The Differential Shop

The Differential Shop Specialty shop for differential, axle, and gear repairs, upgrades and more.

With over 3 decades of experience, let us help restore or improve your vehicle's axle and differential needs.

05/23/2026

Shop will be closed on Memorial Day

Remember, my friends, the day is meant to honor our fallen service members

Pay your respects accordingly

Here's a cool mystery that needs solved!Saw these pics in a group, and the OP has stumped everyone!For reference, these ...
05/22/2026

Here's a cool mystery that needs solved!

Saw these pics in a group, and the OP has stumped everyone!

For reference, these oddball are installed under a 1971 CJ7

My educated guess is some variation on a D25 or D27, MAYBE a D44

Closed knuckles, diff vents on the covers, weird notch on the casting top

Also note the apparent leaf spring perch casting on the rear axle.....

Let's figure this one out, as I have never seen housings quite like these and Im excited to figure em out!

2013 Raptor gets some fresh FoMoCo Performance 4.10s in the 9.75" flavor, along with some other goodies!
05/22/2026

2013 Raptor gets some fresh FoMoCo Performance 4.10s in the 9.75" flavor, along with some other goodies!

So proud of our Bug, she is moving on to 7th grade!!!
05/20/2026

So proud of our Bug, she is moving on to 7th grade!!!

05/15/2026

Understanding Differential Gear Oil and why its NOT RECOMMENDED to mix different types and weights......no gaslighting or bu****it, all information in this write up is based on real world experiences and technical data from major lubricant manufacturers!

It's a long read, so buckle up

Let's begin with an overview-

Much like how engine oil provides a protective layer on moving engine components, differential fluid, often simply referred to as gear oil, does much the same thing for your vehicle’s differential components.

While your engine uses an oil pump to provide pressurized oil to the engine’s bearings, lifters, etc. the differential uses “splash” oiling by way of the movement of the ring and pinion gears slinging the oil throughout the differential housing.

This differential fluid is used to lubricate the gears, differential and axle bearings, and other components within the axle housing. This gear oil coating also provides heat dissipation of the heat generated by the friction of the ring and pinion gear contact (in racing environments some vehicles use a cooler and pump to circulate the gear oil to an external cooler and then back to the housing).

The gear oil also acts as a corrosion inhibitor, acting as a protective oil film coating on steel and cast iron components inside the differential and axle housing.

What is gear oil weight?

A gear oil’s weight, or viscosity, is measured like engine oil by its thickness with a numerical value associated with it—albeit much thicker.

Where engine oil may be in the 10W30 range for a multi-weight oil, gear oil is more often in the 80w90 or 75W90 range.

Like engine oils, the first number shows the oil’s thickness when cold, while the second number denotes the thickness value once the oil is at operating temperature.

Viscosity is the oil’s resistance to flow. Using the correct viscosity oil (and any differential oil additives) is critical for proper operation of your differentials internal components, as well as the ring and pinion gears themselves.

Higher viscosities suit extreme usage needs but can be too thick for some differentials to work properly.

It is always best to use what the differential manufacturer recommends in most cases for optimum torque transfer and axle oil temperature, while usage and climate will sometimes provide slightly different viscosity needs.

And, just like specialty engine oils, you can find gear oil in single weight viscosity offerings as well.

Mixing different weights or brands of gear oil is generally a bad practice, as it can compromise the performance and protection of the gear assembly (too low a viscosity, not enough friction modifier, etc.).

Mixing additive packages, viscosity ratings, and even base oils are all conditions that may lead to reduced effectiveness of the gear oil’s capabilities.

Topping off your differential with an unknown oil (or not knowing what gear oil is in the differential) is not recommended.

So instead of asking “Can I use 80W-90 instead of 75W-90?” to top off your differential, it is best to drain the differential and refill with the correct amount and type of fluid with the proper additive package your differential requires.

Can Synthetics MIXED With Other Oils?!

