Rear End Dilemma

[The Dan]

I keep going back and forth between the 8" and 9". If I go 8" it would be:
8" with 67 center section, Auburn Pro Limited Slip, 3:55 gears. If I go 9" it would be 9" with Auburn Pro Limited Slip, 3:55 gears. I'm around 300-325hp, but waiver as to what I want to do because of the different opinions of what each is capable of. I just don't want to regret anything either way. Help a man out!

 

[reenmachine]

I don't think you necessarily need to go to the expense of a 9" upgrade with 300-325 HP.

 

[Pbum5]

If you have no rearend Go with a 9". It's not that much more and will take a lot more abuse if you keep adding power.

 

[Max Power]

I am not voting till you post some dollar numbers!

 

[ratio411]

Don't waste your money on an 8"...
Let's just assume that your stated power level would not hurt an 8" rear... (it would IMO)
What happens when the mod bug bites you again? You know it will... bolt on a few more HP here and there, next thing you know, the 8" is out classed and chewed up by your engine.
Just do the 9" and have strength to grow when you want more power.
Dave

 

[The Dan]

Max,

To build my current 8" as described $1200

I haven't looked into the 9" yet, but I figure around $1500???

Those that have recently built a 9" care to chime in. And if you got all the parts at cost becasue your Uncles Brother in-law's nephew knows a guy at the parts store, that doesn't count!

 

[67GTFastback]

Max,

To build my current 8" as described $1200

I haven't looked into the 9" yet, but I figure around $1500???

Those that have recently built a 9" care to chime in. And if you got all the parts at cost becasue your Uncles Brother in-law's nephew knows a guy at the parts store, that doesn't count!

I too agree with Ratio, you might as well buy one that will support future mods/upgrades, therefore I would go with the 9". Good luck and let us know which one you choose.

 

[mustangbrad]

If you are done with the engine now the 8" will be fine. If you have any future plans to add power down the road, I would bite-the-bullet and go 9" now.

 

[Max Power]

If they are that close in price, go 9 inch all the way. The only way I would recommend the 8 inch is if you were saving a lot of money and had no further plans for mods.

 

[stangman67]

Max,

To build my current 8" as described $1200

I haven't looked into the 9" yet, but I figure around $1500???

Those that have recently built a 9" care to chime in. And if you got all the parts at cost becasue your Uncles Brother in-law's nephew knows a guy at the parts store, that doesn't count!

Where did you get a price of $1200 for a center section? Seems awfully high.

 

[jaredgoodwin]

9"

I recently faced the same dilemna, went with the 9", no regrets. I picked up ring and pinion gears from summit for $70 less for a 9" than they have 8" gears. Check them out. Helps to offset the additional cost. I don't think you want the rear end to be the weakest link in your drivetrain......

 

[The Dan]

$1,200 was for an Auburn Pro, Gears, Seals, Bearings, 67 Center Section, and Labor.

 

[ratio411]

That is a serious consideration...
8" stuff is expensive and fairly hard to come by due to it's relative unpopularity.
The 9" is the gold standard for all of the performance world and you can get competitively priced parts on any street corner (j/k).
The thing is, the core for an 8" to build is cheap, but then the build is as much or more than the 9".
You pay a little more for the 9" core, but the parts are everywhere, strong, and reasonable due to it's popularity.
Heck, the Nascar guys have used ONLY 9" rears in their cars for decades... no matter GM, Ford, Mopar... that is why gear sets are cheap and available in almost any ratio you can imagine.
When I lived in Charlotte, 9" parts were found everywhere. Good stuff, cheap, run 1 race because the Nascar guys never used a part twice.
Dave

 

[SadbutTrue]

ratio... curious... do you know if Toyota will use the 9" in its Nascar vehicles. That would say something...

But yeah, I would just go with the 9" now. Believe it or not, I think ti will probably end up being cheaper, and be stronger. I was able to convert to a 9 inch rear (reusing my 28 spline axles for the time being) for about $650 total, with a rebuilt 9" third member off ebay and having a shop cut up a housing. You could do the same thing, except with a 31 spline third member and new 31 spline axles for under a grand for sure.

 

[ratio411]

I don't know about Toyota...
I haven't kept up with Nascar since I left Charlotte.
I just thought it was neat while I was there, that you could be like a scavenger picking up Nascar parts for cheap. When one cutting edge head was dropped in favor of another, they would just dump the used heads on the market. If you knew where to go, you could get exotic stuff cheap. Same went for the rear end parts and Jericho toploaders.

Fwiw, I am going to cut the 'pumpkin' out of my 8" and drop in a 9" that I have laying around, then reuse my 8" axles, bearings, and tubes with a 28 spline diff.
They say that you should never narrow or mod a rear end housing from the 'inside', but instead from the flange ends, for strength reasons... so I will weld a back brace on mine when done.
The 28 spline 9" stuff and standard carrier, while not super stout, will handle ALOT more abuse than even a built 8".
Dave

 

[stangman67]

I thought the axles were the weakest link in the 8"? Seems that the 9" rear setup would be as weak with these axles.

 

[67bluestang]

Ratio411 quote: "so I will weld a back brace on mine when done"

I wouldn't weld the the back brace on when done. The back brace should be welded on, then the housing ends should be welded on, but only when using a bar through the housing to maintain straightness of the housing. A back brace really isn't necessary unless you have a high horsepower car and using a transbrake and big slicks. I shouldv'e put one on my Trans Am when i narrowed it, but i never had any problems in 12 years. I left at 5800 rpm against the transbrake, 33X16 slicks, best of 9.00 @ 149.94.

ps: i'd say Toyotas will have a 9".

 

[Mosse]

There was some talk about Curries new 8" pumpkins. Does anybody know about them?

They also have it on aluminum on their web page. 9" rear weights A LOT more than 8", which is an issue if you don´t run only on dead flat roads. At least here north the roads are terrible sometimes...

 

[Edbert]

If you are goiung to stay under 375-400 RWT for the forseeable future then stick with the 8. They are more efficient at transferring power and weigh a LOT less. You can hit the 400+ mark if you get it tricked out, but that will likely cost as much or more than a normal 9 that can take more abuse.

 

[jbsteven]

I am in the market to buy a 9 inch full setup today and need some pointers on where to purchase. I need the rear end, gear and third member.

any ideas on websites where I can find these?

thanks