MGB Gearbox oil change

[mgtony]

When changing the gearbox oil on the B, along with the drain-off nut for the gearbox, does the one for the overdrive unit need removing aswell? I'm sure only the gearbox one had been removed in the past to drain off the old oil.

[na]

Tony
as far as I remember it's just one drain plug but you can take the O/D filter out to clean it too - I'll find and post here the John Twist video that details full OD overalling for you

is there a reason for doing the oil change?

notes for you, should you chose to accept them, no you don't need to thank me or join my many fans and followers on here

Gearbox oil change notes

· for all jobs allow loads more time that you think it will take, never be in a rush

· check for the correct oil to buy

· get the right tools to fit drain/fill plugs

· you may need to clean around both plugs and spray with a penetrating/releasing fluid such as Plus Gas (WD 40 is not as good) and let it soak in then slightly tighten to break muck/rust seal before undoing

· to get a thorough drain of muck have the gearbox oil as warm as possible before draining (protect yourself from hot oil)

· take filler plug out first then drain

· leave to drain as long as possible

· if gearbox has an overdrive unit now is the time to clean the filter too

· clean plugs and threads

· refill with less than 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 can go back in 'dry' hand tool tight

unless the oil was very bad or there's a fault with the gearbox you'll not notice much, if any, major difference with this oil change but it will help maintain and ease the gearbox by having new oil of the correct type at the correct level

also if you do it you know for sure it has been done and when, the old oil will give you a clue to former maintenance by comparing it with the new oil and a clue to the condition of the gearbox if the old oil has metal bits in it

this job is often missed but is so cheap and easy I think it's worth doing every three years (check and topping up if required every 6 months)

[na]

MGB gearbox and O/D (4 syncro)

This video will help for the gearbox – http://www.youtube.com/user/Universitymotorsltd#p/...


These are worth watching to give an overall appreciation of the O/D

O/D Repair part 1 including draining gearbox – http://www.youtube.com/watch?v=XPSgUeHAy8E&lis...

O/D Repair part 2 – http://www.youtube.com/watch?v=LCqPu77EWEE&lis...

O/D Repair part 3 – http://www.youtube.com/watch?v=FHw_o5y0HWE&lis...

O/D electrics – http://www.youtube.com/watch?v=r-WUuz4BzTw&lis...

Fitting an O/D unit to the gearbox – http://www.youtube.com/user/Universitymotorsltd#p/...

Remote control – http://www.youtube.com/user/Universitymotorsltd#p/...

And something to give you a restless night – Lubrication – http://www.youtube.com/user/Universitymotorsltd#p/...

[mgtony]

Only changing it as part of my bit-at-a-time servicing schedule!
Hasn't been done for a long time, so going to give it some fresh stuff. If I put the front up on my ramps, I suppose I should lift the rear onto some axle stands or will it be okay with just the front up?

[na]

mgtony said:

Only changing it as part of my bit-at-a-time servicing schedule!

blimey Forth Road Bridge speed

mgtony said:

Hasn't been done for a long time, so going to give it some fresh stuff.

good man - how about that last video for you

mgtony said:

If I put the front up on my ramps, I suppose I should lift the rear onto some axle stands or will it be okay with just the front up?

depends on the gradiant of the ground or floor

accessing the O/D filter and emptying and refilling to level would be fun

be good if you could (safely) run up a set of ramps at the rear too

get it fully lifted that way you can also take a strong light and inspect all other stuff under there while you have the chance, prevention being better than cure

you could easily change the rear axle oil at the same time for very little extra cost in money and time

[mgtony]

You mean there are other things under the car to look at?

Thanks for those videos, missed that post ealier somehow, just watched the first few, interesting stuff.

Done the rear axle lube back in the summer, should have done the gearbox oil whilst I was doing the exhaust, but hey, one job at a time eh!

Did I post a pic of the pair of ramps I made? Here they are, nice shallow angle to clear the spoiler and gets the car about 7inches off the ground.

