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Old 02-13-2020, 07:40 PM
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New Gear Question

I've read many posts and published articles how to properly break in new gears. Obviously plan to closely follow my shop recommendations but still have a question no one has asked.

I've purchased MANY new vehicles including 6 F150's, 3 4Runners and other 4x4 vehicles. Why do new gears installed by a shop seem so fragile compared to OEM? I bought several trucks which had to be driven over a 1000 miles to get home and there was never a mention of driving slow so the gears didn't over heat? Also NEVER had any gear issues with any of these trucks even towing a 9k trailer. The OEM rears also have synthetic lub installed which isn't recommended for break in from most shops?

I'm curious if someone could explain why the difference? New vehicles don't seem to have any issue with jumping in and driving at highway speeds. I'm sure if it was a problem with gears failing there would be instructions from OEM to follow some type of procedure. With the new warranty it's their dime if they fail! I'm sure if there were problems with driving a new vehicle to fast or far the purchaser would be made aware of the limitations on the rear end?

I'd appreciate if someone can explain what the difference is between OEM versus shop installed gears? I'd like to know why new OEM gears don't seem unduly effected by simply driving the vehicle normally?

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Old 02-13-2020, 08:16 PM   #2
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https://www.randysworldwide.com/reso...gear-break-in/

https://eastcoastgearsupply.com/ft-1...procedure.html

https://spicerparts.com/whatsthediff


Three quick reads from a search. Someone just discussed it recently here too about the quality of the oem gears and the most from the factory is 4;10's. I would just follow the directions for the gear set you buy.

https://www.wranglerforum.com/f274/b...n-2388939.html


https://spicerparts.com/parts/axle/c...pinion-gearing from the site i included above
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Old 02-13-2020, 08:34 PM   #3
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Originally Posted by cthusker View Post
I've read many posts and published articles how to properly break in new gears. Obviously plan to closely follow my shop recommendations but still have a question no one has asked.

I've purchased MANY new vehicles including 6 F150's, 3 4Runners and other 4x4 vehicles. Why do new gears installed by a shop seem so fragile compared to OEM? I bought several trucks which had to be driven over a 1000 miles to get home and there was never a mention of driving slow so the gears didn't over heat? Also NEVER had any gear issues with any of these trucks even towing a 9k trailer. The OEM rears also have synthetic lub installed which isn't recommended for break in from most shops?

I'm curious if someone could explain why the difference? New vehicles don't seem to have any issue with jumping in and driving at highway speeds. I'm sure if it was a problem with gears failing there would be instructions from OEM to follow some type of procedure. With the new warranty it's their dime if they fail! I'm sure if there were problems with driving a new vehicle to fast or far the purchaser would be made aware of the limitations on the rear end?

I'd appreciate if someone can explain what the difference is between OEM versus shop installed gears? I'd like to know why new OEM gears don't seem unduly effected by simply driving the vehicle normally?

Yeah, and I think that's total baloney too. I think the gear oil SHOULD be changed on new vehicles.


I had a front axle seal leak at about 20,000 km's. That's pretty young to have axle leaks. When I opened up the axle to change seals, I couldn't find anything wrong the the factory seals other than the fact they had a rather huge build up of oil/gear dust.


I'm pretty sure that if I changed out that gear oil at maybe 1500 to 2000 Km's (in other words after an initial break in period) those seals would not have leaked.
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Old 02-13-2020, 08:45 PM
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Yeah, and I think that's total baloney too. I think the gear oil SHOULD be changed on new vehicles.


I had a front axle seal leak at about 20,000 km's. That's pretty young to have axle leaks. When I opened up the axle to change seals, I couldn't find anything wrong the the factory seals other than the fact they had a rather huge build up of oil/gear dust.


I'm pretty sure that if I changed out that gear oil at maybe 1500 to 2000 Km's (in other words after an initial break in period) those seals would not have leaked.
Never experienced any leaking factory seals from any of the 4x4's I've owned. Never changed the gear oil as it wasn't on the list of things to change. Having said that perhaps simply the luck of the draw that I've never experienced a problem.

My shop said the oil MUST be changed at no more then 500 miles along with a list of other driving recommendations. I'll certainly follow all their recommendations after spending a good chunk of change getting it regeared. Don't need to create issues with a new install that's for sure.

I'll have a 200 mile drive home so it's simply going to take longer which isn't a big deal. I was simply curious why new vehicles don't have any prohibitions regarding speed or required cool down periods versus after market gears.

I'm simply asking question and making sure I understand the best possible methods to insure the new gears last awhile.
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Old 02-13-2020, 08:48 PM   #5
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Yeah, and I think that's total baloney too. I think the gear oil SHOULD be changed on new vehicles.


I had a front axle seal leak at about 20,000 km's. That's pretty young to have axle leaks. When I opened up the axle to change seals, I couldn't find anything wrong the the factory seals other than the fact they had a rather huge build up of oil/gear dust.


