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Mustang Rear End Gear Installation: Ford Racing 8.8 Ring & Pinion

Created by Jeff Jimenez
Last Updated 8/24/2020

Watch our 8.8" Mustang Rear End Gear Installation Video here. We also cover many ring and pinion questions that most Mustang enthusiast ask about when replacing their rear end gears.

Viewing this install and using the information shared is subject to the terms set forth here - View the LMR Install Instructions Disclaimer.

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Installing a new set of rear end gears in your 1979 to current Mustang is one of the best ”bang for the buck” performance mods you can do. This is especially true of SN95 and Fox Body Mustangs that came with gear ratios below 3.55. Besides forced induction or nitrous kits, there aren’t many mods that will give you noticeable improvements in straight line acceleration like a set of higher ratio ring and pinion gears. Not only will they improve your straight line acceleration but they also help keep you in your upper power band; thus, making installation of rear gears a must for any drag racer.

Now you might be asking yourself, can I install a set of rear end gears in my Mustang? There isn’t a clear yes or no answer to this; however, if you have a good mechanical skill level and a host of specialty tools this project can be done in your own driveway. Be sure to watch the how-to video in this article. It walks you through installing Ford Racing 8.8 rear end gears in Mustangs with a solid rear axle setup.

Mustang Rear End Gear Installation Tools:
  • Bearing and Seal Driver Set
  • Two-Jaw Puller
  • Beam Style Torque Wrench – Inch Pound
  • Large Drifts (Heavy Duty Punch) Tools
  • Dial Indicator (Magnetic Base Works Best)
  • Pinion Flange Tool
  • Slide Hammer
  • Hydraulic Press w/Press Plates and Bearing Separators
  • Common Hand Tools

Another useful tool to help you with the installation is the Ford Racing installation instructions. They can be download here - Ford Racing Gear Install Instructions. Even if you decide to let a professional install your gears, it is definitely worth your time to watch the video and look over the instructions to ensure you know what questions to ask the installer.

So I have covered the why you want new rear gears and even how to replace your gears but you still might be asking yourself what gear ratio is right for your Mustang. For most applications my immediate answer is go with a set of 4.10 ring and pinion gears! For most Mustang enthusiasts with lightly modified to full bolt-on Stangs, 3.73 or 4.10 gears will drastically improve your acceleration and keep you in your powerband. You might hear a few people complain about reduced fuel economy (MPG) with the 3.73+ ratio gears. This can be side effect of these gear ratios; however, you can also see some improvements by getting into better cruising gears sooner. Let’s face it if fuel economy is your top worry then you might need to reconsider modding your V8 Stang. Guys with superchargers, turbochargers or even fully built engines, it may be best to contact your tuner to maximize your rear end gear with your dyno powerband. Having owned many Mustangs with different gear ratios my gear of choice is 4.10 followed by 3.73. If you have a full bolt on ride – especially with a Ford Modular Motor – that sees a lot of drag strip time then you might even consider 4.56 gears.

Mustang Rear End Gear Installation: Ford Racing 8.8 Ring & Pinion - Mustang rear end gear installation

Mustang Speedometer Correction

Once you pick your new rear end gears and get them installed you now have to re-calibrate your speedometer for the new gear ratio. There are a couple different methods of this and they vary by year model. Let us take a look at some of the options for re-calibration:

Fox Body Mustang Speedometer Correction:

Your options are limited on the Fox Body platform. You will need to select the correct speed correction speedometer gear to recalibrate your speedo for new rear end gears. Now you might be thinking this sounds a little complicated but no worries! We have taken all the guess work out of this process with our Speedometer Gear Calculator. Click here to see our calculator: Mustang Speedometer Gear Calculator.

SN95 & New Edge Mustang Speedometer Correction:

If you own a 1994-04 Mustang you have a few different options available to you. The first option is to use an electronic speedometer correction tool most commonly referred to as a Speed-Cal. This has been a proven way to correct speedos for years. It requires some installation and simply reading a chart to ensure you have the correct gear settings entered. If you own a 1999 to current Mustang you have a secondary option – handheld tuners such as SCT SF3 Tuner. With a SCT tuner you can simply plug in your tuner adjust for your new gears and upload the new tune file. While the tuner route is slightly more than a Speed-Cal it opens the door to more benefits that the tuner has to offer – such as custom tunes and a whole list of other adjustments built into the device.

