Car came with 46k miles, shifting was okay but slightly notchy. So, decided to try some different oils. First in was Redline NS, this made a slight improvement but still a little notchy. Next in was Lucas. First shift the next morning produced a prominent crunch. As luck would have it, I came across an oil comparison that week and the Lucas did not fare well so it came out immediately. Next in was a half and half mix of Redline NS and Mobil1 LS 75w-90 off-the-shelf synthetic (2 quarts each.) Very nice improvement. Smoother shifts and no crunch when cold. This will be staying in, I like the change.

 

I tried Amsoil (can't remember which one off hand), Redline NS and now Delvac. None of them totally relieved the cold 1/2 notchy shifting but the Amsoil was probably the best. I think the Delvac is the worst but I'm not going to worry about it and I still have another 4 litres of it. I haven't thought of mixing gear oils but I do mix engine oil (Mobil 0W40 and 15W50 - 50/50% = 7.5W45)

 

Amsoil published an oil comparison test and the Mobil1 did very well. Of course the Amsoil was the best (surprise, they did the test). Anyway, I was moderately pleased with improvement with the Redline NS and since I already had it thought, what the heck, and tried this combination. ymmv

 

Interesting that you're using two different synthetics at the same time. I just got rid of Swepco in my tranny and put in the Mobile 1. Its night and day how much better the shifting is when cold and now rarely ever grinds going into 2nd.. Never considered a combo and never have tried the Redline stuff.

 

There was a gear oil debate (imagine that??) over on Pelican 911 board. Most of the participants ended up into two main camps, Swepco and Kendall. Peter Z highly recommends the Kendall for the 915 (NS-MP dino) and the G50 (Super Three Star synthetic). I recently got my car and am looking to change out the gear oil. The correct weight for the G50 (which I assume is not too different in design from your G50) in my 89 3.2 is 75w90. I've had a hard time finding it, but will come back and post an update.

 

I switched to the Redline due to the praise it has received here and it actually made things worse in my car. I picked up some Delvac and havent had time to change it yet but am hoping for some improvements before I start mixing oils to get a good combo. I think its a car by car base for which gear oil works the best

 

I used the mobil 1 also and have been very happy with the improved feel.

 

You'd think the transmission manufacturer would specify which gear lube works best in their product if other brands performed so poorly.

I use Mobil 1 Synthetic Gear Lube LS, 75W-90. No issues.

 

I had exactly the opposite experience. I think it really depends on what is going on in your transmission and the conditions under which it operates. That's why there is so much disagreement over what is "best." I had a 3rd to 2nd issue and switching to Mobil 1 made it worse. I switched to Swepco and the issue disappeared. FWIW, I am a die-hard Mobil 1 fan for oils.

 

I don't understand either why performance would be so different car to car. I had the same experience as you Jason M - went from M1 75W90 to the Swepco and gearbox behaves much better with the Swepco.


dave

 

my bet, people are trying to make up for mechanical wear with fluid, which just doesn't work that well or consistently.

 

You may be right. There doesn't seem to be one cure-all. Just wanted to give people an alternative. If this combo hadn't worked so nicely I was going to try just M1, then maybe the Delvac.

After 3 changes I've got it down to about 30 minutes, so easy to do.

 

Don't most 6 speed 993s suffer from notchy 1/2 shifts when cold?

 

I just had my gear oil changed; had Delvac put in which was not too easy to find until someone mentioned looking at WW Grainger. Not sure what was used previously as that was 2 owners ago but the Delvac seems to be working fine with no shifting problems.

 

Not if you shift slowly for the first few kilometers...till the transmission and lube warms up. Mine is silky smooth after that. I've seen it before; some things loosen up with mileage.

If you force the shift, I guess it would feel "notchy".