Author Topic: AND BOOM GOES THE DIFF (Read 24835 times)

blackbirdracing · « **on:** April 21, 2015, 05:29:49 PM »

So I destroyed my diff the other day.

Just about cracked the case in half.

What's your guys' opinion on converting my 07 GXP from a 3.73 gear to a N/A 3.92 gear?

Sting Ya · « **Reply #1 on:** April 21, 2015, 06:33:33 PM »

Better off line acceleration go for it !

blackbirdracing · « **Reply #2 on:** April 21, 2015, 06:39:40 PM »

Some guys have told me first gear will be even shorter than it it now...

Which worries me slightly

elff · « **Reply #3 on:** April 21, 2015, 08:17:30 PM »

first gear would be worthless.
I'd want a taller first gear, not shorter in our cars.

blackbirdracing · « **Reply #4 on:** April 21, 2015, 08:23:25 PM »

That's what they make sticky tires for...

Besides, its not that big of a change...

roxer · « **Reply #5 on:** April 21, 2015, 09:53:28 PM »

Quote from: elff on April 21, 2015, 08:17:30 PM

first gear would be worthless.
I'd want a taller first gear, not shorter in our cars.

I think first is already worthless, unless you are rock climbing...

blackbirdracing · « **Reply #6 on:** April 22, 2015, 11:10:26 PM »

New diff is back in.

Not a hell of a lot of difference with new gear set.

POS VETT · « **Reply #7 on:** April 23, 2015, 06:29:13 AM »

What's engine speed at 65 mph in 5th?

blackbirdracing · « **Reply #8 on:** April 23, 2015, 11:22:57 AM »

Just checked this morning for you.

About 2400-2500rpm

elff · « **Reply #9 on:** April 23, 2015, 11:24:34 AM »

Do you happen to know what that used to be?

blackbirdracing · « **Reply #10 on:** April 23, 2015, 11:26:19 AM »

I never paid attention before.

DrJones · « **Reply #11 on:** April 24, 2015, 02:36:07 PM »

I used a 3.23 ring a pinion from an SRX in mine. With 270/650R18 Avon slicks we can hit ~75 mph in second (7200 rpm redline).

elff · « **Reply #12 on:** May 01, 2015, 08:44:41 PM »

In AutoX that is practically an Auto.

How is the season going for you this year?

blackbirdracing · « **Reply #13 on:** November 08, 2015, 11:39:27 PM »

Bringing this thread back from the dead...

went to a dragstrip with my father (he also owns a 07 GXP)

He blew his diff.

has to be a better way.

Our failures have been due to wheel hop.

we need a game plan to reduce if not eliminate the wheel/axle hop.

anyone got any ideas?

DeepBlueGXP · « **Reply #14 on:** November 09, 2015, 06:35:58 AM »

Did you lower his back tire pressure

blackbirdracing · « **Reply #15 on:** November 09, 2015, 07:48:42 AM »

We did not.

I've heard with a street tire lowering the pressure can actually cause the center of the tread to cup inward reducing your contact patch.

and on a stiff summer only performance tire, it doesn't really help as the sidewall of the tire is so stiff

ryansalazan · « **Reply #16 on:** November 09, 2015, 11:51:23 AM »

Quote from: DrJones on April 24, 2015, 02:36:07 PM

I used a 3.23 ring a pinion from an SRX in mine. With 270/650R18 Avon slicks we can hit ~75 mph in second (7200 rpm redline).

This is awesome information! Obviously a very long 2nd gear as well. What about the other gears if you don't mind me asking. Like how are they affected? Can you even do 60 mph in 5th anymore? lol I'm looking to get a shorter rear gear at some point to lengthen my gears. And did you just buy a sex rear diff and install or actually take out all of the gearing? Sorry for all of the questions, this is just something I've been wanting to do for a while.

username · « **Reply #17 on:** November 09, 2015, 03:09:02 PM »

Quote from: blackbirdracing on November 08, 2015, 11:39:27 PM

Bringing this thread back from the dead...

went to a dragstrip with my father (he also owns a 07 GXP)

He blew his diff.

has to be a better way.

