SuperDave4x4

how high should my differential be filled? I had it checked and it was just spewing out when we unscrewed it. Is that too high?

Ruralmedic

If it was warm when checked, that could be normal. Cold check I think is about 3/4" below the fill opening for the rear axle. Overfilling may cause the seal at the driveshaft end to leak.

SuperDave4x4

yeah im just getting this loud whine from some where and it only does it when i give it gas and let off while i slow down. I almost positive is the rear end. its just driving me up the wall.

Mopar1973man

Strange, mine started to leak becuase it was to low 3/4 to 1" below... But when I filled to the rim of the hole it stopped... Go figure!

SuperDave4x4

Do you think because its so full that it could cause my rearend to whine?

Mopar1973man

Actually from what I heard it is the slack in the pinion and ring gear ....

SuperDave4x4

So if i have slack in my rearend how do i get it out? how much would someone charge to do it? its seriously about to drive me up the freakin wall.

Mopar1973man

I'm not exactly sure how to do it....

But first verify it is the problem... Put the trans & transfer in Neutral. Get under the truc and try to twist the driveshaft left to right or vise-versa. If you feel a lot of slack then it is the problem...

To tight the pinion... (someone chime in) I think it has shims that you can replace to change the slack or is it the that you torque the pinion nut?

It's been a long time since I did this on my 1972 dodge P/U!!!

SuperDave4x4

yeah i think its gettin a hair worse now. Its starting to make funny vibrating noise. Im takin it to the *********** in the moring. I hope all goes well....or should i say cheap.

dodgediesel4x4

It could also be a bad U-joint. That would explain the vibration, esp. at certain highway speeds.

Scubasteve

I would find the problem and correct it as soon as possible.

Here is a little story for you.

I was at the tranny shop and a guy had his truck towed in because the drive shaft flew out. The tranny guy asked him if anything was wrong prior to this happening, the guy said " there was a bit of a vibration and noise but I didnt think it was anything bad" LOL!! well the guy needed a new transfer case, drive shaft, fuel tank, rear yoke on the rear end and to top it all off if did some internal damage to the tranny. Moral of the story is when something feels "just not right" fix it before the little things snow ball into a huge EXPENSIVE mess..


for the record the fluid level is around half to three quarters of an inch below the hole.

To much fluid will cause foaming and possible premature seal failure..


Jason

HOHN

I have to take issue with the many posts here saying that overfilling the diff causes foaming.

What is different between 3/4" below the hole, and filling right up to the hole? NOTHING. The gear oil is high enough to partially submerge the gears.

If you look at the demo posted at www.bobistheoilguy.com under gear oils, you'll see that most of the gear oils didn't foam at all, until Lucas oil was added to them. Commercially available gear oils have anti-foamant properties in them.

Finally, overfilling is far more likely to PREVENT a seal failure than to CAUSE one!! Almost all seal failures are caused by them running dry-- overfilling helps to make sure that your pinion and especially axle seals get a good bath and stay lubed.

I've had good results with overfilling the diff, and I intend to to until someone can give me a logical and credible argument as to why this is bad. The foaming theory doesn't hold up to scrutiny to me.

As always, JMHO.
\Justin

bluepp

I agree with HOHN. 3/4 below hole is low level, and concidered OK. But hole is put where it is for proper fill level. Fill till oil runs out hole. You wont get it too full, theres lots of air space above hole.

RowJ

Most seal lost is due to drying out.

Higher quality, Specialty Lubrication Companys, add a seal swellant to keep seals pliable and expanded. These are companys like L.E. (Lubrication Engineers), Red Line, Royal Purple, Shaeffers, Synergyn Racing Oils, and Amsoil (I think, but have never seem the documentation).

These companys also tend to use more & better (longer lasting) anti-foaming additive, as well as Parrafinic instead of Napthinic Base oils, which don't thin out as much when heated.

I have always filled to bottom of hole with no problems.

RJ