TR7 gearbox in a 1.8 Marina.

ronecc · Post by **ronecc** » Thu Aug 06, 2015 7:46 pm

Has anybody tried this mod'? Triumph TR7 4 speed gearbox into a 1.8 Marina? The ratios of the TR are a bit higher, but I do not know about the input shaft dimensions. Does anybody know. I have checked Rimmer Bros, but they do not say how many splines, or length.

Post by **MarinaCoupe** » Thu Aug 06, 2015 8:42 pm

Hi Ron,

The TR7 4 speed input shaft is the same as the Marina 1.8/1.7 - 1" diameter and 23 splines. I don't know about the length though.

Chris

ronecc · Post by **ronecc** » Fri Aug 07, 2015 10:25 am

Hi Chris. Thanks for the reply. Below are the measurements for the TR7 shaft. How do these compare to the Marina? As I do not have my box out I cannot measure. Thought you might have the dimensions somewhere.
shaft length 11 inches
distance end of shaft to spline 1 13/16"
Ron

jiversteve · Post by **jiversteve** » Fri Aug 07, 2015 12:38 pm

Does that mean there is a possibility of rebuilding a 1.8 Marina box with all TR7 parts?

Post by **MarinaCoupe** » Fri Aug 07, 2015 2:14 pm

Funnily enough Steve I was digging back through my Type 9 conversion files and came across these.

The second one below is the 1.3 Marina for comparison

ronecc · Post by **ronecc** » Fri Aug 07, 2015 3:59 pm

That length I have been given (11") must surely be the total length of the shaft. I cannot imagine 11" inside the bell housing. If it is the total length, would that be the same size as the 1.8 Marina shaft, and would that then give you 9mm of spline into the clutch disc?

Post by **MarinaCoupe** » Fri Aug 07, 2015 4:08 pm

Ron

I have never measured the overall length so it's difficult to say.

Chris
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ronecc · Post by **ronecc** » Fri Aug 07, 2015 4:30 pm

Gear Ratios I have found;
TR7 4 speed 1.8 Marina
2.65 3.11
1.78 1.92
1.25 1.31
1.00 1.00

3.05 3.42

Post by **MarinaCoupe** » Fri Aug 07, 2015 4:58 pm

They are great ratios, I think and would make a great gearbox in a lightweight car. I think that the only way you are going to see if it works, is to suck it and see.

If you buy a TR7 gearbox and it doesn't fit then you can resell it on EBay.

Chris
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ronecc · Post by **ronecc** » Fri Aug 07, 2015 5:12 pm

I have just emailed Rimmer Bros. for the total length of the shaft then try and work it from there. If I need to swap shafts, do I need any special tools to extract the mainshaft? It is many years since I had to do that and cannot remember.

Post by **MarinaCoupe** » Fri Aug 07, 2015 5:28 pm

The Marina/TR7 4 speed is doable at home, I rebuilt one a couple of years back with no special tools except some external circlip/split ring pliers.

Chris
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ronecc · Post by **ronecc** » Fri Aug 07, 2015 5:52 pm

Thanks, I have some of those, plus a Haynes manual.

ronecc · Post by **ronecc** » Sat Aug 08, 2015 11:03 am

Rimmer Bros. have just informed me, the total length of the TR7 input shaft is 11". Just need to find the length of the 1.8 Marina now and keep the fingers crossed. If anybody has one laying around, please give it a measure and let me know. Thanks

jiversteve · Post by **jiversteve** » Sat Aug 08, 2015 12:04 pm

If it does match, then a new set of gears alone will add up to £350 so the option would appear to be to purchase a complete recon box from Rimmers, Hoping that you can get away with the £114 surcharge. Externally the boxes look the same!

ronecc · Post by **ronecc** » Sat Aug 08, 2015 12:15 pm

Hi Steve. Yes I am looking at the recon box. The ratios will not be a problem as my car weighs a lot less than a Marina. I have just enquired from Rimmers how many teeth are on the gear end, should I need to swap the input shafts. I can then judge how it will affect the overall gearing.
Ron

Fast Marina Magazine

TR7 gearbox in a 1.8 Marina.

TR7 gearbox in a 1.8 Marina.

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Re: TR7 gearbox in a 1.8 Marina.

Re: TR7 gearbox in a 1.8 Marina.

Re: TR7 gearbox in a 1.8 Marina.