4th gen vs 5th gen rear axle. ZF 9.25 is a inadequate axle assembly for this truck.

crazykid1994 · Jul 17, 2023

RamMan381 said:
I have the original axle assembly so it will be the one getting new parts installed. When I swap axles I will disassemble and inspect what failed. Hopefully it’s just the pinion bearing but I doubt I would get that lucky.

I’m hoping you guys are right and the diff cover is the issue. Although I searched and can not find any evidence of failures caused by aftermarket differential covers. Just marketing by Gale Banks, which he is exceptionally good at and sells an extremely more expensive product than everyone else.

I would look into getting a temp sensor for your rear diff just to watch temps. If it is temps you’ll find out real quick. The other thing is the “finned” diff covers don’t really cool any better since there is no direct airflow across the fins.

RamMan381 · Jul 17, 2023

caulk04 said:
Aftermarket diff covers look cool, that's all. 'Ease of service', meh. The time spent servicing that item vs time spent driving is so miniscule.

I could care less about looks, most people do not buy these covers because of cosmetics but it’s funny to think I am that stupid. Having multiple magnets, oring gasket, and some added capacity is very convenient.

It allowed me to know the condition of my gears without having to drop the cover, scrape rtv, clean everything and reinstall.

I will install the factory cover and run another $2000 test for everyone here.

RamMan381 · Jul 17, 2023

crazykid1994 said:
I would look into getting a temp sensor for your rear diff just to watch temps. If it is temps you’ll find out real quick. The other thing is the “finned” diff covers don’t really cool any better since there is no direct airflow across the fins.

I carry a infrared thermometer in my center console, I have yet to see anything concerning.

I did not check it while towing last time but I was driving faster and it was hotter outside than normal.

Another nice feature of the maghytec cover is that you can easily install a temperature probe into it.

Wild one · Jul 17, 2023

RamMan381 said:
I carry a infrared thermometer in my center console, I have yet to see anything concerning.

I did not check it while towing last time but I was driving faster and it was hotter outside than normal.

Another nice feature of the maghytec cover is that you can easily install a temperature probe into it.

You've gone through more diffs then anybody else i know of,and the only real differance is the diff cover you're using.The 9.25 ZF diff is actually a pretty robust diff ,and i don't think it's the root cause of your issues.The factory limited slip is a bit light,but that's easily cured by going to a Tru Trac
Keep us updated on how things pan out for you .I know i'm curious on whether going back to the original cover cures your issues

Jeepwalker · Jul 17, 2023

I would look into getting a temp sensor for your rear diff just to watch temps. If it is temps you’ll find out real quick. The other thing is the “finned” diff covers don’t really cool any better since there is no direct airflow across the fins.

Note: These work pretty well, are inexpensive, compact, etc. You can mount in or under the dash (fab up a holder). I have a couple I monitor my house boiler & hot water temps when I'm out of town (via a boiler-cam). This one reads F, which a lot of inexpensive LED sensors only read C*. And it has a high range. I extended my temp sensor out quite a ways using about 10 or 12 extra ft of thin speaker wire (all I had at the time) ...to get the length I needed. I toggled back/fourth between the normal and longer wire length and the accuracy wasn't affected. So you could put the LED display in your cab and string the sensor to the rear diff w/o trouble.

You could also fab a holder which would hold the bullet sensor agains the lower rear cover, and cover the sensor with a piece of foam. It should read the diff cover temp pretty accurately. Then you can toggle between covers and test the temps. I just have my boiler sensors stuffed under some foam insulation. It's not as ideal as a threaded sensor well, but stuffed under foam is an HVAC accepted practice where a threaded well can't easily be installed. Just a thought...

https://www.amazon.com/PEMENOL-Fahrenheit-Temperature-76F-999F-Thermocouple/dp/B07X37WH5Z/ref=sr_1_10?keywords=digital%2Btemperature%2Bsensor&qid=1689624067&sr=8-10&th=1

I also have one of these (below) for reading dual-temps, which is good for a boiler (red=discharge, blue=return water temp), but the particular range of this one probably is ok for a rear diff ...but I'd probably go with the higher temp unit above. I can think of other automotive applications for such a dual-temp unit.

