Tranny

[Riley012]

I have a 1982 with a 6.2 diesel. My problem is the tranny doesn’t seem to be shifting into 3rd gear. Any help would be greatly appreciated!

[DmaxMaverick]

How's the fluid level and condition. Low and/or due for service. Dark, stinky fluid?

Which tranny?

If it's a TH400 (HD 3/4 ton or 1 ton), it could be vacuum related. TPV (vacuum valve on the IP), modulator (on the tranny), vacuum pump fail, vacuum plumbing fail. If not, probably due for overhaul.

If it's a TH700R4 (1/2 ton or LD 3/4 ton), the list of possibilities is long, but almost always leads to overhaul.