i see those tb coils are shorter but it depends on the coil weight rating on how much it will compress.
im at 31 1/2'' rear and i dont understand why my tahoe doesnt look that dropped compare to stock height tahoe. but im at about 1 inch of touching the frame with the axle.free travel mod done. now at this 31 1/2'' my rear vibrates going over 25mph due to the angle and length of the drive shaft. i still think its because i have the ''z71'' and my undercarriage supports are taller. lol idk .
im getting my custom upper and lower arms or trailing arms for the rear axle this weekend if it doesnt snow tonight or friday
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here is a link(
http://www.moog-suspension-parts.com/Universal_Coil_Springs.asp) of coils that might fit i havent tried all of them but just to give an idea.
if your axle ends up to close to the frame, notch it right away or you could damage it (crack). i might just bag my truck i saw a set of 4 600psi bags on ebay for less than $200 new!
i really need some drop spindles so pm me if anybody has a pair for sale.
oh btw max i saw your truck the other day it looks even better in person. good luck with the coils.