Topic: Think I blew my rear diff at the track today

[MattM]

Trying to get a ballpark cost on having the rear diff repaired/replaced...

Btw when I say blew I mean I'm at the line at 4000 rpm with my wot box and drop it an I hear a clunk and nothing...doesnt even go back into gear. 

Look under and all the differential lube is leaking out all over the place.

I can't believe it happened!!! Never heard of it happening to these cars...

[elff]

If you have a lift and 2 people, it's not that hard to do, Especially since you will need to remove the axle shafts.  You might want to verify them as well.  The Splines might be toast or at least twisted. 

The internals on these are pretty damn strong, normally the outer housing where the torque arm attaches is the issue, or the axle seals.

You just entered a very small club of people.

PM JohnnyGXP he replaced his due to the housing cracking.   I don't remember the cost. 

[MattM]

Well...I was thinking about finding a used one and replacing it...i don't know that it could be actually fixed, but. The housing did separate.

[MattM]

I'm also thinking it had to be on its way out....im just using Hancock tires not drag radicals or anything for it to blow.  It always had a clunk when I would put into first gear...

[elff]

Should be plenty of donor parts from front crash totaled skys and solstices.  Just a matter of tracking one down

[MattM]

Is there a difference between auto diffs and manuals?

[Critterman]

Don't forget Cadillac as a donor, lower gear ratio

[Gentleman Jack]

Gear rations are good while backpacking in far away lands...

[Sol Asylum]

Gear rations are good while backpacking in far away lands...

They issue those to the military don't they?  That should make it easier to find.

[MattM]

Do you guys know if there is a difference between 2007 diffs and 2008 diffs??  I know in 2008 they were bolted on differently but would they still bolt up to a 2007 without the transmission/diff cradle?

[MattM]

Want to reiterate my questions here.

I need to know if it matters whether the Diff is from an auto or a manual as well as whether it matters if the diff is out of a 2007 (that doesn't have the cradle) or out of a 2008 that does.  Will the 2008-10 still bolt up to the 2007?

Any help ASAP would be greatly appreciated!

[Sol Asylum]

I would recommend you look at a parts catalogue and see what numbers match up between model years and transmissions.

[MattM]

So for everyone.  I found and bought a new diff carrier from performance autowerks and so everyone knows.  The diff that is in an auto trans redline or gxp from 2008plus will fit and bolt up to a 2007 manual redline or gxp.

[elff]

$3000 for a rear diff that does not have a torque arm?
Whoa!!

[Uranium-238]

Three grand is the point with the Camaro where I'd be seriously considering just spending the additional cash on a Ford 9"...

[MattM]

$3000 for a rear diff that does not have a torque arm?
Whoa!!

I'm confused....where is the 3000 coming from?

[Steelmesh]

Hi Matt, Are you running drag radials? 

[MattM]

Hi Matt, Are you running drag radials?

Nope!  Just Hancooks on 18s.  I didn't let any air out of the tires either.  One thing I do remember....I drove around the water box then activated the WOT Box to 4000rpms and let out of the clutch to let the tires spin for a second to clean them off..I do think I remember the tires just wheel hopping so I guess I could have broken it then. 

Now even though I was just on Hancooks we got to Cecil early and were the first to run that morning (right after they sprayed the tacky stuff, so I think that really contributed to the tires trying to bite. 

[Steelmesh]

Nope!  Just Hancooks on 18s.  I didn't let any air out of the tires either.  One thing I do remember....I drove around the water box then activated the WOT Box to 4000rpms and let out of the clutch to let the tires spin for a second to clean them off..I do think I remember the tires just wheel hopping so I guess I could have broken it then. 

Now even though I was just on Hancooks we got to Cecil early and were the first to run that morning (right after they sprayed the tacky stuff, so I think that really contributed to the tires trying to bite.

Dang man you're scaring me    my understanding is that this failure is pretty rare with our cars.  I am curious if the failure mode is similar to what the caddy people deal with.  Awaiting pictures of the destruction!

[MattM]

No pics!

I want to forget about this as quickly as possible!

I feel like it was the wheel hop that did it.  It's just wierd that I went to Cecil last year and same setup (except I had the stock 3/4 tread Eagle F1s and now I have the brand new Hancooks on).  Last year I got some wheel spin and that was just it. 

I doubt the Hancooks are any better than the Eagle F1s in terms of traction though....

[Steelmesh]

Pictures on the internet of broken CTS diffs:

[MattM]

Also....Since I bought the car in 2017 if I would be at a stop light and take it out of gear and put it in neutral then try to put it back into 1st gear it would clunk...

[MattM]

Ugh!  For you I may get a pic....

Is there any explaination for what the CTS' were doing to blow their diffs?

[Steelmesh]

Ugh!  For you I may get a pic....

Is there any explaination for what the CTS' were doing to blow their diffs?

CTS-V = 3,850 lbs with 400 ft-lbs of torque


Diff is just weak for the V application. 

Check out this, they did a bunch of suspention/driveline rigidity mods along with a diff brace.
http://www.superchevy.com/how-to/ghtp-1301-improving-the-2004-2005-cts-v-rear-differentials

Support brace they mention: https://www.bmrsuspension.com/siteart/install/PSB001.pdf

This post (there are mulitple) shows someone built a girdle: https://ls1tech.com/forums/cadillac-cts-v-2004-2007-gen-i/1558820-best-rear-end-fix-gen-1-v-s.html

[Wartie]

I'm confused....where is the 3000 coming from?

Right from you, see below. Short memory?

So I decided to bite the bullet and just got the upgraded Trifecta custom tune to get them to really look at my datalogs.  They did find something that they said they have never seen before.

Esentially, ONLY above 5,000rpms my spark advance intermittently goes from 12 advance to 6 advance back up to 12.  It's obviously not what the tune is commanding and they are having issues determining why it's happening.  FYI it was happening before the tune with Trifecta so I know it's not that. 

Well, they were stumped until I told them that after I got the P0107 code with my MAP sensor the hesitation went away.  They think it's related to the MAP sensor (even though it wasn't throwing a code prior). 

They recommended I go with the 3-bar sensor, but I'm hesitant to spend the money if it doesn't fix the problem.  I'm already dropping $3,000 for the rear diff replacement.