4wd Noise HELP!!! (1 Viewer)

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88chevota

88chevota

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Jun 5, 2006
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Colorado Springs, CO
I posted this here because I figured you guys might now more about these parts than the regular 60's thread.

I have a SM456 tranny to NP205 t-case. when I am in 2wheel drive everything is perfect. When I go into 4 high and hit 3rd gear it starts to make this weird rattling noise, almost like it is trying to pop out of four high, but it stays in fine. I am not sure if it is the t-case or not. Here is were it starts to ge weird. I take out the d-shaft and no noise smooth as ever. put back in the d-shaft, lock the hubs and leave it in 2wheel no noise. only makes noise when 4wheel is engaged with d-shaft in. (does not matter if front hubs are locked or unlocked still makes noise) What the heck. Anyone have any ideas? d-shaft appears to be in good condition. I even regreased it.
 
U-joints in good shape, any play in the pinion or output shaft on the transfer case?
 
Those were all my thoughts too. I'll check the pinion again but everything seems to be fine
 
Everything was working fine two weeks ago, then last night it starting making the noises.
 
do you have a long-slip type of drive line? How are the splines? Pull it and play with it... sometimes under pressure they seem fine... I did the same with my rear driveshaft and it seemed fine until I figured out a blew up my rear end.
 
I was wondering the same thing. I wonder if my front diff is toast. how much play should i have when the hubs are locked and I turn the flange at the diff?
 
88chevota said:
I was wondering the same thing. I wonder if my front diff is toast. how much play should i have when the hubs are locked and I turn the flange at the diff?
Click to expand...

It would be hard to tell how much play you should have with out the diff pulled. Butt if I had to guess I would say 1/4" to 1/2" of play. Make Sher the front pinion flange it tight, And the yolk on the t/c is tight and in good shape.
 
thanks for all the feedback guys. I have checked just about all those things still can't figure it out. So, I went for another drive and noticed that it only does it when I let off the gas. If I am on the gas it sounds fine. I think I might have a little to much play in the front diff. turning it at the pinion I think I have more than 1/2 inch. I'll investigate after it stops snowing and report back sometime this week.
 
grab the front of the drive shaft and see if you can move it up and down, sied to side. the pinion nut ight have backed out some causing your gear pattern to be way too lose and the bearings not having the proper preload.

does the front driveshaft have a cardan joint? they make lots of noise at speed if they have any wear or if they're not properly lubed.
 
drive shaft is nice and tight. no cardan joint. just regular. angles are off a little, but it has been fine for over a month then one day it started making noise. Still have not figured anything out. This is driving me crazy. arg!!!!!!
 
it sounds to me like its the u joints. i have heard similiar noises from time to time before and it was always when i was puttin the driveline in a bind... maybe when you put it in third there is too much resistance and its making the front drive shaft move around. it could be hitting the safety housing thing around it.
 
I still can't figure this out! :bang:

I think i have narrowed it down though. I changed out a portion of the d-shaft and it still does it. It does not do it in 4-low though.

I am going to order a bearing and seal kit for the t-case so that should do it. It sure sounds like it is in there the more I listen to it. I think it could be the needle bearings inside causing it to be slopping around.

I'll report back when I get it done.
 
ok so I was going to order the t-case rebuild kit and I was telling the guy my problem and he said I should look at the front diff and the shift fork slider.

I hate the front diff!!! I wish it has an inspection cover! anyone converted one to an inspection cover?
 
Tony, Trail gear has a Weld on Cap that would be cool to inspect the diff..

Trail-Gear Inc > Axle Housing

have you talked to Andy from CLC?? He runs a Manual Transmission Shop and rebuilds t-cases..
 
Finally!!!!! Thanks to some good buddies who helped me take a good look at everything it is finally fixed. It was a combo of things all in the front driveshaft! Angles were bad, shaft was way out of balance, and the splines were sloppy. I bought me a double cardan from a 85 mini and had it mated to a good cruiser shaft with good splines, got it balanced. I put it in today and drove it. I love it when the only thing I hear is the rumble of the V8. Problem solved. Good luck to all the other guys who are experiencing the same issue.

i thought I had checked everything, I turned, pulled, pushed, tugged to see if anything was loose except at the splined part of the driveshaft. I know some of you told me to check that. Thought I did but it Took someone else to look at it. He just grabbed the splined area and pushed up and down and the thing slopped all around. Thanks guys!
 
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