Rough 2nd gear when cold, but different outcome from different trans oils.

I have two 1999 C2 early builds, a cab with 104k miles and a coupe with 76k miles. When I got the cab, second gear was a clunky rough mess to engage when cold. After warming up it wasn't much better. I then changed the gear oil to Porsche brand, and not too much longer I realized the second gear was perfectly smooth at any engine temp. The whole shifting feels smooth and firm and there is no rough engament at all anymore. Then on the coupe, which I don't have as much driving time on, I have the same second gear knotchiness and hard to get into gear when cold. Warm it's much smoother, but over all the shifter feels loose. This time I used Mobil Delvac as that seemed the oil of choice for models with the LSD (which the coupe has), however i have not really noticed much improvement and I was anticipating the significant improvement that my 104k mile cabriot had. I know the symptoms point to a 2nd gear rebuild in the future, but I'm also left to wonder if the choice in oil does have an impact? I filled both with the method of letting it run out of the fill hole. I have read differing opinions on whether filling with exact measurements is required, though I don't know if that would cause my second gear issue in coupe. Any thoughts?

You could try the Porsche oil, as the LSD is probably worn out at 70+k miles. If it shifts smoother then put in an LSD additive. I think the LSD additive negatively affects syncro smoothness. The LSD additive makes the clutches grabbier and the syncros are clutches after all.

I have a crummy 2nd gear shift too. This thread in the 997 forum discusses an oil additive that might improve the situation. Cheaper than a rebuild. Although I don't know how it would do with a LSD... https://rennlist.com/forums/997-foru...botex-wow.html

maybe the first thing would be to dump the delvac and fill with Porsche fluid. that's what Matt Monson told me and I was skeptical but he KNOWS Porsche transmissions. Remarkable improvement.

Quotes source post: 19996575

The LSD additive makes the diff clutches LESS grabby, it is designed to prevent wheel hop in tight turns. It is a friction modifier that lowers the friction coefficient, makes the oil slipperier and yes, can affect synchros by making them more slippery as well, lessening their performance. -Tom

Quotes source post: 19996785

Yes, that's what I'll probably do to just equalize both cars. It's just so funny, because I spent a considerable amount of time reviewing all the threads and banter about which gear oil for the LSD, and Delvac come out the winner. And one of the big reason was because, "...use Delvac, because Matt Monson recommends that, and he knows Porsche transmissions" I'll have to go find the thread. I will get my LSD redone by Guard at some point, looks like a great option.

What 'weight' oil are you using? Perhaps a Porsche guru could recommend a lighter weight oil. (Kind of crazy, I know, but I once had a 2d gear issue with a Triumph TR7. Had to go to a lower weight gear oil and problem solved. I realize it's apples & oranges to a Porsche ... but just a thought.)

Quotes source posts: 19996826, 19996836

Yes, that's how I understood it too. I'm not using any LS additives, and the Delvac does not contain any LS additives. Funnily enough, looking back through my post history "GTGears" does say the Porsche brand oil, does have an additive specifically made for the Porsches in conjunction with Exxon Mobil, but not a specific LS gear oil. 75W90 , standard weight.

I don't mess around with the different gear oils... If there is a second gear issue I just put a new second gear syncro in the tranny.....You don't have to do a full rebuild or even need any special tools.. Just R&R the trans and pull the rear housing , remove the snap ring on the rear bearing and with a long three jaw bearing puller pull the rear bearing then the 1st gear and the 1-2 slider...You can then replace the 2nd gear syncro and the 1st gear syncro without going any further .. There are several threads in the archive with details and pictures of how to do this.....and if you are mechanically, anyone can do this .... With new syncro's ANY 75w-90 gear oil will do and shift smooth, and use the friction modifier if needed for the LSD ....

Quotes source post: 19996826

D'oh thank you Tom, that's what I get for posting from the airport at 3AM.

Quotes source post: 19996962

Wow, that's encouraging. I hadn't seen that. I thought there was a 40 ton press involved or something. Next question would be what do sliders and synchronizers and whatnot cost?

My rebuilt transmission with LSD shifted like garbage, PO said CMS told him to put "whatever" gear oil in it. Second gear would lock out when hot. Changing to Porsche OEM completely solved it, issue has not resurfaced in over a year.

Mine hated shifting in the cold - especially 3rd and 4th - I had to double clutch or shift very slowly by keeping pressure until it went into gear. I mentioned this issue to my builder when it was in for the engine rebuild. They drained the oil and said the color was reminiscent of a race oil... anyway, they put in LiquiMoly High-Performance 75W-90 Gear Oil and it's been perfect since, no matter the ambient temps.

Quotes source post: 19998876

^ Yes this ^ Reading the specs of the Porsche oil (specifically the cold viscosity measured in mm�/s) it is very close to the Liquimoly. I had some unknown oil in mine and would be a pig to shift when cold. Changed to liquimoly after a bit of research and its sorted now. Not all gear oils are the same despite being rate 75w90 or whatever....read the actual specs carefully on the data sheets.

Quotes source post: 19998596

Yeah, that's my experience too. Y'all can do whatever you want to find something similar but you won't be far wrong with starting by using the secret sauce. If it still doesn't work then you can go from there. The thing is you actually need some friction, just the right amount , to get the synchronizers what they need, if you get rid of all the friction it just doesn't work.