https://www.amazon.com/dp/B0928QY786/ref=sspa_dk_detail_0?psc=1&pd_rd_i=B0928QY786&pd_rd_w=I6Bk8&content-id=amzn1.sym.f734d1a2-0bf9-4a26-ad34-2e1b969a5a75&pf_rd_p=f734d1a2-0bf9-4a26-ad34-2e1b969a5a75&pf_rd_r=PR9SZYCMGN0NYW8WXJXZ&pd_rd_wg=u6ZeC&pd_rd_r=ea53f15c-994c-418a-9a3f-be34f6194030&s=industrial&sp_csd=d2lkZ2V0TmFtZT1zcF9kZXRhaWw

RamMan381 · Jul 17, 2023

Jeepwalker said:
Note: These work pretty well, are inexpensive, compact, etc. You can mount in or under the dash (fab up a holder). I have a couple I monitor my house boiler & hot water temps when I'm out of town (via a boiler-cam). This one reads F, which a lot of inexpensive LED sensors only read C*. And it has a high range. I extended my temp sensor out quite a ways using about 10 or 12 extra ft of thin speaker wire (all I had at the time) ...to get the length I needed. I toggled back/fourth between the normal and longer wire length and the accuracy wasn't affected. So you could put the LED display in your cab and string the sensor to the rear diff w/o trouble.

You could also fab a holder which would hold the bullet sensor agains the lower rear cover, and cover the sensor with a piece of foam. It should read the diff cover temp pretty accurately. Then you can toggle between covers and test the temps. I just have my boiler sensors stuffed under some foam insulation. It's not as ideal as a threaded sensor well, but stuffed under foam is an HVAC accepted practice where a threaded well can't easily be installed. Just a thought...

https://www.amazon.com/PEMENOL-Fahrenheit-Temperature-76F-999F-Thermocouple/dp/B07X37WH5Z/ref=sr_1_10?keywords=digital%2Btemperature%2Bsensor&qid=1689624067&sr=8-10&th=1
View attachment 524849

I also have one of these (below) for reading dual-temps, which is good for a boiler (red=discharge, blue=return water temp), but the particular range of this one probably is ok for a rear diff ...but I'd probably go with the higher temp unit above. I can think of other automotive applications for such a dual-temp unit.

https://www.amazon.com/dp/B0928QY786/ref=sspa_dk_detail_0?psc=1&pd_rd_i=B0928QY786&pd_rd_w=I6Bk8&content-id=amzn1.sym.f734d1a2-0bf9-4a26-ad34-2e1b969a5a75&pf_rd_p=f734d1a2-0bf9-4a26-ad34-2e1b969a5a75&pf_rd_r=PR9SZYCMGN0NYW8WXJXZ&pd_rd_wg=u6ZeC&pd_rd_r=ea53f15c-994c-418a-9a3f-be34f6194030&s=industrial&sp_csd=d2lkZ2V0TmFtZT1zcF9kZXRhaWw

How are you mounting it to the differential cover? Are you using a aftermarket cover?

Wild one · Jul 17, 2023

RamMan381 said:
How are you mounting it to the differential cover? Are you using a aftermarket cover?

Any oil temp gauge will work,just drill and tap the housing for the temp probe.

oil temp gauges with a 1/8th npt probes - Google Shopping

BuschLatte420 · Jul 17, 2023

crazykid1994 said:
I towed my fathers boat. Boat and trailer combined are 9300lbs. Factory lsd 3.92 gear set. No issues. Lifted on 35s. Long tube headers, full catback exhaust, 6.4 intake manifold, and tuned. Truck did not miss a beat. I don’t drive my truck very nicely either. It gets full throttle quite often and goes off-road. I’ve opened the rear and replaced the diff fluid once. Otherwise it’s never been touched. Factory diff cover with just a diff guard on it for off-road.

Cool dog

BuschLatte420 · Jul 17, 2023

RamMan381 said:
Does anyone know if a 5th gen axle will bolt in and work on a 4th gen truck! I am at the point we’re I will purchase one directly from RAM if I can make this work. Only other options are selling the truck or having custom brackets welded to a aftermarket Dana 60.

I am embarrassed but here is the list of parts.

These parts were installed by the most trusted gear installer in Oregon. I have had many Jeeps and he has done gears and lockers in all of them. He is a perfectionist, people in the industry trust and respect him.

#1. Yukon 3.90 gears and auburn limited slip. Gears failed not long after install due to heat. Covered by gear installer warranty.

#2 Yukon 3.90 gears with same limited slip. Gears failed not long after due to heat again….. Gear installer covered half the repair cost and I covered the other half.

