ss4chad

iTrader: (19)

I dropped my 03 GMC (8' Long Bed) with a DJM 3" Lower A Arm in the front and 4" Shackle Relocation for the rear. Was fairly easy and was done over a weekend with with a friend, case of beer and a couple of cigars. Installed new shocks in all four corners and notched the frame in the rear with a DJM C notch for more suspension travel while hauling my car trailer.

I have a vibration at 75mph that gets progressively worse as you go faster. I measured the pinion angle and got 96 (maybe 97) on the rear end and 91 on the drive shaft.

So do I have -5 (or -6) as my pinion angle? Do I need to add shims under the forward part of the leaf spring to a -3 or -4 to get rid of that high speed vibration?

Thanks

Chad

FFDP

iTrader: (2)

You want to measure the angle of both the transmission housing end and the pinion itself.

It's much easier to use 0 as the starting point. So like the transmission is pointing 3 degrees down and the pinion is pointing 8 degrees up as a reference. You'd then shim the pinion to come down to match the transmission angle or be withing 1-2 degrees depending on application.

I use an el cheapo angle gauge from the hardware store that works great.

ss4chad

iTrader: (19)

So I have to remove the driveshaft, do I then measure where the U-Joint attach point is, where the bolt holes are?

Chad

FFDP

iTrader: (2)

No, just measure it from the yoke on both ends.

Make sure both are pointing straight at the ground and measure. Use a mini block or wood or something square if you have to extend it down an inch to clear the driveshaft.

Like this.

ss4chad

iTrader: (19)

Got it, thanks! I will see if I can get it on a lift at the local Oil Change Venue when I get the truck inspected. I will get back with ya then.

Chad

brandon6.0

iTrader: (26)

I thought the angles canceled each other out. say if your trans was -4 downward and rear was 6 upward u would have a pinion angle of 2 degrees. correct?? I always shoot for -3 for the rear-end if its race truck.

01ssreda4

iTrader: (87)

FFDP is correct. Stop measuring the driveshaft!!!! Whoever started that way of doing it should be shot.

Mean Green z28

iTrader: (19)

Nobody was suggesting that, what are you smoking? haha

01ssreda4

iTrader: (87)

I accept flowers and chocolate as apology gestures.

ss4chad

iTrader: (19)

Ok, I got -4 or -5 on the rear end
And -5 or -6 on the transmission
However, those readings were difficult to aquire, might be better to measure it again when I change the u-joints out this weekend and remove the driveshaft.