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vibration/leaf springs moving

C

chevyguy82

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Location
topeka, kansas
this is my first post. i've got an 82 blazer with 6" bds suspension/all spring with 35" bfg mt's. i have a bad vibration when i hit the gas hard from a dead stop and also sometimes going down the road. i have replaced the u-joints and still have the problem. i also have a problem with the bottom leafs moving out. u bolts are tight. i have broken 2 u-joints now. it came with shims already on the spring packs. i lowered the transfer case. angle isn't that bad. do i have to lengthen my driveshaft? it has a new 700r4 connected to a 208. since the lift the driveshaft has come out about 4 inches. i flex it out but fear the shaft might come out. does anyone else run this setup? thanks for the help guys.
 
pics of all the angles will help. what i've heard is 4" lift is the most you can do on a blazer before you have driveshaft issues.
 
so should I get the driveshaft lengthened? what about the leaf springs on the bottom moving outwards? do i have to add ladder bars? i'm not sure what degree shims they are. they came attached to the spring packs. i figured paying the extra for the bds lift, they would have already tried all the angle of shims and it would come with the right ones. i'll try to get some pics and post them.
 
Oh boy oh boy, where to start. There are so many things that you need to check.

First off give us more details on the Blazer.

Vibration on take off.?.? where do you feel it? Can you hear it also.If you have bad angles, with or without a weak trans mount, the torque and push the Tcase over and hit the underside of the body. A pinion bearing going bad will do the same.

Vibe going down the road could be death wobble. What axles?

A big thing here....... I have personal experience with a driveshaft angle that made a noise that sounded like the tcase was coming apart. It happened mostly on decel.
 
sorry guys, i don't have pics up yet. it has a 6" bds all spring lift. transfer case lowering kit. stock 10 bolt axles, ez locker/front and mini-spool/rear. 3.08 gears (way too high). i have replaced pinion yoke and all u-joints. tranfer case mount is new. i just put in a new 700r4 tranny. i always break the rear u-joint. what would make the springs start moving out? i constantly have to adjust them back in. i have had the vibration after breaking the first u-joint. weight is still on drive shaft and doesn't appear bent. my next step was to take it in to the driveshaft shop have it balanced and lengthened. i didn't want to do it if i don't have too. i'll get some pics up this weekend. thanks for being patient with me.
 
Did you torque your U bolts that hold the springs to 150 Ft LBS?( or what BDS recomends) Having then "Tight" is not good enough. They must be properly torqued.
With a 6" lift you should get a longer drive shaft. I had to lenghtn mine with a 4" lift to get rid of a small vibration.
When you go to the driveshaft shop have them check your drive shaft angles. They will tell you what degree shim you may need.
 
Whoa, hold on here... what do you mean by the bottom leaf springs "moving out"??

Not only do you need to have your U-bolts properly torqued, but make sure the pin that holds the leaves together (and locates the axle and bolt plate) isn't snapped, which would allow the whole assembly the wiggle around. There's no reason I can think of that any one of your spring leaves should be moving independent of the others in its pack unless something is seriously wrong. Check the spring and shackle bushings too.

While I fully agree that you'll probably have to go with a longer driveshaft for wheeling, the stock one should be fine for testing purposes on the road. Get this ironed out before you invest in a longer driveline.
 
I'm sure he meens that the overload spring is fanning out a bit. Properly torquing the u-bolts should help aleviate that. The bad vibration at take-off could axle wrap causing the u-joint to bind as well. A 6 inch all spring lift will pull that driveshaft pretty far out and the lack of spline engagement may also be causing vibrations. Additionally that much lift is probably maxing out the driveshaft angle and the u-joint on the transfer case end may be binding as well.
 
I have a '91 Blazer with a 700R4, 241, and 4" lift (and 14BBF). I had to grind the rear driveshaft and yoke for clearance and my splines at the slip yoke are making bad noises (not enough engagement). I am going to drop my t-case and inch (stock location now) to try and get some more spline engagement as a temporary fix until I can go with a SYE and new rear driveshaft.
 
K since this had me on the ropes scratching my head for 2 months. Check your leafspring center pin. It takes 5mins to check its worth it!
 
thanks for all the help guys. i just got back from a wheeling trip. first time out with front and rear end locked, at least ez locker in front and spool in rear. the ez locker is awesome. so much easier to turn. i took my truck places i could never go before. unfortunately i had to get winched out by a big jeep, it did have a chevy 350 in it so that made it a little easier to suck it up. this truck feels so top heavy. i need to get different axles or wider wheels. i'm running the stockers with 35" bfg mts. springs are really stiff. i will torque down the u bolts and see what happens. will let you know how it goes. thanks again guys.
 
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