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Ive got all pretty much all of the parts I need to start my swap now, minus the cooling system, and the rear end. I’m trying to do this whole swap for under $10K, and so far, I’m well under that budget.
I was considering just running the stock rear end for a while, and getting a spare rear subframe and then just swapping it out one day once I get the rear end I want setup in it. Probably going to go with an 8.8 in the end though.
I know the gearing isn’t ideal and Ill be pulling some higher than Id want revs at cruising speed on the interstate, but I hardly ever take the car out of town, so I can deal with that for a while.
I also am using a pretty much stock 5.0 from a ‘94 Mustang GT, so the power output wont be too much more than a standard turbo Miata. Ive seen people run 300HP on the stock rear ends with some of these turbo builds. I dont plan on running that much until I get the 8.8 in.
What kind of modifications will I need to do to the stock rear end since Ill be eliminating the PPF? And is there anyway I can get a driveshaft made so that I dont have the staked u-joints on it? I know I can get the rear of the factory shaft welded onto the one from my door car, but Ill still have that staked u-joint, and I want some that I can service.
Just think about what you are planning to do. A stock diff and axles designed to handle 116 HP and 100 ft pounds of torque and you will be putting 215 HP and 285 Ft-Lbs of torque through it. Axles, CV joints and the diff itself will not handle that much without something letting go and all of that stuff is just below and behind your gas tank. It's not the horsepower that will break stuff. It's the torque and your motor is rated at 3 times the number that rear end, axles and CV joints were designed to withstand. I don't know about you but the thought of an axle whipping around near that gas tank and making sparks when it hits pavement at freeway speeds after a CV joint or hub failure is not something I would want going on behind me. But, then, it sure would be fun to watch since it's you, not me.
It's been done before with no drama. The caveat is you can't run large, sticky tires since traction is not your friend if you run the stock rear. Think of wheel spin as a good thing since it limits the shock load the rear end experiences.
A poster on the other v8 site ran a stock rear for a couple years with a cammed up 5.0. No issues other than the short gearing. But he drove like an old man (cause he was one). You can read a bit of Jim's thoughts in this thread https://forum.miata.net/vb/showthread.php?t=622127. A search would yield more of his low buck, yet excellent work, most of it in a Very small carport/garage and driveway.
"A poster on the other v8 site ran a stock rear for a couple years with a cammed up 5.0. No issues other than the short gearing. But he drove like an old man (cause he was one)."
If you're going to do that just save all the trouble and stick with the stock four banger. A V8 into a Miata will shame the Gold Chain, Red Ferrari bozo's on the track and it costs less than wheels and tires for a Ferrari 458. THAT is a really good reason for doing the swap so that you can DRIVE it.
06-25-2018, 03:41 PM
Stock rear end with a 5.0L?
