I bought an open 1.8 diff for my car from Planet Miata, but now I need to make my last payment for school. It's in good working order from what I can tell, but it's just the guts in the front half of the housing. It doesn't have the carrier to bolt it to the car. The gear ratio is 3.9:1.

$400 shipped, obo.

 

what the **** had a 3.90 open? no miata did.

 

late 70s or early 80s truck... and while the r/p would swap, the actual diff assembly wouldn't.

since it came from PM, either
(1) they pulled the torsen from a 6-spd rear OR
(2) it ain't a 3.90 <--most likely

 

I say show us some pics of the ring and pinion to verify tooth count.

 

I just checked and it's 4.1:1. Guess that's what I get for trusting PM with anything important =\ Anyways, how's the price?

 

Extremely high. You asked. I had someone off to GIVE me on a while back. GL getting 400 bucks for it.

 

Well then, 250 shipped.

 

here's a question i SHOULD know the answer to... while i prefer to have a limited slip rear, my main concern right now is that when i get the new injectors in and start running more power, i'm going to make short work of my 1.6 rear.

the open rear should stand up to the power the same as a limited slip unit, correct, as the 6" vs. 7" ring is the factor at hand? this of course assumes i'm not rockin peg leg burnouts and drifting like it's going outta style. right?

 

Yeah, you'll be good with this rear end. If I remember correctly, the 7" ring gears are good for at least 250hp.

 

Yes, but he will need the bigger Diff housing, no?

 

Yes indeed. The carrier (rear housing with mounts) will need to be sourced. On top of that, a driveshaft and axles (and perhaps the stub shafts) will be needed for the entire swap.