dana 30

i´m wondering if the dana 30 from a cherokee will fitt under a newer wrangler for say the one with spring suspension and if the main frame of the 87 wrangler and the new one has been chenged

Frames for the YJ and TJ are different. Not huge differences,but enough so that it's not cost-effective to swap one into another. The XJ Dana 30 is a direct bolt-in to the TJ platform,and is a good swap as the TJ uses a low-pinion 30 whereas the (early) XJ uses a high pinion model. TJ owners look for the non-disconnect XJ axle to swap in and they generally will use their original axle shafts as they are of the 297-x variety and will swap directly into the XJ 30.