Miata Question

Andy Greene · **Posted:** Fri Jun 18, 2004 5:56 pm

Where would you find a rear differential for a 1990 Miata and how much would you expect to pay (preferably one with a LSD?) It should be an easy swap that would only take a couple of hours right?

What about swapping a working auto transmission for a manual in the same car? Is it worth the effort? I would guess that you could sell the auto tranny and almost break even on the cost of the transmission, but what about other costs and the time involved?

Aaron Buckley · **Posted:** Fri Jun 18, 2004 10:01 pm

In order to get in a rear diff that was worth a damn (non-viscous), you would need to find a '94-97 Miata rear diff with axles (for the axles are not the same).

As far as the auto for manual goes, if it came to that, I would just find another car. You will be hard pressed to find anyone interested in a '90 Miata auto tranny, and the work involved wouldn't justify it in my eyes. - AB

Andy Greene · **Posted:** Fri Jun 18, 2004 11:28 pm

Yeah, I knew the 94-97 Torsen units would require the whole rear-end. Looks like it would take the driveshaft as well.

A full 1.8L engine/drivetrain swap would be nice, but it looks like a lot of work (although quite a few people have already worked through them which always makes things easier.)

It's just something I was thinking of for a project car that I saw for sale. Sounds like I would be better off if I did pick it up to fix the busted rear-end with a junkyard unit and sell it for the car that I really wanted as opposed to putting a lot of money and effort into that one.

TomFreeman · **Posted:** Sat Jun 19, 2004 2:26 am

Miatas are relatively cheap and plentiful. I would not recommend buying an auto Miata to tstart with for a project car. Hold out until you can find one with what you want.

Another reason not to buy a 90 or an early 91 - the short nose crank. After a timing belt change, some of the early cars had problems with the crankshaft bearing because of the short nose crank. This is an engine-ending condition.

Of course there are plenty of 90/early 91 cars still running strong, like Rob Lupella's 90.

Andy Greene · **Posted:** Sun Jun 20, 2004 11:25 pm

FYI, this website has detailed step by step guides for quite a few Miata upgrades/repairs including the differential swap I was asking about: http://www.pacificsites.net/~hakuna/gearhead.html

Doug Jackson · **Posted:** Sun Jun 27, 2004 12:39 pm

Another reason for not swapping a tranny from auto to manual, the auto cars have a different cyl. head, lower compression and less power. Now if you plan on FI then it might work out for the better, allowing a little more boost.

Brad Mackey · **Posted:** Sun Jun 27, 2004 7:34 pm

Andy Greene wrote:

Where would you find a rear differential for a 1990 Miata and how much would you expect to pay (preferably one with a LSD?) It should be an easy swap that would only take a couple of hours right?

Probably not a two-hour job. Also, don't start until you have the tools you need. That includes the special tool to pull the interlock tube out of the longitudinal member that connects the trans. to the diff.

Better figure 6 hours if this is your first one...

Andy Greene · **Posted:** Fri Jul 02, 2004 6:32 pm

Is this the "interlock tube" that you are referring to? The website I'm looking at says just to pry it out.

Scott Johnson · **Posted:** Fri Jul 02, 2004 6:41 pm

I have pried one of those out before (major PITA), however, it is completely unnecessary to remove it in order to remove the tranny.

The brace has enough wiggle room that the tranny can come out from around it.

Scott

Andy Greene · **Posted:** Fri Jul 02, 2004 6:50 pm

^ This is for a differential, not a tranny.

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