Ram ZF Differential and Amsoil Severe Gear

[Zap1967]

I purchased a 2021 Ram 1500 new in the fall of 21. I ran the factory fill until 50k and changed out to Amsoil Severe gear 75-90. This truck is a 3.21 and calls for that (the 3.92 gear calls for a 75-140).

Since around 50k its had a very light “howl” on light deceleration around 62 mph. Only shows up once the fluid is good and hot but the last 3k miles its got a little louder and more broad (60-65). I’m right at 99k as of this week. Had it on a long trip this weekend 3.5 hours unloaded and 2 hours towing. Once it was good and hot I could hear it more than usual.

When I dumped the factory fill it still looked pretty light and honey colored. The Amsoil came out yesterday not looking so great (see photos below). Understand it may be a symptom of the rear end noise. Most inter webs point to pinion gear wear/end play. Under it messing around last night the back lash feels normal/like it always has and there was no end play in the pinion I could detect at all by hand. Maybe it just has some odd gear wear/pattern. I always measure temps on long highway trips when towing and I’ve never seen over 190 on the diff cover. Pinion seal is still bone dry. The other photo is what I was able to scrape off the magnet with my finger (conveniently located just inside the big drain hole so you can access with a finger easily).

I stayed with the 75-90 to keep the excellent fuel economy this 5.7 happens to get (not all do). This time around I figured if it only really surfaces when the fluid is hot something thicker would keep it quieter. I already had some severe gear 75-110 but I picked up some O’Reilly/master pro 75-140 cheaper synthetic in case I need to dump it soon so I’m not wasting the more expensive stuff.

Hopefully I can prolong the life of the unit with thicker lube but I’m more concerned about failure while I’m on a long trip. I tow frequently locally as well as 500-1000 miles from home. Nowhere near the rated capacity of the truck but usually around 4500 lbs trailer with near max payload in the truck. Maybe I’m just doing more than a normal 1/2 ton can handle or I need to be on a 25k service interval for the rear diff. Not real excited about a diff rebuild but I do need to add a limited slip to this one. Settled for non because the deal was too good to pass up in 2021.

Not super impressed with the looks of the Amsoil. May end up sending it in for analysis and if it comes back shining I guess it just makes some noise…

 

[Johnny248]

That does look pretty gross. I had an '11 which called for 75w140, but I ran 75w90 Amsoil for 150k and changed it about every 30k, Mine also came out looking really good?

 

[Zap1967]

Yeah my factory fill looked like it could have went at least another 20k miles. No difference in this change and the towing schedule of the initial fill.

The front diff fluid looked brand new when changed at 50k and the T case looked barely used.

 

[Wheel366]

Send for analysis and maybe email Amsoil to see what they have to say about it?

 

[meep]

I had an 08 Jeep grand Cherokee that developed a little gear howl early in life. Iirc the factory spec’d it for a 140 weight. I took it to one of the most reputable shops in town and they said the would not touch it, they would only replace the axle. I asked them why and he said that they’ve tried several and couldn’t get them right, and then realized that on some of these the axle tubes weren’t perfectly straight. With the axle tubes not straight they never could get the gears set right. i continued to drive it that way without issue and stayed on top of fresh fluid.

My 18 f150 developed mild axle howl, more so when it was cold out. It didn’t put as much hurt on the fluid as your sample shows, but it also didnt get too much worse after it started.

You could consider going to a heavier weight. Amsoil makes a 110 as a halfway to 140….?

 

[oilboy123]

I have a Ford F150 truck, and my daughter an Expedition. I changed axle lube on them and the manual mentioned using 140w when towing. I put 75w-140 in the rear over the quick showing of a 90wt. Front said 90wt, but did not state heavier when towing. I put 75w-110 in the front of the F150. I used Severe Gear in front and rear.

When I read the manuals on both vehicles they stated in footnotes about going to the 140wt when towing for the rear axle. So I'm glad I tend towards reading them carefully. By them saying you could go to a 140 from the 90wt tells me tolerances have nothing to do with having to use one or the other.

If that was my truck, I know I would be running the 140wt.........

 

[Zap1967]

Yeah I’d already ordered some 75-110 but I tossed in some cheaper 75-140 incase I needed to dump it.

Viscosity is all relative to the axle design. I believe the 3/4 ton Ram trucks call for 75-90. Maybe Mopar recommending the 75-140 for the 3.92 gear is just a bandaid for an axle that was never really designed to tow 11-12k lbs.

I’m just confused why the Amsoil looked so bad and what most consider sub par lube(the factory fill) looked so good coming out.

I’ve monitored the diff temps towing since it was new and nothing has changed so you’d think the Amsoil would have held up better over the same interval.

Driving it the past few days with the 75-140 it’s much quieter and smoother though the sound is still there around 62 and deceleration. I also haven’t been on a trip long enough to get it hot yet. Longest run I did the pinion section was 138° and cover was 119°. I’d assume the pinion section will always run hotter as it’s spinning faster and not fully submerged in lube like the back half. Never monitored the pinion section before just the rear cover when towing on long trips at gas stops.

Thanks for the input.

