Correct diff oil 8" ford

[Ianrhall]

I had to change the pinion oil seal on my falcon, has a regular non posi diff. About a pint of thick gloopy black oil came out! The regular gear oil I used was much thinner. I'm pretty sure it's noisier now!
Just wanted confirmation on the correct grade of oil
Ian

[ponymare]

The orig oil was 85-90, but, during its life time a pint or quart of stp may have been added to quiet bearing and gear noise.

[Ianrhall]

Should I drain it, refill and use stp again?

[ponymare]

If its noisy why not find out why and fix it, better than having it go down along the hi way.

[Ianrhall]

Looks like I've messed up the preload tension, will need to get it set up properly, just hope I haven't caused any expensive damage!

[bobss396]

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With old cars, I'd be inclined to use something like a 90W-140 gear oil.

[rich b]

Most every 8" rear I've worked on has needed new pinion bearings and a speedi-sleeve on the yoke.

[Y-Blockhead]

Originally Posted by bobss396

With old cars, I'd be inclined to use something like a 90W-140 gear oil.

The shop that built my 8" recommended 90w-140 from the get-go.

[Ianrhall]

Originally Posted by rich b

Most every 8" rear I've worked on has needed new pinion bearings and a speedi-sleeve on the yoke.

What would cause noise on deceleration?

[Dobie Gillis]

If you notice that the howling noise only occurs during deceleration, then it is a good indicator that the pinion-bearing preload has loosened. Since you think you may have "messed up" the pinion preload I'd vote for that as the cause.

[Ianrhall]

Originally Posted by Dobie Gillis

If you notice that the howling noise only occurs during deceleration, then it is a good indicator that the pinion-bearing preload has loosened. Since you think you may have "messed up" the pinion preload I'd vote for that as the cause.

Just hope nothing else is damaged