RX-7 rearend ?

i have heard on here that this rearend is wider than the stock mazda axle so i was wondering if anyone had the exact width measurement? i'm going to run 18x7.5 wheels with 40mm offset will this combo clear a 2 1/2 BD'ed 4x4 bed? any help or pics of this rearend installed would be great. thanks in advance.

Originally posted by dragginmazda86



i have heard on here that this rearend is wider than the stock mazda axle so i was wondering if anyone had the exact width measurement? i

The measurements are on here... i've posted them before... i'll try and dig them up for ya.

I am running a +40 and will have a 4x4 bed... i am also body dropped 1.5" away from the doors... so you should be fine.

Stock Mazda: Front: 58 3/8" Rear: 58 5/8"

RX7 IRS
Rear: 59 1/8"

Originally posted by dragginmazda86

i'm going to run 18x7.5 wheels with 40mm offset will this combo clear a 2 1/2 BD'ed 4x4 bed?

Yes. Corey and I discussed this at length some time ago, the camber will make you tuck really well, but you still need the high offset because the IRS sheds camber so quickly. That 1/4 inch per side wider that the IRS will be doesnt seem like much, till you realize it adds ~7mm offset in extra needed per side. So if a +32 fits the stock rear, you would need a +40. The 4x4 bed gives about a 1/2 inch to 3/4 inch of extra clearance, but only at the wheelarch, that extra clearance quickly goes away as you move up the bedside. For a bodydropped truck, there is only a slight difference between having a 4x4 bed and having a 2wd bed.

So anyway, yes your wheels will fit. I plan on mounting my IRS a little higher, which will make me need a little more offset, but will also minimize the toe change the trailing arm rears will have with big wheels and lots of drop, and will keep me from chewing up expensive tires.

yeah mine toe's in slightly... not very noticable... but im sure i'll notice the wear and tear on my tires when its finally on the road... my tires were cheap though! haha.

what would be better one out of an automatic or standard rx-7? also i'm running a V8 this rear should be able to handle the extra power correct?

yeesh that is going to be a highway screamer, RX7's have 3.90 rear gears. You can get a turbo II rear end of the same year, it has bigger axles and LSD, but you will still not be very happy with the freeway rpm. Someone mentioned on miata.net about adapting a new ring and pinion gear to lower the rear gears for a V8 swap in a miata, but it was not cheap or easy by a long shot.

I would assume it could handle the power. There is a lot of guys that throw V8's or build up their rotaries to make a lot of power and they are using those rear ends.

Originally posted by Russ-D



yeesh that is going to be a highway screamer, RX7's have 3.90 rear gears. You can get a turbo II rear end of the same year, it has bigger axles and LSD, but you will still not be very happy with the freeway rpm. Someone mentioned on miata.net about adapting a new ring and pinion gear to lower the rear gears for a V8 swap in a miata, but it was not cheap or easy by a long shot.

I have the 3.90 Gear Rear with Brand New Built V8 driven for awile . In the City streets its great fast as hell off the line . On Highway its a Screamer high RPM . I would love to get a new set of Gears for this made or possible swap. Could you point me in the right direction RUSS if possible

sorry, I wont be able to help much on this one. I can suggest you go to miata.net and ask, I was only regurgitating what I read. The 1st gen miata and the 2nd gen RX7 use the same diff from what I remember.