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Discussion Starter · #1 ·
I think my pinion gear is going bad so I am planning on pulling my diff out this weekend. A Ford tech buddy of mine recommended replacing the gears too after hearing the rearend noise (gears aren't whining yet but kinda roar/etc). Bottom line is I don't want to go to all the trouble of pulling the diff and rebuilding the rearend and pay to have it set up again just to find out they whine.

So my first question is do I stay with 3.55's or go to 3.73's? Roughly 600rwhp, only goes to the track a few times a year and I run 26" M/T DR's. And I used the search button already but didn't find a lot regarding this power level, mostly street use and 26" tires.

My second question is, if I am pulling the diff. are there any other "maintenance" parts you would recommend going ahead and replacing? I don't want to do a full bushing kit but if there are certain ones that notoriously wear out etc. then I'd like to do those.

Thanks for any input,
Ryan
 

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doing it with a 2v..
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diff bushings and subframe bushings atleast.. They always look like shit when they come out..

For a street car, personally i like a little less gear.. I was plenty happy with my 3.55s and i wasnt making near 600rwhp..

I also had tried 4.10s, and 3.73s, and i enjoyed being able to stay in the meat of the powerband a bit longer..
 

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horrably stock
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1.Aluminum Diff bushings definately,

2. Maybe a Diff brace if you do not already have one.

3. I would just stick with the 3.55 gear IMO
 

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I spoke with some guys out in Vegas and they say that if you drag race the car then 3:73 gears are ideal for our cars because you can go through the traps at about 6000 rpm in fourth gear instead od 4000 rpm. For the trouble you are going through to pull the rear end out it would easy to put in the bushings while you already have it out. I would call a shop that specializes in rear ends and ask them if there is anything you should change. Good luck!!!!!!!!!!!!!!!!!!!!!!!!!!
 

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Discussion Starter · #6 ·
Thanks for the input guys.

I do already have a diff brace.

James, are you talking about the bolts that hold on the driveshaft? Did 03's come with 12mm or something?
 

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Absolutely, without a doubt, change the fuel filter while the IRS is out. It will be SO much easier to do. It's a real bear to get to with the IRS still in the car.

Jr.
 

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Discussion Starter · #9 ·
Absolutely, without a doubt, change the fuel filter while the IRS is out. It will be SO much easier to do. It's a real bear to get to with the IRS still in the car.

Jr.
I just did this when I added my Fore fuel hat and you are right, it would have been a lot easier with the diff out, lol.

http://www.latemodelrestoration.com/iwwida.pvx?;item?item_no=LRS-4215B 1&comp=LRS

http://www.latemodelrestoration.com/iwwida.pvx?;item?item_no=M4413A 1&comp=LRS

http://store.summitracing.com/partdetail.asp?autofilter=1&part=FMS-M-4700-C&N=700+0&autoview=sku

Replace these parts, and re-shim the diff with 2 of your best used carbon clutches, put them in where 2 steel plates touch together in the stacking order and remove 1 outer steel plate, you will be happy with the results.
I did this shim replacement on my Notch and liked it but with that said taking the diff cover off and replacing the shims in the solid axle is MUCH easier than in this IRS. And I only mention that b/c with the extra clutches does it not tend to wear them out quicker? I really haven't had any issues with the current/stock clutch setup spinning just one wheel so I may leave it as is. Thanks for the links to the other parts, I will check them out.

-Ryan
 

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I'd intall aluminum front diff bushings and a derlin rear diff bushing, at minimum. Subframe bushings should also be high on the list. I personally liked the 3.55 gears with the PD blower. You could also drill and tap the diff housing for a drain plug.
 

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Discussion Starter · #12 ·
You could also drill and tap the diff housing for a drain plug.
That's not a half bad idea. My only negative thought on that is the more holes you introduce to the cover the weaker it becomes and the more places you create for a crack to propigate from. I may see look into doing that though.

Anybody else done this? Did you take it to a machine shop or just drill/tap it yourself?
 

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Not the cover... the housing. You drill and tap the meaty part at the bottom of the diff housing. Many folks have done it without any adverse effects.
 

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I was talking about the bolts that hold the front of the IRS subframe to the car. Most came with 12mm bolts and should be 14mm.
 

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Discussion Starter · #16 ·
Not the cover... the housing. You drill and tap the meaty part at the bottom of the diff housing. Many folks have done it without any adverse effects.
Ah, I like that a lot better!

I was talking about the bolts that hold the front of the IRS subframe to the car. Most came with 12mm bolts and should be 14mm.
Sorry, I meant to edit that up top, I realized what you were talking about after I replied. I have the low profile bolts in the rear holes and I think I checked the other ones before but I'll double check.
 
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