#3 Nitro 3.92 gears “REM polished at weddleindustries”, the same auburn limited slip. Auburn failed after stepping on the gas hard from a stop. Parts went through the gears and messed everything up. I was hard on it but the failure should not have happened and now it’s known that the auburn units are weak in the zf 9.25 rear end.

#4. Nitro 3.92 gears, Yukon guragrip. I believe this was mostly my fault. Having fun, got on the gas from a stop to drift a turn. I got wheel hop and broke a spider gear which then proceeded to destroy the gears. It’s now known the duragrip limited slips are known to break spider gears when abused. I covered repair costs myself.

#5 New factory axle assembly. I bought another stock axle complete with factory 3.92 gears, and factory limited slip. I did not have a dealership setup the gears, is a factory assembled axle. I stopped being so abusive on the truck as well. Towing my travel trailer and dirt bike home from the moto track I started hearing some noise I was not hearing previously. I assumed the gears were failing from the metal I see on the magnetic dipstick. This is where I am today.

I bought this truck new in 2016, it has been absolutely flawless except for the rear axle.

It has been a learning curve.

Yukon 3.90 gears are absolute trash for the ZF 9.25 specifically in the 3.90 ratio. There is not enough teeth on the pinion and if used in a towing situation it will fail. There is a difference between a 3.90 and a 3.92 gear set. This is why my nitro gears and factory gears held up substantially longer than the **** Yukon 3.90 gears. “ZF & Nitro are both 3.92 and have more teeth on the pinion gear”

Previously the trutrac was not available and Auburn was the only one making aftermarket limited slips. The auburns are weak and will not last when abused.

Then the duragrip came out, it’s better than the auburn but the spider gears are known to fail.

Now we have the trutrac. The only downside is they specify 80w90 which is unacceptable for the load towing puts on the gears and will cause the gears to burn up.

I am going to have 3.92 AAM gears REM polished and installed with a trutrac using synthetic 75w-140. I am considering this a band aid and will either sell the truck or find another axle that will hold up.

The super 60 installed in the rams with the max tow option seems like the ticket.

Is the truck 2 wheel drive? If not mixing gear ratios is a big no no

hunterdan · Jul 19, 2023

BuschLatte420 said:
Is the truck 2 wheel drive? If not mixing gear ratios is a big no no

The difference between 3.90 and 3.92 is so minimal, you'd likely hardly even notice, especially if you're only using 4wd when you should be on slick surfaces.

hunterdan · Jul 19, 2023

I've seen reports of these axles killing the spider gears, not much regarding the ring and pinion. If you're overheating bearings, you're either using the wrong lube or lubrication isn't getting to where it needs to be. The videos in the diff covers are accurate, and be what it may, Gale banks didn't get to where he is by selling inferior products. When oil can't flow and gets aerated, you're losing lubrication ability. Not only are you limiting the amount of oil getting to those bearings. But now you're introducing aerated oil to them. Aerated oil doesn't have the film strength to protect bearing and gear contact surfaces. Is the diff cover at fault? I'm not sure, but if I was experiencing the same issues over and over, I'd be trying something different. Either go back to a stick cover, add extra magnets if you want for more particulate protection. You're not getting hot because of the diff cover. You're bearings are getting hot because of a lack of lubrication and/or improper gear setup. Stop throwing money at parts, dig into the parts and do real diagnostics on what's going on. These aren't weak axles and they're comparable in strength to what the other manufacturers are using.

danielmid · Jul 19, 2023

I have the TruTrac installed with factory 3.21 gears and after a break in period with whatever oil the 4x4 shop used I switched to Red Line 75-140 NS and it's been flawless and quiet and locks up great. I don't tow as often as you, 4k lb camper here and there, a few 12 hour interstate drives and a few couple hour up the hills trips and no issues at all. 4k miles and counting on the Red Line. Most other synthetic gear oil adds friction modifier to every formula.

This gear oil (important to use the NS if you go Red Line):

Red Line 75W140NS Gear Oil, Quart | BimmerWorld

Premium high performance and racing 75W140 GL-5 gear oil without friction modifiers for limited-slip

www.bimmerworld.com

crash68 · Jul 19, 2023

RamMan381 said:
You do not tow often, I tow very frequently and over mountain passes. How often do you tow that boat?

If your thinking it's a frequent towing issue, let's see if @VernDiesel will chime in. He transports travel trailers across the country and his truck is flirting with 1,000,000 miles ('14 Ram 1500 EcoDiesel). I think he's replaced the rear axle once.

pacofortacos · Jul 19, 2023

What brand gear oil? I didn't see that mentioned at all.
I tow my boat from PA to Florida mostly every year and that includes going over the eastern mountains and most of it in excess of 70 mph.

