Im looking to change out the front/rear diff fluids.. Ive searched some posts, but theres alot of different answers. I have an 04 cc lb 3.73ls. I deffinatelly want to run syn. I want to know from the people who tow alot which weight/brand they are using, and if any additional additives that were installed. Also, any good online places to buy the oil and gaskets??

TIA

 

The factory fluid is 75w140 syn already and is supposed to be good for a long long time. The LS units need an additive also.

 

thanx.....whats the specific additive??? Is there multiple products out there, or is this a dealer thing??

 

Its a friction modifier. I believe their are several brands out there. The proper way to add it is 2 oz. and check for "chirping" by turning a hard right or left, add 1oz. at a time till the chirping stops. This will ensure that you are getting the most to both wheels by not allowing the clutch pack slip by having to much modifier in it. Many LS units from the factory had too much modifier in them, causing a very weak LS unit, more like and open diff. Several here started draining and refilling the diff and adding the modifier as described above. This corrected a bunch of slipping LS diffs.

 

good info,Ill have to look into all this, hopefully change both diffs today

 

s2gots,

The Rear FMC Sterling 10.5" axle uses Motorcraft Synthetic 75W-140 (6.9 pints) and the Front Dana 60 uses 80W-90 (5.8 pints) gear lube.

The Motorcraft 75W-140 is synthetic, Mobil 1, Redline and Royal Purple also make synthetic gear lube for the axles. They are all good, choose the one you like the best.

 

just what I wanted to hear,thanx guys...helped alot!!