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MG Midget and Sprite Technical - 1500 overdrive

Toying with fitting a 1500 overdrive gearbox in my 1500 read a few articles on line has anyone got any photos of the under side with a bolt on support for the gearbox as not keen on welding one in as it may make removing the gearbox harder any other advise would be welcome.
mark heyworth

Someone (sorry can't remember who at the moment) used to post on here (???? Smith?) had a 1500 o/d conversion he'd done so there may be details in the Archive. IIRC(!?) he often posted on electrics threads.
Nigel Atkins

been through the archives and read them just intrested in a few photos for ideas on the gearbox mountings.
mark heyworth

Aye that would be Steve Smith. But if I remember rightly didn't Guy W do the same thing?
Er - yes he did. Some time ago I found and printed an extremely interesting article he wrote about it, which unfortunately didn't have any photos. But maybe he has some.

Come in Guy.....
Greybeard

I have done one such conversion and used the Spitfire gearbox mounting rubber & plate modified to suit - bolt in, no welding. Sorry, I don't have any pictures.
Chris at Octarine Services

Yes I did this conversion around 20 years ago, and wrote that article though without photos. I then exchanged ideas with someone in the States who wanted to convert his car and he then did an online write-up but this time with lots of photos! I will have a link somewhere on my old laptop. I will dig it out later.
GuyW

I carried out a (1500 Spitfire donor gearbox with o/d) overdrive conversion on my 1500 midget in the early 90's. Reading the posts on this thread, I am wondering why nobody has mentioned that the 1500 Midget existing cross-member has to be cut out, the gearbox tunnel has to be be hammered wider, a new cross-member has to be fitted (welded in my case). Did I do something wrong back then? I still have the car, it's never failed an MOT.

IIRC, my conversion used a Nottingham MG Centre fabricated replacement new crossmember (is that company still in existence?). Coincidently, I was clearing my garage, a few days ago, when I found a (spare) new crossmember that Nottingham MG (in error) sent me in 1992. As mentioned, the crossmember has to be welded in place, to replace the removed original crossmember (surgically removed using an angle grinder).

I have a load of photographs of the work that I did back then. They include shots of the tear-soaked and blood splattered hankies produced during the work (only joking). I now look at that period of my life as a phase of mental illness (half-joking).

Having the overdrive gearbox in the Midget is a bit of fun, but really - the work involved and stress - twenty six years later, I question 'Was it all worth it?'. (Probably not).

I'll see if I can find my photos . . . .

J Thomson

any pictures would be helpful especially the crossmember and gearbox mount
mark heyworth

Hello, Mark.
Re. photos of 1500 overdrive conversion. I'll see what I can find.

In the meantime, just do a Google of "1500 Midget overdrive conversion" and a whole load of info is brought up. Example being >>> http://www.boicey.com/midget/midget_overdrive.html

Looking at the boicey.com images, I don't think my photos will be any more illuminating than those shown on that webpage.

I remain curious as to how other Midget owners did the 1500 Midget overdrive conversion using a 'nut and bolt' solution. It's physically not possible to fit the overdrive into a 1500 Midget without cutting out its original crossmember, and that requires a welded replacement to maintain the car's chassis strength.

J Thomson

J T, you are right of course that the cross member needs to be cut out. But this is then readily replaced structurally with a bolt in replacement, as Trevor Boicey shows in his photos. - It was Trevor that I mentioned earlier who contacted me about his overdrive conversion after I had supplied him with a set of twin SUs to adapt his American spec. car.

And The easiest way to widen the transmission tunnel isn't bashing it with a hammer as there isn't enough room to get a decent swing at it. Opening it up with a scissor Jack is much easier and more controlled anyway.
GuyW

A 5-speed conversion kit uses a bracket and just push fit plug box sections, from their Midget 1500 fitting instructions - "Slide the new reinforcing box sections provided into each side of the remaining central crossmembers as strengtheners. It is not necessary to weld in these sections though you can if you prefer. Seal the edges to prevent water getting in."

Nigel Atkins

Hello, Mark.

I found my photos from the overdrive conversion project, 24 years ago, using the Nottingham MG Parts Centre '1500 Midget Overdrive Conversion Kit' (which consisted of chassis parts only).

I've annotated the photos and have uploaded them onto my Google DriveMemoryCloudMabob. You should be able to see them here, I hope they help >>>
https://drive.google.com/drive/folders/1n00LAaFtNCSJpdFy1SXTZIx7Ck_VN9Qh

If you have any doubt that welding the replacement crossmember is the way to go, just tell your insurer "I've chopped out ten inches of the central crossmember from my Midget, but it's ok because I've shoved some box section into the resultant chassis holes, used some nuts and bolts, and have sealed the gaps with filler." And then see what your insurance company says!

Have fun.
J Thomson

The Boicey one is pretty ugly. If you want to be a historic vehicle you might fail the "not substantially modified" test by cutting into the crossmember in such an obvious manner.





AdrianR

It's essentially the same as in every Type9 5 speed gearbox installation. Of which there are many.
GuyW

Thanks for the pictures is there any chance you could put the dimensins for the crossmember so i can make one similar . how was getting the gngine in and out with the new crossmember in.
mark heyworth

Hi Mark,
Its a long time since I did the 1500 overdrive conversion and I sold the car some years later. But I also have a 1275 with the Type 9 5 speed conversion. Both involved cutting out the cross member and replacing with a bolt on cross member whch I never had any problems with. But in both cases, I removed the cross member to remove the engine and gearbox (together). With the positioning, I don't believe it would be possible without removing the cross member so a welded in version wouldn't work unless it was somehow positioned differently.
GuyW

Hi Adrian,
regarding your comment "you might fail the "not substantially modified" test by cutting into the crossmember"

The DVLA definition includes the exception "The criteria are generic and permit changes made, less than 30 years prior to the declaration, which improve efficiency, safety, preservation or environmental performance."

One might reasonably claim that correctly carried out, an alteration to fit an overdrive or a 5 speed gearbox is a change that "will improve efficiency or environmental performance"
GuyW

Haha! Cunning.


AdrianR

Mark Heyworth (Lancs).

As requested, I have taken some measurements of the (now defunct Nottingham MG Centre) 1500 Midget overdrive crossmember.

I have uploaded the dimensions diagram (as well as some photos of my spare crossmember) on my GoogleTinternetCloudyWossnames (new images N, P, Q, R, S) >>> https://drive.google.com/drive/folders/1n00LAaFtNCSJpdFy1SXTZIx7Ck_VN9Qh

It's a shame that you live a distance from me (I'm west London). The crossmember is a spare that you could have. But postage and shoe-leather costs would make getting it to you uneconomic.

One thing to bear in mind regarding the dimensions shown. From twenty four years ago when I did the project, I have a vague recollection that the four arms are not located ideally on the main body of the crossmember. I think I had to cut off and reweld the arms in more suitable positions before the composite crossmember was finally welded to the car. (Also, don't forget that a length of 1"sq box section is required for the gearbox mount support, not shown on the diagram).

I hope that helps. Good luck with the project.



J Thomson

This thread was discussed between 04/11/2018 and 09/11/2018

MG Midget and Sprite Technical index

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