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Rearend upgrade for V6 buying guide.

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As an international member I have to really look into things and be wise about my purchases because EVERTTHING that I buy for my car har to be shipped all the way around the world which is expensive and in case something is wrong with the parts its too expensive to ship them back in most cases.

Don't know if you we should sticky this too? :drinktothat:

Anyway; I wanted to share my findings and hope it will be useful to others as it has as well.

ALL 1994 to 2010 v6 came with open carriers and 7.5" rear axels. And all were rubish! ..So this is a place thats in desperate need of some upgrading.

You can either choose to build your 7.5" or swap to an 8.8" from a GT or Cobra.

To build your 7.5" axle you will need the following:

- LSD (Tlok)

- Gears

- Bearing kit

- Speedogear (for 94-98)

- Tuner (for 99-10)

- Gear oil

- Friction modifier

And all adds up of course (new prices given, just use AmericanMuscle in our example, I rounded up the prices since $17 is the f'n same as $16.99)

- LSD - $480 - http://www.americanmuscle.com/auburn-hp-28spline-75-lsd.html

- Gears - Motive gears = $170 - http://www.americanmuscle.com/motive-373-9498v6.html

- Bearing kit - $75 - http://www.americanmuscle.com/rearendrebuild1.html

- Speedogear (for 94-98) $8 - http://www.americanmuscle.com/speedo-gear-21tooth-auto.html

- Tuner or speedo calibration tool (for 99-10) - $116 - http://www.americanmuscle.com/ford-speedo-tool-9410.html

- Gear oil - $17 - http://www.americanmuscle.com/royal-purple-max-gear-75w90-gear-oil.html

- Friction modifier - $13 - http://www.americanmuscle.com/frpp-friction-modifier.html

So lets say we have a 96 V6 mustang, in which case we need a speedo gear and not a calibration tool. Then we are looking at a subtotal of $763.

Can we do better than that?

Well lets see; our other option is swaping out the 7.5" with and 8.8" from a GT or Cobra. These can be found on junkyards as well as on Cregslist and different forums for cheaper than this, but lets take MPS AutoSalvage just as an example: http://www.mpsautosalvage.com/sunshop/index.php?l=search_list&s[search]=&s[title]=Y&s[short_desc]=Y&s[full_desc]=Y&s[sku]=Y&s[match]=all&s[cid]=71 - Note: you will still need a speedogear or recalibration tool for the change in rear gearing. It is also recommended that you service the axle when you buy a used axle (Change diff. fluid and rebuild the t-lok (use cobra carbonfibre discs))

This will do (http://www.mpsautosalvage.com/sunshop/index.php?l=product_detail&p=2820) - $575

Speedogear - $8 - http://www.americanmuscle.com/speedo-gear-19tooth-auto.html

Subtotal: $583

Diff: $180!

So in other words, it is $180 cheaper to do the 8.8" swap if we look at purchase price, shipping will vary depending on where you live.

Here is some good info that I will move over from another site;

Pleaso note; the below is ALL written by matt'sdrag95, I will not take credit for it. The only edit that I have done is remove the links he posted, only because his write up was made in 2005 and prices are different now and some of the shops he linked to are no longer in business.

Gear Choices:

2.73(7.5,8.8)-stock 94-98 gear. highway gear, poor acceleration

3.08(8.8)-stock cobra gears 94-98 better acceleration, good top end

3.27(7.5,8.8)-stock 99+ gear. better acceleration

3.45(7.5)-3.55(8.8)-decent increase in acceleration while conserving top end drivability.

3.73(7.5,8.8)-best all around gear for acceleration and highways use

4.10(7.5,8.8)-great acceleration gear for drag racing, limits top end

4.30(8.8) or higher-really only for drag racing where a taller tire is used. not recommended on street where stock tire height is used.

Parts Needed For Proper Calibration:


speedometer gear(on sensor)

3.08-#F1131, 16tooth, dark red

3.27-#F2673, 19tooth, pink

3.45-3.55-#F1150, 20tooth, black

3.73-F1302, 21tooth, red

-DFM17271A, 23tooth, white

4.10-F1150, 20tooth, black

-DFM17271A, 23tooth

-Dodge 25tooth

- A chip to extend your redline, or bump top speed is a good idea as well.


