Ford 9 strength

[rebelce]

I've gotten to the point where it's time to start building up the rear end.  I have a Ford 9 inch and was given a set of 35 spline Moser axles that are the correct length.  I don't have a problem trying a spool and they make them for both the stock case and the larger stronger aftermarket cases.   My question is simply, on the salt, do we have enough traction to warrant going to the nodular case?  It's an XO/GR and will be weighing in around 3,000#.  At some point fuel is also an option, that would put the hypothetical speed between 150 and 200.

[RichFox]

I never used the N case. never had any reason to wish I did. In fact my roadster with a V8 qc never had any breakage when Al had the blown Chevy in it.

[Rick Byrnes]

When racing the Merkur, I used a Strange Aluminum  9 inch housing and a steel spool.  Engine made 525 lbs ft torque and never had a problem.  (With axle failures I mean.)  Weight was 4200 pounds wet.  By all means use the alloy part if you are inclined to.

Rick

[desotoman]

IMO the only time you would have to worry about a 9" ford rearend in a LSR car would be if you had 1200 or more pounds of lead over the rear end and were able to shock load the drive train. 35 spline axles were originally made for drag cars they should have more than enough strength. There are more efficent rearends out there if you are going to be limited on HP. That might be something to consider also, but just depends on your budget. Good luck.

Tom G.

[ddahlgren]

Speed has nothing to do with it at all.. Think ft/lbs.. I would be more worried about it with a diesel and super low gearing going 2 mph pulling a big load..LOL.. I would go for the most efficient gear design rather than a brand. I would also think light for unsprung weight. Currently to my knowledge a spiral bevel lowest drag gearset (Hewland uses them) and an alloy case a no brainer.. You don't have drag slicks or the bite associated so don't bother thinking drag race or even gears made for it they are heat treated differently for the shock loads..
Dave

[rebelce]

Unfortunately, budget constrains keep me from going with absolute efficiency. You have to do the best you can with what you have. It sounds like I could get by with a stock ford 9 center case and pinion support, the 35 spline axles and spool would add to the overall strength.  Does that sound right?

[maguromic]

If you are going with the Ford you can use the 12 bolt Chevy drop in.  This will help your efficiency with the better pinion angles. Finding gears is another story, but they are out there.  Some of the truck gears can be used with a different pinion bearing.  Are you using the NASCAR style floater rear end?   If you are you can do some work on the hubs to minimize drag. I ran both a quick change (Halibrand) and a Ford 9 inch on a chassis dyno, before going with the Ford 9 inch. There are many other things that can be done to gain efficiency on the Ford gears to heat and oil control. We use an aluminum housing and an aluminum center section with a dry sump system. Mike Feldener helped us with the set up on ours.  He is one of the best in the business and has set up some of the LSR cars and does many of the NASCAR team rear ends.  If you want his number, PM me.

[John Burk]

maguromic

What where the results when you compared the 9 inch to the QC on the chassis dyno ?

John Burk

[Sumner]

Unfortunately, budget constrains keep me from going with absolute efficiency. You have to do the best you can with what you have. It sounds like I could get by with a stock ford 9 center case and pinion support, the 35 spline axles and spool would add to the overall strength.  Does that sound right?

We understand "budget" and run a normal 9 inch (2.47 gears) with a spool and it has worked fine for us so far with Hooley's Stude.  You will have no problems.  Due to the traction there I feel you can get by with at least 40% more HP than you could at the drag strip.  We ran a stock Muncie narrow ratio 4 speed (it's for sale) for the last 3 years likewise with no problems and it never would have held up at the drag strip.  Granted at 241 mph we were running all the HP through it, but the shock loads just aren't there off the line or during the shifts.  We have upgraded to a G-Force 4 speed this year for peace of mind and the option of being able to pick all the gear ratios with one being a 7% overdrive which lets us keep the 9 inch and still pick a final drive.

c ya,

Sum

[maguromic]

John,

I tested both at 2.47, from the quick change to the Ford 9” we gained about 6 HP.  It was interesting when we went to the 12 bolt drop in and it jumped to 10 HP.  My car is HP limited and runs on gas, so the only way is to gain the lost HP.  Remember 75% of the horsepower loss occurs in the drive train.

[Rex Schimmer]

At one time I was real negative on the 9 inch efficiency but from testing that I have heard about and also thinking about it a little in the ratios that you would want at B'ville the 9 inch is a good choice. Unless you happen to have a couple of thousand HPs and a ton of weight to make it hook up you will never brake a 9 inch. When you get into the higher ratios, like 3 to 1 or less, the pinion starts to get lots of teeth and the sliding action between the pinion teeth and the ring gear greatly decreases and the efficiency goes up.

Another area is the gear oil itself. Run the lightest you can get away with and also the smallest amount. The real trick would be to dry sump the diff and spray the oil on to the ring gear just past the point of mesh. I talked to a couple of FWD guys once and they had a Chevrolet 4 cylinder with a BIG turbo, claimed it made 1800 hps! anyway they ran a 9 inch diff in the front and since the motor was infront of the front axle they ran a custom built gear box that changed the drive direction to get the power into the 9 inch. Well the custom box was pretty beefy and they normally ran 2 qts of 140 wt in it, they checked the temp one time after a run and it was over 250 deg F! so they next run they put in one qt of ATF,
No heat and they ran 8 or 9 mph faster and a couple of tenths quicker. So there is power in the diff.

Rex

[maguromic]

When we raced in IMSA in the 80’s we were backed by Ford.  At that time Roush did his own tests with a quick change and the Ford 9” He also concluded that they were able to gain lost horsepower.  All the GM factory cars also ran the Ford 9” till recently when all the factory cars switched to the Hewland.

The dry sump system I built is a copy of the one used on the Corvette Lemans cars.  It’s a two stage pump driven by a electric motor (not the rear end), and Mike at Paterson built me a special tank. Working with the local college here we came up with a nozzle spray pattern. (the spray pattern is very important (like on FI system) or you will aerate the oil and loose horse power).  Like Rex mentioned proper heat control is very crucial in keeping the tolerances set or you will get deflection and HP lost. I use a very light oil that I had custom blended for me.  Depending on how much vacuum you are pulling from the dry sump system there are some other things that need to be done.  If you want more info  PM me.

[rebelce]

Seems like dry sumping the Ford rear end and using a lighter oil.  Other than a custom blend, does anyone have thoughts on a lighter oil, perhaps Amsoil and building a windage system?   I've picked up a two stage pump, so there's a start.

[rebelce]

Well, my pump came yesterday and it didn't help the decision making process.  I guess I'm used to having a scavenge side and a pressure side but here I sit with a two stage pump and it's scavenge on both sides (two stage Stock Car Products).   How the heck do you plumb a system without a pressure pump?   Suck like the devil on the housing and let the vacuum pull the oil in from the tank?   

[dwarner]

No instructions came with the pump?

DW