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Rear Axle Question ... 9 inch v 8.8 inch

  #16  
Old 07-09-2015, 08:41 PM
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Originally Posted by johnson.jeff.a View Post

It's telling me that with an AOD, my 29 inch tall tires, and 4.10 gears I'll be winding at about 2,387 RPM to go 75 MPH. That sound about right to you?

Yes. Assuming your AOD has a .667 OD gear.
 
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Old 07-09-2015, 09:19 PM
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The big advantage of the 9" is the ability to change rear ratios with ease in an hour or two. With an 8.8, it's a much bigger deal.

Just my $0.02
 
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Old 07-10-2015, 07:50 AM
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I have a Ford Racing 302 340/HP 350/TQ bolted up to a 302 with a AOD. Disc brake conversion up front, stock suspension (posies springs). My original Dana 44 with a 3.92 holds up well to ocasional beatings and burnouts. It I am on it hard it has a 1 -2 gear chrip. I did convert it to a posi. cruises 70 at just about 2100 rpm with 15x275x60 tires, 28 inches tall. I have been know to run it 80 for a couple hours on end at about 2400 RPM. Dana 44 is rebuilt all new bearings, seals etc. (no leaks) Posi unit was purchased from Randy's Ring and Pinion.
 
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Old 07-10-2015, 08:16 AM
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Originally Posted by Nicholas+ View Post
Yes. Assuming your AOD has a .667 OD gear.
I'm pretty sure all factory AOD's have the same .667 OD gear.
 
  #20  
Old 07-10-2015, 01:28 PM
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Originally Posted by johnson.jeff.a View Post
the stock Dana is leaking badly
Most have advised that I replace it now, while I have the box off the back, and am replacing rest of drive train.
Where is it leaking from? It would be a lot less expense and work to change 3 seals and a rear cover gasket, since any one of those 4 places is all that can leak unless something is broken, than to do a complete axle swap for no other good reason. The original rear is pretty tough and is probably the last thing to break on one of these trucks. Who are these people 'advising' you to replace it?
 
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Old 07-10-2015, 02:03 PM
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Originally Posted by 52 Merc View Post
Where is it leaking from? It would be a lot less expense and work to change 3 seals and a rear cover gasket, since any one of those 4 places is all that can leak unless something is broken, than to do a complete axle swap for no other good reason. The original rear is pretty tough and is probably the last thing to break on one of these trucks. Who are these people 'advising' you to replace it?
Wayne. I believe it is leaking from both the front seal and the cover. No leaks out at the end of the axles.

Understand your point about not fixing what's not broken, and seals are easier than a swap.

How can I tell what gear ratio is in it now? I don't have a tach. I know the transmission is a T-98, but i don't know anything about its internals (other than that I have bad synchros). I've looked for an external indication, but not sure where to look under the 60 years of crusted oil and grime.

If I could get some comfort that the gear ratio would meet my goals (in original post), or that swapping them out wouldn't be a bigger deal than the 9" swap, I'd love to consider the Dana.

As far as who's told me to replace it.... It just seems like 90% of the folks that I talk to (on-line and in local "Classic Car" shops) say something like "I assume you'll want to get that Dana out of there" To my discredit, I have not done alot of digging into the specific reasons... maybe they all thought I was going for 400+ HP... which I am not.

Thanks!
 
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Old 07-10-2015, 03:10 PM
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There originally would be a small metal tag under one of the rear cover's bolts, with the gear counts on it.
 
  #23  
Old 07-10-2015, 03:53 PM
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To find out your rear ratio, leave one tire on the ground and jack up the other side. Mark your driveshaft with a chalk. Put it in neutral and rotate the wheel two full revolutions. Count the number of driveshaft revolutions. I got almost 4 revolutions out of the driveshaft. It's a 3.92 . Dennis
 
  #24  
Old 07-10-2015, 05:04 PM
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Originally Posted by johnson.jeff.a View Post
Wayne. I believe it is leaking from both the front seal and the cover. No leaks out at the end of the axles.

Understand your point about not fixing what's not broken, and seals are easier than a swap.

How can I tell what gear ratio is in it now? I don't have a tach. I know the transmission is a T-98, but i don't know anything about its internals (other than that I have bad synchros). I've looked for an external indication, but not sure where to look under the 60 years of crusted oil and grime.

