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MG Midget and Sprite Technical - Gear Box Oil

The car is generally improving each day and I am getting used to the noises and handling. :-)

General transmition noise has decreased with time (particularly the diff) however 1st gear noise has increased and changed. It sounds a bit rough in first now (not loose or anything) and I know that reverse is on the same shaft so am expecting noise but not worse. I am short shifting 1st generally and the other gears are as they were. Only problems are really when in a multi story like today when I needed to use 1st a fair bit.

So as no doubt the gearbox oil has never been changed I thought I would change it and get rid of any of those possible floaty metalic bits that may have contaminated my box. If its still rough and noisy and getting worse after that I will have to decide what to do.

So at the risk of starting a new oil war (I did not mention bearings but if someone has to then I appologies in advance if this thread causes any acrimony) can you give me the oil of your choice for long term running and maybe as a short term flush for however many miles. Not had to worry about gearboxes before and I have a spare one somewhere but as this is my daily drive and the keep it going and fix it as it goes car I really want to stick with what is generally original and beginning to get its act back together. Also not sure if P reg 1500 box is the same as S reg 78 1500 box anyway.

Thanks in advance. Dave
Dave Squire

all 1500 boxes are the same but I've never owned one so no personal recommendation on what to put in it.
David Smith

ouch....

if the oil has never been changed in the tranny and you are the 1st to have changed it...

Then WOW.... I feel sorry for you, im no paleontologist but id say your going to be rebuilding a tranny really soon

whats happened is all the crude inside the tranny case has turned into a paste and worked.its way into the various bearings and has taken the place of the bearing sleves, and shells which are now worn away

when you.changed.the.oil, all that crude paste got washed away...and now there is alot of play in all the bearings...and alot of new wear is takeing place

id say now is the time to consider a type 9 5 speed conversion...at the very.least, id be looking for a good running ebay tranny

sorry ... that sucks... I hope im wrong... but no oil.change in 30 to 50 years in an MG 4 speed box....that box belongs in a museum of what odd and strange

prop

p
Prop and the Blackhole Midget

Dave,

EP90 is the stuff for the 1500 gearbox.

Dave
D MATTHEWS

Gearbox oil – EP (GL-4) oil which can vary in recommendation some say EP80 for filling and EP90 for top ups others say EP90 throughout

normally now you get given EP80w/90 (GL-5) when buying but GL-4 oils are recommended for the gearbox

for easier cold weather gearshifts and longer lasting oil than the usual ones you could use a modern GL-4 alternative like Castrol Syntrans Multivehicle 75W-90 Fully Synthetic MTF

for a flushing oil you could just use 20w/50 engine oil (yes it is thick enough, the EP and engine grades are not the same and the oils are not strict to the numbers anyway), I'd think 50-100 miles would be enough for a flush more important is to empty out hot

the secret of the oil flush and any oil change is to have the oil as hot as you can from normal use and then leave it to drain as long as possible, same for emptying out present and flushing oil

BTW you're sure it's not the clutch or clutch hydraulics (mc, slave, fluid, flexipipe(?))

you perhaps see now why I always recommend doing a full 36k-mile service/check up (plus the fluids mentioned here and before and in rear axle)
Nigel Atkins

Dave,
if you want them I have notes on oils, links to sites with various views on different oils and the charts to show that how the various types oil viscosities overlap

obviously the different oils are designed for different jobs but the engine oil will be fine for short term use as a flushing agent and possibly a lot better for the gearbox than the oil already in there

as with even using the fully synthetics oil it isn't expensive I'd look at doing the rear axle too (with a different oil)

yours for the asking ... now who sang that?
Nigel Atkins

Its the flushing I think is probably important first. Once I know that the oil is clean I can decide what to do (if anything). I have the engine oil anyway so a doable at the weekend.
Now I know all the 1500 boxes are the same I will dig out the other one and see how it is.

The clutch is fine. I get a bit of slip if I over rev on shift up but my shifting is improving (the other car is a modern diesel so I will adjust as I drive that less) and the slip is getting less so I assume the mechanical clutch parts are freeing up more and more as they get used.

