The 904 won't upshift to 3rd gear.

[Kern Dog]

Hey everyone. THIS 67 Dart....

...Has always been rough around the edges but still ran great. Lately, it won't upshift to 3rd gear. Aside from low fluid level, what else could cause this? The fluid smelled fine and the level was normal. It has a 360 4 barrel, an 8 3/4" axle too.
The KD linkage is set right. It has 4.10 gears so running around in 2nd gear isn't much fun. I've thought of swapping in an A 500 to get the lower 1st gear and the Overdrive. It would be easier to just fix the 904 though.

 

[Syleng1]

If the KD is correctly set to the carb position and the fluid is clean and correct then the options are: leaking seals, slipping clutch pack, loose nut behind the wheel. (Sorry had to throw that one in there lol!) or is the shift lever adjusted properly or does it have a lot of slop and finally just not putting in the proper rooster comb. I’d pull the pan and look for debris, and verify linkage before you pull it. I also recommend using a pressure gauge and check for pressures to verify operation.
Just my humble opinion-
Syleng1

 

[Ricks70Duster340]

Hey everyone. THIS 67 Dart....

View attachment 1716144677

...Has always been rough around the edges but still ran great. Lately, it won't upshift to 3rd gear. Aside from low fluid level, what else could cause this? The fluid smelled fine and the level was normal. It has a 360 4 barrel, an 8 3/4" axle too.
The KD linkage is set right. It has 4.10 gears so running around in 2nd gear isn't much fun. I've thought of swapping in an A 500 to get the lower 1st gear and the Overdrive. It would be easier to just fix the 904 though.

If the fluid is not burned then it could be the drum seals have gone. If there are a lot of miles (or years) on the trans, I'd pull it and throw a new set of seals & clutches into it. Tearing it down would give you an opportunity to look everything over.