Will this gearbox fit my Marlin?

[Robert in Cumbria]

Re: Will this gearbox fit my Marlin?

Sorry if I am rambling, but thinking as I type, and I will have to rummage in the garage to see what parts I have to measure.

Ramble on! It all helps. I agree my idea of modding the bell housing may be fanciful but it depends on the casting, some have more meat than others. This is the smaller lighter 'A' Series engine so it won't experience the same forces as a 'B' Series engine would impose.

I may be able to chuck the bell housing on the clutch release bearing tube, or perhaps between centres, in which case the machining may be easy, if I can spin the bell housing in my lathe. It all depends how much meat is available.

This was one of my sources, Earlpart:

Screen Shot 2012-09-03 at 23.52.40.jpg

[Robert in Cumbria]

Re: Will this gearbox fit my Marlin?

OK, I have now stripped and assessed the 1300 Marina clutch and gearbox from the rusty Marlin which is now completely dismantled.

The clutch driven plate is 8" dia, and the face of the cover plate looks as though it will accommodate an 8 1/2" driven plate. Rimmers tell me the smallest 23 spline 24mm driven plate they stock is 8 1/2"

Perhaps most interestingly, the lengths of the input shafts seem identical, the spigot and the spline lengths seem completely compatible and the spigot Dia. is exactly the same.

To cut a long story short it seems all I need is an 8 1/2" driven plate from Rimmers or somewhere and I will be cooking on gas!

[Robert in Cumbria]

Re: Will this gearbox fit my Marlin?

Today braving a gale and monsoon rain I decided to start the engine again and test the gearbox overdrive.

I refitted the suction filter for the o/d and with a new gasket replaced the sump. The new gasket is MUCH thinner than the replacement but given it's from Rimmers and the correct fit/shape I suppose that's OK?

Using ordinary 20-50 engine oil to test the gearbox and flush out any c**p, I plan to change it for something better after say 1,000 miles or so. I may rebuild it with the Marina lay gear and input shaft to gain the lower gears once I have the rest of the car sorted.

Anyway, back to the test... Engine started back wheel jacked up, o/d wired through a switch. Running the engine @ a brisk tickover my non contact tacho read 840 rpm on the propshaft in top gear, 1050 rpm in overdrive. According to my calcs that equals a 25% increase which is I think correct for a Dolomite 1850 o/d.

It didn't need any encouragement it just worked. Another job ticked off!

[listerjp2]

Re: Will this gearbox fit my Marlin?

Ok I am now very interested!

You say you have a 1300 engine with an 1850 Doli gearbox with overdrive?

Pray tell more?

Did you put this in?

Was it with the car when you recued it?

Is it only the overdrive bit that is from the Dloi.

I am either confused or you could help me here.

Adrian

[listerjp2]

Re: Will this gearbox fit my Marlin?

Stet my questions, its in the thread.

Just to confirm, you are connecting this to a 1300 engine?

Adrian

[Robert in Cumbria]

Re: Will this gearbox fit my Marlin?

Yes, I took the Triumph Dolomite 1850 gearbox, exchange the cast iron Marina 1.3 clutch housing for the Dolomite aluminium one, and used an 8" 23 spline centre plate and pressure plate from an 1800 Marina. The whole lot just bolts on. No issues the the spigot on the first motion shaft, which projects about 8mm from the face of the clutch housing and the spigot is same length and diameter.

The clutch housing is about 200mm deep, front to rear.

The issue, if there is one is the mounting at the back. I made my own bracket and chassis brackets to carry the weight, but it shouldn't be too big a challenge. If you check out my main thread, 'Progress to Date' there should be some pix of the rear mountings.