Anybody experiencing driveshaft vibration after lift and gear change?

I've got an '04 ford f-150 with an Rancho 4" lift. I recently swapped 3.73's for 4.10's - now i've got vibration at 80 MPH.

i was referred to a good offroad shop and they told me the problem is pinion angle. Ok. i shimmed the rear end 3 degrees and yes, a lot vibration went away but i would like to get rid of the rest.

Any idea's ?


Steve

 

yea quit going 80! you'll see better fuel mileage! what are your tires speed ratings?

sure your tires are still in balance?
if your driveshaft was removed was it marked and reinstalled how it was taken out?

sounds like you may need a CV at the t-case if you dont already

-cutts-

 

Your pinion angle shouuld be just below the angle of the driveshaft. I set mine at about 2* below the DS.
Do you have a fixed yoke at the t-case end?

 

Keep in mind that due to torque the pinion will be up a couple of degrees while you're driving. If it looks dead on while everything is sitting still then it's probably out while you're driving (pinion will come up slightly) so you may need to go a few degrees more.

If you happened to seperate the slip on your shaft while doing the lift then double check the u-joints on each end are either in phase or 90 degrees out, not ****-eyed in some goofy angle or this will contribute to vibration.

 

Yep! That is axactly my theory on why my pinion is set 2* below the t-case output.

 

i didnt know that one....wonder how many times ive put mine together wrong....

 

Ok. i will double check, but i think my pinion is dead-on with the driveshaft. So, do i have too much ?


I have yokes at both ends of the DS.

 

you guys are going to laugh at this . . .

i first had a custom driveshaft made because of: sloppy, non-servicable u-joints and the DS was an 1/2 inch too short after the lift.

ok, the funny part . . . the tech who made my DS said he added a balancing weight because he thought i wanted to see it and NOT because it needed it. he said it balanced perfect without the weight.

 

WHAT?!?! That is weird. Who gives a crap if it balances out well without weights?

Glad you got it figured out!

 

My old man had a blazer with same prob, after fixing everything he and the shop could think of they put a shim (i think between the cross member and the frame) where the trans mount is. I told him that's great but there's still one problem........it's still a chevy.
Might check with the local shop and see if that's an option.