9 inch open differential

[Dr Mabuse]

OEM 28 spline axle shafts are a very bad idea with an Eaton Detroit Locker. Any good traction, and they will break -- 31 splines are minimum, and aftermarket are much preferred.

You might prefer an Eaton Detroit Truetrac Differential ...

http://www.eaton.com/Eaton/ProductsServices/Automotive/AutomotiveAftermarket/Differentials/PCT_338418

[Ratbird]

Thanks Doctor! Mike at QuickPerformance told me the same thing. He has the 31 axles, bearings, and seals for around $425. I'll do those when I buy the Detroit Locker. Do you guys think the standard center section case will be strong enough, or should i spend the extra $$$ and go with one of the others, ie, aluminum, or something else on this page?
https://www.quickperformance.com/Center-Sections_c_57.html

Dave

[bn69stang]

Dave you are addicted  lol  , detroit lockers and 31 spline axles is the way to go , and honestly i would buck up for the better case imo see ng how you cheater slicks .. Bud

[Ratbird]

Indeed I am Bud! So can anyone tell me if the first aluminum one is good enough, or perhaps the "S" (Strange) one?
I have NO idea what the differences are, and which one would be strong enough for 450hp.
The one for $399 is out, but that's not too bad because I want to use the detroit locker, and if I buy one of the $990 ones they give me a break on the cost of the Detroit Locker.

Dave J

[cjshaker]

Aluminum is ok for weight savings on a strip car, but on yours I'd go with the iron "S" Strange unit. PLENTY strong. A Strange center section, Detroit Locker and 31 spline Strange axles is exactly the same set-up I have. Plenty good for 450-500hp.

[Ratbird]

Excellent! Thx Doug.

Now if I can get the crow bar out and open my wallet.
;~)
Dave

[Ratbird]

Oh, one more thing. Does anyone have advice on a gear ratio?

Here's what I have now; 4 sp toploader, wide ratio, 2.78 first gear with 28.5 inch tires.

I'm trying to decide if a 4.30 would be much faster than a 4.11 in the quarter. I'm worried I might have to shift to 2nd gear before I even get moving.

This is a street/strip car, but it won't really be highway driven. Maybe eventually in a few years I'll look at a 5 speed for the highway.

I was using this calculator http://www.csgnetwork.com/multirpmcalc.html
(the section at the bottom) and at 55mph with the 4.30 my rpm would be 2788. If I went with the 4.11 my rpm would be at 2665.

At say 96mph (roughly the end of a quarter mile) the 4.30 would be 4867. A 4.11 would be 4652.

I'm really lost on this stuff.

thx, Dave

[bn69stang]

Go with the iron one , and you can get whole center section from roush - yates racing for  $850.00 ish , iron case with detroit locker and gears set up with different ratios .. Bud

[bn69stang]

430 s may be a bit much for your motor Dave , sense we are close we need to just set up 3.89 s , 400.s , 411 s and maybe even some 3.75 s and try them all ..  lol   Bud

[BH107]

Give Dutchman Axles a call. I just had them do a set for my Galaxie, and they turned out great. They were only $380.00 plus shipping, with the bearings and retainers.

I think you are going down the right road. This stuff is expensive enought, but paying for it twice because you cut a corner the first time just makes it worse.

Perfect example, a friend of mine races off road trucks. When he was building the truck they used a complete rear end they got a good deal on. Full floater 35 spline axles, spool, nodular case, all really nice. Well it wasn't quite up to par with the build of his truck. Part way through the first season he broke both axles. Ok, now upgrade to custom 40 spline axles, drive plates, and spool for the old case. Next it was the ring gear because of the 5.46 ratio. Now fix that and go down a little to make it easier on it. Next it was the spool because it was a lightweight spool, the only one that would fit 40 spline axles in their existing case, and of course that ate some other parts up. Now he's working on replacing it all again, including the housing. He's spent twice what he would have originally, and its cost him several races as well.