S197 Mustang Speedometer Correction

If you own a 2005 to present Mustang the only option you should consider is using a tuning device such as the SCT SF3 or SCT iTSX Tuner. Tuners like these offer a vast array of options for the S197 Mustangs and even include pre-loaded custom tunes. If you plan on adding things such as cold air intakes or off road exhaust systems these tuners are also a requirement for these to be installed. For 2005-10 Mustangs you can use the Speed-Cal device to save some money but it won’t bring you the benefits that a tuning device can bring to your vehicle. Do yourself a favor and invest in the tuner.

Mustang Rear End Gear Installation: Ford Racing 8.8 Ring & Pinion - mustang speedometer correction

Common Questions We Get About Mustang Rear End Gear Installation:

Does My Mustang Have A 7.5 or 8.8 Rear End?

  • Easy rule of thumb – If you own a 1987 to present Mustang with a V8 you have an 8.8 rear end
  • Also 2011-2014 Mustang V6s came equipped with a 8.8 rear end
  • 1994-2010 Mustang V6 models featured a 7.5 rear end
  • For more information click here: Mustang 7.5 versus 8.8 rear end

Do I Need To Replace My Differential?

  • If your Mustang only spins one wheel – it is time to replace your differential.
  • If you have a higher mileage Mustang and you know it has never been replaced – do yourself a favor and replace your factory differential or replace the traction lock clutches.
  • The Ford factory differential has clutches inside that wear out over time. Replacing them when changing out your gears can save you a lot of time, motion and money if someone else is doing the work.
  • See our complete list here: Mustang Traction Locks and Differentials.

Do I Need To Replace My Axles When Installing New Rear End Gears?

  • To simply install new rear end gears – No, you don’t have to replace your axles
  • If you are drag racing your Mustang a lot – now would be the time to make the upgrade! You will have your rear end apart. You can save yourself some labor by upgrading now.
  • Shop axles here: Mustang Axles

Do I Need To Replace My Axles Bearings & Seals?

  • No, this is not a requirement to install rear end gears; however, if you notice any leaky conditions or know they have never been changed - this is the perfect opportunity to replace them.
  • It isn't everyday you have your rear end apart - take advantage of this situation to replace any old or dated parts. Save yourself some headache down the road.

Do I Need To Install A Differential Cover or Girdle?

  • No, not to install a set of rear end gears.
  • Aftermarket Differential Coves do offer some added benefits and features that are a nice improvement for your rear end. These include:
    • Oil Fill Plugs
    • Magnetic Drain Plugs
    • Main Cap Load Bolts - Reduces cap walk and distortion
    Since your rear end will be apart it is the perfect time to add one to the installation
  • Shop our full line of covers here: Mustang Differential Covers

About the Video

Mustang Rear End Gear Installation: Ford Racing 8.8 Ring & Pinion

Check out our YouTube channel for even more tech tips, installation videos, how-tos, and more. The best place to go for anything Mustang related!

Published on 2013-11-05
See our full line of Mustang Rear End Gears here: http://www.latemodelrestoration.com/products/Mustang-Rear-End-Gears

Are you looking to improve your ET's? Nothing improves your acceleration and helps you launch your Stang like a set of Ford Racing Rear End Gears! The FRPP ring and pinion gear sets are available in multiple gear ratios for your Ford 8.8 rear end. Each gear set includes the pinion and ring gears, crush sleeve and pinion nut. Here at LatemodelRestoration.com we know that you need more than just the gears to finish off your installation. That is why we are the originators of the Mustang Rear Gear Kits!

Each of our Gear Kits features all the needed parts for you properly install a new set of gears in your Mustang! We include only the best components in each kit. They begin with your choice of Ford Racing Rear End Gears (see below of available ratios) and then we throw in Ford Motorcraft Friction Modifier, Royal Purple Max Gear 75W-90 gear oil and finish it off with a master bearing & shim kit.

Installation of your new ring and pinion gears should always be done by a mechanic with a good working knowledge of rear end gears! We put together this how to installation video to help walk you through the install process. If you feel at any point this removal and installation process is above your mechanical skill level -- you aren't alone. Make sure you take your Mustang and new gears to a good trustworthy shop with experience installing Ford 8.8 rear end gears. This video will help you have a better understanding of what questions you should be asking and what to look for in the installation!

