I have a hot REAR END!

You can drain the $50 oil into a clean container then pour it through a coffee filter atop another bottle. It is slow so you may want to set up a few coffee filter funnel bottles. When it is finally filtered inspect your coffee filters for metal shavings.

If filtered fluid looks ok it can be reused.

 

It may be a while before you get that locker.

If it is quite and temp is in spec there is a good chance it's gonna last.

 

Good synthetics run significantly cooler than dino oil. I would stick with a synthetic. I've found Redline to be the best, but I think the Amsoil Severe Gear is also a good oil. The reason I now run Redline is because the additive package they use has a higher temperature limit. Either one will run 15 to 20 degrees cooler than a dino oil. 75-90 is best for normal driving. I would use 75-140 for heavy duty use like towing. Again, this is from actual measurements and experience on my truck.

 

Mine gets hot too. I'd say it's normal. Be sure you remove and clean the dif breather every time you replace the dif oil. It's the temp changes that cause pressure to build up and release.

 

I have the LSD. The only way I could stop the binding was to use 80w90 dino with additive.

 

I suppose you meant ECGS then.

 

I have to disagree.

I was regularly running about 425hp/415ftlbs torque through a mazda 8 inch rear hooked up to a built LS1/T-56 in my 93 Rx-7 with sticky launches at the track. Even then the weak link was the diff case, not the ring gear.

I have 4.88's now in my toyota diff from Chase at ECGS and he very highly recommends lucas 85w-140. I've noticed that my diff is definitely warm after running on the highway but it isn't so hot that I can't leave my hand on it. BTW, you'll bust the carrier before you ever destroy a ring gear on these trucks.

Have you noticed any excessive material on the magnet plug? Clogged diff breather? I would take that off and clean it. Synthetic isn't necessary for these diffs, I would just go with Chase's recommendation on an 85w-140 dino oil. Surprisingly it's very inexpensive on Amazon.com. 1 gallon is 21 dollars with free shipping. Most auto parts stores charge 10 dollars a quart for lucas non-synthetic gear oil.

 

I think you are too concerned about the temps you are reaching when towing. Up to 250* is normal on the big stuff that works for a living, and with extended drain synthetic lubricants the service intervals for on highway use is typically about 500,000 miles. Non-synthetic will still meet extended warranty requirements with reduced service intervals.

Yes, oil oxidizes and breaks down faster as temps climb, but that is why we do maintenance, and increase it as required when towing, etc. I also would not be concerned with seal failure, assuming they are viton seals, 315* and under is safe for them.

I'm a huge fan of chevron delo synthetic gear oils, but I'm not sure if their 75w90 is LSD compatable, and since I don't have a LSD I haven't bothered researching it.

 

I like synthetic as much as the next guy but I'm not willing to pay the extreme price unless it is a severe service application.
I prefer to use the cheap stuff and change it if it gets nasty.
My Dad's 1966 truck differential just failed last year and it was not wear related; the pinion shaft broke due to fatigue. The conventional gear oil was only changed once after 40 years service; that's good enough for me.

 

Thanks for all the info guys. I did the breather mod as mine stock one seemed iffy I could blow air through it but took a little pressure almost like the valve was sticky.

Also drove about 60 miles on the Lucas and drained it mainly cause I wanted to flush it after it ran for a little while.

I replaced with mobile 1 synthetic only because it was all the store had left. No Dino, no Lucas, nothing but the mobile 1. So I went for a run and the temps were definitely better got an I.R. thermo on it and the hottest temp was 127.

I believe the root cause of this situation was the breather. So if anyone on here hasn't yet do it!! DO IT!!! I will continue to monitor for the next few weeks to ensure that it maintains.

Again thanks guys.
Phil

 

x2..

in the past i have blown 3 rear ring and pinion sets. i used synthetic royal purple with those sets. now with my 4th set im using lucas 80/140 dyno oil as recommended by EastCoastGearSupply. one thing i have noticed so far is the rear diff seems cooler to the touch as compared to when i was using the royal purple..

also with the royal purple the oil always seemed dark,dirty and thin when i drained the oil out to replace the 3rd member..

 

A breather problem won't cause high temperatures, unless the temperature problem is because of contaminated oil. High temperatures combined with breather issues will cause pressure, and vacuum as it cools, which can blow out seals or "suck" in contamination like dirt, water...

For off road use in watery situations the stock breather is an issue by design because it acts like a check valve and will cause a warm diff to suck water past the seals as it rapidly cools in water. So the breather mod is good anyway if you leave the pavement.

 

No noise and 127F.
That sounds good.
That's what my broken in diffs run.

 

I was searching around for normal operating temperature just now and stumbled on this thread. I just recently regeared to 4.56. Still breaking it in so I'm babying the truck for now. Here's my current temp, I was told by my installer that this is hotter than normal.

 

That seems normal to me. I think it was @gearcruncher that had posted up a temp. chart in a thread a while back. Let me try to find it.

 

Awesome, thank you, sir.

 

harbor freight IR temp gun is needed

 

Yup, that's what I'm using. I'm curious what temps people are seeing after roughly 15-20 mins of easy freeway driving to make a comparison to what I'm seeing.

 

Here ya go. This is from a trans cooler thread, but the info about temps were helpful to know. I have a gauge that shows the temps and that is why I wanted to know the limits. Hope this helps.

 

Jeez, that boy did some serious homework. This will be a good read. Thank you very much again @DrFunker !