Gearbox Oil Fill?

[jimd]

Hello,

I bought a 69 mgb a few weeks ago and have been looking for the gearbox oil fill (the drains I have found - one for the box and one for the overdrive + the overdrive filter cover (I think)). The Haynes manual that I have says the fill is either under the carpet inside the car (I've looked) or on the side of the gearbox. Any clues please? Thanks.

Sincerely,
Jim Delaney
Sparta, NJ

 

[tony barnhill]

Passenger side of the tranny tunnel about 1' forward of the park brake...you may have to lift the carpet & then you may find there's no opening through the tunnel so you'll have to fill from underneath - not an easy thing to do but necessary

 

[jimd]

Thanks for your reply. I'll take a closer look maybe later tonight. Also, I forgot to mention that there is a rubber boot flapping in the breeze under the gearbox. It is on a linkage going into the passenger side of the gearbox. I half tried to push it back into the housing but it wouldn't go - yet. This isn't associated with the gear shift is it? And, the fact that it appears to have been flapping there for a long time - is that a concern? Thanks again.

Sincerely,
Jim Delaney
Sparta, NJ

 

[aeronca65t]

Jim:

You may wish to look here for info:

https://www.xs4all.nl/~jdoddema/handbook/hbcare10.html

I'll assume your car doesn't have the dipstick that is on some older MGBs. If it does, the Moss online catalog provides a clear view of the dipstick/filler and other trans stuff. Go here:

https://www.mossmotors.com/Shop/ViewProducts.aspx?PlateIndexID=29014#128

Not sure about the "flapping thing", but are you talking about the speedometer cable? It goes into the right side of the trans and may have a rubber boot on it.

Anyway, welcome to another Sussex County, NJ person (I'm in Andover).

If you need any MGB stuff or advice, you can call Pete McCarthy near you in Newton ("Midnight Automotive" at 973-383-8859).
Pete's very reasonable, has lots of MGB parts-cars and has always provided me with useful advice. He's sort of a "character", and he's one of our little cadre of Brit-car racers here in northwest NJ.

Nial

 

[jimd]

Thanks for your reply. I'll probably be needing a mechanic eventually so I might look up Pete...The boot is on a linkage on the passenger side of the gearbox housing - it isn't on the speedo cable which I can see running from near the back end of the gear box up to the engine compartment and back under the dash. Anyway, I'll be crawling under the B probably tonight to take a closer look...
Sincerely,
Jim Delaney
Sparta, NJ

 

[Baxter]

Jim, the gearbox filler is a tricky bugger to find... Tony's right, but to clarify a little, it's sorta behind the radio console on the passenger side top of the tranny hump. Under the carpet, there will be a body plug. Under the plug, that's the filler. You probably have a dipstick thingy. My '70 does. It's a pain to fill, and likely to be messy.

 

[Bruce74B]

We all know what you are thinking..."mine doesn't have one!" Thats what I thought anyhow when I had my '69 B...but it was there. Then, when I bought my '74B, I was sure it wasn't there too!
But keep looking...it IS there. My 74's is the whole way on top of the tunnel, under the radio.

If the dipstick hasn't been used recently, be sure to rinse it with a degreaser before you pull it to keep the gunk from falling into the tranny when you get it pulled.

One more tip...a needle nosed vice grip makes it easier to get the dipstick out

good luck...and welcome to LBC's and the Forum.
Bruce

 

[Andy Blackley]

Hope you have small hands. Because yoy'll want to try and clean around the dipstick before you pull it out, or else crud may fall it when you remove it. It pretty hard to look inside the opening, so its a "touchy feelie" operation.
I use a HD nylon tie on the end of the dip stick in the form of a loop so that I have something to pull on.
You can fill it or top it off with a funnel and hose, or buy a hand pumper that fits over the end of the Castrol 20W/50 bottle, and add a length of tubing.

 

[Andy Blackley]

PS. The flappy bit somes like a rotted clutch fork lever boot falling apart.

 

[John S Farrington]

If you are filling the transmission that has an overdrive unit, the specification is to use 30 weight motor oil non detergent. If you dont know what is in the transmission now, I would recommend draining the existing oil and refill with the 30 motor oil. Normal gear oil can mess up the overdrive unit. Jack

 

[tony barnhill]

Jack!!! All MGB's with or without OD use the same oil as the engine in the transmission - 20W50 Castrol!

 

[aerog]

There's an old thread on this issue: https://www.britishcarforum.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=4&t=000071 ... filling the gearbox doesn't need to be, and shouldn't be messy at all. I have a top-fill gearbox so I was very apprehensive about spilling oil on my new carpets. I lined the floor and tunnel with a couple layers of newspapers just in case, but ended up not spilling a drop the first try.

 

[aerog]

<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by tony barnhill:
Jack!!! All MGB's with or without OD use the same oil as the engine in the transmission - 20W50 Castrol!<hr></blockquote>

I agree... but the RB owner's manual specifies 90-weight hypoid oil as suitable for both OD and non-OD gearboxes as long as you completely drain one for the other (and don't mix them). I think that's caused confusion for some people following "the book" in the past.

 

[John S Farrington]

I use an overdrive and transmission rebuilder for British that will void the warranty unless you use normal 30 weight motor oil. In all cases, I have had excellent results and no problems. I have encountered overdrive units that have normal gear oil, such as 90 weight, that are operating with no problems. I have noticed however the hydraulic response for the overdrive signal is faster with the 30 weight. I certainly dont recommend mixing motor oil with hypoid or vice, versa. If you explore factory documentation for MG or Triumph you will find that 30 weight non detergent is recommended.

 

[aerog]

<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by John S Farrington:
If you explore factory documentation for MG or Triumph you will find that 30 weight non detergent is recommended.<hr></blockquote>

It does? Where?

I have two sets of factory workshop manuals for MGBs. The earlier cars all have documentation that calls for generally 20w40 - 20w50 engine oil, with one listing for 10w40 (for moderate temperatures). Lighter weight oils aren't mentioned until the temperatures drop to below 21°f.

The book for the later model cars/gearboxes specifies "Use the same oil selected for the engine" (20w50 or 20w40 for above 30°f), with the caveat that SAE90 Hypoid oil can be used but obvious not mixed with 20/50.

With that said I can't believe using straight weight 30wt oil would do any harm, I just have never seen it printed in the factory documentation anywhere.

 

[tony barnhill]

Gotta agree with aerog on this one....I also have original factory books - to include a complete set of tech bulletins! & there's actually a bulletin on this specific issue....engine oil was primary recommendation - & 20W50 was engine oil that factory recommended..now, the 20W50 of that era is a bit different than the 20W50 of today but nowhere near as different as going to straight 30.

 

[jimd]

Okay Everyone,

First and foremost, thank you for all of the advice...sometime soon I'll hopefully pay you all back...actually maybe right now...but first - the gearbox fill was in fact accessible from a hole in the trans tunnel just ahead of the radio, under the carpet. There was a dipstick that I could get out. So that problem was solved okay. The tidbit of info that I have is that I passed a magnet over the magnets in the overdrive filter cover and was able to attract a bunch more of the metal grit/filings that wouldn't come off with the cleaning-in-gasoline procedure. Maybe some of you will like that idea.

Also, the boot that was flapping around is the cover boot for the clutch shift linkage fork? I still haven't stuck it back but will do so soon.

My Haynes book calls for 20w-50 in the gear box (same as the engine) so I guess that is what I'll do.

I have plenty more questions in the offing. Thanks again.

Sincerely,
Jim Delaney
Sparta, NJ