How-to cheap LSD

Here's a quick how-to on LSDs

First pick your donor. For 2WD trucks, a 84-85 RX7 will be your best bet. For 4WD, 86-88 Turbo II is your only option.

To remove the diff, disconnect the drive shaft, and remove the rear wheels. Depending on the vehicle, it may be necessary to disconnect the brake lines.

Remove the 4 axle nuts on each side:


Pull out the axles enough to disengage the differential.

Remove all the bolts on the 3rd member case and pull out the diff. You should be left with this:


Here's my old open-diff and new Rx7 diff side by side:


Front view. Note that the long pinion will require a shortened driveshaft. I'm in the middle of a trans swap, so it doesn't matter for me:)




Check for broken spiders. Every Mazda rear I've seen has one broken:


4wd trucks will require some grinding on the diff mounting flange. I took a couple mils off with a grinder at the 2:00, 4:00, 8:00, and 10:00 positions.

Here it is bolted up:


Now it's time for some 2 wheel burnouts

Dude- thank you for writing this up- I've just gotten interested in making a lsd mazda rear end-

For most of us with 2wd trucks- what options do we have for swapping?

All Rx-7?

awesome write up!!! this works with 2wd 2600 rear too im guessing?



someone should move this to the tech section........

niccceee

I think the best option is the 84-85 RX7. They have slightly different gear ratios, but it's supposed to be a bolt in. These diffs are relatively cheap.

You could also use a Miata Torsen, but be prepared to PAY!

Finally, there's the 86-88 Rx7 n/a, but then you have to deal with the long pinion. On the plus side, these are very cheap. In fact it may be cheaper to pay for a shortened driveshaft, than buy a Miata Torsen.

I've never seen a 2WD B2600 rear in person, but all data I have points to theme being the same as the B2200/B2200s. So my prior post would apply to those.

Forgot to mention, I paid about $200 for the diff. That's a slight premium because it had to come from a TII to fit my 4wd rear. Most of you will be able to use the 84-85 Rx7 or 86-88 N/A RX7 rear. These can be had on car-part.com for $100 or less. Torsen rears, I dunno. Probably over $500.

By this ^ do you mean that you could use the stock driveshaft on 2200's? and what trim level 7 because those old 7's aren't very common in my area. I would like to do this as my truck is for winter/hauling both things that would benifit from a lsd but i just replaced my stock shaft and don't really want to do it again.

Yes, you can retain the stock driveshaft. You may have to change the pinion flange, though.
Only the RX7s with rear disc brakes came with the LSD. These will be GSL trim I think. The 12A will have a 3.933 rear and the 13B will have a 4.077.

very good info & write up lime, hopefully one of the mods will put this in the tech section.....