Understanding the MGB Gearbox Transmission Crossmember Removal, Refitting and Modifications

[@David-wy9jl]

Those extra frame holes are used when mounting the crossmember for an overdrive transmission. Installing the x-member for an overdrive transmission is even more difficult due to restricted access. Great video and thanks.

[@garethgoodchild2643]

I struggled trying to fit my unit using the other frame holes when I switched to an OD box as recommended by John Twist. I eventually used the holes for my non OD box and it fitted fine. Not sure if that is normal but it worked for me. Getting that assembled back on the car is one of the toughest jobs I have found on the B. The frame holes may be for the automatic unit?

[@davidrussellwilks]

Many thanks to both Gareth and David for the extra info on this, I had an MGB GT may years ago with an overdrive 'box but I can't remember which holes it used.

[@gavinkidd5915]

As a MGB owning brit living over here in the USA my ongoing maintenance work has been transformed by using "quickjacks". Gives you more working space under the car, they're portable so ideal for small spaces and safe. Keep up the good work on the MGB videos- superb quality and great technical advice for home mechanics.

[@davidrussellwilks]

Many thanks Gavin, do you have a link to the QuickJacks that you are happy to share? Delighted to hear that you are enjoying the videos.

[@davidsmith6212]

Awesome video and great tip on slotting out those holes. 2 areas of an MGB I have found that must have been deliberately designed to cause massive frustration: the gearbox crossmember and the windscreen frame and your videos give hope for both 😎

[@davidrussellwilks]

I do think the the gearbox crossmember could have been far more user friendly, just a bit more thought on the design would have made it easier to fit. I'm hoping to make a windscreen re-fitting video soon!

[@paulbiegun]

Another well orchestrated video by Mr. Russell-Wilks. Thank you!

[@davidrussellwilks]

Many thanks Paul, glad you enjoyed it!

[@reed-xd8zx]

Absolutely spot-on video of how to do this. I will be slotting my crossmember the next time it is off!

[@davidrussellwilks]

It makes life so much easier!!

[@tkreitler]

Thank you David for another excellent how-to video. I appreciate the time you put into these. I'm sure I will refer back to this when I have to pull the transmission. My next project is replacing the exhaust manifold and all the associated gaskets and broken studs. I haven't done this before and am expecting a challenge. Take care!

[@davidrussellwilks]

Many thanks Trent, I think the manifold studs can be a real pain to undo. Getting them soaking in a penetrating oil a few days beforehand may help. I'm quite lucky as I have an aftermarket system on my car that is fairly easy to take apart. Hope all goes well with the job!

[@bshnabel]

Absolutely excellent detailed video, thank you

[@sundogstudio1]

Once again an excellent explanatory video, David. I have seen a few gearbox removal videos that don't adequately show the mounting arrangement and I was glad to see you show it in detail on the bench. Your videos are always so very well done with meticulous technique which has given me the confidence to tackle the bigger jobs on my own MG. I have plans to swap my 4 speed gearbox for a 5 speed Mazda kit which does not require the use of the original cross member but attaches with a bracket to the frame cross member. Still possibly a challenging job.

[@davidrussellwilks]

Many thanks for your kind message, the Mazda 5 speed does seem a very popular upgrade for these cars. I hope that fitting it goes smoothly for you.

[@MorroccoM13]

Had I not seen this great video I wouldn't have know about the difference when fitting an overdrive transmission. This summer I'm going to pull the drive train from a 1970 B that has an OD tranny and replace it with another 1970 drive train w/o OD transmission.

[@brucefraser5363]

Thank you for that video David. It tempted me to head back under to double check if I’d done everything right but no way! In my case, it’s a 1980 overdrive car. I did it on my back with pretty much everything in situ and it was an absolute bear 🐻 reaching into those little crevices to loosen and tighten bolts. Surely the engineers back in the day could have figured out a better design than that! C’est la vie. Your point re taking care not to strip the threads in the aluminium casing is a very good one. In my case I just could not fit one of the 4 bolts without cross threading it, so I didn’t put it in and drove the car with only three bolts. Looking at it again a month or so later it had shifted to where everything lined up and I was able to put bolt #4 in. So the crossmember gods had mercy on me that day! Great video, thanks again and best of luck on the track!

