Which rear end and why
 

Hey guys..

I need a new rear end for my project so looking for thoughts and recommendations.

The plan is to run an LS9 motor at 600hp + and probably a tremec 6spd gear box.

What rear end would you run and why, and how do you work out the best gear ratios?

The cars primary function will be road car, with some track time (twisty British tracks ;)

Cheers
Amit

9" floater.

Or a whole RS IRS chassis if you have the money.

Thanks for the input guys

any particular brands?

Cant do IRS as I am not paying to ship a chassis across to the UK lol.

why is a 12bolt better than a 9" for power loss?

What are the -ve points for 12bolt over a 9" ?

PS, I am completely new to the world of muscle cars so just trying to learn as much as possible to enable me to make the right choice for my project

I would go 9" (as I did). I feel (my opinion from what I have seen) that they are stronger than 12-bolts and also are cheaper to fix. Sure they supposedly take more power, but its so miniscule I dont think its worth the argument, but thats just me.

I went with a Moser 9"... matched with a DSE Quadralink. :thumbsup:

Fist thing you need to do is figure out what rear suspension set up you intend on going with. Do a search on rear suspension set ups and you'll see why.

All ready have the suspension sorted.

I have a full ridetech level 3 kit.

I am currently favouring the m9 also.

Any other aftermarket worth considering with any particular new or innovative features?

I vote 12 bolt with tru-trac and ford big bearings. Im pretty sure you can get that right from Moser already assembled

rear end
 

It's very hard to beat the speed at which you can change 3rd member drop outs on a nine inch Ford rear end, and do it at home, no special tools required. While the GM 12 bolt, or Dana 60 are strong units, you simply don't have the versatility of the Ford drop outs. The only thing close is Mopar's 8 3/4 rear, but parts & availability are not even close. It's nice to be able to quickly set up for a road course one day & then quickly change to drag race gears the next day. I have 3 different ratios I use, and I simply store the extra gears in the plastic storage boxes Jegs sells to keep them clean, dust free & ready to run. Ford 9 inch parts are as available as small block Chevy parts too, every swap meet & wrecking yard has them. I often buy complete 3rd members as low as $50 on 1/2 price days, or $100 regularly. Most often you will add a posi traction to them, but sometimes you get lucky and find a posi in a wrecking yard, I've found 2 this year so far. Good luck with your build.!

Thanks for the input.

I came to pretty much the same conclusion and have decided on a GMR built 9" full floater with strange engineering Strack and 35spline hytuff axels.

Any comments on my choice?

Yes....bad ass! :thumbsup:

There are no good Posi units for the 9 inch for what we do. The 9 inch is heavy and has a huge parasitic power loss. There is no question in my mind that I would go with a 12 bolt Moser with a Eaton posi.

The wavetrac certenly has not had great reviews when it comes to the auto-cross and road race platforms, I will give you that. But saying that there is no good posi for this "type" of sport is a very bold statement. A statement that is only derived from your opinion, not so much fact. There are several options that guys are currently running and winning with at the events.

saying a 9" is heavy is also very bold, with our housing and the alum case we are actually lighter on average, but there is still a few variables in there. Our floater setup defiantly does reduce weight, and more importantly reduces the rotational mass quite a but over traditional flange end axles. Again, bold statement on your part when clearly there are many variables involved.

As for the powers loss, well that is still debatable. The reduction of rotational mass and increase in efficiency of the floater will already prove your statement incorrect. Now, you can also REM the gears, then run ceramic or even PM series bearings in the case and the 9" is now substantially better then ANY 12 bolt. That is fact, and those setups and components are running in cup cars, NASA, and SCCA.

12-bolt, is not a bad setup either, so please don't assume I'm bashing the 12 bolt guys. In fact we can and have built 12-bolts with components.

The 9inch has quite a few elements that make it more adaptable for these cars / setups. From having a blank sheet (housing) to make link tabs on to the ability to drop out the gearset, the 9 inch is defiantly the preferred rear end of choice. This is based on what you will see out at the track, most are running 9 inch rear ends.

It does make me chuckle how SLO has reserved comment until the name GMR comes up... then makes some very bolt statements. :D

Jason

From the digging I've done the Wavetrac and 9 inch S-Trac are similar (helical) but not the same deal. Something about more gears/increased surface/strength...that's about as deep as I got as it's a way off for my build but the S Trac seems to be getting good reviews for street/strip stuff at present.

Hi Jason, I've followed the build of your floaters from release and I love your work. What centers are the 35 spline guys using in your neck of the woods for strip/track(L&R but not autocross) stuff?

With knowledge like this,

I am glad I have Jason on the case building my rear end

Amit

The difference is so minimal that unless you are driving to hundredths of a second lap times you will never know it!!!

That said a 9" floater is the current hot setup in PT cars. The GMR is the top of the line 9" floater, hands down the best product on the market currently. But it comes at a premium price. There are alternative 9" floaters for more modest budgets from companies like Moser. I installed my Moser 9" floater just a few months before The GMR floater came on the market or I would have a GMR 9" floater under the car now.

http://hayes-ent.com/steve/images/Ca...0112%20001.jpg

Exactly ^^^ The loss isnt going to be enough to base a major part of your decision on.

Check out my build thread in my signature to see why the gmr floater is a premium product. The thought and engineering that has gone into their products is incredible.

I am really excited to get it under the car

Hi iam about 3 miles from Snetterton and go on track days there with my 69 , you,ll get plenty of attention turning up with a muscle car . I have an old school 8.5 10 bolt fitted with an Eaton posi and it does ok for me . Have you driven the Camaro on a circuit yet . Pete

Hi pete.

I havent driven a camaro yet ever ;) or in fact any muscle car

this is my first muscle car build

Amit