so my 79 f150 has the granny 4 speed, 351m, NP205. the transmission is probably gonna need to be rebuild soon because its so noisy. Trying to figure out why it almost slams when i let out of the clutch, as its going into each gear. Its very similar to a very badly worn u-joint, but the u-joints didnt have any play, there was a lot of play when using my hand to rotate the driveshaft with the truck on level ground in neutral, but the play wasnt in the u-joints. Is this normal?

also any ideas why the shifter vibrates and the transmission makes god-awful noise when above 2500 rpm in 2nd and 3rd? when i'm driving in 3rd gear, if i rev it above 2500 rpm or so, it sounds and feels like the transmission is going to fly into 10 million pieces and the shifter vibrates pretty badly, so in 2nd and 3rd i always shift at 2500rpm, which really kills the usefulness of the truck, especially climbing hills.

any advice is appreciated, the truck is a work in progress.

 

have you checked and made sure that there is fluid in your t case and tranny?

 

ehh no i havent

 

i drove the truck today and noticed that the transmission is much much quieter when the truck has been sitting for a couple days, when its cold. As the truck reaches operating temp after a little bit of driving the transmission gradually gets louder and the shifts become more difficult and more harsh. And ideas? Think i need to change the gear oil and transfer case fluid?

 

yeah to me that sounds like you need new fluid. both transmission and transfer case use 140w oil, i just put 85w-140 and it works good.really easy to do, there should be 2 square bolts in the center facing the rear of the vehicle. the higher up one is the check plug, simply stick your finger in there and you should feel fluid, the lower square plug being the drain plug. transmission is the same gig but both plugs are on the passenger side! for both of mine it took around 5 liters, could have maybe used more. oh and id buy extra to flush out the tranny, mine was SUPER frothy and metal filings

 

any ideas how to get the fluid in there without a pump?
i dont have one and dont have much money. this would be my first time changing the oil in a manual transmission, ive always went through cars so fast i never had to change the gear oil

thanks for the good info btw!

 

You just cut the end off a 1l of gear oil and stick it right in

 

oh ok glad to hear theres enough room for the bottle under there! definitely need to do this soon.

 

You should also check the rear end, A worn ring and pinion will also give you the slamming you described.

 

It will also give you a heavy annoying vibration while driving. I should know, i half to feel/hear it every time i drive somewhere. lol.

 

well, did some research online, talked to a couple fellow ford truck friends, and checked with autozone, and the transmission (np435) calls for straight 50W motor oil above 32 degrees, and straight 30w under 32 degrees. The transfer case calls for 80W gear oil. Autozone didnt have straight 50W so i picked up 3 quarts of 40W castrol GTX. after draining/refilling the trans with 40W and the transfer case with valvoline 80w-90, there is no difference, clunk is still present when release clutch after shifting (applying pressure back on driveshaft) its almost like bad u-joints but they seem ok... there is a small amount of rotational play in the slip-yoke section of the driveshaft, don't know if thats a big problem or not. And the trans seems a bit quieter with the new fluid, and the transfer case is much easier to shift now.

Any help is appreciated!

EDIT: also i noticed at random times there is a little bit of clutch drag, because i can feel the gears are still turning when i shift to 1st of reverse, but its random, not constant. The clutch in the truck was replaced, and the flywheel machined. However, the clutch pedal has about 4" of travel where there is nothing happening at all, absolutely no pressure on pedal. The rod that goes through the floor moves, but there is no pressure at all on the pedal. I have a feeling its out of adjustment. any advice appreciated!