• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

Differential oil for 100/4 1954

Share this page

W

Walker sim

Member
Country flag
Offline
I have just purchased an early 100/4 (chassis 150913). It's been in storage for 30 odd years & I am replacing the liquids. 20.50 seems the choice for engine/box/OD, but I'm stuck with a diff oil. The manual mentions the early cars, pre engine 221536, had something other than hypoid. Any suggestions?
 
According to Clausinger your car has a spiral bevel gear diff versus hypoid in later cars. I don't know if the original differential oil spec was different between the two types but since they both involve some gear sliding I think you would be best off with a synthetic GL5 oil, either 75-90 or 75-140. Better diff oils, which stand up best to shearing forces, carry an Extreme Pressure description which costs a bit more but given how infrequently one changes diff oil I would treat your car to the best available--diffs are no place to cheap out. I use Amsoil Severe Gear (EP) in 75-90.
 
Michael - Do you find that the synthetics tend to leak more easily? Found that with lighter oils but not sure if that would be the case with 75/90?
 
Michael--

75/90 diff oil roughly corresponds in viscosity to 30 SAE.
That said, I don't know if synthetic diff oil leaks more because I have never used any non-syn diff oil, but I'll accept the common wisdom that it does.
 
I've run Redline 75W-90 gear oil in both my Healeys' diffs for several years. I didn't notice any more leaking than with dino diff oil. I'm now running Redline 75W-110 in the BJ8 to help quiet some diff whine.
 
The shop that just rebuilt my 3000's rear diff recommended Lucas Synthetic Gear Oil 75W 90 which I had planned to use anyway. About 2.25 US qts. fills the diff from empty. Good stuff. GONZO.
 
gonzo said:
The shop that just rebuilt my 3000's rear diff recommended Lucas Synthetic Gear Oil 75W 90 which I had planned to use anyway. About 2.25 US qts. fills the diff from empty. Good stuff. GONZO.
Click to expand...

Did they recommend synthetic for break-in? What were their break-in instructions?
 
Yes. I know the internet has all sorts of ring and pinion "break-in" instruction, so I asked the builder. He replied: "bolt it in, add gear oil (synthetic), drive and enjoy." I liked the "enjoy' part since it implied "don't sweat it". GONZO
 
gonzo said:
Yes. I know the internet has all sorts of ring and pinion "break-in" instruction, so I asked the builder. He replied: "bolt it in, add gear oil (synthetic), drive and enjoy." I liked the "enjoy' part since it implied "don't sweat it". GONZO
Click to expand...

Having read the ring and pinion break-in instructions it made me wonder why new cars never include such instructions. I don't imagine they are broken in on the line.
 
Gonzo--

Are we are talking about a freshly manufactured ring-and-pinion set such as was supplied by Mike Lempert or did your shop rebuild the differential by setting up the "lash" and perhaps putting in new bearings and/or a new pinion seal? If, as I suspect, it is the latter then the gears--the ring and pinion--were already broken in by previous use, which is why the instructions were what they were. OTOH with a brand new R&P set it would probably be wise to drain the diff oil after a couple of hundred miles to get out any little bits, then refill and carry on.
 
IIRC, the Lempert ring & pinion set we installed came with very specific instructions. The diff can get very hot--mine got almost 'pistol hot'--during break-in and the instruction called for short, then progressively longer runs with a cooling-off period in between, followed by a drain and fill after a few hundred miles. But, I used mineral gear oil for the break-in; apparently synthetic eliminates the need for such a procedure. My Mustang, new in 2008, had no specific break-in procedures so I followed my dad's advice: 'Break it in how you're going to drive it.'
 
Shop rebuilt the diff with new R&P (Moss = AH Spares), bearings and seal and set up lash etc. I'm taking it easy on the diff. Last weekend I took the car out for two test runs of about 15 - 20 miles allowing a "cool down" in between. The Diff did not heat up any more than usual and did not make any unusual noises. Gear oil will be changed in about 500 miles. No leaks from axles, diff pinion seal or join to diff housing after complete cool down. Longer run cycles - 3 or 4 depending - planned this coming weekend. GONZO.
 
"Shop rebuilt the diff with new R&P"

Good going and by all means follow the advice given. Given what I am sure is a substantial investment the rear axle deserves the best care and feeding available!
 
HealeyRick said:
Having read the ring and pinion break-in instructions it made me wonder why new cars never include such instructions. I don't imagine they are broken in on the line.
Click to expand...
Also: [ QUOTE= GONZO; ] Yes. I know the internet has all sorts of ring and pinion "break-in" instruction, so I asked the builder. He replied: "bolt it in, add gear oil (synthetic), drive and enjoy." I liked the "enjoy' part since it implied "don't sweat it". GONZO].
 :iagree: . I am also sure that any routine change of any lubricant can't do any harm to any running components.
 
Back
Top