strongest rear end?
 

Dear RX 7 guys,

I'm doing a v8 engine swap into my '86 GXL via the Granny's Speed Shop Kit. The motor I'm putting in is a 383 chevy. It makes 380hp and 460lb/ft all under 5500rpm. The motor was originaly built for a suberban, but I thought it would be "funner" in an RX 7.

Anyways, every other person I've talked to has told me the stock rear end will either hold together, or break on the first launch at the drag stirp. I'm a stranger to the import / mazda stuff, so I have no idea how strong these rears are. Some guys have told me to try and find a turbo II rear... others have said to put a ford 9" in it (which would be WAY too overkill-- a chevy 12bolt would hold together just as good at my level).

What I'm wondering is, has anyone ever tried putting a corvette rear in one of these cars? It would be plenty strong, and keep the cars IRS (unlike the ford rear). If people are swapping ford rears in here, how hard would it be to swap a vette rear instead? And how much would I need to change? I have a friend who can pretty much make anything out of metal, so fab'ing something unheard of wouldn't be a problem... so please, "let me have it" with all of your suggestions and or concerns!
Thanks,

Brandon

Hey, I forgot something...

If the rear I have now is strong enough, does anyone make smaller gears for it? All that torque (thru a 200-4R) with a 15" tire and 4.10 gears will be pretty unpractical... running out of gear on your way to an 11 sec. pass in the 1/4 mile would be dissapointing. But running out of gear in the 1/8 would be rediculous! :)

Thanks again!
Brandon

the TII diff might be strong enough.

What kind of tires are you going to be using? If you're still using skinny radials, then the stock rear end will be fine, because you won't have enough traction for it to matter. You'll just spin your tires. But if you have grip, then the stock diff will blow up on you.

No idea about the Corvette diff. There are Ford diffs that use IRS, though i'm not sure if anyone's done a successful install.

The tallest gearing you can get for the stock diffs (open/lsd/tii) is 3.90, which is still pretty short for your purposes.

Off to other engine conversions

Cause... uh... yeah... a question about diff strength clearly belongs in other engine conversions... :mad:

About the tire size...
I'm not sure yet, some people have suggested going to the taller 16" wheels (that would help my gearing problem) but whatever wheel I end up with, I plan on using a BFGoodwrich drag radial when I race it now and then. I have a Buick GN and they work extremly well... so it looks like I'll be looking for a stronger rear soon :)
I also have a 91 rx7 parts car with a good rear... is there anyway I could beef that up at all?

(And Dgigitalsolo, if I hadn't mentioned I was putting a small block in my mazda, and only asked about a strong rear for the second gen rx7's my thread probably wouldn't have been moved smart ass!)

And hey, does anyone know how I can correct the thread subject / title to read strongest rather than stringest???
Thanks for the help again!

The reason I complained, is because, in this section you'll likely get no reads, and no help. And every V8 thread on this forum gets moved here, regardless of the merit. The little rotary kids can't STAND for someone to be different. I happen to be putting a 383 in my 2nd Gen as well. A TII rear end can take a LOT of punishment, there are plenty of guys in the low-mid 9's on the stock TII (S4) rear end. Including GNX7, (edit: actually he's in the 11's) who runs a GN drivetrain in his 2nd Gen. www.torquecentral.com check it out if you haven't. You won't find help on this forum.

Oh, and can the "smart ass" crap, I wasn't complaining to you. hang out for a while, and you'll see what I'm talking about, until then, try and be nice-

Sorry,

Hey, I wondered about that after I had worte it (if you were complaining or being sarcastic). I've just been on too many [other] car forums and asked legit questions and had buttheads give me a hard time, I thought you were one of them, sorry again!
And thanks for the help! I have a few people looking for turbo II rears now... how much will one of these rear ends in good shape cost me?

No problem. Didn't mean to come off defensive, I just got confused when I got yelled at for being on your side. ;) Sounds like a sweet project you've got going regardless. Are you on torquecentral? Definitely keep me up to date. :)

Get an S4 '86-88 T2 rear end. They for around $150. Halfshafts are anywhere from $25-45 each. The LSD can be rebuilt with a $50 clutch pack and they are very strong if you ever need to. The S5 '89-91 are non rebuildable and are bank to replace ($500-1100). Guys are running 9's with the T2 unit as noted. I've had mine in for a few years and probably 25K hard miles with no problems.

If your N/A unit is an LSD it should work fine. To check jack up the rear of the car and rotate one wheel. If the other tire spins in the SAME direction you most likely have LSD out back. There is a little LSD tag on the oil fill bolt hole also unless it has been discarded.

You need the T2 halfshafts also as they are specific. The pinion flange where the driveshaft mates up is different than the N/A unit so make sure you do the driveshaft once.

If you don't have an overdrive transmission plan on getting one. A non overdrive tranny just is not a good combo with 4:10's and you will be pegging your rev limiter if you plan to 1/4 mile the car.

Here is the V8RX7 messageboard link:
http://www.torquecentral.com/forumdisplay.php?f=11

Later,

GNX7 (Mark)

Hey let me be sure...

The car does have an LSD rear in it right now... however, we have a guy who says he can get a TII rear and axles for 200 bucks. But before I get them, you're telling me I need to make sure that the turbo rear is from an '86-'88, right???
And by the way, since I'm still pretty new... what's an S4 / S5... and everyone keeps talking about FB or FC cars, what does that mean?
Thanks again for the help!
Brandon

FC (2nd generation RX-7)
'86-88 S4 (Series 4)
'89-91 S5 (Series 5)

I'm not sure how to tell if the rear is from an S4 or not..... but for $200 get it anyway. The size of the pumpkin itself will be much larger than the N/A one.... however it is still a bolt in :).

-MC