Thinking of 4G63 in Miata, 1st bump in the road.

V8s_are_slow · Post by **V8s_are_slow** » Mon Oct 20, 2008 12:54 am

Okay, I've been doing nothing but reading all day trying to research my options. I know a d50 tranny will bolt up to my 91 fwd 4g63t. But here lies the problem that I'm thinking of. On a Miata, the rearends suck and won't hold a lot of power. Some people swap in RX-7 TII diffs with axles. Problem is, I'd need a driveshaft that goes into a d50 tranny, and bolts up to a diff from a TII diff. Trying to think of the easiest way to get this done and the transmission is my biggest obstacle to start off with.

For one, I don't even know how much power a d50 tranny will hold. I've run a 7.7 in the 1/8th with my eclipse and plan to pull the same motor and throw in a Miata and hopefully have more power. I know I could use a TII tranny, driveshaft, and rearend, but then I have to spend like $400 or whatever it is to get an adaptor plate or bell housing and then I'm not even sure about the input shaft fitting like it should. Also not sure about the clutch and flywheels going in. Been reading all day and just have a bigass headache. Can anyone save me some time and give me info if you know it that'd help? Trying to look at the easiest and best route of getting this done if I'm gonna do it. I'd greatly appreciate it.

V8s_are_slow · Post by **V8s_are_slow** » Mon Oct 20, 2008 11:15 am

Why would you suggest that transmission over a TII tranny? I mean I hear they're pretty strong and figure if I can find an old TII car, I could snag the tranny and diff and all as well. Just wondering. Gearing or something? Guess I won't be looking at the d50 then.

75COLT · Post by **75COLT** » Mon Oct 20, 2008 11:29 am

What are your goals first? Then go from there. If you are building just a fun mainly street car, then a w-55 toyota trans would be your most reliable(cost)wise. Its larger than the d50 and more aftermarket support ie.. shortthrow shifters and gears. If you are building a more multipurpose car look at r154 or the ultimate t-56. I also know the late 90's Lincoln rearend will work in your miata. There is a kit you can buy which uses a lot of the stock stuff for the rear. Only the power level is going to dictate which trans to use.

Ian

V8s_are_slow · Post by **V8s_are_slow** » Mon Oct 20, 2008 8:54 pm

Mainly for some street and drag racing. With a motor that'd be running 11's in the 1/4 in my Eclipse and going into a Miata, I'd kinda want it to last. Will the w-55 tranny bolt right up to my block? I don't care for the short throw shifter. But do want something that'll hold some power without breaking and preferrably an easier install. But of course, who wouldn't want that?

75COLT · Post by **75COLT** » Tue Oct 21, 2008 11:17 am

W-55 and r154 both require Bill's bellhousing. The w-55 is what I am using on a stock motor 16g, My car with a lot of the stock components removed and replaced w/ lighter stuff tips the scales just under 2k lbs. W-55 's are a dime a dozen and the one I have was only $50. I would research some more and see what is available.

Ian

GRNDSM · Post by **GRNDSM** » Thu Oct 23, 2008 1:44 am

The driveshaft is the easieast part of this project! Just any driveshaft shaft (there are a LOT of them!) can combine two shafts to your length for under $200.

94+ Miata had a stronger rear end and had an option for a decent Torsen LSD.

I have 94 Miata rear end for my TR7 project, but I still haven't decided if I want to do IRS or a solid axle (probably Ford).

Post by **DJpowerHaus** » Fri Oct 24, 2008 9:13 pm

My 94 Miata's Torsen diff isn't all its cracked up to be. It'll leave 2 marks during a burnout, but if you get in snow and have zero traction on one side it will spin like an open diff. Sucks. Seems like it needs some traction to be a limited slip differential.

GRNDSM · Post by **GRNDSM** » Fri Oct 24, 2008 9:37 pm

Why do you drive your Miata in the snow?

But seriously, what is the limitation of that Miata rear end?