[@davidrussellwilks]

My understanding Bruce is that the overdrive cars are the hardest to work on. Having a ramp would certainly make the job easier, crawling under the car and trying to get your hands in the right please really is not easy. In the past I have over-tightened one of the 4 bolts and damaged the thread, it was fairly easy to fix with a heli-coil though. I was tempted to add one to all the 4 holes but never got around to it.

[@bshnabel]

Nice detailed video, thanks

[@davidrussellwilks]

Glad it was helpful!

[@americanpatriot2422]

Outstanding video and presentation.

[@davidrussellwilks]

Many thanks! Glad you enjoyed it

[@rutgergooszen9774]

Another great video. They are very much appriciated. I replaced all the rubbers a few weeks ago and I managed to remove the four bolts in the gearbox from under the car without having to lower the gearbox (held in place by a lift), with normal spanners. My biggest challenge, as you show, is to put the rubber grommets in the butterfly. Then I built it all up off the car and replaced the hole piece using a second lift under the crossmember to align the holes with the bolts into the gearbox. A bit fiddly but possible. But again I have no overdrive.

[@davidrussellwilks]

Many thanks Rutger, I found having the parts firmly in the vice meant I could use two hands on the rubber grommets to make getting them in a bit easier. I was however quite disappointed with the short time the new rubber parts lasted.

[@rutgergooszen9774]

@@davidrussellwilks I don't race my MGB on tracks so I hope they last longer!

[@davidrussellwilks]

Thanks Rutger, I think it was the oil under my car that made them fail, they had become much softer.

[@deltafoxtrot2]

Great video, thanks 👍. Those gearbox rubber mounting blocks are prone to catching the oil and perish. Mine were like marshmallows allowing then gearbox move about.

[@davidrussellwilks]

Yes, I have ordered replacements, modern rubber does not see to last well at all under the car in the oil etc.

[@oliverscott5353]

Hi David Another great video. Precise and concise. Your car is so well maintained. I was wondering what you use to seal underneath your MG. Is it just painted??? I was thinking of using the black sealant (liquid tar) that they use to fix holes in roof gutters,etc... Any thoughts????

[@davidrussellwilks]

Many thanks for your kind message Oliver, delighted that you are enjoying the videos. I don't use anything at all to seal the underneath of the car, it's just painted. I do clean it fairly regularly and it only does around 1500 miles a year, often in wet weather though. Personally I prefer just to wipe it down with light oil at the end of the season (I never use water to clean it anymore.). I think if your car is a daily driver trying to clean it in this way is not practical. However if the car is not used much I would go down this route rather than using any type of thick underseal. Once the underseal is on it cannot be cleaned up and I think it makes the car harder to work on.

[@davelinkson1]

Great video! Had my gearbox and crossmember removed and found the butterfly assy missing, so have to replace it. What significance does this part have, I'm assuming it takes stress off the mountings coming through the transmission? Thanks..

[@davidrussellwilks]

Thanks for your message David, I think as you've said the butterfly part helps to spread the loading on the pads and is bolted to the crossmember too, this probably helps with any for and aft load.

[@chrispatterson8533]

Hello David, What is the diameter of the holes in your crossmember? Thank you.

[@davidrussellwilks]

Thanks for your message, the holes are approx 2 inches

[@chrispatterson8533]

@@davidrussellwilks Thank you, as always.

[@SM-xm7dt]

David, do you ever use poly bushings?

[@davidrussellwilks]

Yes, I'm a big fan of the SuperPro poly bushes and use them on all of the suspension components.