Gears & Axles - Gear Break-In...I don't get it..

I just put in some Richmond 4.10s. In the booklet it says to break them in by driving for 10 minutes, then letting them cool for 30 minutes...repeat this 3 times. Gear failure will result if this isn't performed.

My question is, why isn't this required when buying a brand new car or truck? What about the cars that get beat on when test driven from the dealer? Something doesn't add up...I mean you would think there would be more gear failures coming from brand new cars if it is SOOO important to break in a new gear. Am I missing something?

Aftermarket gears have a thicker "Fosfate?" coating on them since they are in storage for longer periods of time. When you are breaking in a gear you want to take the coating off slowely since added heat and friction are present and you don't want to break down the oil.

Factory gears are put right into axles with oil and they have a very thin coat on them. Every car and truck is dyno'ed from the factory and they do run them in for a few miles.

I recently bought some 3.73's and they are going in tomorrow, so to be broken in or at least getting there they need to be heat cycled 3 times after installing and then driven nicely to properly break in?

I recently bought some 3.73's and they are going in tomorrow, so to be broken in or at least getting there they need to be heat cycled 3 times after installing and then driven nicely to properly break in?

Yes, and it is a good idea to be easy on them for 500 miles. Bob

What about the people who break their gears in at the track after 1 heat cycle process, and their gears stay quiet?

Ben T.

Racecars do not put the heat into the gear set like a street driven vehicle since they are only driven a short period of time.

Make sure its a broke in with dino oil..... not synthetic....
We dont break in our gears when there new the have them REM finished which takes care of alot of break in probs by totally polishing the ring and pinion Id reccomend this process to anyone with an after market rear its only about 100 bucks..

Well I already put the first heat cycle in with Mobil 1 Synthetic 75W90. Hopefully it turns out ok. The gears aren't whining at all....yet.

I bought motives and did the exact opposite. I installed my gears and drove it straight from the shop to the track and beat the crap out of it. Many many passes later the carrier broke, but the ring and pinion were still golden.

I have installed hundreds of gearsets/diffs and have never "broken in" or "bedded in" as stated, a set in 35 years. Scott@DrivelineSolutions is correct that many aftermarket gearsets are shipped coated with a 'Phosphate', 'Cosmolene' (sp?) or other coating to prevent rusting/pitting during transit or storage. I always wash off any coating prior to installation. I still use machinists dye on the gearteeth to facilitate lash settings and it's much easier to see when the gears are cleaned of coatings. I also only use 'dino' oil with a new gearset. New gears need time to develop a "wear pattern". Synthetic oil clings to the gearteeth and doesn't shear like conventional oil thus taking much longer to create the pattern. Always use a Posi additive to keep the clutches from slipping. It's fine to switch to synthetic oil after about 500 miles but continue to use the additive. REM polishing is great for an all out race car but is overkill for most of us here.

"Scott@DrivelineSolutions Racecars do not put the heat into the gear set like a street driven vehicle since they are only driven a short period of time."

This statement is flat out wrong! Take ANY drag car capable of running about 130mph in the 1/4 cold off the trailer; race it and measure the diff oil temp. Then take your daily driver for a 20 minute 60mph highway cruise and measure the oil temp. If you did you'd retract that statement in a heartbeat.

"Scott@DrivelineSolutions Racecars do not put the heat into the gear set like a street driven vehicle since they are only driven a short period of time."

This statement is flat out wrong! Take ANY drag car capable of running about 130mph in the 1/4 cold off the trailer; race it and measure the diff oil temp. Then take your daily driver for a 20 minute 60mph highway cruise and measure the oil temp. If you did you'd retract that statement in a heartbeat.

Besides, not all race cars are drag race cars. Road race cars build and sustain much more heat in their rear axles/diffs than a drag race or street car ever could! Yes, I know many of them run a diff/gear oil cooler, but it's still a lot of heat over a long time frame.

"Scott@DrivelineSolutions Racecars do not put the heat into the gear set like a street driven vehicle since they are only driven a short period of time."

This statement is flat out wrong! Take ANY drag car capable of running about 130mph in the 1/4 cold off the trailer; race it and measure the diff oil temp. Then take your daily driver for a 20 minute 60mph highway cruise and measure the oil temp. If you did you'd retract that statement in a heartbeat.


I check my axle after a pass in my, 148 mph in the 1/4 car, and I always check my axle after the first pass. It is always warm to the touch but nothing over 90 degrees with a heat gun. I do run my (9310) PRO gears on jack stands for a few minutes when new.

I would disagree with the heat thing I have a temp control device on my rear's thats set to buy pass the cooler untill 260 deg... so temp is between 260 300 deg.... Also If I had a drag car I'd put a 500w heater probe in the housing heats the oul real nice...

Wow, lots of differing opinions. Today I drove the car for 20 minutes, very easy on the gear. I plan on one more 10 minute session, then cool down, then let 'er rip from them on. Hopefully it works out. I am surprised I haven't seen more threads on this.

