Differential Oil Recommendations

[Bob_Spidell]

I wasn't sure myself, come to think of it, so I did some googlin' (I usually trust RL's descriptions):

https://www.rymax-lubricants.com/blog/the-differences-between-gl-4-and-gl-5/

Also, I think we should use the 'NS' version, since the other is more for use with limited slip diffs, as the LSDs basically have a type of clutch and friction is a factor (but I doubt it matters diddly-squat in our old-school open diffs).

Yes, synthetics, as a rule, tend to leak out more, but can be contained. I went to great lengths to seal up my gearbox and OD when I rebuilt them, and they leak a little, but not a lot. My rear end--the car's that is--leaves a couple drops on the floor now and then, but I can live with them.

 

[steveg]

 

[AUSMHLY]

Moss, Dynolite description:
Our classic cars require special fluid and oil formulations, in particular, gear oil. Newer GL5 oils have too high of a sulfur content which erodes yellow metals such as bronze or brass, which are commonly used in British applications. Our cars require a GL4 type oil and this Dynolite Gear Oil is perfect for our classics.

 

[Bob_Spidell]

Wow, a 10-year-old thread comes back to life!

GL-5 may be problematic in a Healey rear-end. There are admonitions around that GL-5 has Extreme Pressure--EP; sulfur and phosphorous--additives that may damage brass and bronze, and David Nock informed me that Healey diffs have bronze thrust washers in the spider gears. David also added that he's used GL-5 for many years and has not seen any damage from it.

 

[AUSMHLY]

I'm planning on draining the old oil out and replacing with new. Not sure what's in there and read don't mix different oils. Is there any product I can pour into the side fill plug hole to clean out any sediment built up in the case inside before I add the new oil? I've read how to's about other cars, after removing the housing plate, they spray brake cleaner. Would it be ok to plug the drain hole, spray an entire can of brake cleaner in the fill hole while turning the tires to move the gears, then drain the brake cleaner?

I could remove the front housing, but not sure how much of the rear end I'd have to take apart. Once I remove the drive shaft to get the front housing off, will that unit simply pull forward and out? Or do I need to remove both axle shafts too?

All I'm looking to do, is drain out the old oil, and replace. But also want to do a thorough job, without making a Hugh project in the process. And possibly create new problems.

Maybe drain the old oil, put new oil in. Drive 10-15 miles? Could that new oil be the cleaner? Drain and replace with more new oil?

 

[steveg]

You have to remove the axle shafts to withdraw the pumpkin.

This looks like a good process:
https://itstillruns.com/flush-rear-differential-7607110.html

Spoiler: they recommend using diff oil as the cleaner.

 

[Bob_Spidell]

I'm planning on draining the old oil out and replacing with new. Not sure what's in there and read don't mix different oils. Is there any product I can pour into the side fill plug hole to clean out any sediment built up in the case inside before I add the new oil?
...

Have considered doing this myself. Mineral spirits--aka paint thinner--was our 'go to' solvent in the past, but it's gotten ridiculously expensive, if you can even find the waterless type in California. The Brits sometimes recommend using 'paraffin' (aka kerosene). I think if you just drive your car for a few miles, then immediately get the car up on jackstands and let the diff drain for a day would be sufficient (that's what I do). The brake cleaner wouldn't hurt anything, and would evaporate quickly, but I think just getting the fluid warm and letting it drain works (you might be surprised how warm the diff gets after a spirited drive; the heat limits track time for some cars). When you get the drain plug out, run a finger around the inside bottom of the diff; if you feel a lot of gunk then a solvent bath might be in order, but remember the diff oil also lubricates the hub bearings.

 

[Michael Oritt]

For purely prophylactic reasons about six months ago I decided to pull the diff out of my 100. I had done this many times on my race cars, all of which use Spridget center sections, and I was quite surprised by how much larger and heavier is the pumpkin on a Big Healey. Getting it back into place alone while lying on my back under the car was a challenge, but the whole procedure is pretty straightforward.

