Hello fellow Blazer owners I need help with a 1979 K5 fulltime 4wd 5.7 350 auto transmission says on servic parts Ident card option either MX1 or Na5 (i figure big tranny issue) Well it drove fine all day then on way home went to get on interstate got it up and going then all of sudden heard engine roar like it was in neutral. Let foot off gas then applied gas again and it drove for few miles then again same thing big rev like in neutral. pulled over shifted through tcase same thing every setting shifted through gears in tranny you could hear it shift start driving good at first then again vroom nothing limped it home very slowly at times other times fine. By the time I got to the house very loud metal banging sound coming from the tranny. I figured when I stoped it would too but when got into drive way put in park and still bang bang bang loud metal tapping. In park and at idle crawled under truck its def something in tranny very loud under tranny pan.

Any Ideas on what it may be is it possibly not the tranny? If so as I am knew to the chevy brand what type of transmission would this unit have I have searched boards and I come up with three possible options it could have. How do I know which it is? And would it be easier to have rebuilt buy used or is it easy enough to pull and rebuild myself with a chilton repair manual? Abyone know costs? PLEASE Help need to get it back on road

 

Unless the trans has been replaced, it will be a turbo 350. And it sounds like a T350 with major internal damage.

My suggestion is to sign up here and follow this. He's a helluva trans builder.

Turbo 350 Build - GM Square Body - 1973 - 1987 GM Truck Forum

 

thanks I will join it not sure if this was a sign of this comming on but the speedometer was way off at 75 clocked behind wife it would show I was doing over pegged 100