6-speed shifting difficulties
 

I have been having shifting troubles, esp with 6-5 and 5-4 downshifts. These get noticed after about 20 mins of track driving.

I had discussed this previously with a couple of forum members, reviewed the forum threads and taken *some* of the advise. I have replaced the shifter bushing with a Miataroadster delron bushing. Unfortunately, he did not have a long lever "short throw" shifter made yet, so I couldn't try this. I flushed the trans and installed Amsoil. I bled the clutch and even shimmed my seat closer to ensure that I was close enough to fully disengaging the clutch... and I am shifting slowly and deliberately. Still, by the end of the race I can't hit the right gate. While I can still work on my heel/toe upshift skills, to my credit, the car won't even shift during the cool down lap. It's fine after it cools down.

I've been told that there is an Al shift fork that expands and binds when it gets hot. Is this the origin of the hot shifting problems? I can shield my exhaust. I can rob the trans cooler off my other car. I suppose first I should install a temp sensor and get some accurate numbers and ask the question if the shifter binding is really because it is getting hot (?).

What oil(s) have you used other than Amsoil?

The Motorcraft stuff worked miracles in my 6-speed, although I was fighting a synchro issue, mostly going from 4->3. I've got my exhaust header wrapped to try and not heat the tranny as fast. Do you have a flat floor or anything else that would interfere with cooling?

Even at stock power, the factory felt it necessary to go to the expense of shielding the exhaust from the trans. If you are making more power than stock then it will be even more important because power is proportionate to heat.

I am having the same issue with a 6 speed trans i just swapped in. i have done some reading and will pick up some Amsoil and see if it will shift smoother. I do have the miata roadster short shifter kit with copper or brass bushing. My shifter feels very loose even while in gear. Speed J does your shifter feel loose while in 5th or 6th gear? or have any play while in gear? i done remember my 5 speed having so much play while in gear. the 6 speed has so much play it actually rattles quit a bit.

To everyone with a 6-speed: my transmission got way WORSE with Amsoil. YMMV

I just put Amsoil in my 6spd after using and being very happy with ford motorcraft. It is still too soon for me to make a judgment on Amsoil.

This may not be helpful, but that doesn't sound right at all.

He might want to check to see that the bolts are tight on the shifter/case cover. They are steel bolts that engage the aluminum in the case and can work loose if you don't torque them down right. It will allow the shifter cover to slide around when you shift.