Diff oil

L

Lewis Stephens

Member
Hi all, Just a couple of questions if I may. 1. Why is oil for the differential called ' gear oil '. 2. Changing the diff oil. When i first got my latest P6B back in 2022 one of the things on my list for the mechanic who first serviced the car, and has continued to do, was if I should get the diff oil changed. He said, no, P6B diff oil doesn't need changing. Now having read other posts and asking Mr AI I'm not so sure. Comments please.
 
Changed mine for the first time in 50 odd years. I can tell you the original oil was very black and quite thin.
I filled up with Penrite gear oil 80/90 AP4 . Nice squeezy bag -so no mess down to the elbow.
 
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Change it. It’s called gear oil because it’s designed to withstand the high pressure shearing action of the gear teeth. Over time that same action will chop up the long oil molecules until they lose a lot of the properties that you need in a gear oil.
 
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Hi Lewis,

Don't take your Rover to that mechanic again, he sounds like a moron.

All oils degrade and should be changed periodically. Your differential oil is no exception.

Ron.
 
Oil is much cheaper than thee mechanicals it protects, so regularly changing oil for a little used car makes sense t me. I ask for all oils, engine, gearbox and diff, to be changed every year at a major service. An experienced mechanic can identify problems from looking at the oil taken out..
 
I'm jumping in on this thread as I think I might renew mine (no idea when or if it has been done), my question is, if I put the back of the car on a couple of ramps, will that impair the draining and refilling if the car isn't level?

Stef
 
yes

if you ramp the front you can jack the rear level using the jack pad behind the rear valance
but do add a axle stand or two off the rear x member as a safety plan
dont jack on the diff or de dion tube unless you like a disaster
have fun
for a life help and a bit of noise reduction try a EP140 its listed as ok
Pete
 
I recently changed the differential oil on my 2000TC. Jacked up, drained, filled til dribble out of filler hole. Then took down off the jack stands to level, a v small amount dribbled out, then wriggled under to get the fill plug in, which I could just manage on the ground.

I really liked that the fill plug had a longer square head to make it easier to get the OE wrench on it. If that was intentional design, tip my hat to Rover Engineers back in the day.

Happy Motoring - Munro.
 
just about to do ours as its up to fit a prop spacer
have the tube and diff levels but a brake leak to examine its either caliper or diff output seal on the next to do list
Pete
 
just refitted the down pipes having drilled out a tapped the manifold the specified studs are two short
no idea why but have used bolts washers and copaslip its on ,
diff level on back burner for a day as tomorrow im off for a tail down taxy ride in alancaster bomber as a gift from my old triumph area wonder what oil she has ????
our gearbox had a cup full of black sludge i guess the diff will be even worse the jobs continue to grow
but we are getting somewhere now , pleased with the engine and gearbox mounts so the thing wont be trying to climb out by itself
happy motoring is just round the corner Ha !!
Pete and son
 
Thought I’d add my penny worth- Ive not had my 2200sc for much more than 18 months, and although the previous owner had done very low mileage, there was precious little paperwork to suggest what, if any, servicing had been done, so I had no idea of mileage since last Diff oil change, if any! I was going to put the old gal up to get at rear callipers to do a full brake fluid bleed, so decided I’d give the Diff oil a change too, possibly the first in 50 years too. I’d already bought the new oil, Castrol B373 SAE90 LSD, and boy was it a revelation to see the colour and state of the old oil as it ran out! It was so black, coal black and thin, probably thinner than old engine oil, so I ran a small amount of flush oil to be sure all sludge was out too, and am glad I’d done it, and will definitely do it on a regular basis now. Far cheaper and so much easier than a Diff rebuild or exchange. Preventative maintenance is simply common sense.
 
Absolutely! Especially when you consider the extreme shearing forces on the oil in the diff. Have you ever felt how hot they get after a good run?
 
The mechanic is actually right. Differentials are normally topped up but the oil is not changed. From memory the oil and gears bed in as a matched set, so changing the oil restarts the bed in process. Fifty year old oil is obviously a different case but the mechanic doesn't know if or when it was last changed, if at all, so won't change it unless asked and certainly not regularly. The Horid smell isn't due to the old oil... It's the oil itself being from a heavier, stinky, fraction of the crude it comes from. Crude itself is much stronger and worse. I live next to an oil terminal, there is a reason they stick them on the edge of town....
 
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the only reason you dont have any planned oil drains on diffs and gearboxes is due to the lack of any
combustion contaminants like you get from engine and their oils many makers do not have a diff drain plug.
if you can re bed a crown wheel and pinion by changing the oil there is some serious doubts about
any life expectancy
pete
 
out of interest just searched the WSM for capacity but its in the handbook 2,25pints hidden near back of the book
there is no references in the workshop manual
I thought Triumph were good at leaving out the one simple snippet but seems Rover do the same
hide simple basic stuff
try looking for wheel nut torque ...its not there
and i have been involved in all facets of truck manufacture including torque control for 40+ years
i find missing basics a bit bizarre
Pete
 
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