I have a 2005 Z51 that is putting 558 to the wheels. Mods include maggie s/c, heads, cam, intake, full exhaust, etc. I am currently running the DTE stage 3 rear end with 3.90 gears but I've got a considerable whine at highway speeds.

The car only has 26k miles and is currently used as my daily driver but i work about 1.5 miles from my house. I get on the highway a few times a week going out to dinner, etc and occasionally going to visit my parents 180 miles away, so I would like to still have a decent highway setup. I'm not a racecar driver by any means but I would like to take the car to the track here and there once the new rear end is installed.

The original owner broke his stock diff housing at the track and replaced it with the DTE. Roughly 20k miles later, I've got a whine. The 3.90 gears are fine for me as this is my first Vette and the only setup I have known.

A few ideas I have gotten are; to have the current DTE rebuilt (but no one can tell me the cost and my shop would have to send it out to DTE to rebuild due to special tools leaving me without a car for a few weeks), replace with a stock 2006 diff and stock gears (but i'm worried about breaking at the track), or replacing with another aftermarket diff (not sure which one would be right for my setup and driving habbits).

Based off of your experience, what would you guys suggest?

 

I thought that C5Z rearends could be mated up to the 05?

That would be the route I'd take in an 05.

 

Just thought I'd throw this out there. It may be a stretch but...
Are you certain the whine is coming directly from the rearend and not a bad wheel hub that is reverberating thru the rearend?
I've seen the exact same symptoms you are describing (whine at hwy speeds) and it was just the rear wheel bearing gone bad.

 

Well, I had the rear end looked at and fluids changed. I was told that it looked like it was going out. What are some other symptoms of a bad wheel bearing though?

The whine is only when i touch the throttle-whether I'm giving it gas, barely touch it, or I'm cruising at a constant speed, but as soon as I release my foot, it's gone. It starts around 35 mph, very faintly, and gets louder as speed increases. I get a lot of rattle in the shifter at higher speeds and at higher rpms the rattle in the shifter is very loud.

 

It's the diff, for sure. I JUST replaced my DTE (the OLD Phil era DTE, not the NEW DTE) diff with 3.90 gears 750 miles ago because mine started the "whine", just as you describe. My diff only had 7500 miles on it. I went to RPM Transmissions, they explained everything to me (why my DTE diff was bad at such a low mileage), and sold me a new diff at a REALLY great price. Cant say enough about the guys at RPM Transmissions. I HIGHLY recommend them.

 

and would use RPM based off feedback throughout the years.

 

What are the advantages of using the c5z diff over the 06+ diff?

Does anyone know what all is involved in converting to an 05 to either a c5z or 06+?

It's my understanding that the 05's used the c5 diff and removed a few mounts to make it fit on the c6 but in doing so, made the diff very weak.

 

Anyone?

 

the c5 dif is cheaper to buy and there are plenty used ones around , just put the 2nd generation c6 dif in or go with the c6z06 dif from rpm

 

After scattering my 05 weak rearend, I decided to retrofit a c5 rear into the car. I wouldn't attempt it unless you were pretty good at fabricating. Do a search in the tech and performance section here for sparo2 and you should find his thread on it.

 

Im currently doing this. Sparo makes a bracket that will let you use the c5z flawlessly. You just have to poke some holes at the cradle, install his bracket and bolt the diff to it. Just be very careful with buying used diffs and having any teeth missing. Im having to rebuild the one i bought because the previous owner didnt noticed. He is sending me gears to get it fixed though so its a hastle but at least hes being responsable.

Good luck and definetely contact Sparo. Sometimes he doesnt answer his pms so contact him throught his email on the forum.