FDNewbie

iTrader: (10)

LOL. Hey, I have no idea whether or not it works...that's well beyond my knowledge base.

Oh and Rob, you back in town yet? Cuz I haven't seen ya in a minute...

jimlab

BTW, here's an interesting document on the changes made to the T56 for the 2006 model year...

http://www.cadillacfaq.com/faq/answers/pdf/t56-06.pdf

Howard Coleman

iTrader: (6)

an interesting thread.

i know this has been briefly touched upon and has been apparently discarded as an option but what about starting w the corvette transaxle?

IF it could be utilized it would solve a whole lot of problems. it would offer a transmission solution, it would offer a rear gear solution and it would, w a bit of machinework, offer an axle upgrade.

i have not closely studied the dimensions and literally don't know whether the clutch is on the engine or the nose of the trans...

i understand it would require a bit of floorpan surgury and of course that MIGHT be prohibitive relating to the degree. if the clutch is located rearward what about relocating it back on the engine and adapting the torque tube to the rear of an FD bellhousing?

please forgive my barging in here but this powetrain problem will become a larger issue as more FD's adopt methanol AI and can routinely turn the boost up to whatever they wish w little egt or knock. it has already prompted a rush to double disc clutches.

howard coleman

wanklin

iTrader: (2)

Howard, Chris C has looked into this a bit. Perhaps he will chime in.

CMonakar

Hi Howard:

That was part of my original 20b project blueprint. Major chassis work would have to be done to accommodate it if it is possible at all. I worked closely with a T-56 shop (had all the measurements) and spent an hour or so on labor with the chassis fabricator trying to figure out if we could make it fit. Our conclusion was -possibly.

What makes it tricky (which I say without having done it) is the length coupled with the width when positioned at the height necessary to line it up with the motor. It is not a true transaxle; it is a full size gearbox bolted to a differential. The clutch is located in the front of the car, but there is still a sizeable bell housing-like piece where the driveshaft connects to the box.

When positioned with the center of the dif where the stock unit is, the gearbox extends forward to roughly where the seat backs are depending on your height. I'm not sure the tunnel could be widened enough to accommodate the box without interfering with the seats even assuming the vinyl center console is eliminated or modified). Also, routing the exhaust around the gearbox would not be easy. I recently test drove a C6 and noticed that the transmission tunnel is about 2x as wide as the FD's behind the seats. I guess that is why.

-Chris C.

Howard Coleman

iTrader: (6)

hi chris,

looks like you a few steps ahead of me. i am going to look very carefully at the transaxle as it solves a lot of fd powertrain problems.

my inclination is to run the corvette axles and design a rear hub that will accept the corvette wheel bearing. keep all locations-pick up points stock of course. perhaps, shorten the axles. the track is 60.7 V 57.5.... however part of the dimension relates to wheel offset which i haven't checked yet.

add a transaxle and say good by to transmission, rear end, axle worries.


i am planning on running the RacingBrake equivalent of the C6 brake package anyway. i could then have the 13.4 inch rear brake rotor w the corvette drum emergency brake.

i do have alot of electronics in both package bays but i am sure i could find another spot. probably in my spare tire well along w the meth fuel cell.

hmmmmm,

howard

wanklin

iTrader: (2)

It's certainly an interesting idea, although prohibitivly expensive for your average FD owner. If anyone can make it happen, Howard Coleman can ;o)

Here's a list of things that I think will need to be done: (assuming a rotary power plant is used)

1. widen tunnel and perhaps create a new minitunnel on the passenger side to allow clearance for the exhaust.
2. fabricate adapter plate for torque tube bellhousing, or better yet, adapt torque tube to mate with FD bellhousing and clutch. (this would save a lot of hassle.
3. custom clutch/hydraulic cylinder and input shaft to torque tube.
4. adapt GM or Wilwood clutch master cylinder.
5. most likely will have to shorten torque tube and drive shaft.
6. adapt axles to fd wheel bearings or swap to C6 setup as you said.
7. modify rear subframe to provide mounting points for transaxle.
8. adapt corvette shift linkage to FD
9. incorporate T56 sensors into wiring

Howard Coleman

iTrader: (6)

thanks for the list...

yes, i like adapting the torque tube to the fd bellhousing.

as to prohibitively expensive.... if you are running 500 hp+ and shelling transmissions, rear ends and axles... and you consider the alternatives, and you can weld and machine for close to zip

and,

you would be doing it ONE TIME.

it is only partially insane.

howard

wanklin

iTrader: (2)

I guess so, around NoVa machining and welding can costa pretty penny, that is unless you do your own work or have a friend. I say go for it.

I'd be interested to get my hands on one of these torque tubes and see what they look like inside. hopefulll the input shaft is thick and long enough that you can just machine the OEM shaft down to mate with the FD clutch and pilot bearing.

I'm also starting to think that a custom rear subframe may be in order as well.... That's another Chris question.