[na]

mgtony said:

You mean there are other things under the car to look at?

course, like where to puncture the holes to let the water out

mgtony said:

Thanks for those videos, missed that post ealier somehow, just watched the first few, interesting stuff.

worth watching if only for background info, hopefully you'll only need to clean the OD filter

mgtony said:

Did I post a pic of the pair of ramps I made? Here they are, nice shallow angle to clear the spoiler and gets the car about 7 inches off the ground.

very nice, I'd need them to be a lot higher to get my belly under and to be able to work under the car

I'm still borrowing some three inch sloped slabs of wood that I have to run the car onto just to get the jack under my too low car front (*%!** lying specialist)

I'm pained to see a constanlty clean and little used car though

do ya wanna see a photo of my unique black mesh K&Ns again

EFA: just a thought you do know the OD should engage and disengage almost instantly and that when you operate the OD switch you don't fully lift off the engine/g/box/OD load and don't dip the clutch

Edited by na on Wednesday 11th January 23:19

[AtticusFinch]

na said:

when you operate the OD switch you keep load on the engine/g/box/OD and don't dip the clutch

Why?? (genuine question) it does not seem to be mechanically sympathetic, I either dip the clutch or adjust/blip the throttle to make it as smooth as possible.

[v8250]

AtticusFinch said:

Why?? (genuine question) it does not seem to be mechanically sympathetic, I either dip the clutch or adjust/blip the throttle to make it as smooth as possible.

You are correct in asking this, Atticus. An MGB OD is a simple electro-mechanical solenoid engage. In fact most OD's of this period use similar designs. Therefore, theoretically, it makes no difference as to whether clutch is used/throttle blipped or not. It's the solenoid that is engaging the mechanical change of OD gear. Personally, I naturally use the clutch in mine for a 'slightly' smoother gear change and have done so on all my cars that have had OD top.

[na]

AtticusFinch said:

Why?? (genuine question) it does not seem to be mechanically sympathetic, I either dip the clutch or adjust/blip the throttle to make it as smooth as possible.

I can’t attempt the technical answer I was told as I can't remember it (something cone and/or pressure?) and I'm not that clever - so see if you’ll accept:

• I was told this by someone old and experienced enough to know as they grew up with and worked on the cars (and older cars that they prefer) and very much into mechanical sympathy

• it was more effective when I used it my sh*theap GT6

• perhaps I used a poor description or in a strict sense used technically incorrect or wrong terminology when I put ‘you keep load on the engine/g/box/OD’ - but I think a layperson would get what I mean

I can’t remember ever dipping the clutch or lifting the accelerator at all or to any great extent when I had a BGT with OD

AtticusFinch, v8250, how about giving ‘my’ method a go and see what you think

Tony,
What does the Drivers Handbook say? (you do have a copy by now surely)

Edited by na on Wednesday 11th January 00:54

[na]

PS I (and I suspect Tony) was joking - you want the car level to drain out all the oil and gunk in the gearbox

get it warm and let it run and drip out for as long as possible you want to get out as much muck and oil as possible

same with rear axle oil

same with engine oil, doing a thorough job is as important as the frequency

and if it's on a lean then the lowest point wont be the drain plug

and you need it level to refill

[AtticusFinch]

na said:

AtticusFinch, v8250, how about giving ‘my’ method a go and see what you think

(you do have a copy by now surely)

Edited by na on Wednesday 11th January 00:54

Call me Atticus (we are all friends here) If I'm at speed and cruising you can feel the clunk (not nice) accelerating under load a big "clunk" (I don't do this) disengaging also a clunk (don't like) unless I blip the throttle

I've been bliping and rev matching for years smoother more comfortable and (I imagine?) better for the drive chain.

[na]

AtticusFinch said:

Call me Atticus (we are all friends here) If I'm at speed and cruising you can feel the clunk (not nice) accelerating under load a big "clunk" (I don't do this) disengaging also a clunk (don't like) unless I blip the throttle

I've been bliping and rev matching for years smoother more comfortable and (I imagine?) better for the drive chain.

