marina overdrive

Post by **callyspoy** » Thu Dec 11, 2008 10:56 pm

hi folks, a bit of a dated conversion granted, but i was curious if anyone had done it, and if so, if the efforts are worth it. i am quite interested in doing it as it seems like a pretty good idea, and will stall my needy desires for a 5 speed! money is far to tight to go and buy one of those right now!
input would be great!
thanks
*callum*

Post by **bigginger** » Thu Dec 11, 2008 11:31 pm

Did they do a Marina with overdrive, then?

Post by **sowden** » Fri Dec 12, 2008 6:47 am

Hi Callum,

I've been interested in this proposition as I also figured an overdrive would give the mog the top end cruising capability it seems (in my view) to lack.

I contemplated getting a J type or similar and trying to fit it somewhere in the drive train, perhaps shortening the propshaft to accomodate it and enlarging the transmission tunnel at some point along its length.

Any thoughts from the modifiers out there?

Post by **paulhumphries** » Fri Dec 12, 2008 9:22 am

Old conversion and outlined in the Owen Burton "Marina to Minor" book.
Bascially you source a Triumph gearbox with overdrive and swop over some of the internal parts with the Marina item so the Triumph overdrive will bolt straight on.
I like overdrives but reckon a 5 speed conversion on a Minor is going to be far easier and probably no dearer.

Pual Humphries

Post by **bmcecosse** » Fri Dec 12, 2008 1:37 pm

Can you not simply use the Triumph box with O/D complete - it may very well fit the Marina A series backplate ? I have to say - a Minor on 14" wheels with a 3.7 diff is highly geared enough for normal road use -and first gear is still very low for extreme hill-climbing. It IS by far the easiest way to drop the cruising revs.

Post by **Alec** » Fri Dec 12, 2008 1:41 pm

Hello BMCE,

that is what I have fitted to my wife's Traveller, and it does fit directly to the Marina backplate. First gear is rather high with a Midget differential though. I need to fit the old Marina gearbox internals someday. Cruises nicely in overdrive, and would be my preference over a five speed gearbox. Not an easy job though.

Alec

Post by **bmcecosse** » Fri Dec 12, 2008 1:46 pm

Thanks Alec - thought so. Another possibility would be an MGB box with O/D - they are not that big - and could be fitted to a B series engine (from 1500 - 1950 available) without any hassle at all - and I don't suppose would be impossible to adapt to A series.

Post by **paulhumphries** » Fri Dec 12, 2008 2:52 pm

The Owen Burton books says the Triumph ratios aren't really suitable.

Paul Humphries

Post by **plastic_orange** » Fri Dec 12, 2008 3:03 pm

paulhumphries wrote:The Owen Burton books says the Triumph ratios aren't really suitable.

Paul Humphries

And all of his other parts/recommendations are

Pete

Post by **ian-s** » Fri Dec 12, 2008 5:53 pm

Surprisingly the Marinaseems to have a higher first gear than a spitfire and a Triumph GT6 has a higher first still. These are all the same box so you should be able to pick the ratios you want.
The ratios are
SPITFIRE 3.5 2.15 1.39 1:1
GT6 2.65 1.78 1.25 1:1
MARINA 3.11 1.93 1.31 1:1

Post by **bmcecosse** » Fri Dec 12, 2008 6:23 pm

The difference in ratios is hardly anything - doubt you will ever need a really low first gear - unless living in the hills ! Obviously the Marina box is 'close ratio' (well, relatively to the Spitfire box anyway) which is nice - but I doubt it will be noticed on the road. But presumably the ratios were ok in the original Triumph ?? So -why would they not suit a Minor?

Fri Dec 12, 2008 7:49 pm

I did it a few years ago and it really worked very well. You will need a triumph dolomite overdrive gearbox not the dolomite sprint gearbox ( as i found out to my cost having bought the sprint box

so do not buy the sprint box i am currently selling on ebay! )

I followed the conversion as described by owen burton and swapped all the gear off the dolimite on to the first motion shaft from the marina so that everything mated up... but according to an early mail in the thread this appears to have been a waste of my time other than the enjoyment of it.

I found the car would cruise happily at about 80 on the motor way and would recommend it if you can get hold of a dolomite box easily.

The support braket at the back of the gearbox was just a bent piece of metal that mounted onto the minor gearbox support.

I took a few pictures as i did it and wrote an article in the techincal tips sections of the owners club mag. If you want to pm me i will scan them and send it to you.

Post by **bmcecosse** » Fri Dec 12, 2008 7:52 pm

Excellent -sounds like the way to go. Plenty of the Dolly gearboxes around -surely!

Post by **callyspoy** » Sun Dec 14, 2008 11:35 am

hi, sorry, i just got access to the computer! thanks for all the input, i think i probably will be going for an overdrive now. i have very fortunately got the bits off Matt for a marina conversion, but before i chuck it on i thought about the overdrive...so yeah...very very temepted now!
now just the hydraulic clutch to worry about...

Post by **bigginger** » Sun Dec 14, 2008 3:35 pm

'peasy

Post by **bmcecosse** » Sun Dec 14, 2008 6:52 pm

Prop shaft will need to be 'special'.

Sun Dec 14, 2008 8:19 pm

The prop shaft is no more special than any change of gearbox / rear axle would require.

My local prop shaft company in bridgend was able to knock one up for me without any problems.

Post by **bmcecosse** » Sun Dec 14, 2008 9:07 pm

Oh yes - i'm sure - but was just pointing out it WILL need to made up as a 'special'.

Post by **callyspoy** » Sun Dec 14, 2008 10:10 pm

i read, and am more then happy to be corrected, that the prop for o/d and non o/d were the same length? if this is the case then i already have one that will work(thanks again matt!) so that shouldn't be a problem... charlie morris minor pm sent!

Post by **bmcecosse** » Mon Dec 15, 2008 11:35 am

Hmm - usually an o'drive is tacked on the end of the box -and so increases the overall length and then a shorter prop is needed. However - it's certainly possible that Triumph managed to fit an overdive on within the length of the original box + tailshaft extension. Clever lads at Triumph in those days!