2nd Gen Non-Engine/Transmission Differential service; want to be sure about LSD

[KRStone]

Good evening,



I want to change the fluid in the differentials this weekend.



My truck is a '96 2500 HD, 4x4, automatic transmission.



I looked at the rear axle today, it has 70 - 20 stamped into the casing, does this make it a Dana 70? There is a tag attached to the cover by two bolts, the tag is approx 1/2" wide by 3-4" long; it has numbers stamped into it, looks like serial numbers. Can't see any other indication of what some people say are LSD tags attached to a bolt.



I need to get my fluid at NAPA, so what's the good stuff? I want to go synthetic.



I have a tube of permatex ultra grey rigid RTV sealant, can I just use this or should I use the cheapo black/red RTV?



Thanks all, I've never done this job myself.



KRS

 

[kenny61]

I believe automatics had the 70 manuals the 70/80 hybrid. In my experience 240k non synthetic has worked fine. any of the sealers work ok, black / red / grey

 

[JMcCoy]

My choices would be Amsoil, Royal Purple, then Mobil 1 respectively. Mobil 1 seems to find a way to leak anywhere I put it. With the synthetic, you will need less friction additive, if any. I currently have mobil 1. I needed one tube of additive to stop the chatter on my Dana 70. Years ago, I did not need any. I don't know if this is due to a change in their formula, or wear to my clutch pack/tires. I would leave a little room in your axle before your test drive. If it chatters, add a tube. If it still chatters, add another. Your front won't need any. Good luck.

 

[GAmes]

I use Royal Purple and no additives are required with it. Just tested my LS a week or so ago on a muddy incline and it works as designed. I did use Mobil 1 briefly until I installed my MagHytec, so I have a gallon of it with additive already added that I need to give away. If you think it is worth the shipping charge you can have it.

 

[Extreme1]

I'd wait until you drive it a few weeks (if it doesn't chatter right away). Then add the Mopar brand LS additive 1 ounce at a time or you will end up with an UNlimited slip rearend. I've never had to add more than 2 ounces.

 

[GAmes]

Car Quest also carries LS additive. Less expensive than the dealer and works just as well.