Changing your rear end gear ratio will require you to recalibrate your speedometer. For 83-95 Fox Body and SN95 Mustangs, you will need to replace your speedometer gear to fix your speedometer. Click the following link to see our speedometer gear calculator to properly select the correct speedometer gear - http://www.latemodelrestoration.com/products/Mustang-Speedometer-Gear-Calculator . If you have a 1996 to present Mustang your best fix is to pick up a SCT tuning device such as the SF3 handheld tuner to correct your speedometer. You can see our full line of SCT Tuners and Tech Videos here - http://www.latemodelrestoration.com/products/Mustang-SCT-Tuners .

When replacing the ring and pinion gears on your Mustang don't forget to pick up a traction lok clutch repair kit or new traction lock differential. The clutches in the factory unit wear out over time -- especially with aggressive driving. Save yourself time and money by replacing these when installing new rear end gears!!!! See our full line of Mustang Traction Lock Differentials and Repair Parts here - http://www.latemodelrestoration.com/products/Mustang-Traction-Lock-Differentials

Popular Gear Ratios:
If you're like a lot of other people out there, you've probably wondered at some point in time whether or not you're capable of installing rear gears in your Mustang. Well, there's no clear-cut answer to that. You will need above-average mechanical capabilities along with some specialized tools. All I can do here is show you how I go about the process and the tools that I use to get the job done.

You'll want to have on hand a bearing and seal driver set-- this will help you squarely and safely install pretty much any bearing or sealed that you come across-- a two-jaw puller to help remove not only the pinion flange but a couple of the bearings as well. You'll need a beam-type inch-pound torque wrench to check the rotational resistance of the pinion bearing once you've tightened down the pinion nut and crushed the new crush sleeve, a couple of large, high quality drifts to drive out old bearing races, a mag base and dial indicator to check your backlash, a pinion flange holding tool. This will help you keep the pinion flange from rotating whenever you're removing the nut and tightening up the new nut and crushing the sleeve. You can buy a tool that's specifically made for this purpose, or you can make your own. Either way, you're going to want to make sure that it can accept a 1/2-inch drive breakover bar.

And a couple of things I hope you don't need are a pinion depth checking tool and a caliber, be it digital or dial. If you're going to be replacing your axle bearings and seals, you'll want to swing by your local parts store and go ahead and rent you a slide hammer and an axle bearing attachment. Finally, a hydraulic press is going to make your life a whole lot easier, along with a good set of press plates and a bearing separator.

Along with the specialty tools, you're going to want to make sure and have a nice collection of common hand tools along with the stack of new parts, most namely a new set of Ford racing gears for your 8.8, along with an install kit and some axle bearings and seals, if you want to make sure that those are replaced, some quality gear oil and some friction modifier. A couple of things you may want to think about is a reusable cover gasket and, if your Mustang has some miles on it, one of these seal savers. That way you don't end up with a leaky pinion seal. From our website, latemodelrestoration.com, you can download and print the Ford racing instructions for this gear install. That gives you step by step written instructions along with all of your measurements and torque specs for the install.

Lift and support your Mustang and remove the rear wheels. If equipped with drum brakes, remove the drums. If equipped with disc brakes, take loose the caliper, remove the pads, caliper brackets, and rotors. Then remove the ABS sensors.

Remove the 10 differential cover bolts, drain the oil, and remove the cover. Remove the carrier cross pin bolt and then the cross pin. Doing one at a time, push in an axle and remove the C-clip. Slide the axle out of the housing.

Noting the orientation of the main bearing caps, mark each cap if it will help you. Remove the two bolts per side and set the caps, keeping them in order, be it right-hand or left-hand. Carefully pull out the differential and keep the shims located in the right-hand or left-hand position.

Mark your drive shaft and pinion flange. Remove the drive shaft bolts. Then remove the drive shaft or tie it up out of the way.

Using the flange holder tool, remove the pinion nut. Use a two-jaw puller to free the flange from the pinion. Remove the pinion from the housing.

Pry out the old pinion seal as well as the outer pinion bearing and oil slinger. Using a hammer and a drift, remove the inner and outer pinion bearing races. Take an opportunity to remove any remaining oil from the rear axle housing. Using a hammer and the race driver, install the new inner and outer pinion bearing races.

This is a great opportunity to replace your axle bearings and seals. Using a slide hammer and axle bearing attachment, remove the old bearings and seals. You can rent these tools at your local parts store. Using a bearing and seal driver, install the new axle bearings fully seated in the housing, followed by the seals. But the seals just need to be flush with the housing, not fully seated.

