84 Mazda Rear end.

When you install an old school mazda rear end on to the 86-93 mazdas, will the drive shaft bolt right up? Do you have to lengthen or shorten the rear end?

Depends. Do you want to stick with the two piece drive shaft? If so, you need to get the drive shaft from the 84, and have the axle end put on your stock drive shaft. Costs about $75 at a good driveline shop.

Or do you want to run a one piece? If so, still get the 84 drive shaft, and have it shortened about 5 inches.

What would you recommend to do. Keep the orignal and but the different end on. Or use the one piece and have it shorten?

Keep you're original shaft and have a driveshaft shop put the tube yoke on it from the 84 axle. Thats normally how I go about it. I prefer the 2 piece driveshaft so that you don't have to mod the tunnel to lay out. You're e brake will still hook up to the 84 axle as well as the flex hose for the brakes. I'm not sure about where you live but around here new brake drums for the 84 and under axle are getting harder to find so heads up on that. Good luck.

On the one I did, I swapped to the one piece drive shaft and removed the carrier bearing cross member. I didn't have to modify the tunnel, and it was on a 24.63" tire. This was done, because the owner wanted a lot of lift, and the truck would do 2 feet without a drive shaft in. But the 2-piece was too short to handle the angles. And it was tearing up carrier bearings and u-joints. Drive lines don't really like operating at a 45 degree angle...

Personally, I would leave the 2-piece in. Its a good design.

Also, as for hooking the brakes up, and the pre 85 axles the brake line is on the driver side, the 86+ runs it on the passenger side. Mazda made it impossible to reverse the lines without changing the wheel cylinders out. So what I did was get a new brake line and ran it to the passenger side, and made a new bracket to hold it in place, and attach to the stock flex line.