Lifted 4" noise when decelerating from 50

[threeonthetree]

Just got the truck back on the road. I have a 1979 blazer frame with a cab and clip on it. Sm465 trans and a np208 transfer. I had the rear drive shaft shortened from my short box. New u joints. All fluids topped off.

My problem is when I am starting out it sounds great up to speed it sounds food as long as I'm on the gas.
If I put it in neutral going 45 it makes a bad grinding noise put the clutch in it still makes it and if I rev up the engine it doesn't change as I slow down it seems to go away. Or if I put it back in gear.

I can't tell were it's coming from. I think my driveshaft is a little short could that be the it?

Please let me know your idea on it.

To short?

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[liftlawssuck]

The shaft seems too short for my liking. I would like to see that slip yoke in a little further. Would help the angle a tad as well. As far as the noise. Don't have anything that jumps out at me but maybe jack up the truck and drive it. Crawl under it and look around. See if you duplicate it while under it. Just make sure it's safe on solid ground. Wouldn't literally crawl under it more like look under it from the side. Have done many times to find weird noises.

[andrewmp6]

Yeah the driveshaft looks way short to me too.

[threeonthetree]

Well I dropped the driveshaft off today to get 2.5 " added.

Do you guys think that this could have caused the noise any ideas on the noise?
Things I should check out never heard it before I did the lift.
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[threeonthetree]

Also with the driveshaft out I can not reproduce the sound by putting it in gear.
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[andrewmp6]

Hopefully the new driveshaft fixes the problem.

[jjzepplin]

I would drop that t-case a couple inches and install a cv joint(like the one that is usually in the front shaft) in that axle at the front. Also check for play in your case. I think the 208 has a chain and they can break...or show lots of slack like a timing chain..

[threeonthetree]

i could drop the t case but i read that it will affect the front drive shaft and the cv will hit.

the rear drive shaft is in the shop getting 2.5 added. i will see if this corrects the angle, slip yoke.

to check the transfer put in 4 and turn the rear drive shaft till the front starts turning. then turn back till the front drive shaft moves that is the amount of slop im guessing?

[jjzepplin]

The front will hit what? Your dropping the whole thing.. Yes if you rock the driveshaft back and forth and it moves quite a bit without the front shaft moving=bad.

[special-K]

No need to drop the transfer case with 4" lift. I have had a quite a few I never did that with and had no problems.I am currently driving an '85 Jimmy with 4" lift. It's funny,I put a 14-bolt in when I lifted and that makes the original driveshaft be the right length.

[threeonthetree]

Well i got the drive shaft back today looks good. it better for 225 bucks.

i got it in and went for a drive the noise is still there.

the noise only happens when i am going about 45 and drop it into neutral.
it is a grinding noise and is really pissing me off. in 4 hi and 4 low and 2wd. havent tryed neutral.

there is almost no play in my transfer and it is topped of with freash fluid as is the axles and trans.

any ideas on the noise??????

this weekend im am going to try to get it on some jack stands and trouble shoot it that way.