Clean off the new pinion bearing races with Brakleen and wipe them down with fresh gear oil. Take your new outer pinion bearing, and coat it thoroughly with fresh gear oil. Then slide it into place, followed by the oil slinger. And finally, tap the new pinion seal into place.

Using a bearing separator and the hydraulic press, remove the old inner pinion bearing from the old pinion and remove the pinion shim. Clean it up, and slide it on to the new pinion. Again using the hydraulic press, install the new inner pinion bearing onto the pinion. Thoroughly coat the inner bearing with fresh gear oil. Slide one of the new crush sleeves onto the pinion, and slide the pinion in to the axle housing.

Inspect your pinion flange. If a groove is present on the seal surface, either replace the flange or use one of the seal saver sleeves to repair your old flange. Slide the flange onto the pinion, and install the new pinion nut. An impact will only get you so far. Some good, old-fashioned muscle is needed to crush the new crush sleeve.

The combination of the flange holding tool and a couple of 1/2-inch breaker bars get the job done for me. Check the tension of the pinion flange often as you're tightening as you don't want to over-tighten. Using a beam-type inch-pound torque wrench, you're trying to achieve 8 to 14 pounds per inch rotational resistance with used bearings or 16 to 28 pounds per inch of rotational resistance with brand new bearings. As with a lot of things, you simply find what works for you and stick with it.

I take a cut-off wheel and remove the cage and rollers from the carrier bearings. Then I use a combination of a block off plate and a two-jaw puller to remove the remainder of the carrier bearings. Remove the ten ring gear bolts, and either tap or press off the older ring gear.

Use the hydraulic press to install the new carrier bearings. Slide the new ring gear onto the carrier, and start a couple of new ring gear bolts to pull it on slightly. Loosely install the rest of the bolts. And snug them up in pattern, and torque them in two stages, first to 35 pound feet and then, final torque, to 97 to 102 pound feet.

Thoroughly coat the new carrier bearings with fresh gear oil. Grab the new races. Clean with Brakleen, and coat with gear oil. Position them on the carrier bearings along with the old carrier shims in the same orientation they came out, and reinstall the two bearing caps. Tighten and torque the cap bolts to 90 to 100 pound feet.

Using a mag base and a dial indicator, check your, backlash. You are shooting for 0.008 to 0.012. Finally, check the tooth pattern with the supplied marking compound. Use the illustrations of acceptable patterns in the FRPP instructions to make sure your gear set installation passes.

Finally, slide your axles back into place. Clean the cover and the housing. And reinstall the cover using one of our optional reusable cover gaskets. Fill the axle housing with new oil and friction modifier, and completely finish resembling the car.

At this point, you'll want to correct your speedometer by using a new speedo gear, a speed calibrator adjuster, or programmer tuner, depending on your year model. Once the car is back on the ground and the wheels are torque, take a test drive. And drive responsibly for a couple of hundred miles, so the gears can set a wear pattern. And that concludes a successful rear gear installation that required no adjustments.

If you're replacing factory-installed gears with Ford racing gears, you should end up just as lucky. However, there are exceptions to every rule. That's where some of these other specialty tools will come into play, like the pinion depth checking tool. It comes with its own set of instructions on how to use it to get the correct measurement to select the right pinion shim.

If your marking compound shows a pattern that indicates the pinion is too close to the carrier or too far away, you'll want to pull this out, along with your caliper, measure out, select your new pinion shim, and start by rechecking your backlash. If your backlash is out of whack-- let's say it's too tight-- then that means, when you're looking at the back of the rear end, you're going to want to move the carrier from the right to the left to give yourself a little bit larger backlash reading. If it's too lose, than it needs to move from the left to the right to tighten it up. You want to take your caliper and measure your existing carrier shims and then use the selected shims provided in the install kit to transfer some of your shim thickness from one side to the other. A quick look at the Ford racing instructions will show you how much of a thickness change will impact your backlash readings.

Also, common sense comes into play as you'll want to make sure and clean everything thoroughly throughout the process and definitely make sure it's all clean before you go back together. That way you don't have to worry about any problems down the road. I also like to keep around some old bearing casings and races for installing the new bearings. This will help you make your installation of a little bit smoother and a little bit quicker.

If you want more in-depth information about our gear kits and you're not viewing this on our website, be sure to click the link below to gather all that information. Also, check out latemodelrestoration.com for more driveline modifications and installations for your Mustang.

Mustang Rear End Gear Installation: Ford Racing 8.8 Ring & Pinion Tech Info

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