I just put new rear brakes on my 1986 K5 M-1000 and now the drums won't fit back on, the adjuster is in all the way, and it seems the I.D. of the drum is smaller than the O.D. of the shoes, could there be more than one drum size for the military K5? The auto parts people say they only list 1, could the drums be warped that badly?
Thanks for any help,
3M186K5

 

*Moving to Full Size K5 Tech* - 1st gen tech is for the s-series trucks as stated in the section description.

Did you replace the drums with new? If not, have you cleaned up the leading edge of the drum bore with a flap wheel? As the drums wear, a lip will form on the inner edge of the drum. This lip consists of the difference between the worn drum bore and original bore of the drum (since the shoes do not cover all the way out on the drum bore) plus rust buildup that can make it difficult to get back on with new shoes.

Are you having trouble with both sides in the same manner?

 

generally there is one shoe longer than the other
If you put both long shoes on one side you will not get the drum on

As said a rust lip on old drums will not let them go back on

A seized wheel cylinder will not let the shoes completely return

Lastly the contact points on the backing plate can scab and hold up the shoes
You should dab some brake grease on the contact points

GM did some weird stuff depending on 1/2 , 3/4 or 1 ton back in the day
They changed body styling , chassis and FI depending on the tonnage and depending on 2 or 4WD
Back in the day the first question we asked was butterfly windows or not
Wish my memory was better on the old stuff