Sounds like the front pump in the transmission is tired.
It's not shifting into neutral, the 3rd gear "drive" band is slipping. Time for rebuild.
if its the GTA with the 5.7, the 700R4 is, in my opinion, the best transmission out there.mine is amazing, shifts on a dime, has a low first gear, and really runs great with the 5.7
700r4 gear shift lever want lock in place
Are you sure that it's third it's not shifting into, and not fourth? The transmission is designed to not permit shifts into fourth (overdrive) until the engine and transmission have warmed up a bit.
the sunshell gear is stripped out
Th350 is a three speed transmission, where as the 700r4 is a four speed automatic fourth gear being an overdrive.
Have the fluid and filter changed
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you have burnt out the 3rd. gear and overdrive. you will have to have it rebuilt or replaced.
My 95 Corolla also has trouble shifting into third gear when the weather is cold. It may take 2-3 minutes on the highway before it finally shifts into third gear. It has 125k miles on it but has been occurring at least for the last 5k miles.
in an automatic transmission when it shifts the belts that hold the planetary gears that control the gear ratios grab the next gear before it releases the previous gear. while the transmission is in two gears at once the engine doesn't provide the power to the transmission so with the lack of tension on the motor it allows it to build up speed before it slows back down when the transmission releases the lower gear What about a manual transmission? Is it normal for it to still do this same thing?