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I've got a '64 Mercury Montclair Marauder I'm trying to build up. All the mechanicals were original when I bought the car 2 years ago, including the rear.

It's a Ford 9" rear with a 3.00 gear, no trac-lok. I have someone looking at it (I don't live in the same state as the car anymore) because I want to put a 3.89 in which is in line with my overall goal for the car. What he's telling me is that the carrier is only good to for up to a 3.50 gear so to do a 3.89 we need to upgrade the casting.

Does that sound right? I'm pretty new to doing this kind of stuff to cars so any help/advice is appreciated.
 

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A ford 9" carrier will accept any of the available gear ratios. Some of the bigger gears (4.11 and up),may require some minor clearancing done on the pinion end support webbing, depending on the case, but those 3.89 gears will bolt right in.

I think your guy is thinking of another rear end.

In the knowledge base here, in the rear end section, there is a table showing common carrier breaks of various manufacturers.

Here is a link to that page for you:
http://ring-pinion.com/content/technicalhelp/default.asp?pid=129

Here is another very good web page devoted to the 9" ford.
http://www.kevinstang.com/Ninecase.htm

Hope this helps, Mikey
 

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Thanks Mikey!

That is interesting and just the kind of info I'm looking for. Just to be totally clear that I understand what is being said I've cut and pasted the relevant part of his email:

We will have to change the carrier or drop out casting this casting is where the ratio change is made. The carrier in your car is up to 350 ratio. If we are going to 389 which I think is the way to go also, we need to change the casting it just makes sense to upgrade to a nodular.

But what you're saying is that we can just get a new set of gears and bolt them into the old carrier, right? Does this hold true if we're going to put a Detroit diff in? If we swap the 28 spline for 35?

Thanks for any help!
 

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Yes, you can just buy gears and bolt them on the carrier and have them set up .It does require some precision work, but any rear end shop can do this. Here in california it is about 2 hours work if the case is out.

You don't NEED to swap to a nodular iron case, but you can.
If you are going to upgrade to a 31 spline from a 28 then I think you will need to get a case with the bigger carrier bearings if yours doesn't already have them.. Also a change to 31 spline axles may require bigger housing ends. You will want to check your housing for the big ends. You probably already have them , but you never know.

3.89 gears aren't any cause for a great deal of "upgrades" IMO.

You can just buy the center section (case) with the gears already installed from several suppliers, this may be the way your guy wants to do it. If so it is only natural that he would want to sell you on buying up.

You need to know what you have before you let him sell you anything. You may already have some of the good stuff already.

Later, mikey
 

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LeadSlinger said:
Does this hold true if we're going to put a Detroit diff in? If we swap the 28 spline for 35?
35 spline? What have you got planned for the car? Sounds to me like you've got the wrong guy looking at your wallet....
 

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onovakind67 said:
35 spline? What have you got planned for the car? Sounds to me like you've got the wrong guy looking at your wallet....
Original plan was to rebuild the 390 with a blower but the parts costs are prohibitive. However, I do want the 390 to be a bit more powerful than it came from the factory, possibly stroke it to a 410 with a 428 crank.

Come to think about it, all this is probably overkill. The factory shipped the 427 cars (425hp) with the same rear ends as the 390 cars (300hp) and they held up just fine.

The guys doing the work is charging me cost for parts (no markup) and $40/hr labor. He's a friend of the family and is basically retired, he just likes working on old cars because it keeps him from just sitting around.
 
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