TBH 350 no third gear

[wazzadakka94]

I have a 1975 Chevy K20 camper special.
It has a 400 sbc, tbh 350, and I belive a NP 205 transfer case.
It runs and drives quite good except that I don't have third gear in the transmission for some reason.


Everything that I have either checked or done:
The fluid looks good, I plan on dropping the pan and changing the fluid and filter here quite soon.
I have adjusted the shift linkage by putting it into neutral on the transmission and the steering column and that kinda worked for a bit.
I have replaced all of the vacuum lines to try and rule that issue out.
Modulator doesn't have ATF coming out of it.
Detent cable has been adjusted correctly.

I have power to the wheels in all gears (even when the trans decides to allow into 3rd).

How do I resolve this issue?

 

[jjester6000]

I have a 1975 Chevy K20 camper special.
It has a 400 sbc, tbh 350, and I belive a NP 205 transfer case.
It runs and drives quite good except that I don't have third gear in the transmission for some reason.


Everything that I have either checked or done:
The fluid looks good, I plan on dropping the pan and changing the fluid and filter here quite soon.
I have adjusted the shift linkage by putting it into neutral on the transmission and the steering column and that kinda worked for a bit.
I have replaced all of the vacuum lines to try and rule that issue out.
Modulator doesn't have ATF coming out of it.
Detent cable has been adjusted correctly.

I have power to the wheels in all gears (even when the trans decides to allow into 3rd).

How do I resolve this issue?

Are you sure that you don't have 3rd gear? That 2-3 shift on those transmission is usually super smooth, so try downshifting it into 2nd from D.

I know that there is probably an issue though, so try unhooking the detent cable and see how it goes since it could be sticking open and causing it to not want to upshift (it shouldn't hurt anything since its not a th700r4). If it is sticky, then the 1-2 shift will be real hard.

Also make sure that your vacuum actuator isn't leaky, or that you don't have a vacuum leak, since that will stop it from shifting as well.

If 3rd gear is actually smoked, it will at least try to shift, but it'll slip real bad.