What are the consequences and/or benefits of mixing synthetic and non-synthetic oil in an engine crankcase, or any other application such as a differential?

Maybe you have been told that an axle housing can be drained of non-synthetic oil and synthetic oil can be added without flushing any of the prior oil residue.....

In general it is never a good idea to mix two different oils in any application.

If this is unavoidable, there are two major concerns, specifically incompatibility between the base oil, and incompatibility between the additives.

The overwhelming majority of synthetic oils, particularly crankcase oils are PAO based.

From a base oil standpoint, there are usually no problems with mixing a PAO synthetic and a mineral oil since both are hydrocarbon based and chemically very similar.

However, extreme caution should be used if the synthetic oil is non-hydrocarbon based.

As for additive incompatibility, the biggest danger is mixing oils with very different additive packages, particularly mixing those with acidic additives, such as most AW and EP oils, with oils containing alkaline additives commonly used in crankcase oils. In this case, mixing can result in a number of problems including additive drop out, loss of demulsibility, foaming problems and reduced oxidation stability.

The best approach is to select the appropriate lubricant for the application at hand and stick with it! If you are forced to mix oil of different types, it is important that either the lubricant manufacturer is consulted and/or compatibility testing is performed to avoid potential problems.

There are four main families of gearbox oils:
• Mineral oils
• Poly-alpha-olefins (PAOs)
• Esters
• Polyglycols, also referred to as Poly Alkylene Glycols (PG or PAG)

Mineral oils, PAOs and esters may all be mixed together.

Only polyglycol type synthetic oils (PG or PAG) may not be mixed with the other lubricant types. They can react together and form gum gels in the casings.

Furthermore, they can sometimes be incompatible and immiscible with other polyglycols.

Basic principle is that your gears never want to get below a floor viscosity, a minimum hot. What happens cold stays in Vegas. Its always too thick cold no matter what you use.
That said, the higher the VI spread, the more the viscosity will stay thicker at higher and higher temperatures.

As long as you do not mix two different synthetic bases you are good, there is a chance that two different synthetics will react and drop solids but if you just added 100% mineral to a synthetic there is no issue whatsoever.

This is also why when switching between synthetics and conventional oils, it is recommended to run which ever type you want to use for a few days between to flush/dilute any of the original left behind, even if it takes a couple of drain and refills.

Better to be safe than sorry!!!!

If you read this far, you are now equipped with some knowledge to better help understand gear oil function and application, and how best to select your gear oil when the time comes.

Thanks!!!

05/12/2026

Happy Tuesday, friends and family!

I have a huge favor to ask, for those of you interested

With the recent changes at the shop, one particular item could sure use some love-

My new Google Business listing is active, and if anyone thats had work done by me is willing, please submit a review!

Your voice DEFINITELY matters

It would mean the world to me and my little family

Thanks,

Greg

Noah Gates recently brought his beloved 1986 Z28 by the shop for some rear axle upgrades, including some 3.73s, a Truetr...
05/06/2026

Noah Gates recently brought his beloved 1986 Z28 by the shop for some rear axle upgrades, including some 3.73s, a Truetrac Limited Slip and more

He was kind enough to provide a photo with his freshly installed wheels and tires, after getting the car home

What do yall think?

definitely a sexy ride in my book!!

NEW phone is ACTIVE!!
04/23/2026

NEW phone is ACTIVE!!

Hey gang, Greg here at The Differential Shop Getting my lunch break yogurt and granola on, thought I would share our new...
04/22/2026

Hey gang, Greg here at The Differential Shop

Getting my lunch break yogurt and granola on, thought I would share our new logo and some other tidbits

Alright, here we go!

