Not shure what to do with my rear when i bought my 84 as a roller it already had 4:10s when i had my small black in it (around 425hp) the rear held up. now that i went big block im not shure that its gona hold up long.... I dont wana buy a 9in or 12bolt i just dont have 2500$. Is there anyway to build my 10 bolt up

 

and is it a 7.5 or 8.5 that came in 1984 z28 h.o cars... also what spline axels can i run

 

As i see it you have only one option. Drive with a very light foot until you have saved enough for the 9" or 12 bolt.

 

26 spline. You can put a cover to support the end caps, chage the fluid as you should. Also put in a posi and stronger axels if you need them.

 

Your rear is a 7.5" 10 bolt with 26 spline axles. However, all parts are interchangable with the later 7 5/8" 26 spline axles and 7 5/8" 28 spline axles.

You can build them to support decent power, regardless of what others say. Follow this buildup: http://www.ws6transam.org/10bolt.html

Or, if you're BB is making a good bit of torque and you've got a high stall converter and sticky tires the 9 bolt that came in the mid-late 80s F-Bodies would be an excellent alternative. They are significantly stronger than a built 10 bolt. And although parts prices for the 9 bolt are more expensive than the 10 bolts, its still much cheaper than a 9" or 12 bolt.

 

Just how much horsepower can those 28 spine axels handle anyway? Does anyone know?

 

I believe it can easily handle 500 HP on an A4. Now on a M5 where you drop the clutch at 5000, that might be a little different.

 

it a Th400

 

Doesn't matter. The thing is that with a stick, when you launch, you might drop the clutch at 5000 rpm or whatever and you shock the system more than if with an A4, or A3 in your case, you probably will launch at about 2000 or so.