New Rear End

[TrueBlueCobra01]

After months of trying to decide what to do with the rear end in my 01 I finally did it.
(1) 04 Cobra IRS (car was totaled and parted out with about 30,000 miles)
(2) 4.10 gears
(3) AC427Cobra's bushing kit :rockon:

I already have MM Coil-overs and FLSFC, as well as 275mm street tires.
The car is getting aligned today and I can't wait to see what it drives like now. I'll post up later tonight about how it is but I'm sure it's ganna be awesome.
By the way, I get all my work done at TPS Motorsports for anyone who lives in the Bay Area :beer:

Edit: It just started raining... :fm:

 

[Tremor]

Should be fun with the 4.10s

Keep us posted :beer:

 

[scotts99snake]

I am jealous!!

 

[1raresnake]

How much did ur coil over cost u?

 

[cobrasvtcoupe25]

So Bobby.... when are you taking me for a ride man? I'm stoked for you! :banana:

 

[gmsux]

Very Nice, you'll love the results.

 

[TrueBlueCobra01]

Well my night was kind of a let down. I picked the car up and everything was looking good. It just got aligned and everything was all set. I pulled out of the driveway and went about halfway down the block, let off the gas, and heard that loud ass howling coming from the rear end. Long story short, the car will be in the shop for at least another day. I don't know if its a bad set of gears or what, but once again, I can't wait to get it back to see how it runs.

 

[cobrasvtcoupe25]

Well my night was kind of a let down. I picked the car up and everything was looking good. It just got aligned and everything was all set. I pulled out of the driveway and went about halfway down the block, let off the gas, and heard that loud ass howling coming from the rear end. Long story short, the car will be in the shop for at least another day. I don't know if its a bad set of gears or what, but once again, I can't wait to get it back to see how it runs.

I'm sure they'll take care of you! :beer:

op:

 

[TrueBlueCobra01]

I'm sure they'll take care of you! :beer:

Oh yeah I know they will. It just sucks cause I've been itchin to see what those gears are like. The break-in period is going to seem like forever.
And don't worry dude, I'll let you take it for a spin when it's all done.

 

[cobrasvtcoupe25]

Oh yeah I know they will. It just sucks cause I've been itchin to see what those gears are like. The break-in period is going to seem like forever.
And don't worry dude, I'll let you take it for a spin when it's all done.

Sweet! :banana: Isn't the break in period about a 1000 miles? What did they say?

 

[VNEMUS]

Well my night was kind of a let down. I picked the car up and everything was looking good. It just got aligned and everything was all set. I pulled out of the driveway and went about halfway down the block, let off the gas, and heard that loud ass howling coming from the rear end. Long story short, the car will be in the shop for at least another day. I don't know if its a bad set of gears or what, but once again, I can't wait to get it back to see how it runs.

If you swapped your 2 front and 1 rear differential mounting bushings to urethane or aluminum, the howling you are hearing is probably the increased NVH (Noise, Vibration & Harshness) due to decreased/eliminated deflection back there.

If you now have the aluminum bushings like I do, you’ll be able to make adjustments to your pinion angle. Properly setting the pinion angle helps keep the vibrations you hear and feel through the driveline, mainly the gear set, to a minimum.

The jump to 4:10 gears shouldn’t create the howling noise itself, if properly installed, but some noise will be there due to the combination of the gears and differential mounting bushings. The increased NVH is one of the trade-offs made to reduce/eliminate wheel hop and increase handling characteristics.:rockon:

Good luck and let us know how it turns out.:thumbsup:

 

[birdman941]

4.10 gears are notoriously noisy.(some aren't, but a good amount are)
For some reason, 4.30 generally are not noisy.
I have seen perfectly setup 4.10's with all new bearings, etc. be noisy.
They replace with another set, same thing.
Sometimes the 3rd or 4th set are fine.
I have no idea why.
Pitch line runout maybe?

 

[ac427cobra]

Any time a car is modded you can expect changes of some sort.

For instance, putting subframe connectors on the car will take the squishy flex out of the SN-95 chassis. Some people refer to this as a "tightening" of the ride. Others may view the ride as being more harsh.

Putting lowering springs or coil-overs on a car will compromise the ride. The ride will be much more firm. It will corner better, stop better and accelerate better. But it will ride worse. Some people want that, others may not.

Same thing with wider wheels and tires. Same benefits as the suspension mods discussed above but on the highway, this may cause your tires to wander or 'hunt' in the grooves on the highway. Some may find this irritating, others may think it's a small price to pay to ride on big meats.

The same modification characteristics can be applied to the IRS mods. All of that rubber in your IRS may make it ride nice and prevent NVH from entering the cabin but the rubber in the IRS is the VERY REASON most IRS owners are unhappy with them. They can't handle the power these cars put down and they destroy themselves if left unmodded. Yet the IRS can be completely transformed into a totally hop free corner carving animal.

This does come at a price. Some elevated levels of NVH will be transferred into the cabin primarily from the aluminum front diff mounts. What you are hearing is the differential gear noise coming from the aluminum front diff mounts. 4.10's are much louder than stock gears. The differential will actually be louder with a MM diff mount set because they mount the rear as well with an aluminum 'hard mount'. My kit utilizes a Delrin rear mount that transmits almost no additional NVH.

If you want to take a Mustang and make it handle like a Corvette or Porsche you can't expect it to ride like a Lexus!

FWIW

:thumbsup::coolman::beer:

 

[TrueBlueCobra01]

Thanks for all the input guys :beer: I know that pretty much everything I've done to the car has increased the NVH and I'm fine with that. But the noise the gears were making last night was some LOUD howling. It's not that I mind the noise, it was just too loud and didn't sound right so I thought something was wrong with it.
I talked to my mechanic today and he says they're checking things out and that it should be ready tomorrow. We'll see how it goes :rockon:

 

[ac427cobra]

Keep us posted! :beer:

 

[gmsux]

Do you know what brand of gears were used? Setup can vary on manufacturerer

 

[TrueBlueCobra01]

Do you know what brand of gears were used? Setup can vary on manufacturerer

Ford Racing. From what I've heard, they're supposed to be pretty quiet compared to Motive and some others.

 

[TPSMak]

Do you know what brand of gears were used? Setup can vary on manufacturerer

Bobby has Ford Racing 4.10 gears and the howling he has is now gone He picked up the car a few weeks ago and is enjoying the new rear end now epper:

 

[ac427cobra]

Bobby has Ford Racing 4.10 gears and the howling he has is now gone He picked up the car a few weeks ago and is enjoying the new rear end now epper:

Thanks for the update Mike! :beer:

 

[BreBar21]

Motive makes most if not all of the FRPP gears at this point. Noise is related to install. I had genuine FRPP gears that made a shitton of noise and now Motive gears that are silent. It's all about install. With that said, aluminum diff bushings transmit more noise, so expect to hear more than stock. It's all worth it when you romp on that throttle though.