The trans in my MM started acting up occasionally in 2016. Would shift in to drive and it wouldn't go in to gear - just sat there doing nothing. Would play around with it and would finally engage. It happened more frequently as time went on so I decided to pull trans and rebuild it before getting stranded somewhere.
Yanked it out last spring and of course life, $$$ and weather got in the way of completing the job.
Today I finally finished the job. Took her out on a 20 mile test drive and it ran great. Got in to the boost a little bit toward the end of the trip and chirped 2nd with small fishtail - love it!
When trans disassembled the entire thing looked like the day it was built, clean clear fluid with zero sediment and nothing on the magnets. The only visible issue was the OD band showed sings of getting hot.
Found the problem causing no drive engagement was the case wore where the OD band servo piston shaft goes through it (steel shaft/aluminum case) which was also the reason the band was slightly burnt. This is a known issue with the AOD/4R70W/4R75. When case wears fluid pressure leaks past the piston causing the band to not engage/slip. This issue is repaired with the Sonex ZipKit, the kit addresses all the problematic issues of the trans.
Really looking forward to driving it now, having boost withdrawals all this time sucked!
Trans rebuild kit with Forced Tail Shaft Lube Mod:
Sonex ZipKit - http://www.transmissionbench.com/
Hardened high capacity Forward drum – Summit Racing https://www.sonnax.com/parts/4373-sm...lutch-drum-kit
Hardened Direct drum – Kenny Brown transmissions (thanks Tbone!)
Hardened 300M input shaft – BCA Transmissions https://www.bcawebstore.com/index.ph...ct_detail&p=14
Hardened 300M stub shaft – eBay
Crossmember – Elkhorn Motors Ford (Thanks Nicco!)
Trans mount – Tasca Ford
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Originally Posted by musclemerc
#6486 of 11,052 03 300B In Black 