The moral of the story is if you want to make 500-600 hp down the road, build the rest of the car for it now if you are changing parts out.

[bn69stang]

Well said , you should always over build drive train  imo   Bud

[cjshaker]

Perfect example, a friend of mine races off road trucks. When he was building the truck they used a complete rear end they got a good deal on. Full floater 35 spline axles, spool, nodular case, all really nice. Well it wasn't quite up to par with the build of his truck. Part way through the first season he broke both axles. Ok, now upgrade to custom 40 spline axles, drive plates, and spool for the old case. Next it was the ring gear because of the 5.46 ratio. Now fix that and go down a little to make it easier on it. Next it was the spool because it was a lightweight spool, the only one that would fit 40 spline axles in their existing case, and of course that ate some other parts up. Now he's working on replacing it all again, including the housing. He's spent twice what he would have originally, and its cost him several races as well.

The moral of the story is if you want to make 500-600 hp down the road, build the rest of the car for it now if you are changing parts out.

Off road trucks are BRUTAL on differentials and driveshafts!

Oh, one more thing. Does anyone have advice on a gear ratio?

Here's what I have now; 4 sp toploader, wide ratio, 2.78 first gear with 28.5 inch tires.

I'm trying to decide if a 4.30 would be much faster than a 4.11 in the quarter. I'm worried I might have to shift to 2nd gear before I even get moving.

This is a street/strip car, but it won't really be highway driven. Maybe eventually in a few years I'll look at a 5 speed for the highway.

I was using this calculator http://www.csgnetwork.com/multirpmcalc.html
(the section at the bottom) and at 55mph with the 4.30 my rpm would be 2788. If I went with the 4.11 my rpm would be at 2665.

At say 96mph (roughly the end of a quarter mile) the 4.30 would be 4867. A 4.11 would be 4652.

I'm really lost on this stuff.

thx, Dave

IF you are sure you won't be highway driving, the 4.30s would make the car feel really peppy and fun to drive.....in town and short distances. Yes, you will be shifting to second quickly, especially with the wide ratio tranny, but that is what will also get the car moving quickly. If you have plans for an overdrive in the future, they would work out pretty well. They also kill fuel mileage and wear motors out if you drive any longer distances without an overdrive. Thinking about hitting the interstate to hit the next town? Forget it. That RPM just shot up to 3550 for 70mph. That's an engine killer.

Realistically, if you want some decent street and road function, the 4.11s are about as deep as you want to go. 3.89s are a nice middle of the road gear for street and performance. Without an overdrive, none of them are 70mph friendly.

[Ratbird]

Thx everyone!
Doug, I was leaning toward the 4.11's and I'm sure it will be plenty fun to drive around the local area. If I ever go all the way to Santa Fe for a cruise it's only 35 miles, and I can slow ride it 50-55 mph to keep the rpms down. This car won't see more than 1000 miles a year so the motor should be good for a long time.

BH107 and Bud, thanks for the reminder about spending the $ and getting what I'll eventually need up front. I've learned that the hard way a few times already. Example; my toploader for $900, then 2 years later I had a David Kee wide ratio large input output shaft kit installed. That makes for about a $1900 toploader that will one day be replaced with a 5 speed.

I'll check the sites you gents recommended today. I was going to go with "Quickperformance", but I'll see if rousch - yates and Dutchman axles come out to a better deal.

Thx again to all!

Dave J

[Ratbird]

Roush Yates has a 4.00 nodular steel, detroit locker 31 spline for $850. Free shipping! Dutchman has the same thing but with 4.11's for $1330 and $50 shipping. Quickperformance has a 4.11 for $1319 plus shipping.

 I'm thinking the Roush Yates at 4.00 is just fine for a 59 T-bird Rat project. That'll give me an SLR of 11.12. A 4.11 would give me and SLR of 11.43 Do you guys think it'll make that much difference?  The car weighs 3680.

Dave 

[bn69stang]

Pull the trigger Dave get the 4.00 and locker from roush , I think they re a good deal .. Bud