I put my 6" skyjacker lift on this weekend and had tires mounted and alignment done on mon, but i still have vibration at takeoff once i reach speed the vibration goes away would this be because of axle wrap and would traction bars cure this

 

yup! should i wonuldnt imagine that your drive shaft is at to steep of an angle so just traction bars shouldo the trick.

 

I have vibration at takeoff as well and like your's it goes away at highway speeds. What exactly is axel wrap and what can it do to my truck if left unchecked? Thanks

 

axle rap is cause by to things one being that once you put in a block the drive shaft is at a steeper angle causing it to bind a little... tracion bars wont fix that you have to lower you axle at the join to make a differance. and two if you have a block when you excelerate you axle twist a little due to the disstance between the axle and your leaf spring. i may be a little off on that but i think thats basicly it.

 

Axle wrap is when the rotating force put on your rear axle causes the actual axle assembly to rotate. This is usually a problem on vehicles that have big spacers instead of adding adequate leaf springs...It's normally only there on takeoff and really hard shifts...once your truck gets that initial surge of torque out of the way, it should go away...I've never heard of axle wrap causing any vibrations at any highway speeds as once the wrap corrects itself, any difference in driveline angles should be corrected.

Anything that secures the axle from twisting could correct the problem...I'm not sure what your lift included, but if it came with some big lift blocks, I'd look into getting a more beefed up leaf pack, personally.

 

My truck is lowered, but the same problem is created. The angled shims used with lift or lowering kits are not accurate enough to maintain the correct pinion angle. This makes for vibrations and excessive U joint wear. I took mine to a driveline shop because I had wheel hop on hard launches. The tech solved my problem by raising the trans tail about 1/2". I did add flapper traction bars later when adding more hp.

 

I had 5" blocks put in the rear of my truck to prevent the back of the truck sagging, seems I may have done more harm than good going that route. Where is the best place to purchase leaf packs for these trucks at? What about going with a smaller block and an AAL?

 

SkyJacker and I believe BDS make spring packs, the SkyJacker (4") you use the stock 2" block and the BDS is a 5.5" pack. KansasJoe sells them (I believe) and knows more about the BDS pack than I do.

Never heard of axle wrap (the torque of acceleration/deceleration twisting the spring pack, thus rotating the axle) being an issue other than under hard launches. Blocks act as a lever for the axle to twist the pack more. Vibration is most likely caused by driveline angle issues. The blocks are tapered, is the tall end forward or back? Best to start with the simple and work toward the more complex issue, rather than assume the worst and ignore the simple.

 

My skyjacker lift came with the new leafs and the shims are in the correct posistion. All the driveline angles are great. I have the same lift as you Bryndon and you would know the angles are pretty good but i can grab a hold of the rear tire while in park and rock it back forth and you can clearly see the rear end shifting up and down so just imagine what all the torque from the truck would do. also my vibes are not at highway speeds they are on acceleration only. That is why i thought the traction bars might be of some help

 

Duh, sorry, I forgot who I was talking to! If you can move the tire, there is something VERY loose! Check for loose U-bolts!!! You should not be able to move the rear end by hand! Something is loose or not installed correctly, check everything closely, there is definitely something out of place. Ladder bars might mask the problem, but not cure it.

Even with the SuperChips in Hi Perf mode and the 37" tires, I don't get anywhere near axle wrap. Check everything and get back at us, but it sounds like loose u-bolts to me.

 

I'm with Bryndon on this. . if your experiencing this on pavement than I really doubt it's axle wrap.

 

I've been thinking about it more, and I keep coming back to the U-bolts - and it makes sense, if the bolts are loose, the rear end will "rock" back and forth during acceleration more than any time. Once you get to a steady speed, it will settle onto the pins in the spring and sit still. With it on the tires, check the torque on those u-bolts.

 

I tightend the **** out them when i put them on, but i do not know an exact torque spec for them what do u-bolts usually get tightend too

 

I thought it was in the SkyJacker instructions, but 100 - 120 ft lbs is probably a good start. Check the u-bolts in general, could have been an issue like something caught between them and the axle. They are the only thing that could cause what you describe.

Remember, a regular rachet probably won't get you that high... in that position (laying on your back), you'll need to brace your legs and body and lean on a breaker bar, or better yet a torque wrench.

 

I'm going to double check most everything this weekend anyway, wheels, ball joints, diff, u-bolts ect. and yes i do have a very good torque wrench the only problem with it is it only goes up to 250 ft. lbs so i had to do some guessing with the lower strut mounts as they are 351 why i do not know. But anyways i'm going to post up some pics of the truck hopefully tonight just been trying to get all the bugs worked out. Bryndon i have a question for you though what did you do with driver side brakeline, man that thing had almost no slack in the hard line, what did you do with yours.

Thanks for the help guys