Synthetic gear lube

[SRehberg]

I just bought the Redline brand of synthetic gear lube for the LS rear end (80-140wt) per D. C. recommendation for trailer pulling. It says it has the LS additive already in it; has anyone used this oil and does it do o. k. without adding the D. C. additive for the LS?

 

[MikeBeggy]

I just changed to the same Redline a few weeks ago and I did have to follow up with 4 oz of friction modifier. Don't run with the LSD chattering (some members think alittle chatter lets you know its working... I just installed a rebuild kit in mine at 150k aqnd I used to be guilty of thinking a little chatter was OK, not any more)The Redline was the closest to not needing any modifier of several bgands I had tried.

 

[SRehberg]

Did you use the Daimler-Chrysler modifier or ? I think I'll just put it in there for insurance to avoid a re-trip to the rear end, while adding the lube. Right now with the petro stuff and the modifier, the rear is nice and quiet, but works really well. This will be my first experience with synthetic in the rear. Thanks for the heads up on the modifier.

 

[MikeBeggy]

I used the last of my Dodge dealer modifier. I bought some Redline for later changes. Also, I found that during summer trips towing, I would have to add a little about every 10k miles to keep things quiet. I am told that the modifier gets used up at higher operating temps. I have the Mag Hytech cover so checking and addind is very simple.

 

[HillCountrykid]

I've been using the 75-90W for about 20-25k miles. I did'nt need any friction modifier. It actually needs a little less. The LS is'nt near as aggressive as is was before going to Red Line.



Since most synthetics already have the friction modifier added, I'm probably going to go back to petrolium based oil soon.



This is just my experience, and may not be the norm.



Brian

 

[klenger]

FWIW, the first time I changed to Amsoil 75W140, I did not need any modifier. I just changed it again at 27K, and I had to add about 4 oz to get rid of the chatter. Don't know why is was different this time.

 

[SRehberg]

Hill Country Kid, I read your post with interest, as this is the second time I have read about the synthetic having to much lubricity for the LS. Did you experience the loss of the LS or it just doesn't grab as well or?



I know one gentleman told me he lost his LS action with the synthetic, so had to drop back to the "blend" of petroleum and synthetic. It kind of scares me to say the least, as I depend upon the LS each year on vacation on one particular dirt road. It makes the difference of getting out or spinning, as I only have 2wd.



All the earlier years before synthetic was the rage, the good ol' petroleum seemed to work good, but I don't know how long the rearends lasted either! I have the RedLine in the garage waiting to go in, but am holding off to see what I should do.

 

[HillCountrykid]

SRehberg, I'm the only one that know of that has mentioned this about the Red Line. I did'nt loose the LS, it just is'nt as aggressive as it was with the factory fluid. When it had that stuff, and some regular petroleum lube after the first change, it worked surprisingly well. For example, when making a turn from a stop it used to hook up and spin both tires. Now, it only does every once in a while. Don't get me wrong, I'm not saying to not use it. The 90-140W may be different, or maybe I'm too particular. But if I have a LS, I want it too work Especially in a 8200 lb. pig.



Brian

 

[SRehberg]

Hill Country Kid,



Thanks for the reply, but I am cocerned about the ability of the LS being compromised. We have a dirt road in Canada that we pull a trailer up each year on our way home, which is only about 400ft. I use to have a open diff on my previous truck and had to be pulled out a number of times. I bought the Dodge with the LS and (knock on wood) have made it each time no problem. If I lose the LS function, I'm screwed, so you can see why I am reluctant to install the Redline if there is a chance of it not performing as it should. Like I mentioned earlier, you are the second one that has made that observation.

 

[HillCountrykid]

Would you be able to get rid of the Red Line if you did'nt use it? If so, and you are worried of the possiblity of loosing any perfermance of the LS, then go get some high quality dino oil and some friction modifier. I was wanting to use synthetic, but if it makes my LS not work as good, I'll just use dino and change the fluid more often.



On a side note, I was using their synthetic MTL to try and help my third gear grind. Well pretty much everyone else was having good luck with it. Not me. It used to go into third a little slow and notchy. Then it started to grind when down shifting. So back in went the factory stuff. No more Red Line for me.

