i probably know the answer to this question but i just thought i would ask it anyways. would a rear end out of a 4th gen bolt up into a 3rd gen?

 

Well if you know the answer, what do you think? And no cheatting and searching for any threads with this question already answered.

 

yes, just make sure you have the right proportioning (combination) valve for which ever brakes the 4th gen diff has.

 

im pretty sure it will, my brother has a 4th gen and they look just about identical, i want to keep the posi and add rear disc.

 

It is a few inches wider. Might be fine with a different offset wheel. Or mud flaps. And as mentioned don't forget to replace the proportion valve for a drum to disc swap. If its an 83 you are working on you will have to find a valve with the line configuration of the 83. My valve on my 84 with disc was differentfrom my 91

 

ok its wider but the mounting points will match up? its not an 83 its a 91 my 83 got rearended. where is the proportioning valve? wider might actually look good though.

 

proportioning valve is mounted directly under the master cylinder, but yes the 4th gen diff will fit easily with little to no modification

 

Its only like 2" wider on each side.
And regardless of what year your car is, if you go to the wrecker to get a valve just don't jump into the first F body you see with disc and grab it. You might find out you have too many brake lines and they don't line up in the respective holes.

 

you are talking about brake lines into the valve correct?

 

Yes. Not all the valves have the same line configuration. But you can easily get a valve for your 91. I looked and could not find my invoice for the part number from when I got the valve for my 91. But new jobber cost I think was around $50 +/-