Noise When in Neutral

[threeonthetree]

Start off i have a 350 mated with a sm465 transmission and a np208 transfer.
axles are dana up front and gm corp 12 out back 1/2 ton

i just got the truck back on the road. today was the first real test drive.

everything is great off the line, shifts smooth engages good.

but as soon as i start to decelarate it starts to make a grinding noise, if i put it in neutral it makes it more and if i push the clutch in it doesnt go away.
espcially does it when i put the truck in neutral down hill if i put it back into gear it goes away right away.

what could this noise be?

all fluids are topped off with fresh oil.

[threeonthetree]

I have been doing a little research on drive line noises. One thing I was finding is that the pinion could be something that is causing this. The truck has a 4 inch lift new u joints.

The axles are new and the only thing different to this truck when I had the cover off the rear it looked good it had a little surface rust because the where not used In 10+ years. The gears are 4.11s in guessing someone swapped them. How can I tell that the pinion has the correct backlash?
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[legendman]

http://www.richmondgear.com/07pdfs/RG28.pdf

[75 big 10]

my 1/2 did the same thing. turns out my pinion nut backed off. i couldnt tell till i had the drive line out then i could move the yoke around

[threeonthetree]

Originally Posted by 75 big 10

my 1/2 did the same thing. turns out my pinion nut backed off. i couldnt tell till i had the drive line out then i could move the yoke around

did you just tighten it back up to spec or do you have to replace anything?

i am thinking of tearing the rear end down this weekend and checking all the bearings.

how can i tell if the pinion is out of spec just if the yoke moves a lot?

[75 big 10]

I tightened it back up for a month or so and rebuilt the rear end. The truck isn't my dd though. It maybe. Sees 100 miles a month.
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[86c20]

could it be the piolt bearing? i know mine makes noise just like that.

[threeonthetree]

Originally Posted by 86c20

could it be the piolt bearing? i know mine makes noise just like that.

i dont think it is the piolt bearing it never made this noise in the old truck.

i checked and there is alot of play in the rear yoke a lot more than the front i took some pictures of it one way and then the other and you can tell.

does this mean that there isnt enough shims in there and the pinion is sitting to far forward away from the ring gear?

here is a link to my build it is only one page. so you guys can see what i have done. http://67-72chevytrucks.com/vboard/s...d.php?t=527797


everything worked great in the old truck.

the only thing different is the axle.

[threeonthetree]

The thing is i think the noise is coming from the front end.
I have a big hole in the floor because this is an auto cab.

the tranny doesnt vibrate when the noise happens

it only makes the noise at speeds of 55 to 45 slowing down on off gas.

no noise in the stall

could it be a front end bearing. the transfer is in 2wd and makes the noise in 4

[76stepsidechevy]

Check the spud shaft between the trans and tranfer case, ive seen those as well as trans output/ t case input shaft wear and cause quite a bit of slop. Most of them were only ten spline there so a little wear makes for a lot of movement.

[threeonthetree]

could this be a driveshaft problem

i have excesive stick out?

what is proper stick out of a np208 transfer case.

[threeonthetree]

[threeonthetree]

[threeonthetree]

is the angle to extreme in the second pic.

is the stick out exxssseeive?

[huahuamick]

Ahh! I stand corrected then, Thanks for clearing that up.

[threeonthetree]

Originally Posted by huahuamick

Ahh! I stand corrected then, Thanks for clearing that up.

do you think that this is my problem?

when i push the truck back and forward i can see the driveshaft pushing the transfer case up and down.

anyone if this is i will have it lengthened this week