treynon

how did you get the custom driveshaft made?

Hyper4mance2k

iTrader: (40)

if it makes power its helpfull. Say you add aturbo and an intercooler. more weight, but more power too And there are plenty of people running over 300 on the stockrear end. It's not an issue unless you plan slicked drag launches in your rxey

racintang

Grannys speed shop sells a ford 8" rear with choice of gears for 750. complete with all stock mounting point for the Rx7 suspension. It's as strong as a 12 bolt chevy plus you can do gear swaps without pulling the whole rear. Hogs head design.

Jon_Valjean

You get a good ruler, take some measurements, track down a FC manual driveshaft and take it to an auto machinist. US$200 later, you're sorted.

Unless your Uncle happens to own the said auto company and you get it done for free

cds00bsmg

iTrader: (1)

ford rear ends are known to be stronger than a 12 bolt GM anyway. The 8.8" can be found in mustangs, and the ones in FOX body units are 4 lug, I think some have rear disks as well.

However $750 for a rear end setup isn't that bad actually.

gerbraldy

looks really nice, I was wondering if the 8.8 was too wide, but now I guess it is not. I'm going to go get a 87 lincoln mark VII for the 5.0/tranny in about 1hour, could I use the rear end out of that car in the FB?

85rotarypower

Yes you can use the rear end from that, just it might be too wide. I'm not sure on that though.

It seems this was never really cleared up, but the 89-97 ford thunderbird, mercury cougar and lincoln mkIIIV all have IRS. Depending on what engine the car had and what year it was, it could have either a 7.5" or 8.8" in either open diff or LSD. Also, it might be interesting for you guys to know that the ring and pinion is the same as the solid axles. I'm not sure about the whole diff carrier being the same, but it could be. Trust me on this. I own a 97 thunderbird with 8.8 rear and LSD, and I know for a fact that its IRS. 88 and earlier versions of these cars were based on the same FOX chassis as the mustang, while the later ones are based on the MN12 chassis.

Wankelguy

I've got a set of 13X7 alloy wheels that came off my friend's GT3 RX3 that I'd like to sell. The fronts have been re-drilled for 4X110mm and the rears fit the 4-lug 8.8" Ford rearend.

stilettoman

iTrader: (1)

You guys are doing a lot of speculation and guesswork about things that are very well understood and researched by people who have been doing V8 swaps for years. I also bought a Lincoln Mk VII to get the roller cam engine and automatic overdrive that I used in my 84 GSL. I still have the 8.8 rear end, but the problem is that it is very difficult to modify properly for the 1st gen installation because you cannot weld to the cast iron center section. It is also very heavy.

I also bought an 8 inch rear end from a mid 1970s Ford Maverick, and it has a 5 bolt pattern for the wheels and is exactly the same width as the original 1st gen RX-7. It has a 2.75 diff, compared with the 3.9 stock Mazda, but lots of ratios are available, together with limited slip diffs. It is all steel , so you can easily weld the brackets on.

I have never used either one because the stock 1st gen differential is light weight, very strong, and quite adequate for street use unless you drive like a complete idiot. The big reason for the conversion is if you don't want to use an overdrive tranny. I am running the stock Mazda and I turn 2400 RPM IN OVERDRIVE at 60 mph. That is really much faster than necessary with a V8 in such a light car, but my engine is well balanced and I am happy with the whole setup. On the freeway, I can out-accelerate most cars without ever shifting out of overdrive!

Before you waste a lot of time and money, I suggest you read the available info on Grannys web site. All this stuff is discussed in detail there.

www.cardomain.com/ride/646433

setzep

I can vouch that a -se rear can take axle hop with 300rwhp. I've never had slicks on the car though.

peejay

Mustang 8.8's have funky thingies on the center casting for the upper control arms.

Ranger pickups, on the other hand, had 8.8's with the 4 liter V6. So did all Explorers, many/most of which had rear disc brakes with proper drum-type e-brakes. And with leaf spring suspensions, it's super easy to get rid of all of the bracketry and put on something more RX-7 specific.

Plus, trucks are a lot easier to find in junkyards than Mustangs.

peejay

Nope.

The 8.8/7.5 rear was introduced sometime in the vicinity of 1980. Before that, the 9"/8" was used.

The 8.8 and the 9" are two wholly different rears! The 9" is really strong, having a bearing support on both sides of the pinion gear and a large pinion offset. Centersection is a dropout type (like the Mazda 7"), with the axles retained at the flange end. Downside is the end pinion bearing cuts into the available differential space, which is why generally you use a Detroit Locker or a spool, since clutch type diffs will only have room for *one* set of clutches. And the high offset means reduced efficiency. Plus, 9" rears are worth a *lot* of money...

The 8.8 is a "GM like" rear with a center casting that the axle tubes press into, a diff inspection cover on the end, and C clip axle retention. They are almost as strong as a 9", and they have less pinion offset for better efficiency (for reduced strength), but the C clip axle retention scares me. If you break an axle, the wheel can leave the car. (Seen this happen a few times) C clip eliminators work for drag applications, but they *cannot* be used for regular street use and especially not road race type stuff, since the eliminators do not deal well with side loads. Plus, they leak.

If you're doing a custom housing anyway, you can just have 9" style axle ends put on. OTOH, you might as well have a 9" center too...

evil_motors

iTrader: (3)

damn peejay you are a dork.. lol just kidding.. you do have alot of knowledge though.. do you read everything that has to do with cars?

Jon_Valjean

I'd like to point out that my choice of modification was based on what was available. There's really not that many big-engined rear-wheel drive cars in this country, and certainly none with exactly the same width as required. I had no choice but to narrow something, so it may as well have been a 8.8" unit. Importing something wasn't an option - last time I imported two lower strut assemblies (30 pounds) from the states, it cost US$200 for shipping. I shudder to think what a 150+ pound rear axle would cost.

This is a temporary measure as eventually I'll go IRS in the rear, and I have to say - if I break a 8.8" 4-spider LSD it would be at launch (so the wheel leaving the car won't unduly worry me) and on top of that, I'd have to be SERIOUSLY abusing it.

I don't seriously abuse cars, so I'm happy with this for the meantime.

gios79rx

im gonna be doin this to car 8.8 hell yea

mbinkley2

Jon_Valjean

Wow, old thread. You might be right but I'm not using a Ford axle anymore so I can't confirm. Swapped to IRS a couple years back.

https://www.rx7club.com/build-threads-293/nissan-240sx-skyline-irs-road-legal-81-fb-completed-plus-fc-1101100/