 

[SRehberg]

I am not sure is I can take the stuff back or not, but for $40 of oil, it's not worth the headache of losing the LS feature. The other person that mentioned the loss of the LS due to the synthetic, was either on the Open Roads Forum, or Dodge-Diesel.org site. He stated he went to the Valvoline Dura-blend, and all was well. On the fully synthetic, it went south on him, but worse.



With the standard petroleum oil, is it only a matter of changing it more frequently to avoid difficulty or does the synthetic provide additional protection that the petro can't? Of course it wouldn't be any good to me (synthetic) if I lose the LS feature. Have you heard of anyone else having this problem with the Redline or other synthetic gear lube? I'm holding off on the gear lube change, until I can decide if this is going to bite me in the butt.

 

[MikeBeggy]

Geeezzz, how does a simple question about adding friction modifier turn into a witch hunt about loss of function of one's axle and throwing out expensive oil. The owners manual was written by the guys who designed your truck and provide warranty for many miles. The manual says use synthetic for towing because it's better under the heat and loads created by towing. You can add friction modifier all day and you won't make your axle not work. Just follow the recommendations of the manual and you'll be way ahead of guessing what might go wrong.

 

[HillCountrykid]

If you can't take it back or sell it to someone else, then give it a try. I'm the only person that I know of that has said anything about loosing some of the function of the LS. I'm probably scaring you more than helping.



I'm not an oil expert, or claim to even come close, but I'd imagine that there probably is'nt as great of an advantage over petroleum based oils in the rear end as there would be in something like the engine. Maybe someone with more knowledge will chime in and give a more definite answer. But I'm pretty sure that the gears will last plenty long for me without synthetic.



Brian



on edit: Mike, yes too much friction modifier will definitely make the LS diff not work. The clutch plates will be too slippery and not work very well. The problem with most synthetics is that they come with the friction modifier already added.

 

[SRehberg]

Mike, It's not that I don't have faith in the manual, but real life seems to be more accurate than what seems like a good idea on paper. I know synthetics are superior in heat durability/stability etc. or else I wouldn't have bought it in the first place. So I am pro-synthetic, just paranoid about losing the LS function. Remember, these are the guys who said 60lbs/ft on the oil drain plug was a good idea too.



I will probably go ahead and stick it in the diff, see what happens and if all is well, then stay with it. If not, it's not that big of a deal to drain it and start over with the petroleum stuff. I have some time before we go to Canada, so I can test it here.



I originally posted asking about the additive because the Redline says it doesn't need it, but to cover my bets, I bought the additive in case.

 

[MikeBeggy]

If you want to check the effectiveness of your LSD, the shop manual outlines the amount of torque to slip the cluthes. I had developed some problems with mine at 130k or so. I made an adapter to put a 1000 ft-lb wrench on one wheel and checked my slipping torque with different amounts of modifier. To make a long story short. it's real difficult to get so much modifer that the clutches loose their grippng ability. I ended up replacing my clutches with dana parts and all is good again.

 

[SRehberg]

Mike, thanks for the info, but I think 1000lbs/ft of torque is more than my body has ability for! I am going to try the Redline and see how things go, I'm just undecided now on whether to add the modifier for good measure. What did you find in your experience... add the modifier or did it do o. k. without it?



I figure I can always go regular petroleum if this causes issues, so being the fact I have the Redline already, I want to give it a go.

 

[MikeBeggy]

The Redline was almost chatter-free as comes out of the bottle. I ended up adding only 4 ozs about a week later. With my Mag-hytech cover, that's about 1/4th of what other oils I had tried. The cover about doubles the capacity. BTW, the 1000# wrench is nearly 3 feet long so it's not hard to use. I got it when I changed my transmission input shaft.

 

[SRehberg]

Mike, thanks for the reply. I would like to get one of the MagHytec covers as well, but they are a little pricey for me at the moment. Hopefully in the not-so-distant future I'll install one, as they look like a nice way to keep the gears cooler and oil changes.



Perhaps I should add the modifier right off the get-go to eliminate the chatter; would you recommend less than what DC does for conventional oil?