved the Mini’s 6 speed box the most. Bone stock, it was easy to drive, heel toe, short throws, would go into 1st at a roll, never balky even in the freezing cold. Amazing transmission IMO and I never felt the need to mod anything on that car.
The 911 had 45k miles when I purchased, and DME showed it was a cream puff with no revs over zone 1. So the car was not dogged. Compared to my prior Mini, the 911 clutch is longer and stiffer, not surprising given the extra engine power. My non-adjusting base clutch engages towards the top. Not sure whether the clutch is towards the end of life, but it hasn’t slipped yet and engages fairly well. Took some getting used to, but it’s not bad feeling. I suspect a new clutch would feel better, but I’ll wait until this completely goes before swapping.
A few issues. First, I had trouble engaging 1st gear from a complete stop, as many have reported. Typically happened at a red light when I’m first in line and looking like a douche in a 911 who can’t drive his car. I did a PTX fluid change and it helped a lot. Only had it happen one more time afterwards when I was rushing to get into 1st from a stop.
Second, as many have said, 1st to 2nd is quite notchy for the first few cold shifts. I shift very slow to avoid grinding. It’s really like the first 3-4 shifts in the morning and then the box feels nice and smooth. The PTX didn’t do much to help this. I understand this is pretty normal and due to different synchro material in 1st and 2nd. Not a big deal, I just take it easy to start. Once warm, the box is very smooth with a rifle bolt feel.
Third, I get a thump in the rear when shifting slowly from 1-2 and 2-3. It took a few months of driving, but I can finally mostly drive without thumping. If I’m accelerating slowly in the neighborhood, I push the clutch in a bit slower and blip the throttle to rev match. The revs drop very quickly on the 911. All my prior manuals would hang the revs slightly after depressing the clutch, so this was a change for me to have to blip while upshifting. Also, if I depress the clutch too quickly while accelerating slow, it will thump. It’s kind of a dance to synchronize everything to avoid thumping, but I suppose it’s the challenge of driving a 911? For the record, I took it to a dealer and my Porsche Indy and they said this thumping was normal on a 997, and even some manual 991s do it.
Lastly, the stock 911 pedals aren’t great for heel toeing. I have wide size 12 feet, so on past cars I’ve been easily able to blip the throttle using the right side of the ball of my foot, while keeping the left side in the brake pedal. The 911’s brake and gas pedals are pretty far apart and the gas pedal sits a lot lower. I can heel toe with effort, but it’s not easy. I’ll try a bit longer to see if it gets easier. If not, I may splurge for the Numeric pedals.
A few questions, would a semi sold motor mount and/or tranny mount help with any of these issues? Also, while I’m not interested in a shorter throw, I’m wondering if Numeric cables and short shifter could improve the shift quality. Any thoughts from folks?
Originally Posted by Bruce In Philly
2009 C2S 164K miles
The manual in my 2000 Boxster S (same as in the 911s) was better. But, it was quirky too.
I think the manual in our 997.2 is a drop in Porsche standards. I don't know if they just spec'd cheaper metals or what, but it is not as good as the last one I had... just is not. Total speculation, but I think Porsche made a decision to get out of the manual business, purposfuly took their eye off the ball, and outsourced the manufacture to Aisin a Japanese company. It is a sunset product.
My recommendation is to change the PTX fluid every 25-30k miles... I base this on the time from a change to when I start getting really annoyed.... no science here but I believe that if I did this from the start, the transmission would be much better overall.
Bruce - Interesting, .. I was sure the manual transmission in the 997 is ZF's.
ewc - As for the hesitation you describe it could be a clutch as the friends mentioned above, and could also be a clutch pedal switch / brake pedal switch.
The hesitation in the low gears at low rpm may be due to these switches (they are cheap parts and their replacement is simple)
This is exactly what I experience. I think Mikemessi described it well above — thumping “when driving slow is related to the quick rev drop and rev mismatch not motor mounts. This gearbox rewards precise throttle control. Hang the revs a little.”