I check my axle after a pass in my, 148 mph in the 1/4 car, and I always check my axle after the first pass. It is always warm to the touch but nothing over 90 degrees with a heat gun. I do run my (9310) PRO gears on jack stands for a few minutes when new.

Scott, I was actually referring to how quickly a rearend will build heat. One 1/4 mile pass and your diff housing is at about 90*. I'd bet the actual oil temp is up around 200 after only one pass. Thats my point. If you took a street car and drove it at 60 mph for a half an hour or so the oil temp would probably be in the 200-220* range.

"Dailydriver - Besides, not all race cars are drag race cars. Road race cars build and sustain much more heat in their rear axles/diffs than a drag race or street car ever could! Yes, I know many of them run a diff/gear oil cooler, but it's still a lot of heat over a long time frame."

I totally agree with this statement.

"CTSmechanic I would disagree with the heat thing I have a temp control device on my rear's thats set to buy pass the cooler untill 260 deg... so temp is between 260 300 deg.... Also If I had a drag car I'd put a 500w heater probe in the housing heats the oul real nice... "

You must be a road or stock car racer and you can't be refering to a street car. You're talking about controling temps (300*+) that Cup cars would normally generate and they have pumps and coolers to help stabilize temperature. As far as installing a heating element in the diff, the only drag cars I've seen with them are the fuel cars and as far as I know they only use them on really cold days. Maybe others use them but I have'nt seen it. Clue me in please.

I just put in some Richmond 4.10s. In the booklet it says to break them in by driving for 10 minutes, then letting them cool for 30 minutes...repeat this 3 times. Gear failure will result if this isn't performed.

My question is, why isn't this required when buying a brand new car or truck? What about the cars that get beat on when test driven from the dealer? Something doesn't add up...I mean you would think there would be more gear failures coming from brand new cars if it is SOOO important to break in a new gear. Am I missing something?

Many, many years ago I put Richmond 3.73's in my old thirdgen. The break in consisted of leaving the shop, driving about 2 miles to a two lane road, a burnout, then raced my buddy's 94 formula. Drove for a couple years with those gears and never had a problem. Ended up swapping them out for GM 3.42's later. The installation of the 3.42's consisted of changing the crush collar, pinion nut, and fluid. Those worked for another couple years til I sold it. They are still going today. Just wanted to share that. :)

You must be a road or stock car racer and you can't be refering to a street car. You're talking about controling temps (300*+) that Cup cars would normally generate and they have pumps and coolers to help stabilize temperature. As far as installing a heating element in the diff, the only drag cars I've seen with them are the fuel cars and as far as I know they only use them on really cold days. Maybe others use them but I have'nt seen it. Clue me in please.[/QUOTE]

Heat in the gear is horsepower.... pretty much every car or truck in the gagarge is running a heater in the drivetrain and get that thing as hot as you dare... transmission also.. we run a cooler to prevent the temps from going over 320ish.

LOL, my very first gear change in my 3rd. gen. was a 3.73 and a few hours later I got a different kinda bill. A ticket and an appointment with the police officer in the city of Eastpoint MI.!

Don't get me wrong but I don't condone that kinda behavior, but then again I have seen customers out with their cars street racing the very next weekend. :eek2:

The reason I stress such a long break in period is because the torque arms on these cars tends to act as a stethascope of sorts, and noise easily transmits from the rear-end up to the passenger compartment. Sure, you can break in the gears by running down the track, but we have found them to end up being quieter if you give them a good break in period. Bob

The reason I stress such a long break in period is because the torque arms on these cars tends to act as a stethascope of sorts, and noise easily transmits from the rear-end up to the passenger compartment. Sure, you can break in the gears by running down the track, but we have found them to end up being quieter if you give them a good break in period. Bob

I am living with the whole road noise transmittied through the torque arm and it sucks! I followed the break in instructions to a "T" and the rearend has whined since day one! I had a local shop reset the gears after about 500 miles but the damage was already done. I'm so sick of the whine and road noise I'm ready to rip the torque arm off and go back to a stock rearend! I've readjusted the torque arm twice which made it a little better but I still get a vibration at about 70 mph.
I'm looking for a quieter gear(which will be properly installed and broke in) The car never sees the track. Any suggestions?

Well I romped all over it yesterday, no problems. The whine increased a bit after intial heat up and cool down, but it isn't too bad. I actually like it to whine a little bit.

richmonds are loud. I put a set in my buddies car a few weeks ago and they are pretty loud. they may get a little louder after a few heat cycles, what was your backlash set at?

richmonds are loud. I put a set in my buddies car a few weeks ago and they are pretty loud. they may get a little louder after a few heat cycles, what was your backlash set at?

I am not sure. They were installed by my friends buddy who works for our County DOT in the shop. Everyone says he knows his shit so I feel pretty good about them...