What do shims do for you?

[chvyhs]

I have a '90 Suburban that I'm putting 6" springs in. I want to know what shiming it will do and why I might need to shim it.

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[lasvegas]

you shim it to adjust the pinion angle. This allows you to rotate the differential to the proper angle for the driveshaft

 

[bee32]

That's it.

Brian
83 K-5 4" on 35's

 

[chvyhs]

I'm sorry, I should have mentioned it's the front end I need to know about.

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[michaelm]

same thing applies but you also lose all your caster when shimming
of course you could restate the question with more info?

 

[CaptCrunch]

Basically like was said the shims make the pinion point up more and eases driveline vibrations. The front is a trade off... the more degree the worse drivability you will have with the alignment. Try and go the smallest shim possible. If you drop your tcase you are going to hurt the angle more on your front driveshaft (but it will ease it for the rear). Generally there is a compromise on the front to allow decent drivability, yet allow the vibes to be not very bad in 4wd. Most trucks are converted to part time now and most times your don't need to be going 55 plus in 4wd. If it is that slick out slow down to 55 in 4wd or whatever speed. What i have seemed to find in my research is w/ 6" springs usually need 4 degree springs w/ the tcase dropped, or 2 degree shims with no drop. I curently have about a 8 to 10 degree shim in the rear for my cv shaft w/ no tcase drop and a 2 degree shim up front.

-Mikey
1987 Chevy K5 Blazer- 350 TBI
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[sinchphoto]

how is the cv joint in the rear working for you? still get vibes?

 

[CaptCrunch]

Well if you have vibes from a shackle flip or diveline angle they work great. I would go with one of Jess's one tone CV's. They are worth the money. I did have some vibe problems but one was a bizarre problem w/ the CV joint which has been since and the other has been the batle of the 1/2 ton rear end.

-Mikey
1987 Chevy K5 Blazer- 350 TBI
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