I have a 77 ford f150 four wheel drive with a 351M, my transmission is np435 with a mated 205 transfer case. Here's my problem when im driving around 65 or 70 and let off the pedal i hear a kind of a grinding sound coming from my trans, at first i thought is was the driveshaft but it wasnt cause i had it rebalanced and the guy said it shouldnt be vibrating and i notice that 3rd gear slides in smoothly but sometimes pop's out of gear. Is it a possiblity that my forks might be causing the grinding sound when i let off the pedal? I appreciate any help you guys offer

thanks

 

Had my 435 rebuilt twice thinking they did a poor job. The noise and vibration would not go away. A diffrent mechanic jumped in put the transfer case in neutral started it shifted through all the gears. Turned to me and said tranny runs smother as can be pull your rear end. Sure enough it was the rear ring and pinion. My biggeest costlyest embarrising mistake I've made.

 

Yeah, i had to swap out my 9in this summer cause the ring and pinion gear bearing's were shot...so it does have a good 3:50 9in in it now...with my trans 3rd gear always pop out when it should just click rite in.

 

Popping out of gear is shift fork wear, or shaft wear in the trans. You should be able to pull the floor panel up and take the top of the trans off in the vehicle, if you're model is made that way.

Who did the rear axle? I had some 4x4 outfit--"The 9 inch experts", put 5 (five) 9"s in my van before they found one their "expert" put together that didn't howl.

 

Well i found my problem...one of the forks was missing that plastic groove that slides onto the gear, the other side had one but the other didnt. So had a donor trans, so i just swapped the top part of trans and swap'd it with mine and i made sure the trans was in Neutral.