I had synthetic diff. fluid put in my truck at 16,600 miles. Only reason I had it done then was D.C. did it as a warranty repair, because they recommend syn. in tow packages and mine was delivered with mineral oil.<br>Anyhow...<br>Those using syn. diff. fliud, what do you use for sevice interval (milage) with syn.? Without the manual in front of me, I think the sevice interval is around 25,000 miles, normally.<br>I do not do a lot of towing, but I have put 25,000 miles on the truck in 1 year. Maybe 5,000 miles of that was towing 4,000 to 5,000 pounds.<br><br>

 

Don't know what the factory recommends but I change once a year which is usually about 50,000. The limited slip tells me when it's time to change. It's gets noisy on the turns. Kenny N4YYX

 

I run synthetic and change about every two years or 50000 miles. I have the mag hytech cover too. This is probably overkill but it makes me feel better. It is cheap compared to a rear end. I pull up to 26000 pounds some times so I figure it's worth it.

 

Did Dodge contact you about the need to change to synthetic? I bought a used 2001 w/tow package and was 40k miles, which means out of warranty period. How do I know if mine was changed?

 

I contacted Dodge on the 800 customer sevice number. Iwas trying to find out if my truck came from the factory with Syn. fluid or not. Dodge does reccomend syn. fluid in it's truck with the towing package. I ordered my truck with the towing package. The girl I spoke wiht at DC, did a little research for me and found that my truck came WITHOUT syn. fluid in the diff. She went ahead and authorized my fluid to be changed out as a warranty/customer service repair.<br>I did not ask for this to be done. I was simply inquiring as to whether or not my truck was delivered with syn. fluid.<br>She offered the change, free of charge, so I accepted.<br><br>How to know if your truck has syn. or not? Change it and put syn. in it. Now you know. That is about all I can say.<br><br>

 

My 02 manual shows the B-Schedule interval at 11K or so....

 

[quote author=jethroish link=board=4;threadid=10772;start=0#105266 date=1045400551]<br>How to know if your truck has syn. or not? Change it and put syn. in it. Now you know. That is about all I can say.<br>[/quote]<br><br> <br><br>If you don't know what's in it, I would just change it.

 

Did just that this weekend. Now got some fancy blue colored synthetic in there. Should see fuel economy gains of about 37%

Got no great amount of love for DC, especially after having to buy my own rear fender liners and underhood insulation, but I will say that fluid levels in both differentials were correct. They don't screw all of them up, though I sympathize w/those of you who have found them to be low &gt;

 

I just picked up 4 qts. of Mobil 1 75/90 synthetic for the rear. Do I fill it up to the bottom of the hole or lower? What kind of lube should I put in the front axle?

 

Fil to the hole and use the same thing in the front axle.