I have a 78 k5 blazer which 1st gear seams to be his only option. R N 1 2 3 4 are all 1st gear. The vacum is good any other suggestions?

 

Manual transmission or Automatic? If it's automatic, then someone has swapped in a 700R4 cause it didn't come with a 4spd automatic from the factory. If manual, something has come loose inside the transmission. You'll have to pull the top cover and have a look inside.

 

you can check/change the vacuum actuator at the transmission. if that is broke or clogged. it could cause that

 

If it's an automatic...

From the sounds of it though, it's a manual. Probably the SM465.

 

yeah re reading it im all confused now. a 4 speed in a 78... but he also mentions vacuum

 

Also mentions that it is in 1st even though the shifter is in R, N, 1, 2, 3, 4... Need to get some clarification here.

 

It is an automatic with 1st gear as its only option meaning no matter what gear i put it in it is always in first even in reverse i go forward. Checked the vacuum its good

 

Even reverse goes forward? Does park work? Possible shifter issue?

 

yep even in reverse i go forward.

 

Doesn't sound like the shift linkage is connected... Can you manually shift it at the side of the transmission?