I'm pretty sure that if I changed out that gear oil at maybe 1500 to 2000 Km's (in other words after an initial break in period) those seals would not have leaked.
That's interesting because usually the fronts are clean at higher mileage than the rear. I did note that on my Rubicon rear at 75K miles the fluid looked new and no metal buildup at all on the magnet. I think the fact that it's not limited slip might have had something to do with it. It's a 4:10 too. Still haven't done my front and I just turned 93K and it's almost ten years old. Did bleed all my brake fluid out once and part of my A/T fluid though..................... I should do my P/S.
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Old 02-14-2020, 12:43 PM   #6
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Originally Posted by deepbluerubi View Post
https://www.randysworldwide.com/reso...gear-break-in/

https://eastcoastgearsupply.com/ft-1...procedure.html

https://spicerparts.com/whatsthediff


Three quick reads from a search. Someone just discussed it recently here too about the quality of the oem gears and the most from the factory is 4;10's. I would just follow the directions for the gear set you buy.

https://www.wranglerforum.com/f274/b...n-2388939.html


https://spicerparts.com/parts/axle/c...pinion-gearing from the site i included above
G2 Axle and Gear's procedure:

All gear sets require a brief break in procedure to ensure long life and quiet operation. The following is recommended before any heavy load and or constant use: Insure the housing is filled to the correct level using the proper lubricant (including additives if required).

1. Bring axle to operating temperature by driving (unloaded) for approximately 15 to 20 minutes. Do not create any heavy shock loads.
2. Let the axle assembly cool completely.
3. For the next 200 miles of operation, drive normally, without any heavy loads.
4. If trailer towing is intended, an additional 200-300 mile break in without trailer is required. This is important! To properly break in a new set of gears, a minimum of 500 miles of driving is essential before constant towing.
5. Change the gear oil after the first 500 miles to remove any metal particles that come from breaking in a new gear set.

I talked to them yesterday (getting G2 gears installed right now) and they said synthetic oil is okay after break-in period, "use 80-weight oil".
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Old 02-14-2020, 01:54 PM   #7
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Not a Jeep, but my ‘02 F350 when new, I was not supposed to tow anything for the first 500 miles
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Old 02-14-2020, 02:46 PM   #8
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Compare that to the new Jeep's break-in procedure (from 2014 manual):

Drive moderately during the first 300 miles (500 km). After the initial 60 miles (100 km), speeds up to 50 or 55 mph (80 or 90 km/h) are desirable.
While cruising, brief full-throttle acceleration within the limits of local traffic laws contributes to a good break-in. Wide-open throttle acceleration in low gear can be detrimental and should be avoided.
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Old 02-14-2020, 06:22 PM   #9
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Dana/Spicer gears are of a much better/special grade alloy, and they are heat treated for enhanced performance and longevity.
I bought my Mopar crate axles in Holley Michigan.
Bolted 'em in, drove down I-75 to 80 east and hammer down for 600 miles.
That was my break in
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Old 02-15-2020, 01:03 AM   #10
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My shop said the oil MUST be changed at no more then 500 miles along with a list of other driving recommendations.

The fronts won’t really get any break in until the axle is engaged (4H or 4L). You can change the oil, but not likely to do much good.
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Old 02-15-2020, 10:06 AM   #11
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Overthinking...

Don't tow anything for the first 500 miles. Change the gear oil at 500 miles. Good to Go!
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Old 02-15-2020, 02:46 PM
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The fronts won’t really get any break in until the axle is engaged (4H or 4L). You can change the oil, but not likely to do much good.
I thought the ring and pinion on front axle was still turning regardless if the hubs are engaged or not?

Am I supposed to wait until I get 500 miles running the jeep in FWD (low/hi) before changing out the front gear oil? Just wondering....
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Old 02-15-2020, 04:29 PM   #13
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I thought the ring and pinion on front axle was still turning regardless if the hubs are engaged or not?

Am I supposed to wait until I get 500 miles running the jeep in FWD (low/hi) before changing out the front gear oil? Just wondering....
They are, but the ring is driving the pinion. Instead of the pinion driving the gear when in 4x4. So different sides of the teeth are in contact.

I plan on giving mine some 4x4 action when breaking my gears in. Maybe engage 4x4 for a few seconds on straight sections of road.
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Old 02-15-2020, 05:16 PM
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They are, but the ring is driving the pinion. Instead of the pinion driving the gear when in 4x4. So different sides of the teeth are in contact.

I plan on giving mine some 4x4 action when breaking my gears in. Maybe engage 4x4 for a few seconds on straight sections of road.
You're not going to be close to 500 miles on the front gears when you are changing the lube for the rears. So do you plan on changing out the fronts at that time or wait until you get more miles on the front gears that have been engaged?
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Old 02-15-2020, 05:48 PM   #15
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You're not going to be close to 500 miles on the front gears when you are changing the lube for the rears. So do you plan on changing out the fronts at that time or wait until you get more miles on the front gears that have been engaged?
I'll just change both.
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Old 02-15-2020, 07:40 PM   #16
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I thought the ring and pinion on front axle was still turning regardless if the hubs are engaged or not?

Am I supposed to wait until I get 500 miles running the jeep in FWD (low/hi) before changing out the front gear oil? Just wondering....
They are not under any load from the engine, that's the difference. Diff shops and Dynatrac have told me in the past to get some mileage in 4WD before thinking about changing the front oil. It won't hurt, but if it was me I would do it again with a few hundred on the front.
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Old 02-15-2020, 07:55 PM   #17
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I was told the factories will buy assembled diffs that have already been broken in prior to install... don’t know if it’s true, don’t care. East Coast told me to break in for 500 and I did, all 4 times that I have re-geared different Jeeps... it’s their warranty so...

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