Howard Coleman

iTrader: (6)

yes, ideally machine the nose of the TT to mesh w the mazda clutch etc.

it would be too much to screw w a chevy FW clutch starter blah blah. then you could use the FD starter, clutch mechanism FW etc. that should be the way to go.

of course i at this moment don't have a clue as to what is actually there to work w.

we have a really big corvette dealer nearby so i just may stop by tomorrow...

hc

gracer7-rx7

iTrader: (16)

Aren't there other real transaxles that may work? Why just the 'vette? Is it availability, price or what?

Just curious...

CMonakar

My plan was to use the FD bell housing. Either way you have to make an adaptor, might as well go the route that doesn't require re-engineering the clutch/starter systems. The driveshaft is support by a bearing at either end of the torque tube so the adaptor could be relatively simple. The end of the driveshaft would obviously have to be modified or replaced.

wanklin

iTrader: (2)

Availability, support and stoutness. The T56 was built for expandable LSx/Viper V10 power and can be readily located, and upgraded.

It would be ideal to use the FD clutch setup because the LS hydraulic clutch release is definitly a weakness of the Tremec design. Most F-body guys prefer the old Borg Warner T56s for that very reason.

FDNewbie

iTrader: (10)

Chris, I'm not sure why your method (whatever it was) involved soooo much work and custom fabrication. jdmluver fit the T-56 in his FD with little to no fabrication work. To quote him (from https://www.rx7club.com/3rd-generation-specific-1993-2002-16/t56-trans-install-474847/):

Howard, re: doing the upgrade once, and doing it right, how about going w/ the Jimlab 8.8" IRS Cradle in the rear, completely eliminating the PPF (no torque tube substitution), and fabricating independent tranny mounts/braces, and calling it a day? I couldn't see how you'd be breaking *anything* that way...and the only custom part would be the driveshaft, which is EASILY done - and in CF at that

~Ramy

wanklin

iTrader: (2)

haha, that's because it was all custom made for him by G-force. Everything about that trans, clutch and cylinder is custom tailored. Easy to install would be more like it ;o)

Jim's Cobra IRS looks promising, but still needs to be proven, but otherwise I agree. Not sure I'm convinced that an 8.8 rear has enough *** to warrant its use for high HP applications like Howard is describing. There's no doubt that the Corvette diff is stronger. I believe the FD rear is plenty strong when mounted properly, just may need to look into stronger axle stubs. I guess we'll have to wait and see ;o)

jimlab

Proven how?

FDNewbie

iTrader: (10)

Slow down there cowboy All they did that was custom was special treating on the inside of the tranny, some upgraded gears (strengthwise), and a bolt-on-outta-the-box tranny to clutch setup. It's not like *anything* has different dimensions. In fact, D&D Performance works closely w/ G-Force, so anything G-Force offers (in terms of an out-of-the-box tranny to clutch setup), D&D can provide as well. I know; I spoke w/ them

I'll leave you two to duke this one out on your own. But I will say this. 1) I have yet to find Jimlab wrong on something, 2) Many of the parts he's using were made to withstand the brute force from much heavier and more powerful domestics, so I personally think it's a stretch to think it wouldn't be much more stout than any OEM parts-based setup.

~Ramy

wanklin

iTrader: (2)

No you slow down Chief ;o) How do you think the tranny input shaft fits into the Mazda pilot bearing and is the proper length? Also, How do you think the non-RX-7 clutch bolts to the flywheel and how does the flywheel bolt onto the engine? How does the hydraulic cylinder have the right throw? and what clutch master cylinder fills it? What pedal? clutch line? what adapter was needed to bolt to the engine? What aftermarket bell housing? What tranny mount? not that any singular item above is difficult in itself....

I'm not talking internals buddy ;oP

I think the Cobra IRS is a sweet concept, it just needs to be taken to hell and back in one piece before it is proven in my mind. Jim, you mentioned in another thread that the Cobra mounting configuration is the reason that the 8.8 Cobra diff is known as an Achilles heel for Mustangs and that your configuration corrects these problems. Would you mind elaborating? How exactly does the failure occur? what is the most common failure exactly?, and how have you corrected this issue?

cheers

Howard Coleman

iTrader: (6)

one item for me is that i am pretty much committed to the FD bellhousing. my twin t04 setup uses two 3 inch downpipes so i need the space between the FD bellhousing and the tunnel. once past that spot they turn and run side by side into a Burns Stainless 2 into one just before the midpipe.

should i go w a normally situated T56 the trans case wouldn't be a problem w my exhaust. i would graft the T56 to the Fd bellhousing.

if i did the corvette transaxle of course i would just graft the tube to the back of the FD bellhousing.

hc

jimlab

A properly sized bellhousing and a pilot bushing, if necessary. This isn't a new concept.

Why use a non-RX-7 clutch and flywheel? Why not just get a clutch disc with a 1-1/8" x 28 spline center hub made instead?

