If you have a failure in reverse gearing in your turbo 400 or 4L80E GM Transmission check the rod length for the reverse servo it could just be a little short and not pressing the band for reverse enough to engage it. Take your time and you can repair this. Drop the fluid, pan and filter. Take off the wiring harness and drop the valve body trust me it will be easier and have the gaskets on hand mine tore they are like 5 bucks. Don't drop the balls and remember there location. Drop the reverse servo and take it apart remember how it comes apart. put the rod back in with the spacer and stick it back in the trans flush mounted. Push up and measure from the back side of the trans and see how far it goes up in the hole. Mine was about 300 thousand in the hole. Add the tip to the rod and remeasure. Mine was at .080 but you may need to grind some off if it is too long. I was told .070-.080 but you need to look up all specs for your transmission. Hope this helps.
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