Location stays the same, updated email, new phone number in progress along with some other legal stuff

Wrapping up on the final few installs for PWD, and officially open for business as of May 1st, 2026 under the new name and such

Primary focus will remain Differential Related services, including gear swaps, traction devices, axle housings, custom fab for trusses, and the like

Exceptions can be made on an individual basis, feel free to ask

I won't be selling or installing items commonly seen thru upfitter type shops, like tires, bumpers, winches, lighting, stereos, engine repairs, etc

Gear and Axle related components and repairs only....most makes and models, so basically, if it will fit on my 11,000 pound capacity lift, I can work on it.....

Bench builds are cool if you dont want to bring me the whole vehicle

no automatic transmission or transaxle stuff, no semi trucks or RV type vehicles

Shop policies are being revamped and moving forward, I will not be able to store vehicles or leftover used/customer owned stuff for any length of time beyond completion of services

Operating hours will remain 9am to 5pm, Monday thru Friday, closed on weekends and most major holidays

ALL SERVICES BY APPOINTMENT ONLY

No walk-ins!

Customers have 24 hours upon notice of completion for services to pay their final tab

All services will require a parts deposit upfront, labor due on completion

Labor only services will require a 50% deposit up front

Customer supplied parts are okay, but it remains the customer's responsibility to provide the correct items needed, and their will be NO WARRANTY for customer supplied parts

Labor rate will remain at $150 per hour

Scheduling for services will depend on shipping lead times and parts availability

Average lead times on new parts is 7 to 10 business days

I will provide a 10% discount off Labor for Law Enforcement, Military Personnel (active duty or retired) along with EMS and First Responders

I will also provide a One Year warranty on Labor, with no milage limit, provided post install gear break-in procedures are followed, in addition to any parts manufacturers' warranties

All quotes issued will be valid for 30 days

I do not sell the following brands- Yukon, USA Standard Gear or Nitro Gear

Most all other major brands available, like Revolution, Spicer, Elite Gear, AAM, Motive, Richmond, etc

Note- my labor warranty DOES NOT apply to any vehicles used for racing purposes, weather or natural disasters, Acts Of God or anything thing else deemed abnormal for the commonly accepted use of a motor vehicle

Forms of Payment Accepted will be cash, check or Zelle/Venmo

Credit or Debit Cards will be accepted at a later date to be announced

Folks, one other thing to address-

I am a one man show, and I do not "rush" my installs....setting up gears is a specific process, and sometimes a given job can require more time than the average.....and sometimes s**t happens

A customer's lack of planning does not constitute and emergency on my end

If you want it done SUPER FAST, go somewhere else and deal with them cutting corners

If you want it done right, by someone with over 30 years of professional gear and axle work, come see me and I will be happy to help

Okay, until next time, my little spacemonkeys

PROSIT

2-Cut AAM rear end going back together for this Ram 2500. Work trucks often take abuse and many miles. When that rear-en...
01/21/2026

2-Cut AAM rear end going back together for this Ram 2500. Work trucks often take abuse and many miles. When that rear-end goes out, let us help get your work horse back in commission.




Gear maintenance and proper use. Understanding that a new ratio isn't a free for all, do as you please. The pinion gear ...
01/18/2026

Gear maintenance and proper use. Understanding that a new ratio isn't a free for all, do as you please. The pinion gear and bearing set's will spin up toward 1k times more per mile, depending on ratio change. What's does that equivalate?? More FRICTION and HEAT. Fluids will need changed in lesser mile intervals than factory, and top end highway speeds will need to be respected.

Most gear failures are due to overheating and abuse.

Micro-fractures will occur as the gear surface gets overheated and undergoes its cooling cycle. Most drivers will experience the official POP!!! the next morning as they make their first handful of casual accelerations. The gear will break individual teeth off at those sites of micro-fractures, and it's time for a rebuild!!





Address

3333 County Road 119 Suite 98
Hutto, TX
78634

Opening Hours

Monday 9am - 5pm
Tuesday 9am - 5pm
Wednesday 9am - 5pm
Thursday 9am - 5pm
Friday 9am - 5pm

Telephone

+13252484000

Website

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