No 3rd gear
 

When I drove my 83 300SD today it was missing third. It shifts fine from
1st to 2nd, but 2nd to 3rd is like it is out of gear. It revs freely. I know the
trans is going to need major repair but does anyone know what failed. It
worked fine till today and 1st, 2nd and reverse are perfect. Just NO 3rd ,I am
not sure if 4th works, because I never pushed to find out. I also changed the fluid and filter today, did not help. Thanks Jay

Does the SD have a bowden cable? If so try adjusting it. It could also be your transmission modulator. It can be adjusted as well.

Is that the original untouched tranny at 321k?? :eek: If so, I'd say it did its job and deserves replacement or rebuild. Sounds like you lost a clutch pack inside the tranny possibly...about time at that mileage. Fluid changed recently? Could always try a few cheap things first to make sure....I am betting it has died and needs work though.

Yes it is the original untouched tranny. I know she did her job. But it did not give any signs. My last two tranny failures started slipping and acting up. This one worked perfect last night, then gone today. I will be in New York in the next few weeks and will be driving back to Newfoundland Canada. I need to find a used trans somewhere in between. Know of any..... Thanks. Jay

Wow..that's a lot of miles on the first tranny. Well done. Agree with pawoSD. Could be clutch pack or B1 piston (less likely), but in either case transmission will have to be removed.

Try disconnecting the kickdown button underneath the gas pedal. Could be it in these 'overnight' cases.

Bowden cable and vacuum regulator will not keep it from getting into 3rd indefinitely. If it NEVER gets there at any rpm, it's highly unlikely that it's one of these 2 components.

I assume you've redlined it in 2nd? did you check the fluid? If it's going towards a gray/black, that's grit from your dead clutches.

mine did similar going into 4th, it was my b2 piston. apparently, the o-rings wear grooves into the sleeve, and require replacement of both the rings and the sleeve. the tranny was shifting fine up to 4th, then it just spun until I manually shifted it from 3 to 4th... fresh rebuild and I am good to go!
John