If I could get some comfort that the gear ratio would meet my goals (in original post), or that swapping them out wouldn't be a bigger deal than the 9" swap, I'd love to consider the Dana.

As far as who's told me to replace it.... It just seems like 90% of the folks that I talk to (on-line and in local "Classic Car" shops) say something like "I assume you'll want to get that Dana out of there" To my discredit, I have not done alot of digging into the specific reasons... maybe they all thought I was going for 400+ HP... which I am not.

Thanks!
If you've been driving it and it works, makes no strange whines or clunks, you're probably good to go for a long time. The number one reason most guys swap the rear for a 9" is because it's the easiest way to get a higher, more highway friendly rear ratio when running a 1:1 top gear in their trans. There are (or were) thousands of 3.25 9" truck rears laying around for the taking. Since you're going OD, that's not an issue. The most common ratio for your truck is 3.92:1. A 4.27 was optional. Either way, it will be well suited to use with OD. If you pull the cover to fix the leak, you can count the teeth on your ring and pinion gears and calculate the ratio that way. 2 birds killed with the same rock.
 
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Old 07-11-2015, 03:42 PM
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Originally Posted by ALBUQ F-1 View Post
There originally would be a small metal tag under one of the rear cover's bolts, with the gear counts on it.
Ross, Bill, Wayne, Bryan, Dennis (and probably missed someone), based on your comments, I spent time examining the old Dana today. This is what I found out...

The gear tag is still there and says 47/11 ... I think that means 4.27, right?
I can turn the drive shaft slightly (maybe 1/4 inch +/-) with the tires firmly on the ground. Is this level of "slack" ok?
Based on the calculator I've been using, 4.27 gears, AOD (.677 Transmission Ratio), and 28.5 tires should get me to 70 MPH at under 2,400 RPM. I'm fine with an ave highway speed of 65-70 (for this truck).
The leak seems to be coming from the front (where the drive shaft enters housing).

So bottom line... If (a) I don't need posi, (b) don't care about easily being able to swap gear ratio in/out, and (c) will not exceed 400 HP (probably won't exceed 300) for this build....

Should I just replace the seals on the Dana, and use it with my new AOD/302? Would make the project easier/faster, and get me on the road sooner (big deal to me).

Really appreciate any opinions to consider.
 
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Old 07-13-2015, 12:53 PM
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In short, yes.
 
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Old 07-16-2015, 11:37 PM
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Originally Posted by johnson.jeff.a View Post

Should I just replace the seals on the Dana, and use it with my new AOD/302? Would make the project easier/faster, and get me on the road sooner (big deal to me).

Really appreciate any opinions to consider.
I'd say that would be my 'plan A'. You can always change out the rear later if you find you hate it or it isn't working for you. But for now, you can use it and save a bunch of money, time and hassle.
 
  #28  
Old 07-17-2015, 04:09 PM
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I bought my 2002 Explorer 8.8 rear end for $200. I got a bit of a deal due to knowing the owner of the junk yard. Here is something to consider....

The 9 inch, great selection of gears and parts to make it bulletproof and to fit your exact taste. You will have drums so that can be good or bad depending on what you want.

I wanted the 8.8 for these reasons:

8.8 is stronger, the explorers come with trackloc (posi) and 31 spline (beefier) axles. I got the 3.73 rear gear and disc brakes.

If I were to but a 9 inch posi rear end I wouldve cost me more to have the same setup, even though It was closer to a direct fit.
 
  #29  
Old 07-17-2015, 04:40 PM
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Originally Posted by mustangmike6996 View Post
8.8 is stronger.
No, it is not.

That said, they are very good rear ends. They are more than strong enough for all but the all-out race-style engines out there. They're about the same as a GM 12-bolt...But they're not stronger than a 9".
 
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Old 07-17-2015, 10:47 PM
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Originally Posted by Flat Ernie View Post
No, it is not.

That said, they are very good rear ends. They are more than strong enough for all but the all-out race-style engines out there. They're about the same as a GM 12-bolt...But they're not stronger than a 9".
The downfall of the 8.8 is the axle tubes not being welded.

The downfall of the 9 inch is the flex in the housing.

The upside of the 9 inch is the endless amount of parts available (at a $$ price)

The upside of the 8.8 is the standard Trackloc and disc brakes for a fraction of the cost.
 

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