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Help with front vibration issue 1991

R

RJB44

1/2 ton status
Joined
Dec 3, 2005
Posts
238
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1
Location
Northern Virginia
Hello -

Hopefully you folks can help me with a continuing issue with my truck. I have a 1991 Blazer, which I bought about two years ago. It already had a 4 Inch lift on it with new wheels and tires. Since day one, it has had a vibration at low speed. You can feel it through the entire drive line. I replaced the u-joints on the rear drive shaft, that didn't help. I recently had the rear drive shaft lengthened and balanced. I put the shaft back in and it still vibrates between 15-30 MPH. The truck has automatic front hubs. Someone suggested that I take out the front drive shaft and see if there is any difference. I don't want to keep throwing out $$ in trying to figure this out. I just want a decent ride in the truck.

Thank very much for input.

RJB
Northern VA
 
is the transfer case been lower about 1". if not try that.
 
I'd pull that front drive shaft out since its free to do and could help you eliminate components. That said it could be the auto hubs acting up and maybe your front shaft splines are in rough condition.
 
i was having the same problem with a vibration in the front. turned out it was a wheel bearing. i jacked the truck up and spun the wheel and immediately found the problem. replaced bearing on both side of truck and no more vibration. hope this helps.
 
why all the work on the rear if you have front vibes :dunno:
what are your rig's specs? axles, t-case. got pics of your drivelines?
 
check your ball joints & wheel bearings. if you haven't replaced your axle u-joints in a while, now would be a good time to do that too
 
Ok, removed front driveshaft, no change

That vibration is still there between 15 - 30 mph, most harsh at 25 mph. Although when I slip it into N at those speeds, the vibration seems to go away. So it appears it is just when it is under load. I guess I just have to move to another possible cause and see where it takes me. Ive got a feeling this is going to be a costly or drawn out process. Primarily b/c my schedule is so tight, I don't have the time to do much of the work, and taking it to a shop will be $$, with no guarantees on correcting the problem. At least the CK5 forum will help me along the way.

Thanks again for all your help
RJB
 
I left you a PM, but sounds like your problem is the driveline angles are incorrect.
 
x2 Both angles need to be the same. From your tcase vs. your rearend. Borrow an angle finger from someone and correct with new shims if need be.
 
Pics of my driveline

As requested by the folks responding to my post, I have added pics of my driveline. FYI.. I have removed the front driveshaft in my effort to eliminate causes of the vibration.

Feedback welcomed.
RJB44

Driveline1.JPG

Driveline2.JPG

Driveline3.JPG

Driveline4.JPG

Driveline5.JPG
 
Incorrect driveline angles. The angle at the t-case versus the driveshaft need to be the same as the angle at the axle yoke versus the driveshaft.
 
I hate to say it, but you wasted that money on the d-shaft mods. Tou really need to do a SYE on the back of that rig.:crazy:
 
4X4HIGH said:
Incorrect driveline angles. The angle at the t-case versus the driveshaft need to be the same as the angle at the axle yoke versus the driveshaft.
Click to expand...

I don't know, from the pics it looks like they dropped the tcase and lifted the rear axle pinion up, so the angles seem close enough, the one thing that could be happening is that when he first takes off, the pinion is kicking up further from spring wrap, which is making the angles all screwed up, then when the speed is up, the load lightens and the angles are better.
The only way to cinfirm is an angle finder on the 2 ends, you want the rear axle yoke to be about 2-3 degrees down from the angle at teh other end so when under load it will equal out. it looks like you ar emore equal at rest now.
 
imiceman44 said:
I don't know, from the pics it looks like they dropped the tcase and lifted the rear axle pinion up, so the angles seem close enough.
Click to expand...

I disagree, it looks to me like the pinion is rolled up too high, especially since it should actually have a couple degrees more angle in it than the t-case end. The pinion is going to be nearly stock angle when it's corrected, which will add angularity to both u-joints (also something you don't really want). That's why I recommended the SYE.:dunno:
I do agree that he needs to put the angle finder on it, and figure out the exact measurements.
 
The pictures don't do it justice, someone needs to really place an angle finder on it all and correct it for the angle of the truck on the ground if the ground isn't level.

One other thing, even if the tires are balanced, they could be out of round, it looks like you are running them with alot of pressure in them, as if they are riding on the center of the tread. I've messed up this way too before.
 
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