Inliners International Forums General Discussion Drive Train Ford 9 rear end strength

OK guys, I'm trying to build a car for Bonneville and need an opinion. For Bonneville, where your traction is limited but car weights and speeds are high, is a stock Ford 9 inch strong enough? I have 35 spline axles and a big bearing housing but don't know if I also need to go to a nodular iron case and Datona style pinion support. I'll use a spool and can get them for either style case. Thanks, I'm stuck on this one and am not sure how to go.

The additional strength that the 9 inch Ford gained part of its reputation from is the fact it uses a 3rd smaller bearing at the tail end of the pinion gear. What kind of engine and torque number do you expect to be running? With limited available traction on the salt I'd think the tires would be the safety valve that will prevent the rear axle from taking severe abuse. If the tires can't resist the torque then the rear drive shouldn't suffer. In drag racing and oval track racing where traction is everything it is a different story.

Having said that I would built a good quality rear but not overbuild it and lean more toward insuring good lubrication for the anticipated speeds.

Jimmy Six once told me he was making, if I remember right, about 600 Hp on fuel. This will be a 320 Jimmy with a stock head. If the planets align, the Gods of the flow bench smile, maybe 450 with a tailwind. The expected speed, if all goes well, would be in the 180 range, weight will be around 3200# I'm not too worried about shock loads, it's the potential warping of the case and subsiquent gear binding that I fear. There is always hope that it will live as is. I'm really just giving JD a chance to dig out his old combo's so I can get a look at them. Care to elaborate on the lubrication part a bit more?

Armond

The nodular iron case is stronger yes You may also want to add The Back brace That is welded to the houseing That goes from end to end. This will make the whole tube much stronger.

For good lube I remove any casting flash and parting lines from the inside of the carrier housing and also smooth or relieve any potential dams between the axle tubes and the center housing where they meet. Coat at least the inside of the carrier housing with a coat of Glyptol.

Choose a gear lube based on what the experienced and successful racers are using.
The pinion rpm isn't going to be any worse than the engine rpm but the ring gear could be spinning at big numbers according to the ratio. This I assume is where your heat concern is focused?

I'm not a LSR guy as you know so I'm having a little trouble understanding where all that heat would come from in just 7 miles, ambient temps acknowledged. Is warpage a common problem for vehicles in that speed range?

From my understanding (not experience) when you put a lot of torque and RPM on a stock case, it warps a tad, this misaligns the gear teeth and causes excess friction. The rest, as they say, is history. This probably wouldn't happen in any situation I'll be in. Where do you find Glyptol paint?

Glyptol is commonly used to coat the insides and windings of electric motors. It is that red colored paint you see when you look inside one.
Check with a local electric motor shop or perhaps even W.W. Grainger. Alternately, engine builders used Rustoleum back in the good old days to promote faster oil drain back through the block valley and upper cyl head areas. With either paint cleanliness is an absolute must before applying.

I think eastwood still sells it??

I believe you're right Larry. Might be the best source if it isn't available locally.

At 450hp I would have no concerns whatsoever about strength, especially with the aftermarket axles you already have. At 180mph I would possibly consider cooling, but with a racing synthetic I might even skip that.

The "extra strong" (9" Ford) "rear end" is mainly for the Drag Strip crowd, isn't it??

It takes a lot of power/torque/strenght to get started/move the weight, from 0 to 1,320' and win etc.

I don't think It's the same at Bonneville.

Happy trails.

Even though it's not the most effecient rear end, having that drop out center section really makes it easy to change gears. Now that there is a center section that accepts Chevy gears, it's even better. I went ahead and bought a 35 spline spool and will shorten the housing when it gets here. Synthetic oil is a must and I've been researching cooling but don't want to get too complicated too soon. I'll look around locally for Glyptol first, then hit up Eastwood. I want to thank everyone for their input, it sure helps!

For efficency you will be way ahead to use the center section with chevy 12 bolt gears. At your power level the 9" is way strong enough.

I have always been told the 28 spline 9 inch was good for 450 ish Hp. I would add the back brace if you are concerned about housing flex.
If you have a lubrication concern I would recommend a set of inner axle seals. I think 'Seals It' makes a set.

I wouldn't count On That Nexxussian.
Seeing That I broke a set of stock 31 splined axles I sherd off a 1 1/2 Off one axle and twisted
up the Other one. In a posi unit.Now I run a 33 spline and a spool.

How much power were you putting to it at the time?

I had it on a Chassi Dyno which was about 15 yrs after the motor was Built and I was pushing right around 325hp @ the rear wheels give or take a little I could find the paper work.So that is about the best i can remember. and I was launching the car right at (no less then) 5000 rpms .With a 4:56 gear an a M20 4speed

The stock axles seem to be the weak link. If you have aftermarket axles and a spool, you should be good to around 700.

