Thoughts on rear diff upgrade

[Fignewton]

I've got a 2010 2SS with a few mods making 460hp at the tires. I'd like to go to a lower gearing of 3.73 or 3.91 I'm not worried about losing top end and I don't drag race it. I may do some autocross in the future but it's mostly for curvy back roads and the occasional burn out. It has a ZL1 shifter and a Mantic 9000 clutch.
I guess what I'm asking is will the stock diff handle the lower gears? I don't want to go through the expense of the ZL1 rear end upgrade if I can just do the gears and/or carrier to achieve my goal.

[frankwjr]

yup...do 3.91's and I am adding a LPW cover as soon as it arrives..

the 3.91's will make the car feel 1000 lb lighter...

who did your tune? gonna need an update..

peace

[acammer]

Honestly, an M6 car has a plenty fat enough over-drive in 6th gear to pull a 4.10 comfortably on the highway, and be a blast everywhere else. Unless you start running real sticky tires, you don't need to worry about hurting the rear end, and typically the failure point will be the axle (although you definitely can tear them up beating them - be nice and they'll take you a long ways).

[Joe M 2012 2SS]

Whatever gear you decide to get, do not buy a Motive or Richmond gear, unless you enjoy a loud whine from your gearbox.

The stock posi has clutch packs. They wear out. An Eaton True-Trac has no clutch packs.

[acammer]

Originally Posted by Joe M 2012 2SS

Whatever gear you decide to get, do not buy a Motive or Richmond gear, unless you enjoy a loud whine from your gearbox.

The stock posi has clutch packs. They wear out. An Eaton True-Trac has no clutch packs.

That's interesting - my Richmond 4.10 is nice a quiet even with BMR poly bushings in the diff. Sounds like you may have experienced some less than perfect installs.

[CatTracker]

The stock rearend will not hold up if you are doing digs! Believe me I know from experience.

[frankwjr]

Originally Posted by CatTracker

The stock rearend will not hold up if you are doing digs! Believe me I know from experience.

so tell me sumthin...joined 2015 and this is your first post? huh...so I guess I should not be able to do this over and over at the strip...
or even this?


or how about Bill BFASTNOTLAST runnin mid 10's on basically a stock diff...


setup properly and used(not abused...lulz) they can take a beating but everything has a limit..


OP IMHO ur good with stock and your goals.....peace

[acammer]

I agree with Frank - I hammer my rear end on the drag strip and street quite a bit. I have heard stories of them being weak - but I haven't found that to be the case.

I believe there is a lot you can do to mitigate rear end problems. Keeping wheelhop out of the equation is hugely important - diff and subframe bushings are important there. Preloading the driveline with the e-brake goes a long way as well to reducing the shock and wind-up you get if you just dump the clutch.

B.Sharpes related to me that when he was down in the 1.5x 60' times he'd get about 15-20 passes on OE axles - but the rear end held up ok.

[TWOFORTYZ]

Originally Posted by Joe M 2012 2SS

Whatever gear you decide to get, do not buy a Motive or Richmond gear, unless you enjoy a loud whine from your gearbox.

The stock posi has clutch packs. They wear out. An Eaton True-Trac has no clutch packs.

If only they made a locker or better yet, and E-locker for these rear ends, around 20K I noticed my stock LSD clutch packs were not nearly as willing to grab as the 120K limited slip in my Ford or the 75,000 mile VERY abused R200 LSD in my old 300ZX. The Nissan would drag a tire in dirty parking lots for goodness sake, what was GM thinking being this conservative? I have no need for more strength, but would have to buy a 9" conversion if I want both wheels to spin every time they're told to do so.

[olblue75]

TruTrac or a Z28 Torsen!!

[johnnyb305mia]

Dont want to thread jack, but my 1le has bone stock rear end id like to put an lpw cover on it and billet main caps. What else would you guys suggest for fortifying it? Plans with the car are its goig turbo i have most of the parts just need a kit fabricated from kyle over at powersource percormance and we will be in business but will be 800+. I run a 305/45/18 Nitto NT05R as well.

[olblue75]

Originally Posted by johnnyb305mia

Dont want to thread jack, but my 1le has bone stock rear end id like to put an lpw cover on it and billet main caps. What else would you guys suggest for fortifying it? Plans with the car are its goig turbo i have most of the parts just need a kit fabricated from kyle over at powersource percormance and we will be in business but will be 800+. I run a 305/45/18 Nitto NT05R as well.

You might wanna get rid of the clutch pack LSD and go with a gear driven like a tru trac or a eatin found in the Z28. I scored a really low mileage Z diff.

[acammer]

Originally Posted by acammer

I agree with Frank - I hammer my rear end on the drag strip and street quite a bit. I have heard stories of them being weak - but I haven't found that to be the case.

I believe there is a lot you can do to mitigate rear end problems. Keeping wheelhop out of the equation is hugely important - diff and subframe bushings are important there. Preloading the driveline with the e-brake goes a long way as well to reducing the shock and wind-up you get if you just dump the clutch.

B.Sharpes related to me that when he was down in the 1.5x 60' times he'd get about 15-20 passes on OE axles - but the rear end held up ok.

Just to add an update to this - as soon as you say something is good to go, that's when you'll have trouble. I hurt my rear a few weeks ago - pretty sure I have a nasty chip in the face of a ring gear tooth. It's at a shop right now to have a new set of 4.10's installed - I'm going Motive this time. Also, I'm going to add the LPW diff cover for additional strength and rigidity to the whole setup.

I still don't think the rear end is weak - my 4.10 was early Richmond's which are notorious for being problematic. Additionally, they lived in a TT car before they migrated to my car, so I don't think they've had an easy life at all. I'm hoping the Motive set along with the cover will stand up even better, I guess we'll see.

[ttshovel]

the issue is the deflection of the aluminum under heavy load. the best bang for your buck upgrade is the zl1 diff. by the time you buy a cover, gears, and a truetrac you're about the same cost of a diff and axles