I heard that my vert's diff is the same as the TII diff, Is that true? I searched, but to no avail.
Thanks

 

Is your vert turbo from the factory?
Did someone swap out your rear for a turbo diff?
If not, NO.


-Ted

 

What Ted said is right.

I've got JDM 13B swapped into my vert. I did a full swap by getting a driveshaft, diff and half shafts. Actually I think the vert has the worst gear ratios of all the differentials

 

^Yup. The vert came with the NA diff and the 3.9 ring and pinion from the automatic cars.
The TII rear end is a 4.1 gear ratio.

 

Only the 88 vert came with the 3.9 all the other year verts including the automatic came with the 4.1...

And the Turbo uses a 8 inch ring gear, while the vert uses the same size 7 inch ring gear that all the non turbo coupes did.

 

yeh alot of people have the confusion that all verts came with the 3.9,
but when i did my auto> 5 speed swap using a turbo driveline i saw that they were the same.

 

so how would one tell just by looking at it; what they have? I have a vert, but im not sure, i would like to know more about differentials because those and clutches were some of the only things i knew nothing about. i installed my clutch and everything and now i know plenty. still no knowelage in the diff.

 

Opps, thanks for clearing up my misinformation Icemark.

 

marshall 13b-if your vert is not an 88 then you have a 4.10 rear end. the only thing is that it isnt limited slip.

 

+1 for Icemark clearning things up

 

It is an 88, however I have no idea whats really under there, from what I understand, the car has a rebuilt title, and I also know the motor was replaced. So that just leads me to beleive that its very probable that the tranny and dif have been replaced...

So I put my car up on jacks, put it in first gear (so now the rear wheels are free rolling) and I was able to grab the drivers side wheel and the passanger stopped. So that means no lsd right?

 

Turn the wheel.

If the other wheel goes the opposite direction, it is a Open Diff (or worn out LSD).

 

I did not know that. I have an 88 'Vert - I guess I'll add a diff swap (might as well go LSD while I'm at it) to my list of intended mods.

If I swap the diff for one with a different ratio, won't the speedometer be (more) incorrect? What do I do about that?

 

Yes.

1) Get the right speedo gear that goes into the trans.
2) Take it to a trans shop that can take care of this job.
3) Don't do it.


-Ted

 

That's basically my question—if I need to change only the driven gear/speedometer gear housing (easy!), or if I need to also change the gear on the output shaft itself.

I have a transmission on my workbench right now that I'll be swapping into my 'Vert in a week or so, so if I need to do something internal to the tranny, now would be the time.

I have searched, by the way—both on the forum and the general web, and the best info I found was on a Miata site. He had links to RX-7-specific pages, but they were all dead.

Plenty of posts talk about swapping trannies, gears, GTUs rear-ends, etc. on this forum, but almost none discuss proper speedo gear swaps for quasi-accurate speed. I daily-drive my 'Vert, so I'd like to have mine reasonably accurate.