When shifting into reverse at higher idle can feel and hear loud 'CLANK' drive makes

[BobEhud]

And wouldn't you know this would start when im out with a bad neck injury and cant take it to my job ( i run shops) it only happens in reverse and im fighting all my instinct to look under it while the wife puts it in R but a cervical collar will sometimes teach you a little common sense.

Oh one tidbit this is a 91' with one ton running gear both axles were not to long before i picked it up from PO.Its 454-carbed Barry Grant 750 vac with electric choke that works properly (which mean one pump turn the key fires right up fast idle speed 1400 rpm,idle speed 775-800,when warm) when truck has warmed can barely feel or hear a thing.400 turbo,205,custom drive-shafts...Ceramic headers,flowmaster 40 series true duals,Edelbrock intake...and one thing having owned a few of these not a single drip from anything...lol.parked it on a cut up frig box the night i drove it home to see what leaks needed fixin...i was very pleasantly surprised...

Im thinking trans mount..????

[Crawdaddy]

I'm thinking either slack in the ring and pinion, or low transmission fluid. Low transmission fluid could cause the transmission not to build pressure when you first shift it into gear, and it then quickly builds the pressure, thorwing it into gear and jerking backwards. Reverse is a pretty low gearing so it would have plenty of torque to do it.

[BobEhud]

hope like all hell your wrong on the pinon and ring gear...he just spent almost 3 grand having both done..it feels more toward the middle of the truck..i never thought about trans fluid and reverse is geared so much lower than drive the TC wouldn't engage as hard...okay will have someone check my fluid level...damn i hate that...lol...