Our failures have been due to wheel hop.

we need a game plan to reduce if not eliminate the wheel/axle hop.

anyone got any ideas?

* Launch at a higher RPM to break the tires loose decisively.
* Poly nose bushing on the diff.
* Z0K rear crossmember (or a brace + stiffer bushings on the rear).
* Never launch with TC/ESC enabled. Always fully disable.
* Don't use "stronger" axles, leave those as the weak link.

More extreme:
* Build a "cage" for the case to hold it together.

First four have solved my wheel hop, even when launching on concrete pads with very sticky (street) tires.
Item 5 has saved me a lot of money, the one time I broke something.

I'm on 265 RE-11s with over 400 ft-lbs of torque.

blackbirdracing · « **Reply #18 on:** November 09, 2015, 03:25:10 PM »

Poly nose bushings on diff???

We are both GXPs so we have torque arm. I thought the diff bushings were only for the N/A or auto guys...

I guess the ZOK crossmember include stiffer bushings right?

Perhaps one of our vendors could make some stiffer bushings for the rear of the diff.

blackbirdracing · « **Reply #19 on:** November 09, 2015, 03:27:55 PM »

Also add we are on the same tire.

bfg comp TA v2

255/45/18

miller11386 · « **Reply #20 on:** November 09, 2015, 03:49:18 PM »

Ok... so basic things to know that hurt a diff ring gear. Wheel hop and slamming the gears.

Lots of ways to avoid wheel hop. Softer sidewall tires, Solid/stiffer mounts bracing the diff, stronger axles, etc.

All of which are useless if you don't have a good pre-load on the gear and slowly slide the clutch when leaving. How do I know?

This is a ring gear in my diff.

Strange spool differential, 10.5 slick tires, upgraded axles, solid billet aluminum cover, solid rear mounts, 1 pieces drive shaft, and billet aluminum couplers.

If you drop the clutch too quickly on any diff, no matter what the upgrades, you will hurt an oem gear. This is why I'm (hopefully)going to a softer "Pro" gear that should take more shock and abuse than a normal oem gear set.

So no matter what upgrades you do, the driver is the most important feature in the launch of a manual trans car.

blackbirdracing · « **Reply #21 on:** November 09, 2015, 04:07:23 PM »

It's not the ring gear that is breaking.

it's the case or diff carrier.

I will inspect further, but I know on mine the case is what was broken.

it appears to attempt to rip the mount off where the torque arm mounts to the carrier, or case

I'm changing to BC coilovers, using energy suspension control arm bushings. Talking to Dave @pwerks to develop some stiffer diff bushings, where it mounts to the crosmember.

and looking into some slicks.

elff · « **Reply #22 on:** November 09, 2015, 04:17:20 PM »

The DDM ProBeam or the ZOK Crossmember sounds like it might be the solution for you.
These both strengthen the connecting beam that the diff attaches to. The DDM Probeam is stiffer than the ZOK one.

There is a good chance you are twisting the beam that the diff connects to on your launches and when it snaps back to the original untwisted state, that force might be transferring to the case causing it to break.

Dave@DDMworks · « **Reply #23 on:** November 09, 2015, 04:20:28 PM »

If you are on the stock suspension, you are definitely going in the right direction going to the BC's or an aftermarket shock setup that is adjustable. Also, the control arm bushings replacement will probably get you taken care of. As the cars are getting older the control arm bushings are starting to fail on higher horsepower cars and that is allowing the movement of the suspension and the wheel hop to start, then on stock worn shocks the hop can not be controlled. You are on the right path to get it taken care of though.

Good luck with it,
Dave

blackbirdracing · « **Reply #24 on:** November 09, 2015, 06:16:08 PM »

I just received my BCs from you Dave...

Also I have the werks rear brace. I used to have the kappa sphere reBar but it got bent when I backed into a parking median

I've heard you can use in conjunction with the probeam.

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Author Topic: AND BOOM GOES THE DIFF (Read 24835 times)