Recalcitrant Plug

[armscor 1]

My trusty Ford Lynx 4F27E Auto Trans is playing up, hesitant to go into Drive when cold, so first step diagnosing fault is to do a Line Pressure check.
I tried removing the 1/8" NPT plug, awkward position so I could fit pressure gauge but could not remove.
The plug is a square drive, 7mm across flats and corners rounded off, none of my 12 point sockets fitted and impossible to get a adjustable wrench on it.
So started making the tool, many hours in front of me to mill the hex and make a 7mm square hole on my slotter.
Machining on the lathe and the penny dropped, use a tee handled tap wrench and removed with ease, happy chappy.
Did the line pressure and all within specs, next step remove valve body and do air pressure test on clutch packs and band servo.
Was really nervous when checking line pressure at WOT in D and R with my Wife in the car with both feet on the brake.
Installed new 1/8NPT with an allen head drive so can be easily removed next time
Car manufacturers go out of their way to make it difficult for you unless you have the special tools.

[GlennW]

Thar's a standard 9/32" square socket for 1/8 pipe plugs.

[armscor 1]

Hi Glenn,
Working 40 years in the oil industry have never seen a 9/32" square socket for removing the plugs, we must have used pipe wrenches or crescents, unfortunately could not do this with restricted access.
Checked online and Amazon has them for less than 5 dollars!!!
Learn something everyday.
Now hopefully someone on the forum can help me solve my trans problem.

[John Evans]

When is the last time you did a fluid change? And filter?

[armscor 1]

Abought 15000 miles ago.New filter, trans oil and new pan gasket.

[spro]

Did you inspect the oil for gnashing of teeth? It may be seals and such. There is an additive Tran X or something which does work .