C6 trans question

[Dooster]

I'm looking to buy an 84 6.9 w/ C6 auto. Guy says all forward gears work fine, but no reverse. Says it acts like its in neutral. If im not mistaken it sounds like a fluid/vacuum issue or the actual linkage is messed up, but its been awhile since ive worked on one of these trucks, just looking for more experienced insight.

any input appreciated.

 

[FarmerFrank]

Sounds more like the linkage. If I'm not mistaken one of the forward gears and reverse share some hard parts in the trans so if all the forwards are fine then internally reverse should be good.

But I'm not expert.

 

[trackspeeder]

Reverse uses direct (third gear) in its function.

Check the fluid level.
Check the linkage.

If the fluid and linkage checks out. You will have tp dig into the tranny to find the problem.
With all forward gears working, it could have a bad reverse clutch.

 

[OLDBULL8]

Read the last paragragh about the backup lamps. That will tell you if the linkage is set correct. With the key ON engine OFF, select Reverse, check backup lamps for ON.