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MG MGA - T9 and angle drive

Hi all,
This week I fitted a 5 speed T9 box in my 1600 MGA.
When I use the speedo cable that is supplied with the Hi Gear kit I will have the speedometer be recalibrated.But in the archieve I could read that the longer speedo cable gives a wobbling speedometer reading.
So I was thinking of ordering an angle drive.Pros are that I don't have the speedometer being recalibrated, that I can use the original speedo cable and will have a stable speedometer reading.
So now the question.
Can someone give me some help on calculating the gear ratio in the angle drive.
I have 165/15 tires, a 4,3 rear axle and a KPH speedometer.On the dial is the type number and the number 900(I think a MPH speedometer has the number 1440).

Thanks,

Herman
H. Jorens

Hello Herman,
seems like I have the same problem with my MGA recently.
Which gear rating did you finally choose for the angle drive ?.
HLA Laffer

Herman

I can't answer your question but others on the forum know the ratio you need. But just to clarify one point about the longer cable option that routes across the right hand floor. The wobbling speedo was due to the supplier inserting too small a drive cable inside the outer. This caused the cable wind up, then release, causing the wobbling. The cables supplied now have been modified and the wobbling is no longer an issue.

I have the Richfield right angle drive, but I went for the straight 1:1 and recalibrated the speedo. Never given me trouble since 2003. There are are number of fitting and access issues that are well documented in the archives. If you cannot find them we can tell you all about them.

Steve
Steve Gyles

Herman,
I did the same as Steve and had my speedo recalibrated to get it matched with the 5-speed box.

This may be the easiest way for you if you dont already know which ratio is fitted to the 5-speeds speedo drive output.

I took mine to JDO Instruments in Keithley W.Yorkshire and they got it spot on.

Some recalibrators ask you to jack the car up, then measure the circumference of the tyre, then spin the wheel to measure how many turns the prop shaft turns so they can calculate the overall ratio.

JDO however just asked me to drive my MGA for approx 10 miles with a modern car following behind, both cars having the trips zeroed from the start.

JDO from the difference, can then calculate the speedos percentage error and recalibrate to suit. (I drove mine for 20 miles to give them a more acurrate reading)

They got mine spot on and it even matches my sat navs reading.

I also had them change the main beam indicator from red to blue as I prefer this.

Colyn
Colyn Firth

Contact Hi Gear. I'm sure he can help you, especially if you buy the angle drive from him.

Jim
JL Cheatham

After installing my Sierra box I calculated the ratio for the speedo cable gearbox by using a GPS and driving at a constant speed and comparing the speedo reading with the GPS reading.. Did it a few times to ensure consistency, It has worked well for many years now...and did not need all the intervening car part physical dimensions .. only maths division skill.
Neil Ferguson

This thread was discussed between 06/03/2011 and 07/08/2016

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