BobbyT

Since buying my 993 three years ago with 19,000 miles on it, I've had a little crunch or graunch shifting from first to second, and sometimes from second to third, especially when the transmission is cold, even if I pause in neutral. This problem improved as the transmission warmed up, but never really went away.

Previously I tried several different gear oils trying to reduce this problem: Swepco, Specialty Formulations MTL-R, and Mobil 1 SHC. I tried hard to feel an improvement with each of these, but in reality there was little or none.

A month or so ago, I convinced myself that the problem might be corrosion on the transmission input shaft, so I had the transmission pulled and everything lubed per Porsche specs with the special lubricants. There was some improvement (maybe).

I talked to my favorite tech (Don Kravig at Precision Motion in Riverside), and he said that maybe the gear oil was too slippery, and therefore the synchros couldn't work quickly enough. Then I remembered years ago being told by Vern Covert (anyone remember Vern?), who ran a great shop in West Los Angeles, not to put any additives in the transmission for that same reason.

Next I tried Valvoline 80W-90 plain vanilla, dead dinosaur gear oil, and there was noticeable improvement.

I sent an email describing the problem to Roger Brown at California Motorsports, and he gave a similar response--could be worn internal parts, or could be gear oil too slippery. He recommended Redline 75W-90NS, which has no friction modifiers, as the best thing to try. I called Redline and they confirmed that this gear oil is specifically designed for quicker shifting, by allowing the synchros to grab better and quicker.

Filled the gearbox with Redline, problem gone!

AOW162435

Bobby,
Great write-up. It seems quite a few people deal with one or more vexing shift problems.

I'm on my second fill of M1 SHC and am very pleased with the gear engagement. It sounds like Redline may be the solution for those experiencing notchy shifting.


Andreas

tj90

Great information Bobby. Where did you get the redline and how much $$? How many miles have you been running this stuff?

Im currently running around 10k miles with MTL-R. I noticed an improvement from 1st to 2nd when tranny cold, but Im still careful and shift slowly when cold. I wonder if the redline would further improve shifting when cold. I originally was using M1 and I dont think Ill be going back to that lube.

NYC 993

I've read countless threads on this and have only seen problems on upshifts, has anyone experienced this on the downshift from 3rd to 2nd? Mine crunches more than occasionally there unless I let the revs drop and slowly "feel" the synchros engage. matching revs doesn't seem to smooth things out. Going to do a trans and engine oil change next month and trying to decide what to put in, so many choices!

2ndof2

This is all very interesting....

I too have had the 1st to 2nd gear notchy-ness to the point of the thing grinding (man I hate when that happens!!!) The problem usually only happens when the car is cold but its never been a silky smooth transition from 1st to second like on other cars I've owned.

My mechanic suggested using Swepco when I last changed the tranny fluid but this didn't resolve the issue. It improved things but I still grind going into second when its cold unless I really crank up the RPMs and sort of pull back and slightly to the right when I hit resistance....even this approach when the car is cold doesn't always work perfectly. When the car is warm it seems to go into 2nd gear much, much better.

Is this about what you experienced with your car Bobby? If so I would be very interested to see what switching to Redline does for the car.

matt777

I have heard of this problem on other manual gearboxes. The logic is that too much of a reduction in friction results in improper syncro operation so stick with the intended dino oil. Who knew?

chris walrod

Good to hear this problem is solved.

I just changed mine last night in the turbo. I used standard fill Mobil1 -- I have had the best luck with this.

The po of my last car tried Swepco -- I changed it back to Mobil1 once I owned it and shifting improved afterwards.

BobbyT

tj90: I ordered directly from Redline, and it was about $50. If you order, be sure to specify the NS version. They have another 75W-90 that DOES have friction modifiers--it is not what you want.

NYC 993: I've never had the problem on downshift, but I think the same concept applies--too slippery gear oil equals poor synchro performance.

2ndof2: What you describe is about what I experienced. Interestingly, the email from California Motorsports (Bobby Hart's shop--they know their stuff) said in caps, "NO SWEPCO". Don Kravig also opined that Swepco was too slippery. I also renewed the four little plastic bushings in the shift lever and the two ball cups in the shift brace rod recently to eliminate any monkey-motion in the shifter. I had tried the factory short shift lever, but I think it makes one tend to shift too fast and create more wear--no problem in a race car where you are going to rebuild the transmission once a season, but not for me.

RallyJon

My car had conventional gear oil in it and it was very balky when cold. Not an issue in CA, I'm sure. With Mobil SHC in it, the shifting is faster and it's easier to get by the synchros occasionally when cold, but the overall feel is much better and lighter.

This may a be a stupid question, but aren't better synchro performance (which requires more friction) and maximum gearbox longevity and minimum power loss (which requires less friction) contradictory?

BobbyT

RallyJon: I think you are exactly right. The trick is to choose a gear lube that strikes the best balance between longevity and smooth operation.

slider

+1 for Redline....changed the gear oil about 1,000 miles ago and very smooth, especially when the tranny is warmed up.

notbostrom

this has been discussed on the ferrari board ad nausea for smoothing the 348 gearbox.. The redline is the oil of choice and has become a "must do" mod for all 348's. There has also been some experimentation with other redline gear oils with very good results... it really is magic!!!!

Pete Lech

I have a Limited Slip diff. Don't these need the friction modifiers?

For now, I just up shift slowly until things warm up.

LAT

notbostrom; which Redline gear oil specificaly?

RallyJon

Just to be clear: Friction modifiers DEcrease the amount of friction. And the regular Redline (and most other gear oils) have some amount of them. So the NS version signifies a lack of friction modifiers for more friction. If you have a plate type LSD, you need some friction modifiers in the gear oil or you'll chatter.

How much is the right amount to facilitate the synchros (less) and smooth LSD operation (more) is the tricky part.

Redline actually sells friction modifier additive separately, so I guess you could start with the NS, and try to find the best compromise yourself.