jaholmes

I recently had my transmission fluid changed with Mobil1 75-90 Synthetic Delvac and now I grind / buzz 2nd hard when down shifting from 3rd. I also get a little buzz going from 2nd to 3rd. BTW, this is at the track, street driving is ok so far. Seems to happen when I am driving harder and don't match engine RPM with gear changes; should I be double clutching. Some people complain about Mobil1 but it is recommended by Porsche. The shop that did the change noted the old trans fluid was dirty. Before this I had zero gear issues at the track and I am there often. Could it be a mobil1 re-formulation issues...Delvac...

I had the clutch flushed at the track thinking the clutch wasn't engaging properly and still the same issues.

I have also been trying to track down a notchy clutch problem. So when I had the trans fluid changed I also replaced the clutch slave; still notchy. Can the clutch slave cause my 2nd gear issue. I am planning on replacing the metal bushing in the clutch assembly to see if it fixes.

So now after reading a few 2nd gear issues I am starting to think the worst. Is the notchy clutch actually the throwout bearing and point to a clutch problem. Is the buzzing 2nd gear a clutch issue. I don't think it's the trans itself because I am not having other issues. I am close to 49993 miles.

I am not really in the mood for a clutch and still have the notchy clutch. Although a clutch is cheaper and I can get the LWFW while they are in there. I am definately not in the mood for a new transmission. Although this would be the time to buy a G50/31 and turn my C4S into a C2S.

2Many Cars

I'm sure there are some oil experts here who can get into more detail but I know in general synthetic oils in manual transmissions can sometimes be too slippery. The oil needs to have a slight amount of "stiffness" in order to help the syncro rings work properly. It sounds like the oil formulation you are using is fine for street use but perhaps a bit too slippery for the demands of track use. This won't solve your clutch problems but before you assume you have a big tranny problem try a different gear oil.

jaholmes

Yeah, I read through all of the gear oil posts. It makes me think that the new Mobil Delvac 75W-90 gear lube is not the same as the old Mobilube 75W-90 SHC gear lube. This sucks. So then I need to find the right modifiers. It looks like the MTL stuff may work. Maybe it is too slippery because it seems like I am overshooting something.

Yeah, the clutch is a different topic I just hope they are not tied together even remotely.

rconnon

I get the notchy second / third shifts when the tranny is cold.. but thats been reported quite a bit here from my searches. some say it's due to the syncros others say it's the fluid in the transmission. Mind you i dont experience this when it's hot and i'm really beating on it.

but your not alone thats for sure. i know 3 other 993s that are experiencing the same issues personally.

jaholmes

Have you changed the gear oil recently. By chance what flavor are you using. The gear oil for me is definitely hot. How about what the other guys are using / used I would like to know what additive is needed.

GeoT3

I just changed my tranny fluid using Red Line synthetic 75W 90 and so far so good... no issues at all.

they have two formulations. one for limited slip and non limited slip. make sure you get the right one.

rconnon

Last time it was changed was 60,000 mile service before i bought the car (20,000miles ago) it's on the list of things to do.. but from what i've been reading people are experiencing this with the M1 products. i'm going to replace the current fluid with Motul 75W-90.

I haven't researched it too much as to whats the best gear oil to put in.. i guess its greatly dependent on how the cars driven.

rconnon

have you read this?

https://rennlist.com/forums/showthre...smission+fluid

jaholmes

Yes I did, a few times. This is where I got the feedback to get Mobil1.

I am trying to track down http://specialtyformulations.com/ because their site is not working right and I would like to talk to them.

The Shop that did the fluid change also recomended BG Gear oil products. Mixed results and trial and error is starting to really bug me. I have conteplated getting rid of my C4S over this and other nagging issues.

bgiere

Specialty Formulations is no longer in business...The Delvac is substantially identical to the old Mobilube SHC....You may want to try Valvoline Dura-Blend 80w90...It is a semi-synthetic and I have found that it can bring the synchro's up to speed a little faster... has cured a few of my notchy shifting friends transaxles...Redline is a terrific lube, but is even more slippery than Delvac, if the lube is the problem it may make it even notchier .Hope this helps!

jaholmes

Thanks. I think my issue may be synthetic vs. non. The dealer says they use good 'ol Mobil1 75-90 gear oil, not the synthetic stuff. Even RTFM, it doesn't say synthetic. At this point I have to try something becuase what's in there is driving me crazy and will probably no more damage then good.

nile13

To resurrect the discussion... so... what was MTL-R? Was it MTL 75W90 with some friction modifier? If so, does anyone know what it was or can duplicate it?

Failing that, should Delvac be used on a street car?

PG993

Jim.

I had similar problems with the 2 and 3rd gears, especially when driving hard and on downshifts. I tried some synthetic 75w90 oil from porsche- realy expensive stuff something like 40CAD per litre that my tech recomended. It did not help at all. In fact it was terrible. I then tried the Motul Moltygear 75w90, which I think is semi synthetic. This oil was much better. The shifting is stil notchy but a huge improvemnt over before. Perhaps this improvement has something to do with the increased resistsnce going from all syntehtic to semisynthetic like some of the other guys are suggesting.

Paul