MTFCA Forum

My 26 TT has a Chicago trans and Ac brakes. If while slowing down I apply steady pressure on the brake pedal for 10-15 seconds the trans will pop into neutral. Scarey when approaching an intersection. The Ac brakes don't seem to help slow me down. Maybe they aren't adjusted properly. What is the problem?

It cold be a linkage wear or linkage adjustment issue, among others.
It's not a good idea to apply steady pressure to the Model T transmission brake for more than a few seconds at a time without briefly releasing the pedal and then re-applying pressure. Regardless of that, the axle gears should not jump out of mesh at any time.

I have restored several different aux T transmissions. Not yours specifically. I prefer Jumbo Giants.
They all are very similar in design.
Shift forks attached to rods. The rods have detents for large ball bearings pushed by springs to retain their position. (stay in gear selected)
In order of failure - Springs get weak or rusty not applying enough pressure to the ball bearing. They can stick from rust in the disengage/compressed position. The shafts can have enough wear in the detents to allow a less than secure lock. The shift forks can be severely worn. That wear added to by slop in the system. The teeth in the gear can be worn down to engage less than designed, that engagement exacerbated by other slop & years of pooping out of gear.

Bonus hint: Extra wiggle in the shift lever is from wear in the shift forks engagement slot. The shifter end was a machined ball end narrowed flat on the sides. It should fit without extra slop into those shift forks slots.

The problem is in the Chicago transmission, and it's a serious one. It needs to be disassembled and thoroughly inspected.

John has some excellent observations and suggestions in his comments above... except maybe for this one...

...other slop & years of pooping out of gear.

Too many Chicago-style hot dogs?

Rod, on the brake adjustment, you should have the AC brakes adjusted to where they engage first & followed by the stock T brake in the transmission to engage. At least that’s the way I did it on advice from my mentor years ago. Best John