Clutch hydraulica all fine, no leaks etc. and good in traffic. Its definately first. All other gears fine.
Dave Squire

Dave,
thorough hot drain of what's in now, put in flush oil then thorough hot drain of that and for not much money put in Castrol Syntrans Multivehicle 75W-90 Fully Synthetic MTF as it will help with the shifts especially in cold weather

mind if your present oil is thin metal flake soup any change may help

(CE - the Syntrans can't fully overcome worn box or clutch)

while your under there you might as well do a thorough hot drain the r/axle and put in for longer lasting oil with less cold weather drag a modern alternative like Castrol Syntrax Longlife 75W-90 (GL-5 spec*) or Mobilube 1 SHC 75W-90 (GL-5 spec*)

(*GL-4 spec oil is recommend for the gearbox but the more modern GL-5 is considered fine for the diff)

http://www.opieoils.co.uk/p-737-castrol-syntrax-longlife-75w-90-formerly-saf-xo-75w-90.aspx

http://www.opieoils.co.uk/p-806-mobil-mobilube-1-shc-75w-90-fully-synthetic-supreme-performance-commercial-gear-oil.aspx

for what it's worth,
• for all jobs allow loads more time that you think it will take, never be in a rush

• (check for the correct oil to use)

• get the right tools to fit drain/fill plugs

• clean around both plugs and spray with a penetrating/releasing fluid such as PlusGas (WD40 is not as good) and let it soak in as long as possible then (try to) slightly tighten to break muck/rust seal before undoing

• have the axle oil as warm as possible before draining (protect yourself from hot oil)

• take filler plug out to help drain faster

• leave to drain as long as possible

• clean plugs and threads

• (check axle breather is clean and clear)

• refill with about ¾ of stated quantity of oil then top up very slowly until at bottom of threads leave excess to run out (can take ages if you overfill)

• plugs go back in 'dry' hand tool tight
Nigel Atkins

edit beat me to finding links

http://www.opieoils.co.uk/p-739-castrol-syntrans-multivehicle-75w-90-fully-synthetic-mtf-replaces-smx-s-75w-85.aspx

links are to show oils, you may be able to get them cheaper on eBay or elsewhere, always allow for P&P
Nigel Atkins

Quick question Nigel as I'm at work and planning on heading to the motor factor on the way home... What quantity of EP90 is required for a 1275 box?

thanks in advance
graeme jackson

never mind. a brief encounter with google found this site...
http://www.mgexperience.net/article/mgoc-basic-2.html

which suggests I should be using 2.25 pints of 20/50 for the 1275 gearbox (not EP90). Now to find a conversion site cos I'm pretty sure halfords don't work in proper british measurements.
graeme jackson

Graeme,
as usual you'd find the answer in the Handbook - and I quote '2¼ pints (2.7 U.S. pints 1.3 litres)'

why run around looking for info that you've then got to check when a reliable source is available that doesn't need a internet connection, mains or (unreliable) battery supply or worry about were you can put in down or not get it damaged

it isn't necessarily 20w/50 oil, you could look at using 10w/50 and I'd look at using a good quality synthetic instead of the old style 'classic' engine oil
Nigel Atkins

I used parafin for flushing out my rear axle (after I'd overdone it with the KSeries engine round the uphill Martini) - should work for gearboxes too. Must emphasise that the diff wasn't loaded - the rear wheels were off the ground.

I drained and filtered the parafin though a cloth, and re-used.

In all, I think the same parafin went round the loop 6 or 7 times before it came out clear, running the car in 4th at around 1500 revs each time for 30s or so.

EP oils are very sticky, and you really need something like parafin to wash all the cr*p from the various gears and surfaces in a diff or 'box.

You won't believe the amount and range of debris that emerges.

HTH

Anthony
Anthony Cutler

What Nigel said for oil or a synthetic gear oil of your choice.
Daniel Stapleton

This thread was discussed between 14/02/2013 and 15/02/2013

MG Midget and Sprite Technical index

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