Differential Oil and Sounds

Do different gear oil weights made a difference in how the differential sounds?

Was hoping someone would chime in by now. I'd like to know as well.

My 8.25 has howled since the day I bought my XJ at 88k. I'm up to 122k now and it howls just the same. No worse, no better and there is no pinion bearing play or strange wear inside the differential. I've changed the fluid three times with 75w-90 or 80w-90.

I'd try 75w-140 to quiet it down, but just havent got motivated to mess with the issue.

Are you trying to quiet down a differential OP?

Been watching as well.

Runs perfectly quiet until warmed up good. Then a growl on neutral load between power and coast. If I am going down the road at 60 and push the trans into N, the sound is very distinctive. Putting load back on makes the sound to away.
There is not discernible bearing play when yoke is manipulated without the driveshaft on. I retightened the yoke nut to 180 lb/ft. It was almost loose. But made no difference.
Sound is only present under neutral load when warmed up.

I put Castrol D 140 gear oil and a pint of Molybdenum gear additive in my beater YJ with bad carrier bearings (way bad). It quieted it down around 30-50%. I ended up replacing the bearings six months later after the weather warmed up a bit. One thing I did notice was their was a noticeable resistance (like I was towing a small trailer) when it got really cold out 0-5 F., it took a few miles for the gear oil to warm up. The gears were quieter though, when the oil was cold and thick.

I do remember my carrier bearings were noisier in reverse than in forward gears.

Some of the Sake Burner and Bimmer sites have long discussions of using certain 140 weights with significant success. Bought a bottle yesterday. I will do a drain and fill today and let you know.

But 0-5 F? You are hearty people!

if the yoke was loose the pinion bearings are FUBAR.

the 8.25 pinion bearings are a crush sleeve pre-load. Putting 180 ftlbs on it is not correct. The pinion nut is to be tightened until a certain turning torque is achived. typically 35-40 in-lbs on new bearings.. around 10 in-lbs for used.

heavier weight oil will do nothing to cure the problem, only the symptom.

Digger87xj said:

if the yoke was loose the pinion bearings are FUBAR.

the 8.25 pinion bearings are a crush sleeve pre-load. Putting 180 ftlbs on it is not correct. The pinion nut is to be tightened until a certain turning torque is achived. typically 35-40 in-lbs on new bearings.. around 10 in-lbs for used.

heavier weight oil will do nothing to cure the problem, only the symptom.

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Just wanted to throw out there that there are solid spacers and shim kits out there to replace the crush sleeve for the 8.25

If yours has this replacement, then 180 ft-lbs is fine, but the fact it was loose is cause enough for bearing replacement.

Digger87xj said:

Just wanted to throw out there that there are solid spacers and shim kits out there to replace the crush sleeve for the 8.25

If yours has this replacement, then 180 ft-lbs is fine, but the fact it was loose is cause enough for bearing replacement.

Click to expand...

I'd do whatever the FSM recommends. I've never had a 8.25 in an XJ, but have had many in Dodges. It is possible to jam the driveshaft at full spring compression (sitting on the bump stops) on a bumpy road or trail, on some Dodges. The slip yoke runs out of play and you jam the driveshaft into the collapsible spacer. I read in some places re torquing is acceptable, in other reference material it says you must replace the sleeve. I always replaced the sleeve.

My test has always been if I could turn the pinion by hand, it was likely to be OK, if it was so tight I needed leverage to turn it, it was likely to overheat and completely fail soon.

With a little practice you can turn the pinion by hand and feel if it is spalled and rough, too loose or too tight. To do a real preload inch pound test you have to pull the carrier and just test the pinion, I always cheated and left the axles and pinion in, made sure the brakes ween't dragging and tested that way.

I'm by no means a differential expert, but have done a few and was always successful. My guess is there is a little leeway between perfect and good enough.

Something else I always do is catch the oil in a clean plastic pan and run it through a sieve, then drag a magnet through the oil. If you have chunks in the sieve you have serious issues. More than 2-3 grams of metal filings on the magnet and it had to come from someplace, likely wear and tear on your bearings. Many bearings are surface hardened and get softer the more wear they have. After the surface metal is worn off the bearings start to spall and shed chunks. I also smell the oil, red hot nearings tend to give the oil that burnt smell.

Overtightening is to be avoided, excess heat can kill bearings quick, they may wear in, they may get red hot, loose the temper and fail quickly. Kind of a hold your breath and hope for the best kind of thing.