Topic: Rear Diff Part number help

[Yamatr3]

I am looking for the part number for an updated rear diff to fit the 2006 year car.  I have been on GM Parts Direct and they do not list what I am looking for. I am wondering if it is even an option?  I want the 2nd gen diff, with limited slip and a 3:73 ratio. Help please.

[MomsSol]

I am looking for the part number for an updated rear diff to fit the 2006 year car.  I have been on GM Parts Direct and they do not list what I am looking for. I am wondering if it is even an option?  I want the 2nd gen diff, with limited slip and a 3:73 ratio. Help please.

I had the newer diff put on my '06 .. it will take some research as there is no paperwork involved with this.  I'll have to go find a two year old thread and see if that part number changed or if they just updated it for the new diff.

Here is a pic of the old vs new diff that was installed - IIRC the ratio was still the same though.

[Yamatr3]

They have 2nd gen diffs listed with limited slip, but not in the 3:73 ratio only in the 3:91 ratio.

[snaponbob]

Curious about the desire for the lower numerical final drive. IF you find a lower gear someone will have to reprogram your ECM so that the speed sensor is correct. Assuming that there is better fuel mileage to be had may be incorrect, and you WILL loose acceleration.

[MomsSol]

They have 2nd gen diffs listed with limited slip, but not in the 3:73 ratio only in the 3:91 ratio.

I may be wrong, but isn't the 3:91 for the GXP?  The NA has not changed the ratio IIRC.

[Yamatr3]

I may be wrong, but isn't the 3:91 for the GXP?  The NA has not changed the ratio IIRC.

I just checked the Pontiac website and the 3:73 is in the GXP and the 3:91 is in the NA. 

So, I wonder why they are not listing a part number for a 3:73 limited slip 2nd gen.  Hmmmm.

[Yamatr3]

Curious about the desire for the lower numerical final drive. IF you find a lower gear someone will have to reprogram your ECM so that the speed sensor is correct. Assuming that there is better fuel mileage to be had may be incorrect, and you WILL loose acceleration.

You are correct in your statement, but I have aftermarket guages and an LS2 V8 in my car.  I currently am running a 3:23 rear end gear and am thinking of changing.  I am trying to decide If I should go to a 3:73 or a 3:42.  Either way I want to buy a whole brand new rear so hopefully the issues I have been having will go away.

[Yamatr3]

Ok, I believe I have this figured out.  The reason there is no 2nd gen 3:73 listed, is because the GXP is the 2nd gen.  However, this brings up the question about the torque arm.  I know it can not be retrofitted to the older models, but did the early GXP's have the new torque arm rear end or did they have the replacement rear end like Moms pictured?  Can someone with a 2007 GXP look at theirs and tell me if it looks like what is in the picture?

[MomsSol]

I just checked the Pontiac website and the 3:73 is in the GXP and the 3:91 is in the NA. 

So, I wonder why they are not listing a part number for a 3:73 limited slip 2nd gen.  Hmmmm.

Thanks for the clarification ... I just had it backwards!

I just researched to old threads and I found no part numbers listed.  If you want I can email a contact and see if indeed the NA still uses the old part number but with the newer 'improved' diff. (which is suspect is the situation). 

I'm pretty sure that they "axed" all the old diffs and are now using only the newer version (like the one in the picture I posted) for any 06 that has to have the diff replaced.

[Critterman]

I believe they added the torsion bar during the production year and the earlier models did not have it.

[Yamatr3]

Thanks for the clarification ... I just had it backwards!

I just researched to old threads and I found no part numbers listed.  If you want I can email a contact and see if indeed the NA still uses the old part number but with the newer 'improved' diff. (which is suspect is the situation). 

I'm pretty sure that they "axed" all the old diffs and are now using only the newer version (like the one in the picture I posted) for any 06 that has to have the diff replaced.

Thats ok, I was just wanting a second gen diff, but I guess they don't make one for my car with a 3:73 ratio.

[snaponbob]

IIRC, the torque arm started into production in late July. It requires a different diff AND transmission that have the bosses to bolt up the arm.

[Sol Asylum]

Can someone with a 2007 GXP look at theirs and tell me if it looks like what is in the picture?

I have a 07 GXP, manufactured in late Feb 07, the dif looks like the one in the lower left of Momsol's picture.  Its my understanding that all GXPs were like this and that GM delayed production of the GXP/Red Lines until they had the torque arm mod worked out.

