Interesting info on the marina diff

[listerjp2]

Alternative Differential

1st April 2016

Out of interest I emailed ‘Practical Classics’ last year, about fitting a Triumph diff to a Marina axle casing as I was sure they had done it in the past on one of their project cars. Much to my surprise, when I looked at the latest edition (I am a subscriber) March 2016, there in print was a reply!

They state that The Marina, Ital, rear wheel drive Dolomite, TR4,TR5,TR6, four speed TR7, Spitfire, Herald, Vitesse, and 2000/2500 share the same final drives, with various ratios.

David Ward has fitted a 4.1 - 1 Spitfire diff to Angel De Souza’s Teal with success a few weeks ago, so it looks like the dreaded Marina diff problem may have been solved?

Of course, you can only fit the differential gears, and not the complete back axles, as the mounting points and springs are different. Also of course, the Spitfire and Herald etc. are independent axles, but it will mean that if you need a replacement diff for a Marina, a Triumph item will be much easier to source, either second hand or reconditioned from people like Rimmer’s or Moss’ if all else fails.

Differential.jpg

Adrian

[marlintom]

Re: Interesting info on the marina diff

finally, an answer to a question that's been bugging me for ages now! thank you!

[b_caswell]

Re: Interesting info on the marina diff

Don't rely on all that info... the 2000/2500 big saloon diff is a completely different(pun not intended) animal. I doubt if the TR type will work either.

The herald/Vitesse diff does use the crown wheel and pinion design as in a Marina but it is set up in a different front carrier so you would have to rebuild it into a Marina type carrier.

Yes the Dolomite 1500 and 1850 (but not Sprint) and TR7 will go straight in.

[andyf]

Re: Interesting info on the marina diff

Hi Ben, I think they are referring to the Crown and pinion meaning that it's possible to get the marina diff rebuilt. I thought that I had already read that somewhere else on the forum

[stevejgreen]

Re: Interesting info on the marina diff

Strange that this subject should resurface yet again.
In short and for ease, the crownwheel and pinions from the Dolomite range (not sprint) all match the Marina range and add a few ratio possibilities. These gear sets are common to other small Triumph Cars.
Rebuilding a differential is not really a job for a home mechanic, it's probably best left to the professionals.
For a direct replacement of a complete differential centre a TR7 4 speed drops straight in, as discussed on this forum.

For more information on the available ratios and speedo drives and loads more on Marina Axles. Here or there


Or even more around this thread from 2010

This has been discussed on and off on this forum a little searching for differentials or axles will turn up loads of info.
If you have an original 1.3 Marina differential it will have a 4.11 ratio. The 1.8 is 3.63. It is considered that the 1.8 is tougher than the 1.3.
The differential centre can be swapped by simply pulling the halfshaft and unbolting the complete centre assembly.
Some Trials Marlins were fitted with Marina Van axles but these were a very different beast and are now very rare.
Sources of Marina diff centres are from TR7 (4speed) Dolomite 1850 (not Sprint)

Other than that you are into axle swaps. The first problems are that all the suspension brackets will need removing and new ones welding in place, also the diff nose will vary so the prop shaft will need shortening.
Possibly the best is to use a Dolomite Sprint primarily as the wheel PCD is the same as in the track. This has a ratio of 3.45:1.
I have completed and documented this on fastmarinamagazine.co.uk.
Other axles can be fitted but there may other problems as the diff centre castings will be larger with a greater offset so will not fit between the seats on a SWB car.
If you would like more help contact me direct at stevejgreen(at)btopenworld.com

173 45 25

[b_caswell]

Re: Interesting info on the marina diff

Hi Andy, Yes but not with the 2000/2500 big saloon or the TR 4-6 type, the crown wheel and pinion are different to the Herald Vitesse type. Ironically when Marinas were current the diff crownwheel and pinion set was used to rebuild Vitesse and GT6 diffs.

[greyV8pete]

Re: Interesting info on the marina diff

FWIW many, many, moons ago I had to replace the C/W and pinion in my TR3A. Had to wait a while for parts as it was the same part number as the Triumph 2000 saloon and they kept eating them so stock was desperately low. Peter.

[christopher.bogue2011]

Re: Interesting info on the marina diff

Been there, done that.! I have fitted the TR7 four speed auto diff to my Marina casing. Easy mod which has changed the ratio of the gearing allowing much better driving particularly on the motorway. The downside is that it has reduced the acceleration slightly but then with the Fiat 2.0ltr Twin Cam up front it is not really a problem. I bought my replacement diff from Rimmer Brothers. It wasn't cheap but the benefits have outweighed the costs.
Chris

[stevejgreen]

Re: Interesting info on the marina diff

Several people have been the TR7 4speed route. Whether Auto or Manual for a 1.8 car. I think they would overwhelm a 1.3 car. Both these diff centres are identical to the Dolomite range (not Sprint) that don't have the Spitfire/Herald cast diff hanger brackets, so there are several other options readily available.
When you look at the combined cost of the necessary gears, bearings, shims etc, it's not really financially practicable to try to rebuild your worn one, without specialist tools, when a factory refurbished one is available from Rimmers or many other Triumph parts outlets.
I know of several people who have a small pile of those parts underneath their workbench or up in the attic, that ultimately will be weighed in for scrap.

It is a shame that magazines sometimes publish erroneous or misleading information, especially when the judicious use of the MOC forum search button can provide specialised, better and more detailed, accurate information.

[cameronfurnival]

Re: Interesting info on the marina diff

It is a shame that magazines sometimes publish erroneous or misleading information, especially when the judicious use of the MOC forum search button can provide specialised, better and more detailed, accurate information.

Good point Steve, maybe you cold pen a letter to PC and correct them? It would be a good bit of publicity for the club too

[stevejgreen]

Re: Interesting info on the marina diff

Good point Steve, maybe you cold pen a letter to PC and correct them? It would be a good bit of publicity for the club too

Interesting that you suggest that a non elected representative of the club should write on behalf of the club. Can I use the club logo on the letter?