If I understand correctly, the 9 bolt is stronger than the normal 10 bolt, correct? Not a 9" strength (or is it?), but stronger than the GM 10 bolt.?

But replacement parts, different gears, etc., are quitea bit more expensive, huh?

 

Yes, the 9 bolt is stronger than the 10 bolt, but nowhere near as strong as a 9". The 9 bolt is relatively uncommon, so parts for it are rare and expensive.

 

Thanks. I had heard they were stronger than a 10 bolt, but not sure how they compared to a 9 inch.

I knew the parts were more expensive, especially due to the "limited" production of them. Not near as many 3rd gens go them, as the 10 bolts. I guess that is a good reason to hold on to my spare 9 bolt. It even has the same gears! I could blow out my GTA rear, and be going again the next day, with no speedometer problems even!

 

I knew they had a Dana name, but couldn't recall, so I searched...

"The 1987 350 cars had a Borg Warner 9 bolt 7.75" otherwise know as the Dana M78..

The 350 car had 3.27's on a limited slip 3 series carrier.. Using tapered axles instead of c-clips.. Officially the Dana M78 is only rated to hold 300ft lbs. but most of the rear ends see 400-500ft lbs. regularly.

In America, this rear end is refered to as the 9 bolt. If you leave the country its the Dana M78. Your supposed to change the oil every 7,500 miles! using 4 ounces of additive and the rest gear lube.. I forget the weight. Its like 80w-90 GL-5 which is 10 bucks a quart.

You can identify this rear end because of this 9 bolt pattern and the rubber drain plug. If your lucky it has disc brakes.

The rear end is supposed to be as strong if not stronger than the corvette dana 44. The replacement part for troubled 9 bolts from gm was the dana 44. The reason being is that these rear ends were manufactured for Holden Corporation a subsidary of GM in Australia by Borg Warner."

 

The main problem with the 9 bolts isn't even the expense of the parts, but the lack of new parts for them. Nobody sells new posi carriers for them, and about the only gear ratio you can buy new for them from the aftermarket is 3.70's. The bad thing about not being able to get a new posi unit for them is the fact that the posi is a bad design, and quite prone to burning out the cone clutches frequently. The 10 bolts are a bit weaker, but the vast availability of replacement parts at a lot cheaper prices more than makes up for this. The best solution if you need a stronger rearend than stock is to get an aftermarket 9 inch or 12 bolt that's custom made for our cars. They're expensive, but readily available if you're building a really stout thirdgen.