I’ve been able to adjust my driving to mostly avoid thumping. If I’m accelerating slow, I’ll push the clutch in slow, hang the revs and shift without a thump. If I’m accelerating fast, I’ll push the clutch in quicker and engage the gears quicker. Rev drop when going fast is less of an issue because you’re changing gears quicker. Try that and see if it helps.
These gearboxes definitely take some precision to drive. I ordered the FF orange transmission inserts and Rennline semi solid mounts which are all on sale right now. Although I’m a bit nervous about the FF inserts because a lot of people say it gets noisy. On my old WRX, I once installed Kartboy transmission mounts and the gear whine drove me nuts.
Originally Posted by nellborg
I've got that occasional dull thump, too, in my '11 C2S with 32k miles when I use the clutch. Offhand, I can't say whether it's during engaging or disengaging it and, like I wrote, it's not there all the time. Since I've only had the car for about 2 months, I wasn't sure if this was normal or not. The previous owner did replace the transmission mounts not too long before I bought it.
Yeah my main concern with the thumping and notchyness was whether there is something broken. But it seems normal from everything I’m hearing. The original 5 speed WRX gearboxes did have a reputation of being made of glass. It was honestly a pretty terrible transmission but it taught me how to double clutch out of necessity because the 1st and 2nd synchros were so bad!
Originally Posted by Hindsight2010
I don't have a thump - that I have noticed when shifting between gears while driving, but I HAVE noticed a thump when letting out the clutch pedal while stopped and in neutral. I've always thought it was odd. It's a very subtle thump, and I notice the engine RPMs dip down a bit. When you let the clutch out in neutral, the input shaft on the transmission with all the gears on it go from standing still to spinning at the same speed as the engine, and one could assume that this will create some amount of load, including the load of churning the transmission fluid and squeezing the excess between the gears as they turn and mesh, but I haven't noticed that load in any other manual transmission except the 911 so it has always struck me as odd.
As for shifting, I had an actual grind sometimes when going into second when cold. Replacing my shifter and cables with the full Numeric setup fixed the grind, but cold notchyness is still there. My theory is that the synchros are kicking back a little bit on that 1-2 shift and all the rubber in the stock setup cushions that kick-back and doesn't allow the synchro to keep moving until full engagement which then results in the grind. The main cause is the use of steel synchros I believe. But you already knew that.
At least these transmissions are bullet proof - if not without character. I would very much rather have a Getrag for sure. But I'm glad we don't have breaking transmissions as an item to keep high on our rainy day fund list. I haven't even ever heard of one breaking. Same is not true for WRX transmissions (which is what I came from previously).
Bumping this up since my install of a bunch of Function First products, which pretty much cured all of my criticisms of this transmission. See my edited original post.
Oh, and I also installed some 991 exhaust tips which are subtlety more oval. I’m enjoying the new look.
Awesome! Glad to hear the Function First stuff fixed things up. What did you opt to go with from them? I've got about 52k miles on my 997.2 4S and thinking I should do similar.
FF engine mounts, Shift Right shifter bushings and cable ends. Note that my Indy charged $450 to install the bushing and cable ends if you are factoring costs. Or you can try to install yourself. Personally whenever I try to install something, it’s always everything that can go wrong, will go wrong! So I leave it to the pros.
Originally Posted by msequence
Awesome! Glad to hear the Function First stuff fixed things up. What did you opt to go with from them? I've got about 52k miles on my 997.2 4S and thinking I should do similar.
Bumping this up since my install of a bunch of Function First products, which pretty much cured all of my criticisms of this transmission. See my edited original post.
Oh, and I also installed some 991 exhaust tips which are subtlety more oval. I’m enjoying the new look.
Thanks, I was inspired by EMC2’s photos. Note that I had a hard time fitting these tips on my own because the bolts on the 991 tips are on the opposite side vs the 997, and the bolt was therefore hitting my exhaust pipes. My Indy was able to get them fitted though.
11-23-2020, 10:09 AM
