Arnie Chamberlain

Car is an 02 coupe, 6 speed, stock motor, A&A Supercharged, 535 horse on a Dynojet, 305-35R18 Nitto 555Rs (Drag Radial) all the time, primary uses are commuting and the occasional trip to the drag strip.

When the car was N/A I installed a 04 Z06 trans in it along with a SPEC twin disc clutch because the stock trans wasnt shifting well, I have since read that the standard coupe trans ratios are better for high horsepower cars. I still have the stock trans sitting in the garage.

Car has 3.42 rear end and I took it apart and installed C6 Z06 half shafts and C6 Z06 steels, frictions, and belleville washers in the posi.

Just the other day I blew the passengers side case out of the stock diff with a good launch on heated tires on the two step. After two years of abuse I guess it was my time.

My question is where to go from here....

• Another stock or C5Z06 3.42 diff, pull the C6 parts out of my old one and install if they are in good shape, replace if they are damaged.
• Worth ponying up for an aftermarket diff? Switch ratios? My fear is that 3.73s plus the Z06 trans is really deeply geared.
• Get a trans/diff brace or no? Already have the Pfadt trans mount but still have stock motor mounts? Replace motor mounts?
• Which trans brace is suggested?
• Would I have any success running a 3.15 diff with a Z06 trans or would that make the car a real slug?

Suggestions are appreciated.

4DRUSH

Call RPM Transmissions

Arnie Chamberlain

That's very helpful advice. What would be the benefit of calling RPM vs building the diff myself, keeping in mind that I already have all the Kent-Moore J Tools for rear end service, have a shot peener at work, along with the proper dial indicators and whatnot, and know how to set up a rear end. Back in the day of building Mitsubishi drag race transmissions (old DSMer here), we would just shim them a little tight to get more life out of them.

Looking on their website I do not see any difference between their stage II rear end and the one I built for my car, if there was an aftermarket case they were using, or anything like that, I could see it, even the stage III and stage IV rear ends only include a quaife and/or 300M shafts, neither of which were what failed on my car.

Just trying to understand the benefit of paying someone else to do something I can do.

NukeC5

Well you defiantly should protect a high power setup with solid engine/Trans mounts and the Trans/diff brace. ECS's brace is the best out there. Higher ratio gears actually lighten the stress on the drivetrain from what I hear. Don't quote me on that, but supposedly it lightens the load. So going to 3.73 or the like should give both performance and reliability.

slow ride

It all depends on how much you want to spend. The cheap fix would be fine and add the c6z pinion support, but nothing is bulletproof in these cars with a stick. You could add a ECS brace, but people break rears with those also. Then you could switch up to a c6z or even better a zr1 rear and adapt the tail housing to them and get all the c6 suspension stuff. The 3.15 gears would be a little much for your power level and the huge gap in gear from 3rd to 4th in the m12 t56 you have would make it even worse.

mdaniel

If you're changing the gears anyway I would probably go with a 342.
I'd also install a DTE/whoever else makes them now differential strut brace.
And I wouldn't take a 6 speed C5 down the track with a drag radial. Too brutal.
Get a set of ET Streets for the track. Much easier on parts.

easyvette

been here done all this and still blew the freak out of my rear ends. Simple solution if you enjoy the car and plan on keeping it.

C6Z06 trans and rear end. You will not be blowing it apart. Pay a bit more up front but the in very near future its well worth every penny! Or else covert the car to automatic those rear hold up much better on launches.

Spend 3K on a C5 rear that can blow first outing
spend 3K on a trans rebuild and who knows but the T56 is good. Prefer TR6060
Trans brace. And after that's all done you have done very little to actually strengthen anything with the rear casing.

yooper

I vote for the strongest diff housing as a foundation.

2000BC

2000 STS TT FRC 6 speed with 3:42 diff stock. I did the same thing. Hole shot and blew passenger side to bits. Bought a used built 3 rib diff with 4:10's, added 3/8" tunnel plate, DTE Brace, already had Hotckkiss sways and Bilistein sports. Much stronger than my original parts and a totally different car BUT you better enjoy shifting a lot!!! Luckily I love the setup and should handle my moderate street abuse.

mdaniel

You're going to find the weak link in your driveline pretty quick launching with drag radials off a two-step.

mcshocks

DTE makes a side cover for that issue, I just rebuilt mine with DTE parts in a 3 rib case, did all the hard parts (pinion support, cryod 3.90 gears, carbon clutches, upgrade both shafts, billet side cover, new bearings, etc) super easy with the J tools, spent more time waiting for the shims.

jbsblownc5

I have to give Unitrax the nod, they built me a 373 Quaife dif, treated the ring & Pinion gear, and machined it as well, so it would take the rear cover with the built in pump from the C6 Z06. We added another cooler for that...

I run their diff in both my cars, and find their work to be second to none!!!

2000BC

Unitrax built mine too but your spirited driving is a much better testimonial to their quality than my commuting to work!

zeevette

I recommend a Ford 9". And ladder bars.

Arnie Chamberlain

Ended up finding a low mile 04 Z06 diff locally for $450. Gonna tear it down, inspect it, put in the upgraded parts and reseal it and put it in along with an ECS brace and hope for the best.

Thinking about changing my tire strategy too, going with a standard 18" for street driving and something stickier for the track, only issue is I have with that is I installed C5 front brakes on the rear with C6Z51 rotors so I believe I am limited to 17" or bigger wheels which pretty much eliminates any slicks. Hoosier makes a 28" tall 17" slick, can those fit in the fenderwells?

slow ride

You might hate the wheel spin on the street without a DR. Just don't do two step launches on the radials or get a clutch you can ride out a bit more. Good score on the diff, swap the parts and keep the shock down.

NukeC5

You can fit 28" if you get the measurements right. But taller wheels make for less gear effect. So since you are tearing the diff apart anyway, consider upgrading the ring and pinion to 3.73.

It turns out that a lot of diffs are removed because of gear wine. I just just the same thing. Bought a used 3 rib 3.42 diff, inspection came back perfectly fine, installed it, had loud gear wine. It's not something you can tell. So my recommendation is to change the ring and pinion out no matter what. Even if you go with 3.42 again.