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Final Drive And Speedo Drive Questions


Best Answer MiNiKiN , 31 March 2021 - 07:14 AM

The 3.44 final drive is perfect with the 10" wheels. I used to have a 1275 MG Metro engine in my tenner and it topped out at 100mph with brilliant acceleration.

Can't say anything on the speedo drive as I used a BMW 02 dash :shy:

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#1 Matt Zane

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Posted 31 March 2021 - 07:04 AM

Good Morning,

I'm getting ready to swap my 998 for a 1275 metro engine.

I've been doing some reading, and I understand that with 10" wheels the final drive (3.4:1) won't be a pleasant experience.

I also understand that the speedo drive won't give an accurate reading because of the metro's larger 13" wheels.

Could I please ask for some advice for the FD? I'm looking for a fun country roads experience, I'm not massively interested in high top speed, as long as it'll cruise at 70.

In terms of the speedo drive, the car is a 1974 mk3 with the 90mph central speedo binnacle with oil and temperature gauges.

I'm going to give minispares a call and ask them what else I'll need for the swap.


I look forward to hearing from you, and thank you in advance.

Matt

#2 MiNiKiN

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Posted 31 March 2021 - 07:14 AM   Best Answer

The 3.44 final drive is perfect with the 10" wheels. I used to have a 1275 MG Metro engine in my tenner and it topped out at 100mph with brilliant acceleration.

Can't say anything on the speedo drive as I used a BMW 02 dash :shy:



#3 62S

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Posted 31 March 2021 - 07:40 AM

I think a 1974 Mini 1000 would had a 3.44:1 final drive from new. If you have the original speedo it should have 1280 below the mileage reading.

I don't know what speedo drive gears would be in an MG Metro gearbox but the correct parts will be on Guessworks website and they are easy to change if required.

#4 Matt Zane

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Posted 31 March 2021 - 07:45 AM

The 3.44 final drive is perfect with the 10" wheels. I used to have a 1275 MG Metro engine in my tenner and it topped out at 100mph with brilliant acceleration.


Can't say anything on the speedo drive as I used a BMW 02 dash :shy:


Fantastic,that is great news!

Edited by Matt Zane, 31 March 2021 - 07:46 AM.


#5 Matt Zane

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Posted 31 March 2021 - 07:47 AM

I think a 1974 Mini 1000 would had a 3.44:1 final drive from new. If you have the original speedo it should have 1280 below the mileage reading.

I don't know what speedo drive gears would be in an MG Metro gearbox but the correct parts will be on Guessworks website and they are easy to change if required.


Brilliant, I'll check the speedo and consult the Guessworks website!

#6 Matt Zane

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Posted 31 March 2021 - 07:49 AM

Sorry guys! Both answers solved my question, but I could only credit one!

#7 Spider

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Posted 31 March 2021 - 08:29 AM

I also agree that a 3.44:1 Final Drive Ratio for a 1275 is ideal. Taller drives I feel takes the life from them.

 

You'll likely have a 6:17 speed drive now. I don't think you'd find the correct ratio gears here, but a close 'match' would be 6:18 when going from 10's to 13's.

I'd actually suggest you stick with the 10's.



#8 nicklouse

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Posted 31 March 2021 - 08:37 AM

Good Morning,

I'm getting ready to swap my 998 for a 1275 metro engine.

I've been doing some reading, and I understand that with 10" wheels the final drive (3.4:1) won't be a pleasant experience.

I also understand that the speedo drive won't give an accurate reading because of the metro's larger 13" wheels.

Could I please ask for some advice for the FD? I'm looking for a fun country roads experience, I'm not massively interested in high top speed, as long as it'll cruise at 70.

In terms of the speedo drive, the car is a 1974 mk3 with the 90mph central speedo binnacle with oil and temperature gauges.

I'm going to give minispares a call and ask them what else I'll need for the swap.


I look forward to hearing from you, and thank you in advance.

Matt

3.44 is perfect for a 10” wheeled car. 
 



#9 Matt Zane

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Posted 31 March 2021 - 09:26 AM

I also agree that a 3.44:1 Final Drive Ratio for a 1275 is ideal. Taller drives I feel takes the life from them.

You'll likely have a 6:17 speed drive now. I don't think you'd find the correct ratio gears here, but a close 'match' would be 6:18 when going from 10's to 13's.

I'd actually suggest you stick with the 10's.


I definitely will be sticking with the 10's , my thought was that the speedo drive on the gearbox would be set for the larger 13" wheels as its coming from the metro, and I'll have to correct the speedo drive gearing for my 10" wheels.

Could I pull the speedo drive from my original 998 a series and fit it to the 1275 a plus?

#10 Spider

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Posted 31 March 2021 - 06:19 PM

Could I pull the speedo drive from my original 998 a series and fit it to the 1275 a plus?

 

Yes, no problem.
 



#11 sonscar

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Posted 01 April 2021 - 07:23 AM

Before fitting the motor I would check the diff currently fitted as it may not be a 3.44.the 998 metro engine in my mini was a 3.76 easy to do now as things could have been changed from standard.Just my 2p worth.I fitted a 3.44 and it is markedly nicer to drive even with a 998.Steve..

#12 Matt Zane

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Posted 09 April 2021 - 10:10 AM

That is a good shout.

I did an engine number look up on the Guessworks website following the last message, and it said that my 998 also has a 3.4:1 diff ratio.


So the gearbox speedo drive should be a straight swap.

I've got a big box of bits on my dining room table, with all the bits (hopefully) I'll need to make the swap.

I'm going to try and give the engine bay a little love between the 998 coming out, and the 1275 going in.

Wish me luck!

#13 Cooperman

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Posted 09 April 2021 - 09:37 PM

The rolling radius of a 13" wheel with 175/50 tyres is almost the same as 165/70 X 10".
The 3.44:1 FDR is what the original 1275 S had and it gives 16.5 mph/1000 rpm in top gear.
In fact, your car will be very much like a Mk.1 S to drive.

#14 Matt Zane

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Posted 12 April 2021 - 08:24 AM

The rolling radius of a 13" wheel with 175/50 tyres is almost the same as 165/70 X 10".
The 3.44:1 FDR is what the original 1275 S had and it gives 16.5 mph/1000 rpm in top gear.
In fact, your car will be very much like a Mk.1 S to drive.

 

Thank you Cooperman, that has put a big smile on my face! 



#15 Cooperman

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Posted 12 April 2021 - 12:12 PM

I just did the calculation again and a 175/50 X 13 tyre has a 4.1 per cent greater rolling radius.
That is about 1 cm which is less than a tread depth.




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