 

[Arc]

You shouldn't hear any noise from the rearend. If you do something is wrong. Even my 05 with 180k on it doesn't make any noise and when I change the gear oil it's always clean, front and back.

 

[GW.]

I suspect you have a problem not related to the oil you’re using.

 

[Pablo]

I suspect you have a problem not related to the oil you’re using.

With 100's if not 1000's of users here reporting Amsoil SG fluid looking new after 50K+ miles, I believe you are correct.

Still a used oil analysis could have been useful. Mainly looking for intrusion/contamination. Appearance isn't everything, but I didn't see how many miles on the Amsoil 75W-90 - it almost looks like water/moisture with bubbles like that.

And way back in the early 90's, before I was an Amsoil dealer. I had a Dana diff kill the thrust bearing very shortly after changing to Redline. I blamed the fluid at the time. Natural human tendency. Probably not related at all.

EDIT TO ADD: If you would have asked me about this application, I would have mentioned about the SAE gear oil reclassification of 90 split to SAE 90 and SAE 110 100°C viscosity ranges. I would have clearly recommended SAE 75W-110.

 

[travis8352]

My 18 calls for 75w-140 regardless of gear ratio and ive used factory, mobil 1 and niw amsoil with no noticeable difference

 

[Zap1967]

Yeah, I’m not sure how water contamination would be happening here. It’s leak-less at all the seal points and it’s a pavement princess that never gets near deep water. This fluid drain had exactly 49k miles on it. I’ll likely send it in an analysis and see what it says. I’m extremely picky that everything I own is operating as new so this will bother me until it’s perfect again.

Might plan on a rebuild while I’m out of town in a few weeks (without the truck). I miss the days when everyone just ignored axle services and had no issues.

I’ve really never had luck with the 9.25 (newer versions). 90s/early 2000s stuff we used to tow with and abuse in plow service never had issues.

My 2010 was under the pinion nut recall and only lasted another 5k after the recall. Rebuilt right around 60k and by 138k it was howling again (that truck was a whole other story).

Maybe it’s time for me to bite the bullet and upgrade to a 3/4 ton. Not sure I want to daily an HD truck though.

 

[crashz]

I just changed the oil in a Dana 80 equipped truck and it came out worse than yours with only about 25,000 miles on it. It was admittedly a store brand 80w-90 oil, but it was nothing short of gross. But I was wondering the same thing? Low miles, relatively light work and short trips. Why so bad?

The poster who mentioned water might be onto something. It may not be enough to turn the oil into mayonnaise, but maybe its condensation or aggressive underbody washing (which I do)? I'm thinking water intrusion of some sort.

 

[Zap1967]

Oh yeah I didn’t think about that. I do an under body so maybe I need to take a look at the vent on the axle. Again, have always had the same wash package on this truck since new.

 

[Dr_Dr3i]

I've got the 3.21 LSD rear end and I drained my OE fluid at about 32K miles. It was a bit low from the factory and it was super dark, like yours in the pic.

The new stuff I put in was perfectly clear (Valvoline 75w90 full synth with the LSD additive) and I made sure to fill it until it started draining out of the fill hole. It's whisper quiet and good peace of mind knowing that I've got new fluid in there. I also tow our boat-on-trailer weighing in around ~5K lbs to/from the local lakes all summer long.

 

[Silverado12]

I had an 08 Jeep grand Cherokee that developed a little gear howl early in life. Iirc the factory spec’d it for a 140 weight. I took it to one of the most reputable shops in town and they said the would not touch it, they would only replace the axle. I asked them why and he said that they’ve tried several and couldn’t get them right, and then realized that on some of these the axle tubes weren’t perfectly straight. With the axle tubes not straight they never could get the gears set right. i continued to drive it that way without issue and stayed on top of fresh fluid.

My 18 f150 developed mild axle howl, more so when it was cold out. It didn’t put as much hurt on the fluid as your sample shows, but it also didnt get too much worse after it started.

You could consider going to a heavier weight. Amsoil makes a 110 as a halfway to 140….?

I work in trucking and have talked to car haulers who told me they've seen drivers tweak rears by not tying them down properly. This was in the early 2000s, so maybe things have changed?

 

[Zap1967]

Just changed the T case and front differential and the fluid looked essentially new. Maybe just a little usage on the front differential looks wise.

This round probably had more 4x4 use than normal. Had it engaged for about 400 miles in a snow storm towing a couple years ago. Otherwise it’ll go into auto if it’s rainy or snowy and in auto on boat ramps or in our grass barn lot so we don’t slip a tire moving trailers around.

Mailing the rear fluid sample tomorrow for analysis.

 

[danielmid]

I've got a 15 Ram 1500 with 3.21s that calls for 75-140, I would go at least 110 but 140 runs fine in these diffs.

Do you have a gear or off-road shop nearby that you can show the noise to?

 

[Zap1967]

Nah. We’ve got an old timer that’s been doing it his whole life locally. He’s currently got my brothers 98 TA there for a rebuild that’s been a long time coming. Diff rebuilding is one I don’t have in my personal arsenal yet.

Got the oil analysis back and despite how bad it looks they were very unconcerned with the test results.