I use Redline gear oil and change it every 2 years - never a problem - all stock. I don't even use the 140 but rather the 110.
Currently trying Shaeffers gear oil - just hauled the boat/full bed/cab down last week, will go back and pick it up in 2 months.

pacofortacos · Jul 19, 2023

danielmid said:
I have the TruTrac installed with factory 3.21 gears and after a break in period with whatever oil the 4x4 shop used I switched to Red Line 75-140 NS and it's been flawless and quiet and locks up great. I don't tow as often as you, 4k lb camper here and there, a few 12 hour interstate drives and a few couple hour up the hills trips and no issues at all. 4k miles and counting on the Red Line. Most other synthetic gear oil adds friction modifier to every formula.

This gear oil (important to use the NS if you go Red Line):

Red Line 75W140NS Gear Oil, Quart | BimmerWorld

Premium high performance and racing 75W140 GL-5 gear oil without friction modifiers for limited-slip

www.bimmerworld.com

Nothing wrong with Redline with additive - have used it for years and it's needed if using a factory limited slip.
Put it in with about 3000 miles on the truck, sitting close to 60k miles now - 90%+ are either towing or loaded highway miles. Actually used 75-110 for most of the time.

Most of my towing trips are 22-24 hrs one way - boat/trailer weights varied between 4500-6000 lb./always full bed of tools/parts/luggage/etc.

pacofortacos · Jul 19, 2023

And for real tough situations there is always the Redline heavy Shockproof gear oil - always a good option in extreme situations.

danielmid · Jul 19, 2023

pacofortacos said:
Nothing wrong with Redline with additive - have used it for years and it's needed if using a factory limited slip.
Put it in with about 3000 miles on the truck, sitting close to 60k miles now - 90%+ are either towing or loaded highway miles. Actually used 75-110 for most of the time.

Most of my towing trips are 22-24 hrs one way - boat/trailer weights varied between 4500-6000 lb./always full bed of tools/parts/luggage/etc.

That was for the TruTrac specifically, Eaton recommends no fluid modifiers and the NS formula meets that recommendation.

RamMan381 · Jul 19, 2023

I run Amsoil severe gear 75-140.

Here is an update on the issue, I may have jumped the gun do to prior trauma from all the failures I have had with aftermarket parts in this axle.

I pulled the cover and found nothing wrong.. The oil looked great and the lower magnet was not full of metal. I jacked the rear tires off the ground and spun and inspected everything visually as much as I could without taking everything apart. It all looked great. Although there was more material on the dipstick magnet than normal I found nothing.
Also the mag-hytec cover looks square from the outside it is actually very smooth on the inside.
I did however notice that the bushings on my zone control arms have completely failed recently. I think the noise I was hearing is possibly from the axle rotating up under load towing my travel trailer and it was creating u-joint noise. I called zone and they have a new bushing design that does not fail so quickly.
Regardless I am still building my other axle with a trutrac, AAM 3.92 gears “which will be REM polished”, just to have. I will swap it in and have my gear guy inspect this axle under my truck now to see what he finds. Maybe nothing, maybe a bearing somewhere.
I also purchased a diff. Temperature gauge to help me with the PTSD this axle has caused me .

MaxTow Double Vision 250 F Rear Differential Temperature Gauge Kit - Includes Electronic Sensor - Black Gauge Face - Blue LED Illuminated Dial - Analog & Digital Readouts - for Trucks - 2-1/16" 52mm https://a.co/d/c6TrmMq

RamMan381 · Jul 24, 2023

The lower ring gear is my new AAM 3.92 and the upper ring gear is a Yukon 3.90 that was replaced a few years ago.

The AAM 3.92 ring gear has 47 teeth and the pinion has 12 teeth. The 3.90 Yukon ring gear only has 39 teeth, which means the pinion only has 10 teeth and it’s substantially smaller than the 3.92 gear set.

From my experience the 3.92 gearsets are more durable. OEM, Nitro Gear, AAM, are all 3.92.

1 MEAN66 · Aug 19, 2023

Have You ever had the driveshaft pinion angles checked. When off a degree or two can really mess things up. Loads going through the pinion change ( u joints usually fail first but NOT always). It needs to be in spec. through out the suspension travel.

4th gen vs 5th gen rear axle. ZF 9.25 is a inadequate axle assembly for this truck.

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