Slow shifting

Hi, I’ve had my car running for about 6 months now and for entire time I’ve been battling slow shifting from 1-2, 2-3, and 3-4. The shift from 1-2 feels like it really has to work the synchro…

To diagnose, I’ve jacked the car up and had a helper start the car in first with the clutch pedal pressed. The input shaft moved a little but quickly stopped. So, I swapped the trans to a spare (I’ve got a few, I also endurance race a 944). Same issue. I then swapped the clutch, self adjusting LS7 clutch to a spec clutch (stage 2). Through it all the shifts are just super slow.

Any other ideas on why the shifts could be slow?

Thank you,

Jason
1988 944 NA with LS3 and AOR

Torque tube bearings or torque tube alignment?

How would the torque tube bearings contribute to it?

Clutch in, I can spin the prop shaft and input shaft to trans by hand pretty freely.

Do you have any vibration or noise? Is it hard to get into reverse?

I had an issue where my car was hard to get into reverse wasn't shifting properly into the others gears. It was the torque tube alignment. I loosened off all the adapter bolts and started the car and let everything find its center. Then I tightened everything back up and the problem was gone.

No vibration or noise, but yes, it’s hard to get into reverse (and 1st). I jus assumed that was due to wear on gear teeth.

That said, you’re thinking that a misalignment between the prop shaft and engine could be causing significant pilot bearing drag?

Ya, sounds like it. It's worth a shot anyway

I agree. I’ll give it a shot. Thanks!

If you find the TT in good alignment and spins freely with the clutch disengaged. Look at your shifter and linkage. When it’s all worn out you may not achieve proper throw for a smooth gear shift in the gearbox. Those factory rubber bushings aren’t the best for long term durability. Only944 makes a gorgeous and durable set of linkage. I have a new shifter, shift rod and short shifter kit and the movement is precise and complete whereas before it was iffy at best.

What fluid are you using in the trans? The ZF 016 can be fussy, mine likes RedLine MT-90 and doesn't like some of the other fluids the 911 guys swear by.

I've been running Redline 75-90NS (I've run this in my racecar for the last 10 years, never had an issue with shifting like this).

The racecar is an '85 944 NA with a homebrew turbo setup that we race in Champcar and 24 Hrs of Lemons. We've got over 400 race hours on the chassis and have only been through 2 transmissions.

Interesting. That 75-90NS is what the RedLine website recommends for the '89 turbo (mine's an AOR) but the MT-90 is what it recommends for the '85 NA. You and I are backwards!

But anyway, I agree the NS oil is a good choice and probably not your shifting issue. I had similar shifting trouble when I tried the Swepco 201 the 911 guys like.

Rich