Axle advice needed

[kusanagi]

Hi, I need a spot of advice on my axle components.

I have been stripping my 9 Inch axle down to get it ready for a change of ratio and new bearings and have come  across a couple of problems.

The first problem up, is when I removed the third member and inspected it I found that it had a crack running  through the rear pinion support rendering the third member scrap for my use, so I have decided to build an totally new third member assembly to my specs. I now need to choose a third member, there a several I am looking at:

Summit racings nodular iron case

Strange engineering's S nodular iron case

Strange engineering's Pro series case ( preferred choice )

Are there any other cases I should be looking at.

Next problem is too do with the axle shafts, being that my shafts are 28 spline at the moment and the engine will be producing around  380 too 450 BHP ( flywheel ) with possibly about 400 foot pounds of torque, what's the opinion on my shafts living with these power levels, would it be worth upgrading to 31 spline ( which I am trying to avoid due to the cost ) plus I have a small bearing axle so I will need the special bearings for this conversion and I have been told that these special bearings are no good for street use because they are too small and burn up ( have been told that I need to have large bearing hubs fitted to my axle which also means new back plates and drum assembly's ), I need people's opinion if this is true or not.

I will fitting a Daytona pinion bearing conversion ( probably a Strange iron one ) and a corresponding yoke, I will also be using Timken bearings where possible.

I  am looking at an Eaton Truetrac LSD or should I be looking at a plate type LSD.

Lastly I will also be getting a new crown wheel  and pinion, I was looking at a ratio of 3.70:1 do you think this is ok or should I look at any other ratios as the car will mainly be used for shows and will not see hardly any motorways ( I will also be fitting an 4r70w at a later date ). Also any crown wheel and pinion makes recommended and any I should avoid.

A few specs on the engine and gearbox:

351c, 3v alloy heads, solid lifter Lunati 411A1 cam, other internal mods to match the cam, sequential injection and spark, headers, 2.5 inch bore exhaust system.

FMX gearbox with a B&M shift kit fitted and will be getting a 2800 stall converter.

Any help and advice is greatly appreciated.

 

[Canted 393]

Try these guys they ship world wide, and make an excellent product. I would run a 3.70 gear.

https://www.quickperformance.com/Ford-9-Complete-Center-Section-Third-Member_p_36.html

 

[Kilgon]

A lot to think about. As far as the 3rd member case I know Strange has a good track record. For ring and pinion I have always had good luck with Yukon and Richmond. A 3.70 will work fine for just local driving. You will be turning around 2800 rpm @ 65 mph. I currently am running a 3.70 with a 2800 stall behind a built up 460 with C6. Don't know about the special bearings. A 28 spline axle will hold up to around 400 rear wheel horsepower before the sound of inevitability, the snap you hear when the axles break under heavy acceleration. If you can squeeze the dollars I would switch to a 31 spline. They are about 30% stronger. You could try to find a good used housing if going to go that route and save a few dollars. Figure around $300 to $500 for a set of axels. You will be better off to do it now if you can afford it.

 

[rackerm]

A lot to think about.  As far as the 3rd member case I know Strange has a good track record.  For ring and pinion I have always had good luck with Yukon and Richmond.  A 3.70 will work fine for just local driving.  You will be turning around 2800 rpm @ 65 mph.  I currently am running a 3.70 with a 2800 stall behind a built up 460 with C6.  Don't know about the special bearings.  A 28 spline axle will hold up to around 400 rear wheel horsepower before the sound of inevitability, the snap you hear when the axles break under heavy acceleration.  If you can squeeze the dollars I would switch to a 31 spline.  They are about 30% stronger. You could try to find a good used housing if going to go that route and save a few dollars.  Figure around $300 to $500 for a set of axels. You will be better off to do it now if you can afford it.

With 3.70 gears...."You will be turning around 2800 rpm @ 65 mph." Are you sure about this? I am running my cleveland with a C6 AND 3.50 gears and a truetrac antislip. I register 3,200 on the tach. I plan to go to 3.25 or 3.00 gears to reduce the rpms and be able to take the car on longer trips.

 

[73pony]

At 65 MPH with 3.70 gears and a 1:1 final drive ratio, assuming a 26" tall tire your RPM would be 3,109. With a 3.50 all else the same it would be 2,941. He did mention installing a 4R70w at some point, the final drive on that being 0.667 putting the 65 MPH RPM at 2,074 with the 3.70 gears and 1,962 with the 3.50 gears. Hope this helps.