It's adjustable, but you will need a push style clutch cover as opposed to the FD's stock pull style.

Wilwood or other aftermarket M/C.

Stock. You do like to complicate things, don't you.

Braided line. It grows on trees.

See below.

You can use a stock bellhousing and an adapter plate, a universal aftermarket bellhousing and adapter plate, or have a custom bellhousing machined like AutoIllusions did.

Custom, obviously, since the FD has none from the factory.

Seems to me that the drifter who slightly bent the first one, then bent the tabs on the second one because he didn't tighten the bolts properly is a good trial case. If not, the guy currently running 10.5x with a 100-shot of nitrous (609 RWHP) is.

You can blame me for a lot of things, but not for people being slow to install my parts in sufficient numbers or not having enough RWHP or low enough time slips to satisfy whatever your need for proof is. It's not like I reinvented the wheel here. The differential is proven in much heavier cars making far more horsepower and torque than most LSx conversions will.

No problem.

Too many bushings. To give the Cobra a cushy ride, Ford "double-bushinged" the rear suspension (see image below). Not only are there rubber suspension bushings (as you'd expect), but there is a second set of 4 rubber bushings connecting the rear subframe to the car. There is also a big spongey square bushing connected to only one side of the rear of the differential (not shown).



The end result is that you have a car with a lot of power that is prone to wheel hop and generates a lot of complaints about drivetrain noise (the Cobra I drove clunked loadly on each shift and it was brand new). Still, the IRS differential typically tends to hold up well until you take the car to the drag strip.

The mounting tab on the cast aluminum rear cover typically sheers off. It results in the loss of the differential fluid (obviously), but typically no damage occurs to the internals.







Cobra owners typically replace the rear subframe bushings with Nylon bushings to eliminate some of the slop and install a brace on the differential cover.



I followed in the footsteps of what has already been proven to work on Factory Five Cobra kit cars behind big blocks (top two pictures) and duplicated their mounting system for the FD (bottom picture) which supports the rear of the differential evenly and does not allow excessive twisting. This has worked fine so far, but I'm also developing a rear brace that works with my cradle for "serious abuse" cases.

Howard Coleman

iTrader: (6)

wow.

looks like the way to go. thanks for the info.

hc

wanklin

iTrader: (2)

Thanks for the post Jim. My point is that the statement, "jdmluver fit the T-56 in his FD with little to no fabrication work" is a bit of a stretch. Not to say that it is incredibly difficult to mate a T56 to a rotary power plant.

I agree that it is not you fault that your parts are collecting dust. I look forward to seeing these procrastinators install these dusty IRSs and validify your design and hard work. It appears that you have a solid design, my only concern would be NVH since the front end of the diff is solidly mounted to the subframe. Nice looking piece though I must say.

I think the FD housing is victim to the same mounting issues, and is stronger than most people give it credit for. But talk is only worth so much. I'll pound on my Ibruglio IRS and keep everyone updated with real-world feedback.

jimlab

Not by much. Most of the parts are probably available off someone's shelf.

I know I've seen rotary T56 adapter plates somewhere before. Probably Australian. Probably even have a picture of one somewhere in my ~10-year archive.

So far, the only one who has complained has been Chris Heiser, who bought Moroso gears that whined excessively. Of course, my cradle got the blame for everything, as usual. LS1-FD panicked and changed his rear mount based on Chris' posts. Still, it's not a bad idea to add bushings to the rear mount as long as they're rigid enough not to allow excessive movement.

If you take a look at pictures of broken OEM casings, it may be cast iron, but it's extremely thin to keep weight down... compromising its strength. The 8.8" housing is much stronger despite being aluminum (it's a much thicker casting) and lighter (14 lbs. vs. 36 lbs.).



There's more here than "talk". Ford didn't put the 8.8" IRS differential in the highest powered sports car in their history* because it was weak. Just because the application has changed doesn't mean the differential starts over with no history.

*The Ford GT is technically a supercar and has a transaxle anyway.

FDNewbie

iTrader: (10)

Rob, call G-Force or D&D, and ask 'em if YOU need to make ANYTHING custom. They'll tell you NO. G-force especially has been tailoring to the need of high hp FDs for YEARS (esp. the Puerto Ricans). Like Jim said, EVERYTHING you need is available "off the shelf." You only need to place an order, and provide them w/ the cash.

AGAIN, ask jdmluver if he had to hunt down a SINGLE person or part to make ANYTHING custom. I'm sure he'll tell you no, b/c G-Force has some guys who are VERY familiar w/ the FDs. In fact, one of them OWNS an FD So yes, my statement of "little to no fabrication" still stands

Heck...tell ya what. If fitment (to my specs) isn't an issue, I'll prove it to ya

~Ramy

jdmrxluver

there is no serious modifications look at the pics on the first page that i posted, the only real mod is mounting is the starter because you have to grindoff for starter fitment. Mike at gforce owns an fd himself.