I think that I have a shudder or slight vibration between 20 and 30 mph. It is just slight. Could this be caused by the shackles and if it is would shims fix the problem/pinion angle?

It was lowered about 2.25 inches. Thanks for the reply.

 

You will need to shim the rear axle to get the proper pinon angle
back.****

 

sorry to jack thread... **** you have any exhausts left?

 

I also have a 2003 Lightning Dark Shadow Gray L. Yesterday, I used DJM Suspension Lowering Shackles (2") to lower the truck.
Got 1 1/2" drop right away and figure I may get a hair more in the next few days. Anyway, IF you do have a slight vibration after the install of your shackles, I believe you have two options.
First option is to get shims and shim things. Do a search of all posts here related to shackles and you will get a good idea just what shim size to use and how to install the shims.... oh, and about using your newly purchased shims with the stock shims. Your other alternative would be to re-install your shackles and change the holes you use on the shackles so you get a slightly less drop in the rear of your truck and hopefully bye, bye vibration. With my 1 1/2" lowering I got zero vibration from the multiple 0 to 110 mph road tests I did. My guess is you will opt to go with the shims but then again a change in the shackle holes you use may straighten things out for you.

 

It's just that I hate to raise it up at all since it looks so goood sitting pretty much level. If memory serves me correct I believe for every two inch drop you need to add two degrees. I'm not sure but will do a search at get some idea.

 

FWIW, here's a pic of the 2-degree shims that came factory installed on my 2003. Not sure why only 2003's have them except for the fact that the 2003 has higher rated rear leaf springs (which indirectly seems to raise the rear end of all 2003's by like .75").



The pinion angle I measured with a parallelogram protractor (empty vehicle with half tank at rest in PARK - engine off) was 5.7 degrees:



Your mileage may vary, but you want to get your before and after angles as close as possible. For my 2003, I had to REMOVE the shims to restore the factory angle, and I have no driveline vibrations when coasting now. You may have to add shims to your truck to get it back (but you'll have to measure the angle on another 2000 or get the angle from a friend/online). Also don't assume the factory angle is necessarily "golden." You may be able to reduce driveline vibration and "humming" with a slightly lower or greater angle! Additional note: remember you're measuring the angle of the shaft relative to the pinion nose, NOT the horizon. So even if you had to add a shim (especially a wedged shim with one side thicker), you may not be raising the back end up very noticeably at all, more likely you'll just be rotating the axle so the pinion nose goes up or down.

 

BTW, here are some basic diagrams I made that help illustrate what happens to the pinion angle and suspension when dropping the Lightning with front coils and rear shackle only:

 

Sweet diagram there guy! But won't the front hanger stay the same after the drop? You show it moving down a bit...sorry to be nitpicky

BTW This mean you have a sonic blue now?

 

This diagram is correct, but the overlapped version may be confusing. The front hanger stays in the same relative location (hard-wired to the frame), but the whole truck drops. So that's why it looks like the hanger "moved." The hanger mount would not "move" if you replaced it with a different Belltech replacement. But otherwise, all rear spring mounting points to the FRAME are still the same as before, just moved down in space with the rest of the lowered vehicle. (Note, the bottom of the shackle also moved down by the same distance). The only part that really changes "location" is the top of the shackle where the spring is now held "higher" relative to the frame (i.e. closer to the bed) because the new shackle is longer.





Yes, sonic blue for me now. The fastest color, right?

 

Rotate the stock pinion shim to have the fat end towards the rear of the truck. I have fixed 20 Harley trucks, several Supercrews and a few Lightnings. The stock pinion shim is a 2 degree shim!
Good luck!!

 

You can also try various size/degree shims from any 4X4 retailer to get it just right. I had to remove mine, turning it 180 degrees wasn't enough.

 

I've got a 2003 so I guess that I'll have to reverse the shim. If I would have known all of this before I would've just had a shop do it all. I'm not sure that I'm comfortable reversing shims. This is why I hate mods.

 

<- Stupid me... I didn't read your sig carefully.... I saw '00 and didn't seee the "EB!"

 

Ya you're prolly right...I'm just a little slow...kinda like my truck right now without any mods. Sonic blue has its work cut out for it to be the fastest, but I see it happening!

 

What, I plan on doing is swapping out my '03 L leaf springs and front / rear shocks with the '02 L leaf springs and front / rear shocks. I believe the front coils on the '02 and '03 are the same so i'm not changing those out. I'm doing this mainly because the ride quality on the '03 is a little stiff for my taste.

My questions are..... Will I have the pinion angle problem by doing this? Will I have to remove the shim's since the '02 don't have them? Also, are the shackles on the '02 and '03 the same size or should I purchase the '02 shackles as well? Thanks.