Friction Modifier

Ok I need some help. I had 4.10 mopar gears and install kit from Moe's installed back in October by a local shop. Well on Wednesday I had them fix a diff cover leak. Drove the truck home and maybe drove it for 30 miles the next day. Here's the problem. Last night we were headed to San Diego from the Phoenix area with our travel trailer which is well under the tow rating of this truck and I got about 160 miles from home and got flagged down by another motorist for a bad smell. I limped it to the rest stop just up the road and the rear end was smoking and just stunk like burnt oil. After a very long wait I had the truck and trailer towed all the way home along with me and my 4 other family members. I checked the fluid just now and it isn't low. My question is, could the shop have not added friction modifier? Would that have caused me to smoke a bearing or even the wrong fluid? I have driven this setup for close to 20k miles and have taken my trailer to California, northern AZ a few times and all the way to Yellowstone and back with no issues.

I have never heard of lack of friction modifier causing smoking. Imho,

4x4? Did you change both gears front and back?

Burla said:

4x4? Did you change both gears front and back?

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I'm two wheel drive

Could he have gotten metal shavings in the housing when he cleaned the gasket maker off? I was standing right in the door way to the shop as he was working on it and didn't here him blow anything out.

Have you torn down the rear end yet? Was it a bearing , or another part. What does the fluid look like? Any "trash" in the fluid? Was it full? Do you have limited slip? What type of fluid did they use when they re-filled it?
Jay

Pull Ya said:

Have you torn down the rear end yet? Was it a bearing , or another part. What does the fluid look like? Any "trash" in the fluid? Was it full? Do you have limited slip? What type of fluid did they use when they re-filled it?
Jay

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No I have not. I am planing on having it towed to thier shop on Monday but want to have some idea's of what it could be. I should not have had this problem in less than 20k miles unless they did something wrong or it was premature part failure. I am pretty sure the tech reused my old fluid because I watched him clean out a bowl real good.

Just a wild guess sounds like maybe a bearing getting extremely hot and cooking (Burning) the fluid that's possibly what the smell was.
Maybe the bearing was not installed properly? Just grasping at straws's

SyN said:

Just a wild guess sounds like maybe a bearing getting extremely hot and cooking (Burning) the fluid that's possibly what the smell was.
Maybe the bearing was not installed properly? Just grasping at straws's

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I'm thinking it was a bearing too but why would it go so long before giving me a problem? I took the trailer on a 2600 mile round trip to Yellowstone and back with out a problem.

Just thinking out loud but even though the bearing may have been installed improperly?
normal use it did not create enough heat to cause an issue but once a load was put on the bearing it caused it to heat up to extreme temperatures and begin cooking the fluid which made the smell?

SyN said:

Just thinking out loud but even though the bearing may have been installed improperly?
normal use it did not create enough heat to cause an issue but once a load was put on the bearing it caused it to heat up to extreme temperatures and begin cooking the fluid which made the smell?

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Ok I would agree with that except this isn't the first time it has been under extreme temperatures. The truck went with the same setup over 2600 miles with the trailer to Yellowstone and back and it was loaded way heavier, with out a problem. So why now?

This is not a friction modifier issue and likely isn't a lubrication issue. Just for the info of it..

I don't protest to wager a guess what is wrong or why, and due to the smoking I didn't put forth this idea earlier. But, ester based gear fluid takes temperature way better then mineral oil, deals with pressures and keeps heat away as well. Now, because you are smoking, I think that issue is severe. But look at what group 5 (redline oils) will do for you in your application.

While Redline isn't a PAG, it has very similar characteristics. Just the lengthened oil change interval alone should be enough for everyone to run ester based gear fluid. There is no ground oil in group 5 oil. It is like having 60 degrees Fahrenheit in the bank, and also has the ability to lower operating temps. It is what we call win win. The only sad thing in my opinion is that every gear fluid isn't made with ester base stocks, or at least 1/2 of them. Many arguments can be made whether or not to use esters in the crankcase and all are valid, there are very few reasons not to run an ester in the gears, they pay for themselves in that application many times fold. On the off chance there is something wrong between what mineral oils can keep you protected to the performance you get from esters, I post this up for your consideration. But with it smoking, it is likely fatal with whatever fluid you use. You might opt for this after you fix what's wrong, gl.

long article esters

gear fluids

Did they set the preload on the bearing correctly? If not, its going to toast them and possibly damage your ring set.

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RFMRAM said:

Ok I would agree with that except this isn't the first time it has been under extreme temperatures. The truck went with the same setup over 2600 miles with the trailer to Yellowstone and back and it was loaded way heavier, with out a problem. So why now?

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No idea! This is over my head! Without being there & witnessing it with my own eyes & nose.

Any possible chance it could have been a Outside wheel bearing failure?

He got dirt in the diff when he did the reseal... if it was a bearing issue it would have happened on the last long trip.
Friction modifier is only for use in LSD and lack thereof will cause ratcheting when going around corners.

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Not because of friction modifier you don't even need it that would only cause issues with the lsd not the bearings. Dirt in there really wouldn't do much as the detergent in the lube would surround it and dissolve it. I believe it was not setup correctly. Without you mentioning it I am guessing you have a 1500 with a 9.25 rear? They are not easy to setup from my understanding and if backlash is set wrong your going to have issues. Only way to find out is to rip it open and assess the damage.

Yeah I doubt it has anything to do with preload. The bearing would have went out a while ago. I think he got dirt or metal in the oil but I doubt they will fess up to that. It's at the shop now but they won't be able to look at it until tomorrow. I plan on throwing a finned higher capacity cover and synthetic oil. We will see what they say tomorrow.

I did the G2 cover which looks like a mag hytec just to be different but either are good.

Ok so the shop found that the ring and pinion coating *** chewed up and the clutchs were fried. I have talked to Moe's and two other shops here in Phoenix and they have all said if they didn't add the friction modifier it would have ate up the clutch's causing it to overheat and chew up the gears. By the way I owe a huge thank you to Moe's. He is warrantying the gears and hooking me up with a install kit for free. They also are giving me a good deal on a new mopar diff. The shop that did this still isn't accepting responsibility but I will be waiting until it is done to really push for them to cover the cost. If not small claims court I go. I have to much mechanical knowledge to know that this doesn't just happen after close to 20k miles on the gears and just so happens the shop changed the fluid two days before. This kind of stuff happens due to either not enough oil or the wrong oil and I know it had enough oil. Also Moe's said they have never had a set of mopar gears returned after that long.