Laertes

Encountered a new issue today. On a high speed sweeper at the end of a long straight, when going from 5th to 3rd, had fairly consistent trouble getting into 3rd. I would have a lot of effort to get the shifter in, accompanied by a crunch or short grind. Have never had this issue before. Car would go into (and out of) 3rd gear on any other spot on the track without issue, and also felt completely normal on the drive home. Issue was only at this one point on the track, which is also the only place I would go from 5th to 3rd.

Does this sound like a synchro issue? In this particular corner, I shift directly from 5th to 3rd, with a big blip to compensate. Historically it's been an easy shift, and I'm usually able to get it into third smoothly with a good rev match and the car doesn't flinch at all. But today it was.... not smooth.

Thoughts?

Spyerx

High lateral down shifting issuers are pretty common. Make sure your oil is fresh, was it hot out? You can try semi solid or sokid engine mounts and tranny mount and cup cables. It seems those that have fully solved put cup steel synchros in with these mods. My car on rare occasion will do this to 2nd if I'm rushing. Take your time and don't Rush the shift if I'm easy on shifting it always works. I have wevo mounts Cantrell tranny and cup cables delvac oil.

Laertes

Thanks for the thoughts. I don't think this is the typical 2nd to 3rd upshift issue under lateral loads (I'm very familiar with that). This issue is occurring at the end of the straight, with the car still going straight before turn in. The transmission oil was changed mid season (I do it twice a year). It definitely did get a little better if I was a bit slower and more deliberate. Ambient temps in 60s, so I don't think heat was the issue.

Jamie_GT3

Laertes,

Are you still running the dynamic engine mounts? I know Roland pulled his and replaced with Wevo's and all of his shifting issues magically disappeared.

Turn 2 at Pacific is still pretty highly laterally loaded, so if the dynamic mounts are on their way out could be more movement back there than there was before.

You're pretty gentle and deliberate with the gear box, I'd be surprised you fried a synchro...

ngng

What happens when you double clutch?

etchhead

I have a few situations on track where I need to drop a few gears (4th to 2nd) but feel it is probably safer to me to heel-toe my way through 3rd then 2nd. Works better with my muscle memory and ensures I don't money-shift.

KaiB

Common with our air-cooled cars.

The tip regarding engine mounts is probably the best one.

Spyerx

Ok, in my head I saw a long straight into a sweeper, where you are trail braking and down shifting :-) I change my tranny oil same as my engine oil... maybe overkill, but its just cheap insurance me and about ~$100 for shop to do it while doing engine oil.

paver

Drain the trans oil again and see if there is metal on the plug.

Cbwell

I'm curious about your mention of the typical 2nd to 3rd upshift issue, I just experienced this for the first time my last time at the track. I had a helluva time getting into 3rd coming out of corners and trying to complete passes. What's the best way to avoid this?

Spyerx

For me it was: ensure fluid is fresh, wevo engine mounts, cup shift cables, and cantrell 60a durometer tranny mount ... and most important is don't rush the shift.

Cbwell

Cool, thanks. I've been eyeing the Numeric shifter as well, probably couldn't hurt.

Spyerx

I opted for the 996 cup shifter with cup cables. Love it. I think the best shifter for these cars is the CAE unit.

Macster

Probably not a synchro issue though of course if this symptom appears at other times and more frequently then it could be a synchro issue.

If this behavior occurred after some time on the track it might be explained by clutch fluid being hot and probably past its change by date, unless the clutch (and brake) fluid have recently been flushed/bled. Even on the street I have experienced clutch and shifting issues with past its change by date clutch fluid.

Regardless, I like the advice about the engine mounts. One of the first mod's I made to a car I auto-x'd was to install a torque strap to keep the engine from twisting on its mounts. This cured a nasty throttle problem -- the linkage was twisting as the engine was moving about on its mounts. I do not recall any shifting issues but that might have been because the throttle linkage problem was so bad it had my full attention.