-(Automatic transmission) A chip is needed to electronically correct the speedometer.(this can also be used to bump top speed, and redline.)

-(Manual Transmission) You can use a speedcal to correct the speedo.

Answers to FAQ:

-A T-lok differential is a version of a limited slip differential. It is unlike the open carriers that come stock in mustang v6’s. A T-lok allows power to be applied to both wheels once slipping occurs. It is fully possible to have equal power transferred to both wheels at the same time.

-Yes, you can change your gears and not add a t-lok if you so desire. Just remember that you will not benefit from increased traction associated with a limited slip differential. You will only benefit from faster acceleration.

-Used gears and T-loks are ok only if bought from a reputable company, or you know the previous owner of the gears. If the gears were meshed well, and there is no signs of abnormal wear, then they will work just fine for you and not cause any noises.

-Installing a set of numerically higher gears will do two things to your gas mileage:

1)Decrease gas mileage during highway travel, because you will be driving at a higher rpm then stock.

2)Increase gas mileage around town because you can find yourself driving the same mph, but one gear higher(ie, 40mph in the low end of 4th, instead of 40mph in the higher end of 3rd.)

-Depending on how steep of a gear ratio you buy, you can expect up to a half second reduction in elapsed times at the drag strip.

-All v6 mustangs come with 7.5 rear ends with an open carrier differential. They can roughly handle 300hp. Using sticky tires, such as slicks, and launching at high rpms can cause breaking even if you do not have 300hp.

-A 8.8 is a much stronger rear end than a 7.5. The actual rear end itself is larger, which allows the parts inside to be bigger(carrier, differential, gears), thus making them stronger. Many people swap to 8.8 rear ends because it can be more economical to buy a whole 8.8, or a used 8.8 than replacing, and installing parts on a 7.5. The axles and brakes are interchangeable between the 7.5 and 8.8 axles as well providing the differential in the 8.8 is not made for 31spline or larger axles(stock 7.5 and 8.8 is 28spline).

-Other alternatives to a Ford T-lok, are performance limited slip differentials made buy Eaton, Auburn Gear, and more. These limited slip differentials have the ability to handle much more power than a Ford T-lok.

-A good general rule of thumb, best gear choices for all around performance are 3.73 for manual transmission cars, and 4.10 for automatic cars.

-It is NOT required that you purchase a chip for a 94-98 car.

Customer testimonies:

Monkey(1998, auto)

i have 4.10s with Auburn posi in an 8.8 carrier.

got the whole setup for 615 shipped on ebay

i love the 4.10s. They make my auto come alive. City mileage is still great, and highway is still really reasonable too

slvr2000stang(2000, auto)

I put 3.73's & a t-lok in. Both were purchased from gefracing:

I am very happy with the way it drives now. It climbs up in RPM's quickly and that makes it fun to drive.

greenflash00(2000 auto)

4.10s and T-lok from gefracing:

All i can say is...well...4.10's ARE ABSOLUTELY AMAZING!!!!!!!! My car pulls sooooooooo hard now. 2nd feels like 1st used to feel, and 1st is just insane. If you stomp it, HOLD ON!!.....I can actually feel myself being pressed against the seat quite a bit. I had to drive about 140 miles home from the shop, (interstate) and as of right now, the mpg is just slightly less than with the stock gears. VERY slightly less. I know that there have been a lot of 4.10 success stories recently, but they really amazing.

Source: http://3.7mustang.com/vb/f6/everything-you-need-know-gear-swaps-etc-29525/

Overall Conclusion:

It is cheaper to do the 8.8" and you get a stronger axle that will hold much more power.

Remark; it is also easier and cheaper to find maintenance parts for the 8.8" than the 7.5", and there are more and better aftermarket parts available for the 8.8" as well.

For international members: The cheapest forwarding company to use for heavy parts is to my knowlage http://www.shopusa.com/ - They also have a neat price calculator for your total cost as well.

How to: Do the 8.8" swap?


How to: Install an LSD in a 7.5"?


Edited by MMR
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