99c5vert

My 7 replica has a solid rear from a 1980 supra. I think this car had something like 90-110 horses. The rear does have a TruTrac diff, which is a Torque sensing design.

The rear suspension is a 4 link design, with 2 radius arms, 2 torque arms and a panhard rod.

So far, it has held up with the LS1, mostly because (I think) 225 tires are easily blown away on a 1650 lb car. I'm somewhat worried about increasing traction. I am suffering from axle hop, and have broken a panhard rod as a result...

I know RX-7 LS1 conversions are pretty popular. Do those guys normally stick with the RX-7 IRS setup, or switch to a solid rear?

I'm kind of thinking about the possibility of replacing my solid rear with a subframe to support a IRS setup.

The car's handling is very good right now, so I'm almost guaranteed to screw that up as I sort out the IRS setup.

My gut tells me when it's all said and done, the IRS may end up heavier than the solid axle setup I have now.

I'd apprecieate thoughts, pics, pros and cons, etc... from any of you who have some input.

Scooter70

iTrader: (1)

I believe that the FC RX7 guys use the Turbo II rear which is stronger than the non-turbo rear. Depending on the width of the car, what about using C4 Corvette parts? They're very popular among those updating older Corvettes (and other full-size GM cars) to a newer style suspension. The 6 speed cars had a Dana 44 (I think?) which is supposed to be stronger than the one in the automatic cars.

Just a thought.

-Matt

99c5vert

Thanks. That is an option. I'm worried about weight though.

I'm still at the stage of whether it's even a good idea to think IRS.

manman

iTrader: (3)

The 93 and newer rx7 rear end's are not to bad all the weight comes from the center section the housing. Its a giant cast Iron thingiee. That's why they get a center section from a 99+ IRS cobra. Its aluminum, and theres more gear ranges, and stuff.

Schitzo

iTrader: (6)

There is a bunch of IRS setups out there you could look into: jaguar, RX7, Thunderbird, GTO, C4 Corvette.

I am most familiar with the C4 IRS. I have one and will put it in the next 70-73 camaro I get. It is all aluminum and the shocks and monoleaf can be replaced with coilovers. I don't know how much it weighs but I would not describe it as a heavy unit.

The dana 44 out of 84-96 6sp cars is the way to go. The reason I am going to use this rear end is because it more adjustable than a factory leaf spring setup and minimizes axle wrap and wheel hop which translates to better handling.

With a properly installed C4 IRS, you can maintain the good handling and it can handle more power than your current setup. Here is one on a chevelle. The coilovers are not installed yet.



On the other hand, you could just beef up your current setup and be done with it since it already handles good.

CHarris

iTrader: (5)

A vette rear would be pretty easy to work with. You can get a Dana 36 for about $300-500 end to end and start working on it. The D36 might hold in your car since its 1/2 the weight of a stock vette. Later on you could step up to a D44 center... all the other parts are the same. You can see from the pics that it could be narrowed easily if required. Just shorten the half shafts, swap to rod end camber rods (the lower rods in the pic) and swap in rod end toe bars and you'd be set.

The C4 also uses two trailing arms per side that are very short due to the driverseat location right in front of the bulkhead. In your car you want/need a very compact system too. Might be a very good choice for you.

AND its got that sweet chevy lug pattern that we all love... if that matters to you

redmist

I just saw a vid of a Z06 doing a 8.46 1/4 mile. IRS has gotten a lot stronger.

I'm using Porsche 930 CVs with chromemoly cages and chromemoly stub 28 spline axles. The BMW rear I'm using is good for 580 Ft Lbs of torque.
I'm partial to the german stuff as it is usually over engineered, much stronger than the stats they publish.

93Polo

iTrader: (5)

I agree. How much power are you planning on running? The D36 maybe a good option.

If you are fabbing everything up a C5 IRS with a Ford Cobra 8.8" chunk might work.

99c5vert

Schitzo PM'ed me a diagram of the C4 setup. The trailing arms look very similar to the length of my radius arms on my rear. So that might work... and yes, I'm partial to chevy

99c5vert

My car will not require much power (400 horses will be plenty in the future).

John McGraw

400 horsepower and a manual transmission will prove to be too much for the D36 rearend. With this level of power, a D44 rear will be a much better choice. The D36 will live real well with this much power on an automatic, but the shock loading of the gears with a clutch type trans is just to much for this rear to live with long term.


Regards, John McGraw

unclemeat

Also check out VBS on an internet site!!
They have MANY vette upgrades!!!
Hope this helps
(VBS= vette braking systems - I think)
- Unclemeat

badtexasZ28

just to clarify, the 84 vette was only optioned with a D36 in it....i found out the hard way since i bought the rear out of one for my styleline conversion

JD_AMG

You have an LS1 in a 7 replica!? Dear god! Pics now!

99c5vert

here you go... couple of pics, followed by a short vid...




This is from the first drive in February after the engine conversion... I think the tires were trying to tell me something

http://filebox.vt.edu/users/arebrahi...ioncropped.wmv

Schitzo

iTrader: (6)

Thanks for the info. I stand corrected.

Yo 99c5vert, cut the tires some sluck

99c5vert

I got a set of Toyo Proxes RA1's... now they just spin quietly

93Polo

iTrader: (5)

Usually I would agree but the 7 has much less weight and he most likely will not be drag racing searching for 1.6 60' or quicker times on slicks. D36s have lived deep into the 11s in C4s granted that was behind an automatic.

99c5vert

That's true... if it can live in a 3000 lb car into the 11's, I'll never break it.

One question I have though... currently I have a TrueTrac diff, which is similar to a Torsen or Quaife type differencial. Do they make that for the C4 rears? I have never had the opportunity to do a side by side comparison, but from what I've heard, torque sensing diffs are better for autox applications. Also, there are no clutch packs to wear.

John McGraw

You may be right, but I tend to allways lean to the cautious side. I have used D36 rears on 400 hp cars with automatics, but using them in manual transmission cars never left me with a warm fuzzy feeling. In any case, the D44 is a lot more durable center section even though they are more bucks at the junkyard.

Regards, John McGraw