With the half-shafts out I clean out the axle housing from both ends with brake cleaner and use a jack to raise up each end to promote better drainage. Having a source of compressed air is a big help. Before reassembling I run a small magnet around the center to see if there are any metal bits floating about. Soaking the paper gasket in water makes getting it over the studs much easier. Some people eschew sealants--I use Ultra Gray.

Bob's report of David Nock's saying that there are bronze thrust washers in the diff is interesting news and I wonder if bronze is as susceptible to attack from sulphur, etc. as is brass. In any case I have been using GL5 diff oil in all of my cars with no issue.

 

[John Turney]

Reality check: Who disassembles their engine to change the oil?

Drain the oil, if it doesn't look like brown metal flake, refill it. If it looks like metal flake, maybe disassemble.

 

[Michael Oritt]

John

Next time you go for a colonoscopy ask the gastroenterologist can he get a good look in there if you just wipe real well.

 

[steveg]

This manual-transmission-only channel has interesting info (along with semi-recommendations) on the two types at the end of this video:
https://youtu.be/Z7NpsMZ9pBQ

 

[Rob Glasgow]

That's a great video. It nice to see someone who knows their stuff and can present it clearly and concisely without the need to interject profanity every 5 seconds. Thanks for sharing. You just got to love YouTube done well.

 

[AUSMHLY]

You can find almost anything on the net. Auto-RXplus.
This a product that is suppose to clean the differential, and many other car parts.

Anyone heard or used this product?
I'm/we're always Leary of "snake oil" products. Not saying it is, just buyer beware.
https://www.auto-rx.com/differential-cleaning

 

[Michael Oritt]

The idea of putting the residue into suspension does not sound appealing to me.

 

[gonzo]

Hssstay away from additives. Take your car on a favorite drive to warm up the diff, then let drain a few hours. Pump in some good synthetic gear oil - buy 3 qts - I used:

 

[AUSMHLY]

Gonzo, any reason you prefer the synthetic SAE 75W-90 over the non synthetic SAE 80W-90


Would the synthetic be more likely to leak? I have drip issues now.

 

[gonzo]

Perhaps...
My diff was rebuilt when the 3.5 ratio ring and pinion were installed. The gear shop doing the work - who specializes in classic cars including British iron - strongly recommended Lucas Synthetic. Since the pumpkin gear assembly was removed, the diff's paper gasket was replaced along with a light coat of Permatex Gear Oil RTV Sealant on surfaces, diff threads and 1/2 in. fill and drain pipe threads. No leaks...yet.
If you want to avoid synthetics, then use their thicker stuff -

 

[AUSMHLY]

What's the pros/cons of using a multi grade mineral gear oil?
80W-90 vs 85W-90 vs straight 90w

 

[steveg]

What's the pros/cons of using a multi grade mineral gear oil?
80W-90 vs 85W-90 vs straight 90w

You'll have a tough time finding straight 90w. Amazon has a few used in marine and other special applications. Red Line MT-90 is a great GL4 for the Toyota and other non-Healey manual transmissions. You'll see many 75w-90 and 80w90 synthetic and mineral oils.

The transmission expert in the GearBoxVideo channel referenced above says either synthetic or mineral works fine.

 

[steveg]

Wow, a 10-year-old thread comes back to life!

GL-5 may be problematic in a Healey rear-end. There are admonitions around that GL-5 has Extreme Pressure--EP; sulfur and phosphorous--additives that may damage brass and bronze, and David Nock informed me that Healey diffs have bronze thrust washers in the spider gears. David also added that he's used GL-5 for many years and has not seen any damage from it.

Ditto:
The transmission expert at GearBoxVideos agrees with David Nock in that in rebuilding thousands of transmissions he has never seen any actual damage to yellow metals from GL-5. He says theoretically if you boil the GL-5 it could etch the yellow metal but in practice all he's ever seen is a slight color change.