03 rear differential fluid level

[Fiver]

Just changed out rear diff fluid @ 57000 miles (second time), actually measured fluid drained and replaced with same amount. Could not touch top of fluid through fill opening so added additional half quart, still can't feel it. When I changed the fluid last time (@ about 15k, went to Amzoil) I filled to about 1. 5" from bottom of plug opening as I remember reading that filling clear up would result in an overfill situation on these particular year and model trucks. Can anybody update that information for me and also, with no sign of leakage, why would the differential have apparently lost some fluid since the last change? I plan to add additional fluid until reaches 1. 5" or so from the top unless someone provides a good reason why I shoudn't. Thanks for any info, guys (gals?)

 

[Bob V]

Look hear 2003 TSB's

 

[Fiver]

Thanks Bob, I thought that was the case. Still curious as to why I may have lost some fluid over time though. Absolutely no sign of leakage anywhere but I may have originally misread the level when I last changed the fluid. Perhaps that's most likely.

 

[EDankievitch]

was your truck parked on a hill crossways? your gear lube might have ran down one of the axel tubes?

 

[MickeyMiller]

Just so that I'm clear, it's the '04 11. 5" that had the filler plug too high, correct? I change my diff/trans/tcase fluids every 25K and have been filling the diff's to the hole, on level ground. I think we've gone backwards a little... as a kid I had a '40 Ford coupe, with a '48 truck engine, Edmonds heads, '39 floor shift, and Model B spoke wheels! I drove that for 5 - 6 years and never changed the dino trans or diff oils! Didn't even think about it!

 

[rbattelle]

The TSB says 1/4" from the bottom of the fill hole, +/- 1/4 inch. I always fill until it runs out the hole.

Ryan

 

[steved]

Although I haven't read that TSB in some time, I thought it applied to the 10. 50?



As for your missing fluid? Either the ground could have not been perfectly level both times or even the position of the differential inside the case could cause the level to fluctuate.



As ryan indicated, right up to the fill hole. My aftermarket pan actually runs almost 1. 5" higher than stock... never had a problem.

 

[Fiver]

Thanks guys. The truck has been level for all readings. Did not know that the position of the differential itself could affect the reading. Will go ahead and fill it to the bottom of the fill hole (or thereabouts).

 

[amsoilman]

Your diff. should take nearly 4 quarts to fill. (actually 3. 8 according to the TSB) This figure is for a 11. 5 axle.

If your diff. is leaking, you should be able to see the leakage somewhere. And as Steve said, perhaps when you filled before, the ground was not very level.