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Newb Drivetrain Vibration Questions

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loudnslow

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Raleigh NC
Just picked up an 87 Blazer
350/700r4/np208 (looks like the tc was lowered with the stock 1" spacers)
It has a 4" suspension lift and 3" body lift

It has some pretty heavy vibrations on deceleration above 45mph.
I've done some reading/searching and my conclusion is that I need to lengthen my drive shaft around 3". The pinion bearing feels fine, but I haven't checked the fluids yet. I will also check the angles, but they don't look all that far.
What I'm confused about is that from what I've been reading 4" shouldn't make the shaft exposed so much. Is it possible there is something else different?

I don't want to spend money on a cv shaft, is just lengthening the one I have is cheapest or can I get a different driveshaft from another vehicle?

Thanks.
 
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I called a couple of places and it'll be around $160 to retube the driveshaft.
I measured and there's now 4" of the yolk showing, so I need to lengthen 2".
Would zero rates+shackle flip be a better choice? It'd be slightly more expensive, but I can get rid of the blocks at the same time.
 
i dont think the lift is your problem. 4in is pretty standard, and you shouldnt even need to shim the axle or anything along those lines. especially if the TC has been lowered.

hmmmmm... vibration on deceleration... meaning weight shift forward.... personally, id check your front wheel bearings.
 
Well, it doesn't even have to be real deceleration. I can just left off the throttle some and it starts. It doesn't feel like it's caused by weight shifting forward. It's pretty loud too.
I'll check the bearings tonight.
Do you mean 4" lift is pretty standard or 4" of the DS showing is?

Is there a place to find driveshaft lengths for other vehicles? I'd rather get a 2nd shaft and shorten it.
 
Its your Drivelive angles. You will keep throwing ujoints until you fix the angle.

I would cut and re-weld your perches, and or get a c/v and a longer shaft.
 
I have a shackle flip rear with a 14bolt FF and I have driveline noise when coasting above 40 mph. I am certain it is an angle mismatch. I have the np208 as well and I am noticing some slop in the output bushing. I tried some 4 degree pinion shims and that didn't fix the problem. I think a SYE and a CV shaft is the solution, but that will be some $$$.

Does anyone know where to get a good deal on a SYE or a slip yoke CV?
 
Check your motor mounts. I replaced mine and it solved alot of the vibration but not all of it. I have the same problem and i have narrowed it down from everything to the driveshaft angles. I am removing my 208 in favor of a 205 so i am going the superduty front driveshaft route so hopefully that will solve that problem.
 
I checked the angles and pinion and the tcase are almost identical, so I don't think that's it. But the angle at each joint is 17*, which seems kinda high.
The rear ujoint is a little loose so I'll swap that and there is some play at the slip yolk. I checked the motor mounts and it looks like they need to be replaced too.
Lots of possible culprits, but I did order zero turns and a shackle flip kit :)
 
loudnslow said:
Just picked up an 87 Blazer
350/700r4/np208 (looks like the tc was lowered with the stock 1" spacers)
It has a 4" suspension lift and 3" body lift

It has some pretty heavy vibrations on deceleration above 45mph.
I've done some reading/searching and my conclusion is that I need to lengthen my drive shaft around 3". The pinion bearing feels fine, but I haven't checked the fluids yet. I will also check the angles, but they don't look all that far.
What I'm confused about is that from what I've been reading 4" shouldn't make the shaft exposed so much. Is it possible there is something else different?

I don't want to spend money on a cv shaft, is just lengthening the one I have is cheapest or can I get a different driveshaft from another vehicle?

Thanks.
Click to expand...


I have an 87 with the exact same setup exept for the body lift. Real bad vibes after the 4" lift. lowered the t/case 1" and was fine for 4 years. Like others suggested, your mounts are prob bad, or u joint.
You might want to consider getting rid of that much body lift.
 
klink said:
I have an 87 with the exact same setup exept for the body lift. Real bad vibes after the 4" lift. lowered the t/case 1" and was fine for 4 years. Like others suggested, your mounts are prob bad, or u joint.
You might want to consider getting rid of that much body lift.
Click to expand...

Replaced the transmission mount (shot), rear u joint (slight movement) and swapped the 3" for an ORD 1" body lift.
The vibration is still there. It's not quite as bad, but still loud.

Next steps are new motor mounts and I'll probably try to put in the zero rates and shackle flip this weekend.
 
New motor mounts, shackle flip w/6" shackles, 10* shims, new transfer case bushing/seal.
The vibration is almost gone. It's a hell of a lot better but I haven't checked the angles after all that. It's good enough now, I'm going to just drive it like this.
 
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