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MG MGA - closed ratio gearbox

Hi,

I've got my transmission out of the car. I've heard that it's very easy to tell if it is a real closed ratio transmission. (It was sold to my dad as one decades ago, but you never know.)

Anyway, here are some pictures:

http://img442.imageshack.us/img442/5558/sany0145cn0.jpg
http://img515.imageshack.us/img515/6554/sany0146ox6.jpg
http://img168.imageshack.us/img168/7941/sany0147im7.jpg
http://img169.imageshack.us/img169/3900/sany0148ld2.jpg

The transmission worked fine and I used it for about 2,000 miles in the last year. Assuming it is a real close ratio transmission, what would be a fair price to sell it for?

Thanks,

Darian

Darian Henderson

Darian,

Close-ratio refers to the gear ratios being closer together. They are sought after because the car is much more driveable, especially in competition. First gear is 2.445:1 compared to 3.64:1 and the big gap between second and third, which is very noticeable when driving the car hard, is much reduced.

I'm not sure if you can tell from the numbers stamped on the housing. Close-ratio gear clusters were provided for gearboxes to be converted and this may have been done to your dads car at the same time as the Derrington head was fitted.

To find out, I guess you need to remove the inspection cover and count the gear teeth. I hope someone can chip in with the numbers here!

Neil
Neil McGurk

BTW, I forgot to mention, you appear to have a 1500 low starter position gearbox, that means it is extremely unlikely that it was built as a close-ratio box by the factory. What will you replace it with?
Neil McGurk

Thanks. Is the inspection cover the one I circled in yellow or blue?

http://img20.imageshack.us/img20/5849/inspectioncoverju3.jpg

Darian
Darian Henderson

"What will you replace it with?"

I'm going to put in a Nissan 5-speed. If I ever want to sell the car (very,very unlikely) I figure I can hunt down a regular MGA transmission from someone who swapped in a 5-speed. I'd prefer that someone was using this transmission (assuming it is what I've been told it is) than to have it sitting in my garage for another 25 years until my son decides to deal with it...
Darian Henderson

Blue,
I wish it were in the UK!
Neil McGurk

Put it in first, turn the input shaft, and count how many times the output shaft turns. Should tell you what you need to know.
Del Rawlins

Full agreement with Del, its best to mark the input shaft and output flange with a dab of paint so you can see the starting and finishing points.

Regards,,,JB
J Bray

Well, I talked to my dad, and I'm 100% sure it's a close ratio gearbox. He ordered it straight from Derrington in England when the exchange rate was more favorable on this side of the Atlantic. My how times change...

Anyway, here a picture of the inside. I'm no expert, but it looks like it's in good condition.

Thanks,

Darian


Darian Henderson

Obviously Del's comment on just turning the first motion shaft and measuring the output turns is the quick way to check if a gearbox is close ratio.
However, as Neil asked about the teeth numbers I have attached details in two images (this posting and the next one).

It is possible to get slightly different answers from some published figures when doing the mathematics, but this is not an error, it just depends on your method. If you calculate the equation in one go, or do each part of the equation separately reducing the number of decimal places each time.

Mick


Mick Anderson

The second image is attached.

Mick


Mick Anderson

I did do the sums and worked out approximate engine speeds at some point so I could work out what I had in my car. It's very easy to tell by driving, as with the CR box you use first gear a lot more, and often find the need to double de-clutch.

30 mph in first is about 4500 rpm with a standard diff
Dan Smithers

This thread was discussed between 09/03/2008 and 10/03/2008

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