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Rumbles when I let off gas

ccso503

ccso503

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Joined
Dec 30, 2007
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Location
Henrietta, Texas
Im experiencing a problem with vibrations when I let off the gas. I have a stock everything 1987 K5. It runs pretty fair with little problems.

I hear and feel the vibrations around 45 mph +. It sounds as if it is coming from the rear or center of the Blazer. I havent pinpointed it yet. It sounds like something is dry maybe. It only does this when letting off the gas. I can get back on it and the sound and vibrations are gone.

Im clueless. Help me.
 
Definitely sounds like a u-joint. I suggest replacing them immediately before you're stranded with a broken u-joint on the side of the road after throwing your driveshaft while doing 70 mph. Ask me how I know ;)

Anyway, if you just bought the Blazer, that's one of the first preventative things that should be done. It's hard telling how well the P/O maintained them.
 
Pull your driveline and take it down to a good driveline shop and have it rebuilt and balanced. Cost less than $100 = Smooth sailing.
 
I'll go and get new u-joint today. I thought it mught be, but w/ lack of exp I thought I would ask. I'll let you know if that fixed it. Thanks.
 
Do you mean that it is showroom stock? I agree with the others about the ujoints. If the truck is lifted, an unmatched driveshaft angle will do the same thing.
 
Which U-joints do you guys recommend... a sealed ujoint or one with a grease fitting? I've heard sealed are stronger, but they are sealed.

Lastly, any recommendations for a drive shaft shop in Southern California?

Thanks!
Hijack over.
 
Blue85 said:
The truck in your avatar is stock?
Click to expand...

everything is stock except for crate GM Goodwrench 350 with no mods, put in by the PO. TH350/208 with who knows what has been done to them (nothing as far as I can tell). ~4.5" llift, 35x12.50x15 AND THE STOCK 2.73 GEARS!!!:doah:
 
Yep showroom stock except for thr lift that the previous owner put on. I switch the 39.5 to 35 for now untill I get the feel of what I need to change out in order to run things right.
 
I would take a close look at your rear driveshaft angles. There was a time when I thought mt Tcase was gonna explode, it was so noisy. I replaced it with a spare one to no avail. I changed the driveshaft angle and the noise went away.

Put the ujoints in first. You need them. See if the problem goes away, and for how long. If it comes back in a few days/weeks, your driveshaft angle is probably chewing up the joints. If it goes away for months+, you fixed your problem.
 
So what would the fix be for the angles? I dont thin kits ebough, but the T-case looks like it has been turned down and 1 " spacers on the bracket.
 
kablooie said:
Which U-joints do you guys recommend... a sealed ujoint or one with a grease fitting? I've heard sealed are stronger, but they are sealed.

Lastly, any recommendations for a drive shaft shop in Southern California?

Thanks!
Hijack over.
Click to expand...

These are the guys I use when I buggered my joints and was too pissed and lazy to fix my own fockup. Very happy with the service. Might be something closer to your house in L.A. though.
Hoby
http://www.drivelinesinc.com/index.htm
 
Leper said:
Do you mean that it is showroom stock? I agree with the others about the ujoints. If the truck is lifted, an unmatched driveshaft angle will do the same thing.
Click to expand...
Will a 4" lift put them off? Im fixing to lift mine , but if it puts them off Ill have to save up to fix that :(
 
I've got a mess of problems now. I just replaced my u-joints after throwing the shaft, and now about a week later, I'm getting the same nasty vibes. I guess that means I gotta go spend my whole tax return on getting this issue fixed. My question is, what can they do about it when I have a 208 with a slip yoke? Is there any way they can use a CV joint on it still? Or will I most definitely have to swap a 205 or something in it? Sorry for the hi-jack, but I figured while we were on topic I would ask up.
 
nad said:
I've got a mess of problems now. I just replaced my u-joints after throwing the shaft, and now about a week later, I'm getting the same nasty vibes. I guess that means I gotta go spend my whole tax return on getting this issue fixed. My question is, what can they do about it when I have a 208 with a slip yoke? Is there any way they can use a CV joint on it still? Or will I most definitely have to swap a 205 or something in it? Sorry for the hi-jack, but I figured while we were on topic I would ask up.
Click to expand...

double check to make sure your straps are tight, first. You may have bent the driveshaft, that will cause the same thing. If the shaft looks ok, and the straps are tight, remove the ujoints and pop the caps off and see what the internals look like.


Dafey..... Usually a 4" lift will not cause this problem. Usually.
 
when i first did the lift on my blazer it was doing the same exact thing, I would let off the gas and get that vibration. I put a set of 4 degree shims on the rear axle and solved my problems.
 
What will the internals look like if it's actually chewing them up? I do have another Blazer shaft, but its got different weights on it so it's not balanced for my particular truck. I guess I could give it a shot. Also, is there any way to just use a CV shaft from a Blazer with a 205? Just hammer the ujoints into my slip yoke?
 
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