So This is my 17' Super Duty with 8" BDS Long Arm Kit. First drive in the truck after modification and I get a vibration
at about 65 is is very noticable on acceleration. Not sure what to do. Hard to diagnose from pics only I know but
any help is very much appreciated.

 

Does it go away at 70? 75? 80? Sometimes trucks have a nasty resonance speed that changes with different road surfaces.

Most likely 8" is too much for the drive shaft. May need custom drive shafts, carrier bearing drop, different pinion angle, or all three. That's a lot of lift.

 

Yes only vibes from about 65-75 and is much worse under load/acceleration. Very fine vibration also...Really appreciate the help since
the 4WD shop I used apparently can't get it figured out

 

If you haven't already, call BDS. I'm sure they have good customer service. They may know what to look for or inspect.

 

The vibration is probably a driveshaft phasing/angularity issue. The U-joint angles need to be the same ar each end. Based on the picture, you also now need a longer driveshaft.

 

It looks like your driveshaft has been pulled out a bit [by the black ring I see] and the angles at the u-joint look a bit aggressive! I am guessing you will need a CV joint installed where the t-case u-joint is. This will also lengthen the shaft. The lift kit guys don't always disclose all the other mods a guy may have to do to make your system work! The rear of mine has been lifted 3" and I have a vibration now but luckily it is at low speed.

 

i hate to say it but your 4x4 shop doesnt sound very competant. clearly that slip yoke is pulled out a mile. you might damage the tail shaft bearings if you keep driving it. ujoint and pinion angle are probly in need of serious help as well

 

I'd get a custom made driveshaft that makes up for the lift at a minimum. Maybe have the tires double checked for balance. Double check the front end, double check torque on all bolts and as mentioned above find a better shop, a BDS lift shouldn't give you issues and more importantly a shop that cares will exhaust all options to remedy the issue not brush you off and just say hey its a lift what'd you expect ... on a side note I'd sure like to see some pics of that monster

 

I'd say it's driveshaft angle and it looks like it's pulled out pretty far. Don't they use a driveshaft spacer on some lift kits?

 

Most commonly it’s the shaft out of balance ... I just put and 8” rough country kit but I haven’t had any issues except my front shaft is too short...Just a here and there thing...

 

Can we see the truck and the lift?!? lol. I wanna see what that kit looks like on the truck!

 

Is there an available option to eliminate the slip joint? Tcase drop? Just throwing out ideas from my experiences in the Jeep world...

 

An SYE? Not that I know of.

 

looks like some agressive shaft angles to me....not feeling the carrier bearings shimming is right...bump it up to bsd.

 

I don't think the shop who did the lift put the index ring on the transfer case.. I also believe those rear blocks have the wrong pitch which is adding to the u-joint issue..