[2kwk4u]

Just curious, Yamatr3, why are you changing away from the 3:23?  Are you able to put all that power down without lighting up the tires in the first 2 gears right now?  I can't remember what setup you have.  Are you still running the stock Aisin trans, or did you go to a T-56 or similar with your engine swap?

[Yamatr3]

Just curious, Yamatr3, why are you changing away from the 3:23?  Are you able to put all that power down without lighting up the tires in the first 2 gears right now?  I can't remember what setup you have.  Are you still running the stock Aisin trans, or did you go to a T-56 or similar with your engine swap?

I think with the LS2, I will always be looking at how to put the power down better.  I like the 3:23, but I would like the car to accelerate a little faster.  I really want to go to a 3:42, but I want to buy a brand new diff with the updated torque arm and vent. 

I do have a T56 trans in my car.  I have had to have the diff out of my car three times now and have bought 2 of them.  I just want to buy a new one, put it in and be done with it.  I just put in a used Cadillac one and have to take it out because of leaking seals.  A new diff is approx $1500.  Everytime I have to do something to my diff, it costs my $350 minimum.  I could have bought a new one by now.

Thanks SA, now that I know it is the diff I want, I can order one.  I want to see if the cadillac has the second gen diffs too.  I don't think they do.  If they actually do, then I could order a 2nd gen in the 3:42 gears I want.  I might just do the 3:73 as thats what Mallet does.

[DeepBlueGXP]

Have you thought about using the Quaife

http://www.autotech.com/quaife/differentials/diff_apps.htm

[Yamatr3]

Have you thought about using the Quaife

http://www.autotech.com/quaife/differentials/diff_apps.htm

I had a Quaife in there.  It works good, but is much louder than the stock clutch type set up.  The Quaife is an all gear driven LSD so it is a little noisier (gear whine).  You don't notice with the top down, but with it up, I hate it.  When I did my drive shaft, I eliminated the rear rubber coupler at the diff.  I wanted to push more HP in the future and didn't want to worry about that item.  My drive shaft is aluminum without the rubber coupler so noise transfer through it is much higher.  Due to that set up, I am guessing this is the reason I get more noise in my car.  Thats why I am thinking of selling off the Quaiffe LSD and going to a stock Sol diff with LSD, but I really want the lower gear ratio.  I have spoken to people that have Quaiffe with the stock set up and they say they don't notice anything different.  In hindsite, I should have left the stock rubber coupler on the drive shaft.  Now if I go back to it, it's going to cost me about $500 to change the drive shaft, reinstall it, etc.

[DeepBlueGXP]

But I don't think the stock 06 LSD isn't a posi rear end

[lil goat]

You may want to give the guys at RMR a call, they run the Kaas differential in the Red Bull Solstice, and have a ton of different ratio's they changed the diff 3 times last year at Englishtown to get the right ratio. I am not sure what other changes they did to use the Kaas, they run the same diff in the GTO that has the LS-7 motor so it has to be very strong.

[lil goat]

Did you see this on ebay 3.23 setup for a V-8
http://cgi.ebay.com/ebaymotors/Parts-Accessories___2007-solstice-sky-custom-built-getrag-V8-ls2_W0QQitemZ260338364919QQddnZPartsQ20Q26Q20AccessoriesQQddiZ2811QQcmdZViewItemQQptZMotors_Car_Truck_Parts_Accessories?hash=item260338364919&_trksid=p4506.c0.m245&_trkparms=72%3A543|65%3A12|39%3A1|240%3A1318

[Yamatr3]

Did you see this on ebay 3.23 setup for a V-8
http://cgi.ebay.com/ebaymotors/Parts-Accessories___2007-solstice-sky-custom-built-getrag-V8-ls2_W0QQitemZ260338364919QQddnZPartsQ20Q26Q20AccessoriesQQddiZ2811QQcmdZViewItemQQptZMotors_Car_Truck_Parts_Accessories?hash=item260338364919&_trksid=p4506.c0.m245&_trkparms=72%3A543|65%3A12|39%3A1|240%3A1318

Thanks for the heads up.  This is what I currently have except I have the Quaiffe LSD and want to change gear ratios.  I appreciate you giving me the heads up though.