 

[Bentworker]

https://www.moserengineering.com/1971-73-mustang-ds-and-ps-spline-31.item

I'd run forged axles with that kind of power unless you plan on running hard narrow rear tires as the fuse.  You have 2 choices with 31 spline axles- you can run "large bearing" 31 spline axles in a small bearing housing using the goofy conversion bearings - or you can give up a small amount of strength and run 31 spline axles that are for a small bearing housing - and use the stock small bearings.  Maybe contact Moser or the manufacture of your choice and see what they suggest.

Stock 28 spline small bearing shaft OD is 1.378"

Stock large bearing shaft OD is 1.562"

As for the third member - any nodular iron option should be fine.

 

[Kilgon]

A lot to think about.  As far as the 3rd member case I know Strange has a good track record.  For ring and pinion I have always had good luck with Yukon and Richmond.  A 3.70 will work fine for just local driving.  You will be turning around 2800 rpm @ 65 mph.  I currently am running a 3.70 with a 2800 stall behind a built up 460 with C6.  Don't know about the special bearings.  A 28 spline axle will hold up to around 400 rear wheel horsepower before the sound of inevitability, the snap you hear when the axles break under heavy acceleration.  If you can squeeze the dollars I would switch to a 31 spline.  They are about 30% stronger. You could try to find a good used housing if going to go that route and save a few dollars.  Figure around $300 to $500 for a set of axels. You will be better off to do it now if you can afford it.

With 3.70 gears...."You will be turning around 2800 rpm @ 65 mph." Are you sure about this? I am running my cleveland with a C6 AND 3.50 gears and a truetrac antislip. I register 3,200 on the tach. I plan to go to 3.25 or 3.00 gears to reduce the rpms and be able to take the car on longer trips.

Sorry on that.  If running a standard 205/75 14 (26" diameter) rpm will be around 3100.  I don't know where the 2800 came from. I think I was thinking of the stall converter when I typed the rpm. My tach reads about 3000 - 3100 on mine at 65mph.

 

[kusanagi]

I forgot to mention my tyre size which is at the moment 255/60 15 cooper's ( 27 inch tall ) and I my be changing it for a 275/60 15 BFG not long after the car goes back on the road.

I did look at quick performance and had considered them but I know someone over here ( UK ) that got a quote on shipping and they were very expensive to ship out of the USA, but I will keep them in mind as they have the cheapest complete third members that I have come across that aren't unnamed.

 

[73pony]

I used quick performance as well and was very happy. But as I am in Iowa as well shipping was very cheap for me.

 

[Kilgon]

Quick Performance definitely would have all the parts you need. Out of the hundreds of high performance site's across the US another couple you might try are https://www.speedwaymotors.com/ - https://www.summitracing.com and https://www.jegs.com. They have comparable prices to most of the other speed/performance sites. Don't know how shipping to your side of the pond will compare to other stores or if they even ship overseas.

Just out of curiosity how available are the high performance parts over there locally?

 

[kusanagi]

I have used Summit Racing and Jegs before ( for my engine build ) and I have been getting most of my comparison prices from them, with both of them it works out cheaper to buy the parts separately from them and build the diff myself than try and get the exact spec of complete third member complete from them, also the shipping is not to bad from either of them, plus they sort out the import duty and VAT for me.

As to availability of parts over here I have only three places which I have found so far that might do the parts I need but they are all fabricators for racing and I do not know what there pricing is like as there web sites say to contact for pricing ( never a good sign ), but I will contacting them over the next couple of days to find out the prices and availability of parts anyway.

 

[Kilgon]

I have used Summit Racing and Jegs before ( for my engine build ) and I have been getting most of my comparison prices from them, with both of them it works out cheaper to buy the parts separately from them and build the diff myself than try and get the exact spec of complete third member complete from them, also the shipping is not to bad from either of them, plus they sort out the import duty and VAT for me.

As to availability of parts over here I have only three places which I have found so far that might do the parts I need but they are all fabricators for racing and I do not know what there pricing is like as there web sites say to contact for pricing ( never a good sign ), but I will contacting them over the next couple of days to find out the prices and availability of parts anyway.

You said it - "Contact For Pricing" is like saying it going to cost you an arm and leg along with your first born.     Sounds like a good place to open a speed shop retail store.

Good luck on your build.   Let us know how it go's.

 

[tony-muscle]

I had an excellent experience with Strange. I got their already assembled third member with their S-series case, Truetrac, Daytona bearing, 3.5 gear, in addition to their 31 spline axles with pressed bearings and built-in oil seals. Working great so far!