But make sure you put a spacer in the pinion, not a crush sleeve! I killed 3 sets of pinion bearings before I got smart, but I have a 6 speed and a locker in a relatively heavy car.

Yep that they sure are. my axles are from strange
33 spline and if i remember right They are good for up to 700 Hp. And if I Brake them I get a Free set of 35 spline.I beleave thats what they told me When I bought the 33s.

Man that's one sweet warranty.

Moser sells a "lightweight" nodular case, I run one in my Mustang, it is 22 pounds, cheap at $235.00, and good for 600 horse.

Seems like it may be the best bang for the buck out there. Some of the heavy duty nodular cases are upwards of 40 pounds....eek.

What are you going to run for rear brakes?

You went WAY overkill with the 35 spline axles, but that is a good thing. Someday I'll assemble my mess of parts and go terrorize the street with my 425 hp mustang... Peter

NOT an inline, but still a bit weird... Ford 351 C stroked to 377"



Here is a picture of the Moser case.

One item to consider - the 9" takes mores power to turn than a chevy 12 bolt - the aftermarket has 9" cases to install chevy 12 bolt gears into.

I thought that was the 'high pinnion' 9 inch only?

Just before my annual journey to Mecca (Bonneville) I cut and welded up the rear end housing. The axles came from Leo's old Chevy after it rolled, as well as the Wilwood disc brakes. I simply can't afford the conversion to put Chevy gears in a Ford 9. When it's built and running, when I'm looking for that last 2%, then I'll do it. Weight really isn't too much of an issue on the salt, as the track is generally smooth. I think for the initial runs, the rear end will remain relatively stock with the exception of the 35 spline axles and spool. I have most of what it will take to dry sump it later. Anyone know what kind of nozzles to use for spraying the oil?
That engine!?, hummmm, must like inlines a lot, looks like two straight fours on a common crank.

Armond, the Model A roadster that we took out to Bonneville for the last 9 years started out with a Latner quick change. It was basically a '39 Ford pickup truck rearend with the rear section cut out and a boxed housing fabricated to hold the quick change gears in. These were built up here in Ontario in the early 50's. The owner took the quick change out 3 years ago and put in a GM Metric 7.5" 10 bolt rearend. After much research, he discovered that this rearend takes the lest amount of HP to drive it. If I remember correctly, the 9" Ford takes about 15%, the GM 12 bolt was about 11% and this one was about 9%. He did make up new tubes with a full floating spindle on the end so you don't loose a wheel if the axle happens to break. This combination has worked great for him. Just have to figure your gear ratio out ahead of time. Have to remember, you are not running on asphalt when you leave the line and with the Model A, he only has 3rd and 4th gear in the Muncie and we push start it. As for torque, it is running a 436 cubic inch Hilborn Injected Nailhead Buick (the original dump truck motor) so I don't think the Jimmy would be any harder on the rearend than the Nailhead was. PM me if you want more info.

I'ts already been determined that a 'launch' on the strip is much more load than will ever be seen at Bonneville.

More than that, he won't be running a 4.56:1 gear, I'm certain. Therefore, the loadings on the axles will be miniscule compared to what you're discussing.

Armond
There is also kits out there That replace the C clip in the chevy rears For the 12 bolt and I do beleave they also now make one for the 10 bolt.

Yes, there are several ways to put together a GM rear end. If I knew the the correct ratio, it would be the best way. That's the trouble. Many cars are geared too high and simply won't pull it or too low and can't achieve the top end speed. With a GM rear, it's a pain in the rear (no pun intended) to change. Unless you know the Cd, rolling resistance and RWH horsepower, there's no way to know the best gear ratio. That's why I decided to initially use the ford 9. That's also the reason I'm try to figure out how to make it more efficient. It does take more power to turn but it's easy to change ratios. Because I'm just a Po-boy, it has to be trial and error. There just ain't no way to get there from here!

What about the Chrysler 8¾" rear? Many seem to give it the same accolades as the 9" Ford, I know one person who says he got sick of changing 9" ford centres and that's why he went to a Dodge.

If you decide to put cooling on your rearend, you don't have to put sprayers on it. Nascars have a suction hose hooked up to the drain hole, hooked to a single stage dry-sump type pump (I'll bet a power steering pump of some sort could be substituted here), hooked to a trans cooler type thing on the frame somewhere it gets air, hooked to another hose that's hooked to the fill hole. That's all there is to it. You get a dirt track pinion that has a pulley on it (they drive an alternator off it), fab some brackets, and there you go.

I don't blame you for running the 9" till you get dialed in. If you ever decide to run the 12 bolt, the best answer is to order your axles with large ford ends, and weld 9" housing ends on the housing when you narrow it. In my experience the C-clip eliminators tend to leak.

Also, go to www.musclemotorsports.com for every 9" ratio ever made. They sell new & used nextel cup surplus.