Marina gearbox replacement

[eannab4]

Hi All,

Just after joining so I may as well start with "hello"!

I need to replace my '74 1800 gearbox but find it difficult to get a direct replacement here in Ireland.
I have just bought a good 1500 Dolomite gearbox as I think it is a close fit.

Where i need the help is how much work is envolved in swapping the input shaft from my original box into this replacement?
Does it even swap over for me?

If this is all too much work what other box will fit as a straight swap?
Does anybody have any lying around that they will sell?

Thanking you,
Eanna.

[crashbang]

Type9 ford box fit but needs a bit of work I dumping my old one and fitting a ford one now but got to make a prop shaft

[locost_bryan]

iirc the Dolomite 1500 matches the Marina 1300 gearbox - input shaft 1" 20 splines 1st gear ratio 3.41
The Marina 1800 input shaft is 1" 23 splines 1st gear ratio 3.11

Lots of info on Triumph gearboxes here (Spitfire/Midget/Sprite, but Marina and Dolomite get mentions )

[eannab4]

Cheers lads.

@crashbang
I should have said that what I have is actully a Marina based kitcar. A Ford type 9 has been considered but as far as I know I don't have the space for it.
"I dumping my old one and fitting a ford one now"
Does that mean you have an 1800 box for sale?

@locost_bryan
Your right ya, the input shaft is different but do you know is the gear on the end of it the same? How many teeth on the 1500 box?
I'm hoping that I could still use the 1500 box by just replacing the input shaft.

[locost_bryan]

Cheers lads.
@locost_bryan
Your right ya, the input shaft is different but do you know is the gear on the end of it the same? How many teeth on the 1500 box?
I'm hoping that I could still use the 1500 box by just replacing the input shaft.

Jump onto Chris' MarinaCoupe site, and have a look at his overdrive gearbox page. iirc he fitted a Spitfire box to his 1800, and had to change the input shaft.

[MarinaCoupe]

Exactly right Bryan. The Dolomite 1500 and the Spitfire 1500 gearboxes use the same ratios and are interchangeable, so early 1500 Dolly matches early 1500 Spitfire etc. However the internal coggery (ratios) changed at some point. When comparing the lay gear cluster, the drive off the input shaft has two different numbers of teeth either 13 or 15 teeth. There are two different input shafts early and late. The dimensions and number of splines are the same, the number of teeth on the gear are different.

So the question is; is the Marina gearbox equivalent to the early or late Triumph box? My money is on the late gearbox, but I can't say for sure. I had that box built up for me before I started rebuilding my own gearboxes and didn't ask enough questions to be 100 percent sure.

[locost_bryan]

Found this gearbox info here, attributed to John Kipping of Canley Classics.


MK IV 1500 USA 73-74 FK
1500 12/74 - 10/79 FM
1500 USA 75-80 FT
1500 79-80 FR

Gearbox numbers:
GB Herald 1200 )
GE Herald 13/60 ) Three synchro boxes, casings interchangeable, as Spitfire FC/FD
HB Vitesse 6 ) 6 cylinder gearset not interchangeable with 4 Cylinder

HC Vitesse 2L )
DG Toledo ) Four synchro 3 rail, casings interchangeable, as Spitfire FH & GT6
YC 1500 RWD ) Vitesse/Dolomite/GT6 gearset not interchangeable with Spit/Toledo/1500 RWD
WH Dolomite 1850 )

DN Dolomite 1300 )
DR Dolomite 1500 ) Single rail boxes, casings interchangeable, as Spitfire FR/FT
YD 1500 RWD ) Dolomite 1850/TR7 gearset similar to GT6, not interchangeable with Spitfire etc.
WM Dolomite 1850 )
CG TR7 4 Speed )
Note 1: Marina boxes and Midget 1500 (?) boxes casings not numbered.
Note 2: Triumph use GR as a prefix number for reconditioned gearboxes for all models and it is therefore meaningless

[eannab4]

Hi,

Thanks for the replies.

I have opened the 1500 Dolomite box that I got so that I could swap the input shaft.

It doesn't match. Both are non overdrive boxes with the same casing numbers but the shafts and inner gears are different.

My input shaft has 23 splines at the end of the input shaft
18 worm inside box - helical gear
24 teeth inside box - gear at inner end of shaft
7 x 1 inch shaft - length x diameter

The 1500 box has 22 teeth inside the box on the gear at the end of the shaft.

I have ask some sellers of different Dolomite, Triumph and BL boxes for details to compact but still haven't found a match.
Does anybody know was the complete 1800 box used in any other model or is it simply a matter of opening up and checking if my input shaft will fit?

Could Rimmer Bros fit my shaft to a suitable box?

Thanks again,
Eanna.

[JubileeNut]

You have to be careful as the main shaft on a Marina box changed. Early ones had a small end and the later a larger diameter end on the shaft which fits the first motion gear shaft you have a picture of.
If the number of splines are 23 then the first motion shaft is 1800cc or I think 19 for a 1300? never seen a 1300 so don't know the exact number.

Beware of other changes as I have many parts from 1800cc marina boxes and they also changed the teeth pitch on the laygear and reverse idler and the outer syncro ring they all mesh with.

I doubt rimmer bros will help unless they have parts to sell that you need. And the parts are thin on the ground.

[locost_bryan]

If the number of splines are 23 then the first motion shaft is 1800cc or I think 19 for a 1300? never seen a 1300 so don't know the exact number.

20 splines for 1300

iirc Dolomite and Spitfire 1500 have 3.75:1 or 3.50:1 1st gear, Marina 1300 is 3.41:1, and Marina 1800 is 3.11:1

Some useful info here. Claims the Spitfire 1500 got the new single rail gearbox from the Marina, but with the previous Spitfire's ratios.