Weird grinding noise when decelerating

[PsychoticDeadGuy]

Ok, i asked this question a while ago and everyone told me to change the u-joints...so i changed the the whole rear driveshaft and new u-joints. the noise is still there...the tranny has enough fluid and so does the trans case. i am thinking it could be the chain in the np208...it only does it when i let off the gas...it could be a long grind or it could be on and off...help please.

 

[coptezr]

mine did that too and i shaved my gears.

 

[outlawtorn]

my 203 did that... I was told it was slack in my chain.

 

[chevyin]

grinding

Mine did that allso, and it turned out to be the pinnon gear had come forward and was hitting the spider houseing when you took foot off gas. It was 12 bolt GM.

 

[MTMike]

Mine did that with 12" of suspension lift. Put stock 56's & a shackle flip back there and it quit. In my case, it was improper driveline angles.

 

[PsychoticDeadGuy]

ok, my rear end is good. how much if any should i be able to turn my driveshaft while my tranny is in park...(tires off the ground)?

 

[Leper]

Try putting the truck in neutral before you slow down and see if it gets better or worse or stays the same.
Doing that can point you in the right direction

 

[81jimmyslt]

Mine is doing the same thing (NP 208) My shaft is too long, and on deceleration and braking hard I get grinding. I'm pretty sure it's coming from the tcase. I'm going to push the axle back for now and check the housing.

Someone mentioned slippng chain?

 

[PsychoticDeadGuy]

well, the easiest fix so far seems to drop the t-case down a little bit. i ran it with a 4" lift and i lowered the t-case down about 1/2" and there were no problems. well now i have instead of blocks, i have ORD zero rates, and shackle flip and a 14bff which raised my truck up about 2 more inches from where it was...i am hoping it is the driveshaft angle...i am going to make a new spacer for the tranny mount to bring it down about 1/4-1/2" more...i hope it will work...i wont be able to do this until monday so i will post up my story when im done.

 

[81jimmyslt]

anyone else have any ideas?

 

[PsychoticDeadGuy]

i will make the spacers tonight and will either put them on later tonight or tomorrow and i will let you know how it works

 

[PsychoticDeadGuy]

well, i put some spacers to lower the crossmember of my tranny which in turn lowered my t-case and made the angle for my driveshaft alot better. the spacer was only 3/8" thick but there are no more vibrations or grinding sounds...i feel much better now about it. hope this helps out someone else...

 

[MTMike]

well, i put some spacers to lower the crossmember of my tranny which in turn lowered my t-case and made the angle for my driveshaft alot better. the spacer was only 3/8" thick but there are no more vibrations or grinding sounds...i feel much better now about it. hope this helps out someone else...

Glad to hear!

 

[81jimmyslt]

I moved my axle back 1.5" but I still have grinding on deceleration. When I brake hard it's awful, grinds so much.

Any more ideas?

I'm going to lower my t-case again but only use the spacers on the t-case.

 

[PsychoticDeadGuy]

its from the rear end coming up a little and screwing up your drivline angle at the t-case...lower it about 1/4-1/2" and it should go away.

 

[Blue85]

It could be just from mismatched driveline angles, but it could also be that you have a U-joint maxed out for angle. When you decelerate, the back of the truck comes up and this increases the U-joint angles. You would be able to see shiny spots in the yoke ears.

I was also going to suggest a loose pinion nut, but if lowering the T-case helped, that probably wasn't the problem.

 

[down4thakrown]

i got the same thing wrong with my 205.i was thinkin maybe it was just a little slop in the gears and them just catchin up with each other. other ck5 members said the same.