Atticus, my sh*theap GT6 used to do that

well either your car's faulty or my memory is (has been known, many, many times)

your car's profile photo I think I've seen under another name, I might have remembered wrong though, always wondered about having an Alpine instead of a B (always makes me think of Get Carter)

[AtticusFinch]

Yeah I used to be Chard.

Get Carter good film (no tart in the boot though) you forgot Dr No & St Trinnians

[na]

AtticusFinch said:

Yeah I used to be Chard.

yes of course

AtticusFinch said:

you forgot Dr No & St Trinnians

sorry, with the exception of the humour of Roger Moore Bond films bore me, most action films do and if it's the latest st.Trinians films I've not seen those

also I was a wrong with how I put OD use - altering now

[na]

Tony, many apologies, I should have put -

the OD should engage and disengage almost instantly (my BGT did)

when you operate the OD switch you don't fully lift off the engine/g/box/OD load and don't dip the clutch

what does the Driver's Handbook say on this Tony?

I don't believe he has a copy

[mgtony]

I do have a copy of the handbook, promise. I've always just switched it into overdrive when cruising in 4th,usually changes in smoothly just like an auto box.
Never seen the point in using it in third although was reading a thread a week ago where people always went from 3rd,overdrive 3rd,4th,overdrive 4th.
Not sure if the handbook has operating instructions for the overdrive, it's in the glovebox so will have a check when I take the car out on Saturday. (as long as it's not raining )

[na]

mgtony said:

I do have a copy of the handbook, promise. I've always just switched it into overdrive when cruising in 4th,usually changes in smoothly just like an auto box.

both good to hear

mgtony said:

Never seen the point in using it in third although was reading a thread a week ago where people always went from 3rd,overdrive 3rd,4th,overdrive 4th.

on the RB cars it's easier to operate the gearlever and OD at the same time as the switch is just a flick of the thumb but on the earlier cars the OD switch is on the far right of the dash so to operate gear leaver and and OD at the same time would mean both hands off the steering wheel so I don't think the OD was designed to be operated that way

I used to use OD 3rd for overtaking and accelerating on slip roads as it extended the gear's range very quickly I'd then just change to OD 4th

I don't know about earlier or later cars but on my '74 BGT OD 3rd was same as being in 4th so effectively 5 gears not 6

an overdrive is a good component to have but not as good as having a 5th gear IMO

mgtony said:

Not sure if the handbook has operating instructions for the overdrive, it's in the glovebox so will have a check when I take the car out on Saturday. (as long as it's not raining )

show off, just because you have a glovebox

I don't think it's mentioned but, as has been seen, I could be wrong

It was heavy persistant rain here all morning but from midday full sunshine but I'm sure some would mark the whole day as rain because the roads will take an a short while to dry out

[alfa pint]

Overdrives seem to have their individual characters! My old B was a sweet changer and definitely didn't require any use of the clutch to make it smoother. My current B is a bit more abrupt. It's not too bad shifting it in, but it doesn't half jerk out when I disengage it. For that reason, I tend to use the clutch when disengaging.

I use the overdrive in 3rd all the time, only occasionally missing it to go to 4th and then clicking it in. I find it especially useful when overtaking just to get the extra revs and not have to lose time dipping the clutch.

[na]

alfa pint said:

My current B is a bit more abrupt. It's not too bad shifting it in, but it doesn't half jerk out when I disengage it. For that reason, I tend to use the clutch when disengaging.

could this perhaps indicate a small fault, see the videos in my post above

alfa pint said:

I find it especially useful when overtaking just to get the extra revs and not have to lose time dipping the clutch.

yes I did too - nice to find a B owner that overtakes and goes fast enough to use 3rd OD towards the top end of the rev range

of course your statement will cause distress to some B owners, overtaking, going at higher speeds