djwimbo

I did a search but didn't come up with much.

What are the weak points of the stock diff? I found the mount/cover upgrade from Harrop, is there much else I need to worry about? It is a stock LSD right? No problems holding up to a H/C combo?

It will end up in a Non-GM vehicle that will be tracked, dragged, and daily driven.

Buzzmanb12

iTrader: (11)

Check over on LS1gto.com, lots of good info over there. M6/A4 car? The A4's are a little easier on the drivetrain. I put 506hp/511tq at the wheels thru my stock diff for about 2 very hard driven years before it gave up. I think it would hold for a good while with H/C and if not you can find them pretty cheap.

djwimbo

333CI >7K rpm engine + M6 trans in a 3000lb car = fun.
I'm only looking for 400-425whp, high C/R, "small" displacement.

Thanks for the info, that's mostly what I needed to hear. If you guys aren't breaking them often, then I won't. Especially being >1000lbs less in track form.

Summerwolf

iTrader: (3)

I have about 85K on mine, been to the track multiple times I autoX more than drag race. I have always ran sticky street tires (not drag radials) and I have full suspension including the harrop cover. The car puts out over 400 HP and spins to 6.9K and the posi still works 100% and I am not nice to the car by any means.

If you're going to use the stock gearing you might want to look into a rebuild kit and the posi spring tuning kit before putting your project together just to make sure you'll be fine no matter what but I haven't see too incredibly many of these diffs break. People complain about them whining quite a bit but I've never personally had an issue.

Edit- this is behind an M6 too

djwimbo

I'll probably keep it stock gearing. I like a bit of highway gearing, not that the T56 doesn't already have a double overdrive, but it's nice to have.

Thanks for the info, that lets me keep some confidence that it was built well enough to handle some upgrades.

Have you ever taken a look at your axle stubs to see if they're stressed?

Summerwolf

iTrader: (3)

I have cut a few 1.9-2.1 60 ft's before but always bungled up the run somehow when I cut a good 60 ft....don't know why I have never been able to get a super nice run pieced together honestly, no excuse. The axle stubs (being the "weaker" 2004 variant) show no signs of stress or twisting. A lot of people running drag slicks or drag radials have twisted the axle stubs though so I suppose as long as you're just running a sticky street tire its probably luck of the draw. After repeated launches on drag radials or slicks though they will stress from what I have seen/encountered.

djwimbo

sweet, thanks again.

This car won't be much or a drag car, but it will definitely make a few passes for a baseline. I'm going more along the route of a daily driver + weekend track days(road course).

Summerwolf

iTrader: (3)

Thats exactly what my car is, and it has 85K on it. Streetsweeper HT cam and some massively ported 243's along with all the bolt ons and tuned. I have 275's in the back (which is about the widest you can generally go on the back of the goat) and I have full suspension with the harrop cover. Thats my experience, others might be different. I heard horror stories of the stubs and cv half shafts so I bought spare 05-06 ones off a friends' car that upgraded to the BMR pieces when he twin turbo'd his car. I autoX the car, have taken it on a solocross course and done a couple track days, but I have been to a lot of drag racing days as well. Good luck with the project and please keep us all updated!

djwimbo

275/285 is about all I'll be able to fit in the rear, even with heavy fender rolling it will still poke out a hair with a 285.

This is a "budget" build, so if I can I'll avoid the Harrop cover. It does look like a very quality piece though.

It won't be officially started until spring/summer, but I'll do a full write up. Look for some B/A TIG usage throughout the build.

KrautBurner

iTrader: (5)

600+rwtq / 1.5x 60' times / 40,000+ miles and 300+ passes
mine is still fine

Dom

iTrader: (2)

I've done searches and came up with nothing. What is the stock differential in the GTO? Is it clutch type like Auburn or gear type like Torsen?

Rob

iTrader: (6)

Its a DANA. M80 if I remember right. Its basically an updated version of the old BW 9 bolt in 3rd gen F-Body's. Very strong for a little rear.

The axles and stubs are the weak link in the rear.

A_VAS

iTrader: (16)

Dom,
it is a cone style kinda like an Auburn...the cones are steel on steel so no clutch material.
There is a gear type available now as a bolt-in from Eaton (Detroit TruTrac)

djwimbo,
I have a couple spares laying around and some parts, if you find needing anything let me know. I have a buddy in Waterford MI area so if you can't find a diff local I could have him take one out there for you next time he's here....assuming you can wait a few months.

Summerwolf

iTrader: (3)

at 93K now I have replaced the cv half shafts with 05-06 units and my rear gears are beginning to whine.

Replacing it all with 3.73's and an eaton true trac within the next month or so. I have been getting rediculously sideways and abusing this thing lately though and I think thats what might have finally done her in.

juicedgta

so this is a little off topic


where do you find gears for these and is it just like any other RP install

GFORCE1320

iTrader: (15)

The GTO rear is a great rear once you put some of our stubs in it. We ran 9.41 on the bone stock rear with just our Level 2 half shafts and stubs.
We also run our carbon fiber driveshaft which reduces the driveline shock off the line.

Summerwolf

iTrader: (3)

I had to order the GTO gears from australia a company named difftechnics....never did a R&P install I had a shop do them that have done the rear end before (used in a couple other cars) and they said it was a somewhat "tricky" rear end as far as getting the bearings and all that but that the setup was fairly straightforward.