06-30-2015, 03:53 PM
Join Date: Jun 2015
Total Cats: 0
90 Miata Transmission Upgrade(s)/Rebuild
Hey everyone, picked up a $40 5 Speed with the shift **** sawed off at the turret ball. I've rebuilt transmissions from a variety of makes and models.
I must say the internals are some of the most frustrating with the many C-Clips and Roll pins. Not to mention the large nuts and long shafts..
Anyhow the transmission in the car is doing all right. Got some noise on overrun, that quieted up after the change to Torco MTF. It has not gotten worse, but will need replaced in the future.
I have reviewed the parts diagrams on Jim Ellis Honda, and have saved copies of the gear shafts and forks for the years 91, 93, 94, 97, 99; and for the most part they look the same, apart from the turret changing. Also, I have reviewed the parts list at AdvancedAutosport from Dave as well as a few other threads and sites.
I have also come across the TSB regarding fixing the 2nd Gear, sleeve, hub, and synchro on these older units, as well as an updated unit in the 94+. These hub/sleeve/synchro are different part numbers despite everything else connected to it having the same part number, including the shafts and shift forks. Why is the TSB for the 90-93 call for a different assembly than 94+? Can I use the 94+ in the 90? Differences? This is what makes me confused.
Along with this there also is a TSB for the shift change lever, A>B>C without a clear explanation for what changed. This adds to list of potential parts to pick up from Mazda, unfortunately not from MazdaSpeed, maybe I will have to go to a few AutoX to sign up, if the transmission lasts.
It seems that in addition to the standard Bearing, Synchro, and Seals, I plan to upgrade this as far as possible while it is open. I have heard talk of shift forks being updated by Mazda, several time, but lack the recent part number, or adequate description. Is it on the interlock side or the hub side?
In addition, I plan to replace the reverse sensor, the 5-R rod, all the C-clips, roll pins, springs, copper washers, nuts, other damaged parts during rebuild.
I was hoping the collective minds on here could help me devise a list of current parts that can be used to upgrade even the oldest transmissions to the best condition.