maztang (ryan)
+1y
found this through a series of talking to peeps. a guy on street source told me to go to fordcouriercollector.com cause he is from australia and i was talking to him about dropping a v8 in my 83 and doing the rhd conversion. well i went to the site and saw that he posted this up about the rearend that i want to drop into my 89...
...The stock RX-7 rear axles are amazingly durable (internally, the parts are similar in size and even stronger than the Chevy 10 bolt that comes in the newer Z-2. While we offer bolt-in narrowed rear housings and axles for the 1st gen. cars, unless you are REALLY going to abuse it, we suggest you try the stock rear first. There are many V-8 powered 2nd gen RX-7s on slicks running mid-10 sec 1/4 mi times on the stock rear, a feat that requires 475-500hp. The clutch type limited slip up thru '88 is very strong 4 pinion style much like the diff design used in the Dana 60. Although it may be hard to believe, the rotary powered RX-7 drag racers are probably harder on the rear than the V-8 powered guys. The reasoning behind this is that most all rotary powered RX-7 drag racers use a manual transmission, a metallic clutch, and a heavy flywheel spinning at 9-10K rpm to assist the low torque rotary in launching the car. An incredible amount of stored energy is released into the rotary drivetrain to launch the car, enough to launch the car well even if the rotary engine died on the line. In the case of the V-8, plenty of torque is on tap to allow low rpm starts, also making it much easier to modulate the power to make the most of available traction.
...Here is a list of the rear axle gear ratios that came stock in the RX-7...
'79-'83 ALL.......................................3.909
'84-'85 ALL (except GSL-SE)..............3.933
'84 GSL-SE.......................................4.083
'85 GSL-SE.......................................4.077
'86-'91 ALL (except automatic)...........4.100
'86-'91 automatic (except convertible)3.909
'88-'91 convertible............................4.100
'87-'91 Turbo II / GTU.......................4.100
'89-'90 GTUs (T-II rear).....................4.300
'93-'95 w/ manual trans....................4.100
'93-'95 w/ automatic trans.................3.900
...The 1st gen RX-7s all used a 7" dia. ring gear.
Cars with rear wheel disc brakes, such as the GSL-SE, all came with a limited slip differential.
The '84-'85 cars used larger diameter axles, and have a larger spline in the differential side gears.
The axle side gears can be swapped, allowing the different axle diameters to be mixed and matched.
Higher gear ratios for the 1st gen cars are available, a 3.683 ratio (came in the '79-'82 RWD 626, and is available new), and a 3.308 ratio (came in the '82-'84 diesel powered Ford Courier and Mazda B-2000 pickups, not available new anymore).
The '79-'85 12A cars all had a 4 on 110mm wheel lug pattern (hard to get wheels for).
The '84-'85 13B powered GSL-SE cars had a 4 on 4-1/2" wheel lug pattern (same as 4 lug Ford Mustangs, etc).
This is from www grannysspeedshop com