89 k1500 new 700r4 reverse acts like it slips a tooth...a little help? lol

[dogdemon420]

truck is older than me but ive had it for 7 years this is the 3rd tranny ive put in it. never had any problems out of the tcase. have put it through some hell but it was completely fine when the tranny went out. the rear slip yolk is always been pretty rough to put in but it never had any issues. it shifts through all the gears. the only problem is with the rear driveshaft in it will make a quick grind once given gas in reverse. if you just let it roll itself without applying any gas its just fine. i had one of my friends to hold the brake and give it some gas in reverse and it seems the yolk is skipping a tooth. i checked the yolk and the output shaft and they both look perfect. im at a loss guys help me out i need some outside expertise before i rip my hair out lol

350sbc 700r4 trans np241c tcase

 

[zora]

Did you try applying a chalk mark to the two components to confirm it is skipping a tooth?

 

[dogdemon420]

noi didnt but it may not be skipping a tooth. it only does this in reverse. put in reverse and let it load the gear. then give it gas to back up and it shudders and smooths out. if you do this and hot brake it you can see the knuckle of the slip yolk spin a good 3/8 of a turn but to make it happen again you have put it in drive and then repeat the process . and going down the road in 4th you can let off the gas and touch it again and it will shudder and smooth out and be fine. but the 4th gear is a constant its like its got something holding it back