Best Rear End for 409

[La Hot Rods]

What transmission are you using?

 

[La Hot Rods]

So all of this info leads me to a question or two. How much horsepower (approximately) does it take to turn a 12-bolt, or a 9-inch or any other rear end? My third members, once broken in, seem to turn relatively freely. I was surprised to read Mark's post that a car lost .2 just by switching to a Ford gear, that would seem like a fair amount of HP was involved. I have heard this before, but I have never seen it quantified and I have to idea what it takes to turn a rear gear.

Must be why Strange makes a dropout for the 9 inch that takes 12 bolt gears.

 

[Don Jacks]

What gear is in it now?What cam is in the engine? If you're running about 236 or better at .050 and an automatic trans,then 3.73 for short tto moderate driuving,3.55 if long road trips are planned.If the cam's smaller,3.55,or 3.36. A 10-10.5 compression 409,using 817's,aan Edelbrock single 4 bbll.intake,a 650-750 carb.,and a 224 inttake cam ,bolted to a 3 speed automaatic trans would be fun with 3,.08's.It depends on your combination an dseires.

 

[Don Jacks]

So all of this info leads me to a question or two. How much horsepower (approximately) does it take to turn a 12-bolt, or a 9-inch or any other rear end? My third members, once broken in, seem to turn relatively freely. I was surprised to read Mark's post that a car lost .2 just by switching to a Ford gear, that would seem like a fair amount of HP was involved. I have heard this before, but I have never seen it quantified and I have to idea what it takes to turn a rear gear.

Part of that .2 is due to the fact that the 9 is somewhat heavier than the 12 bolt as well.

 

[RAG 65]

What transmission are you using?

Turbo 400

 

[quik9r]

tire height has impact but 331 342 355 gear

 

[rsavage]

I removed the original 4.11 (saved them of course) and put in a posi 3.36. I run 235 70 15 tires, original 4 speed, and I can drive at 60 at approximately 2600 rpms. That is right where I wanted to end up. With the original 14" tires and the 4.11's I was at 3000 rpms at 50. It has the original engine and I wanted to both drive and preserve it.

 

[427John]

Turbo 400

Assuming some sort of big block with the Turbo 400, I would go something in the mid 3's 3.36 or 3.55 nothing lower, the larger and more powerful the engine the less gear you need. If you're talking a small block I would be considering a Turbo 350 especially if its a 283 thats light on torque and then I would consider dropping down to a 3.70.

 

[Greg Reimer]

Seemed to me that one of the aftermarket sources offered a 9 inch carrier that took 12 bolt gears. That would be a good low friction thing for anything that has a 9 inch and wants an edge.

 

[RAG 65]

Assuming some sort of big block with the Turbo 400, I would go something in the mid 3's 3.36 or 3.55 nothing lower, the larger and more powerful the engine the less gear you need. If you're talking a small block I would be considering a Turbo 350 especially if its a 283 thats light on torque and then I would consider dropping down to a 3.70.

2500 stall or 3000 stall or something different?

 

[Don Jacks]

Depends.On a mild cammed,10 or so compression street operated car,2,000.IF it's going to see any strip action,2500.Gear selection matters as well.

 

[427John]

If it were me and I was going with the 3.55 gear I would stick with the stock converter, I wouldn't bother with a looser converter for the uses you stated unless I went with a 3.08 or numerically lower ratio. A nice 409 backed by an auto with 3.55 gears will have plenty of pep, for cruising you will appreciate a tight stockish converter.