The 3.5 is perfect for me. With my TKO600 in 5th gear at 80 MPH, is about 2,200 rpm. Cruises great and plenty of power in 1st gear to spin the tires with little effort.

-> I have my old third member if you are interested in a case. I have it for sale with the gears, but a worn pinion bearing.

In regards to the 28 and 31 spline axles. The other day at a car show I was talking to a guy that drag races his Mustang. He had a supercharger and slicks. He mentioned that he has run his 28 spline axle for many years with no problems. Take it for what is worth it. If you will be replacing everything may as well go with 31 since it won't cost anything else besides the axles.

 

[kusanagi]

Well I phoned one of the firms in question ( this place had been recommend by a member of an owners club I belong to ) and had a very good talk with the person who I spoke to, he gave me a price on some 31 spline shafts ( £350 + VAT ), bearings ( £80 + VAT ), retainers ( £20 + VAT ) and studs ( £22 + VAT ) which was not too bad but he recommended that I stay with my existing 28 spline shafts as I am staying on street tyre's and he did not think that I would break them.

I also got a quote on a complete third member built with a Strange case, Eaton Truetrac, Daytona pinion support, Timken bearings and a ratio of my choice ( £1425 +VAT ) which was not a too bad a this price as this works out about the same as getting a complete third member of the same spec from one of the major company's ( Summit, Jegs ) but with much cheaper shipping ( about £25 against £140-£220 from the USA ) plus if I have any warranty issues I only have to deal with a UK supplier.

So it looks like I might go for this supplier instead of buying the parts separately and putting it together myself as I would only be saving about £150, all I have to do now is finalise which ratio to go for.

Thanks for the offer of the case but after shipping costs to the UK I might as well go for a new case.

 

[Spike Morelli]

I have been running a3.50:1 trac-loc in my mach for many years. It revs somewhere around 3500 at 70. I don't think that's high rpm. It seems like there are many guys here on the boards that are skittish of rpm. If you are truly building your car as a "high performance' car, you should be building for somewhere upwards of 5000. In many cases, people who install a high performance camshaft, and then overdrive, to limit the engine's rpm, are missing the whole point. Decide whether or not you really intend to have a high performance car, or have a Grand Tourer street car. Shelby GT-350s came with 3.89:1 gearing. Would you shy away from driving one? Drag cars prefer a certain gearing, roadrace cars on a short track, another, roadrace cars on a long track yet another, salt flat cars go even higher ( lower numerically ). My relatively mild Engle hydraulic flat tappet cam is right in the pocket, and "on the cam" at 3500. I am assuming most here on the boards modifying their engines have an even more aggressive cam than mine, and probably require a larger rpm window to benefit from it, so as long as your engine has been truly built for performance ( from the inside out, not just bolt-on ), don't be afraid of gears.
P.S., I run a stock case Ford 9" with 28 spline gears, stock axles too. It works well for me.

 

[mrgmhale]

Our 73 Mach 1 had its 302 2v replaced by the prior owner with a 1994 F-150 351W (not C), using 1969 351W 4v heads. The engine is built as a moderately street.strip performer (360HO at the crankshaft). To help goose a more spirited level of performance he replaced the original 2.79:1 rear axle gears with a 3.5:1 TractionLok set of gears. At 60 MPH in 3rd gear (C-4 auto) the engine would turn at about 2,950 RPM when cruising with no load other than maintaining that speed on a flat surface. The tires are P235R60 x 15. The other year the C-4 began to slip badly in Wide Open Throttle 1-2 upshifts. Rather than monkey with the tranny, I used that as an excuse to replace the C-4 with an AOD.

Wow! What a transformation. I still have great low end performance from the 3.5:1 TractionLok, but I now cruise at 60 MPH turning just about 1,950 RPM. Plus, the engine has plenty of torque and horsepower to push through the increasingly significant air resistance at higher speeds. What a fun modification that turned out to be. I ended up getting the best of both worlds, a pony car with enough power and good gearing to be able to make low speed performance (off the line acceleration, launching off "the line") lots of fun, while also being a terrific cruising machined with plenty of punch to it for whatever comes my way.

 

[c9zx]

The small bearing burning up is nonsense. On street tires the 28 spline would likely live but, go with the 31 spline axles. If you have the 3V heads and the other bits are matched to use the head flow, you should make WAY north of 400 flywheel HP.