Quotes source post: 19997825

I would agree that fiddling with different gear oils might at best only delay the inevitable, and that is to service the synchro(s). If you've been grinding engagement teeth, you may well find yourself also replacing 2nd gear and its shift sleeve (really, the whole synchro assembly). I'll caution you that when you remove the 1st/2nd synchro assembly, unless you are very careful and a bit lucky, you will likely find its three detent *****, springs, and blocks go flying. 1st/2nd is in particular prone to this, and putting it back together takes some finesse, as does reinstalling the assembly on its shaft without things flying apart again. Not my favorite task. Regarding the 40 ton press, it is needed only when it comes to pressing 3rd through 6th fixed (non-shifting) gears off the pinion shaft, which is necessary when servicing its front bearing. Getting the reverse, 1st, and 2nd shifting gears off requires one or more good quality bearing pullers. Good luck,

Quotes source post: 20001384

As much as I have enjoyed working on things, I don't see taking the transmission apart to one of things I'll likely tacke. Somewhat ironically, I went for a drive today and 2nd wasn't notchy at all. It was pretty cold out too. It still doesn't feel very "good" though if you know what I mean. I'm pretty careful going into second. Not going to help my eventual track times!

Quotes source post: 20001384

I agree with Kevin here, if you are mechanically inclined and feel froggy enough to tackle the 1st-2nd Sycro's , while ordering the Syncro's get 2-3 of the springs,*****, blocks, because you will probably loose 1 or 2 in the process ... You wont be the first to launch one into the abyss.........

So like magic the rough shifting has improved dramatically. I don't really understand why, just suddenly the cold shifts are not like trying to get a semi into 1st gear. But it's not 100% and every once and a while it just feels crap, to the point now I'm scared of 2nd because I don't know what it's going to do. I'm tempted just as an experiment to drain the Delvac and put in Porsche oil. I can't imagine it would be a difference, but I'm still left only comparing my cab which I did the porsche oil and it was like a new transmission in regards to 2nd.

Quotes source post: 20035533

Oils while seemingly the same general overall specs can be quite different, especially their cold viscosities measured in mm�/s. I found the liquimoly 75w90 is the closest to the factory Porsche stuff (i couldn't get hold of) and consequently worked a lot better in my transmission based on what was previously used. From my understanding the synchro's in our gearboxes are particularly finicky and require a specific mm�/s range to give enough drag for them to work well.

My car had similar issues, here are the steps I took: First I installed the numeric shifter, flushed the transmission fluid with Swepco, replaced the engine mounts with new mounts, and added a function first transmission mount insert. The cables looked great and seemed firmly in place. This helped a lot. I don�t think the shifter actually did anything for the issue, but I really like it. I definitely needed new engine mounts and the flush was good. But� I still had a minor issue. So, while having the car aligned, I asked the tech (a 911 specialist) to see if he could figure it out. He looked, safety-wired the cables in place and test drove it - No issues. I�ve been driving it for a while with no issues. I think the cable was moving a little. Ultimately, you might have a 2nd gear issue, but I would take care of every other low hanging fruit until you get there: shifter cables Secure the cables fluid g-box 2nd gear detent engine and trans mounts clutch bleed clutch pressure plate

I'm close to 144,000km on mine, so I decided to change the diff and tranny oil. I went with the recommended liqui moly GL 4+/5 and a split 30/70 can of ceratec. Much to my surprise, the shifting now is significantly notchier cold. The shift from 2nd to 3rd is particularly bad. Not a happy camper...

Hey guys, fwiw, I have been using Miller Nano 75w90 competition gear oil for over a decade and a half. I have had alot of track days over the years and have had no issues with shifting nor my Guard LSD. But yeah, we will all eventually need to rebuild gear boxes and LSDs. https://performanceracingoils.com/mi...tion-gear-oil/

Quotes source post: 20037032

oh that's a shame, why the ceratec? Maybe that's not helping? Other than correct viscosity you shouldn't really need additional additives in a gearbox.

[QUOTE=SimJen;20037883 why the ceratec? .[/QUOTE] all in the pursuit of smoothness. Serves me right

Quotes source post: 20038299

except in this case it's not... hopefully you can sort it

Sharing my good luck to those with this problem.. 3L of Mobil PTX from Suncoast took care of my extremely difficult when cold and slightly better when warm 2nd gear with a 2/98 996 including factory LSD. It was so bad that I almost double shift into 2nd evenin every time just to avoid popping out because it was not truly in gear! It shifted poorly when I bought it last Oct at 118k, currently at 120k. I have PO service records and an Indy shop changed the fluid 5 yrs ago at 98k mile, it did not specify the fluid brand other than synthetic 75w90 and it was def not OEM fluid. The old fluid looked and smelled nasty for just 20k miles, with no metal bits I can see (yay!). Drained 3L and took all 3 L. I encourage others with 2nd issues to try this fluid.

I'm noticing now that if I push the clutch pedal ALL the way to the floor I'm not having any issues getting into second gear. My other 996 is more foregiving with the clutch pedal. But this coupe seems to want it all the way down. Also, if I don't press it all the way to the floor, it won't recognize it as depressed and I can start the car. Is it a red-herring that pushing the pedal firmly to the floor makes the 2nd gear shifts seemingly better?

Sounds like a clutch bleed would be beneficial just incase its a failing slave cylinder. A bit of air in there might cause the clutch to not fully release? perhaps?