Rear-End Options?

[Chillin014]

Thanks doober! I wont waste my time on that ad though. I may pick up that ebay posi unit though! Where are you looking for prices on the other parts?

looking at this Strange gear. Might upgrade to a t56 so dont want to get anything too high.

 

[Doober]

If you're thinking of a T56 you'd actually be ok with a 4.10, since 5th gear on most is .5:1, putting the final drive to a 2.05:1 (typically 700R4 with 3.73s is about 2.61:1 in 4th). I got the prices on the axles from Summit, and they also carry support covers too (but you may find one of those cheaper on eBay).

 

[w_hale81]

i 2 am also havin some rear diff issues.. i got a ford 9'' already set up 4 my 86 cutlass wt all 4 adjustable trailing arms and also i got hardend 28 spline axles .. the car has a fresh stout 355 wt a very fresh built th350 trans.. the info i am lookin 4 is the best tire and gear size 2 go wt 4 da 1/4mi .. i really hate 2 buy 2 diff things that arent goin 2 work wel together .. thinkin bout 411s wt a spool since its guna b a street strip car.

 

[Doober]

Spools are general not street-friendly. Some say otherwise, but they put a lot of stress on the axles. A locker would be better for a street-driven car. For a tire your widest possibility (at least on a Malibu, not sure what other cars are like) will probably be a 275, you'll probably have to roll/trim the lip of the fenderwell. Backspacing will depend on the width of the rearend, factory width is around 4-4½" max I believe, do some measuring to be sure... measure outside-to-outside on the frame rails (or wheel tubs, whichever are wider), and I'd say add 1½" or so overall to accommodate for sidewall bulge. Measure the width of the rear across the axle (NOT housing) flanges with the discs/drums on the axles. Subtract your frame/wheel tub measurement (say it's 47", add 1½" making it 48½") from the axle measurement (I think a stock G-Body is around 57-58"). Divide that by 2 and you'll have a rough estimate on what to aim for on backspacing...
58 - 48½ = 9½"
9½" / 2 = 4.75" - meaning you can run up to about 4.75" backspacing. This may not be accurate though, it's just a rough guess on measurements, you may have room for more backspacing (wider rearend), or require less backspacing (narrower rearend).

Ideally you would have the exact same on either side, but if the rear is slightly off center you may have fitment issues on one side (which may mean you have a whole different problem altogether). Another thing you could do (and will be more specific for your application) is to mount something to the hub that will extend up parallel to the wheel mounting surface, then measure either side of it to see how much room you'll have.

 

[jimmyp618]

i run a 295/10.5 /15 MT ET drag radial bout the widest thatll fit.

 

[w_hale81]

yeah just thought bout goin wt aspool cuz it mite drive itself 2 the track no extreme cruisin r nothin -- i am runnin a 275-60-15 tire now but was thinkin bout the 411s cuz i can run a bit of a taller tire cuz i have some clearance cuz of the tuffer talller springs i put in

 

[jimmyp618]

Gear wise i run a 3.42

 

[Chillin014]

You could use 26-spline, they're just not as strong as 28. If that posi unit is a gov-lock unit, pass, they're no good for performance applications. The other thing is you can get brand new axles for less than $25 more, regardless if they're 26- or 28-spline. Since you don't want 4.10 the only thing I'd look at from that ad is the posi, and I'd even pass on that unless it was rebuilt with really good parts... because...
http://cgi.ebay.com/ebaymotors/CHEVY-GM ... ccessories

In the time it took me to write this post I just found you a set of new 28-spline axles & 'new' 7.5" 28-spline posi for roughly the same price. Add an aftermarket support cover (they start around $150 I think) and you'll have pretty much everything you need to strengthen a 7.5" (granted you still need gears).

Good luck whatever you do 😉

Went ahead and ordered that differential. 😀

 

[Doober]

Sweet 😀 If I had the $ to spend I'd probably do the same, because I have major traction issues with the open rear

 

[Chillin014]

I hope to have that problem some day. lol.

So 28 spline axles will slide right in with this new differential?