black gear oil

[TexasRob]

Ok finally went through and replaced all the fluids in my truck after buying it two months ago and everything looked great except the front diff. The fluid came out blacker than the oil... I carefully inspected the magnet on the drain plug and there was very little metal shavings on the magnet. I fished around through the drain plug hole with a magnet and didnt pull out any metal. I then flushed with new fluid and replaced. was wondering if I should go more into it or the fluid just might have been old.

 

[SST 1953]

Are you sure someone didn't replace the fluid with Royal Purple?

 

[TexasRob]

i dont think so. the rear diff was regular 80/90 so by my logic why do one diff in expensive oil and not the other. especially the front that doesnt get used as much

 

[SST 1953]

Only other reason is burnt clutches

 

[Chevy1925]

Only other reason is burnt clutches

There are no clutches in the front diff

 

[JoshH]

The rear diff should be Synthetic 75w90.

 

[btfarm]

The rear diff should be Synthetic 75w90.

Agreed...Same with the front.

 

[TexasRob]

so i get that i should be running 75/90 illl fix that but should i tear my front diff apart or just leave it be since no pieces came out

 

[Chevy1925]

so i get that i should be running 75/90 illl fix that but should i tear my front diff apart or just leave it be since no pieces came out

IMO, if you spin the tires and here no nasty noises, spin the driveshaft and here no noises, fill it with oil and be done with her. It sounds like someone just had not changed the fluid since new

 

[btfarm]

Typically, when these were new and you decided to change your differential fluids after break-in, you would find 2 things to notice right away:
1) The rear was 1.5-2 qts low and smelled like grape soda. (Thus "grape Juice")
2) The front fluid drained out with a nasty, snotty yellow color.

If you ran either for way too long they were black. Just change 'em and go. If you scatter something in there it'll be closer to silver color

 

[TexasRob]

I changed the fluids today to 75/90. Thanks for the input. I'm gonna check the front diff again in about 3k when I change the oil again, just to be sure.

 

[adeso]

my front diff fluid looked like crap with shavings in it when I first changed it, since then I have beat on it more than you will and still going strong