The GTM Supercar Build Log

Sticky Shifting Dilemma and CAI Reinstalled

After each of my several longer drives in the GTM (20 min+) I noticed something that should not be happening – after 20 or so minutes of driving it became really difficult to shift the transmission into gear. I can only describe the feeling as ‘sticky’ or ‘sludgy’, as it would still shift fine, but it took considerable effort to move the shifter up and down into gears.

My first thought was it was because I did not have the trans oil cooler running. My second thought was that the clutch stopper was potentially stopping the pedal too soon and the clutch was never fully deactivating when shifting and when it heated up it was creating friction, and thus the sticky shifting. I activated the cooler pump, moved the clutch stopper back some more, and hit the road. Same problem after extended driving.

After numerous replies on the GTM forum I turned my attention to the thicker of the two shifter cables that run from the Brandwood shifter box to the trans shift rod. This cable controls the fore and aft motion of the shifting (ie: going into gear), and it also runs very close to the exhaust. The responses I received pointed to a potential overheating issue with the cable, causing the shifting issue. I ordered an Earl’s Flame Guard insulation sleeve for the cable, but in the mean time I used some extra 3/4″ corrugated high-temp resistant wire loom to wrap the shifter cable. I took the car out for the longest drive to date and when I pulled back in the garage the shifting was as smooth as it was when I first started the car. Problem solved 🙂

With the shifting issue taken care of, I set to reinstalling the cold-air intake. To create a buffer between the exhaust and the intake sleeves I actually just loosened the exhaust collars and rotated them so the bolts that run through the collars would support the intake. I then stuck some Thermotec heat barrier to the bottom of the sleeves where they rest on the collar bolts. I took an extended drive with this configuration and it worked great. Intake air temps dropped from 140+ degrees at speed when previous drives were logged, to 75 degrees. HUGE difference. Leaving the car at idle for several minutes after the 30+ minute drive had the IAT’s sitting at around 100 degrees. Previously the IAT’s would see 150+ degrees while idling. The CAI is pure win.

Leave a Reply

You must be logged in to post a comment.