Hi everyone,

I own a 1971 Lincoln Mark 3, got its transmission rebuilt 2 months ago because of bad seals, so I decided "well, might as well have a full proper rebuilding while I'm here"
Replaced all the seals, o-rings, clutch plates and steel disks, bands and so on (I gave the transmission to a trusted mechanic to do the job)

Once the trans was back on, it worked fine as it should have, but it had some funky shifts while going from 2nd to 3rd, by that I mean that while the transmission was ice cold, it worked perfectly, 1-2 and 2-3 shifts were smoother than modern days transmissions, then by the time the tranny warmed up a bit, it did not want to engage 3rd gear, it did only if I let go completely of the gas, the moment I put the slightest pressure on the gas pedal, it downshifted to 2nd gear, then once the tranny is nice and warmed up to temperature, it does engage 3rd gear but with a pretty long upshift, kind of consistently

Up until today I didn't really pay much attention to it, but today I did a slight pull, going WOT from 10mph to 70-80mph (all at operating temperatures) and when I let go the gas it seemed as if the car braked, not just engine brake
Stopped the car, put it in neutral, put it in drive and it all worked fine after this
Worried for this, I got home and checked the trans fluid level (put the car in neutral after going through the gears) and it had a burnt smell coming from the dipstick tube and has some bubbles on the dipstick itself... and noticed that the fluid level was 1.5/2 inches above the max on the dipstick

Could the problematic 3rd gear engagement and bubbles/burnt smell from the fluid have been caused by the overfill?
Thanks in advance, everything helps!

Also, forgot to add, when I got home after the "slight" pull and "scary part", when I put into reverse it did a double "clunk" like if it engaged twice, a first clunk and then a second one half a second later, still engaging fine with no slipping

 

There is the question of did your mechanic check every valve in the valve body for foreign matter and assure they were clean, most guys don't do this.
If it wasn't done, it could move and create a different problem or maybe none. No fun guessing.

 

I'm sure he did, I went to the mechanic shop while the tranny was disassembled and he was working on the valve body, disassembling and cleaning valves and springs, so they should be clean

 

When a trans is overfilled,it has a tendency to create air bubbles in the fluid ,which can cause erratic application which can contribute to a slipping condition that generates heat , a transmission's worst enemy.
You might try changing the fluid and filter , but adding the correct amount of fluid and see if that gets rid of the problem.