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MG MGA - 5 Speed Geadox - Right Angle Adaptor
I've got a Type 9 fitted to my A and I've read that Hi-Gear do a 90 degree drive adaptor so that the cable is straighther, no cutting of tunnel, more stable speedo readings, etc. I phoned them and choked on the price, which seems to have gone up a LOT recently and they said they were supprised how much it had gone up to - about doubled in the last year or so.
After a bit of googling, I have tracked down a purveyor of such drive adaptors at a much more reasonable price (about £50), but they do different ratios and options such as working backwards or not.
So, the question to all those in MGAland who have such a device fitted to thier 5-speed box is:
"What ratio is your adaptor (hoping for 1:1), and does your speedo work in reverse with this adaptor"?
PS If I get some good responses, I might even post a link to the site (once I've put my order in!) ;-)
|I have one from HiGear. It is a 1:1 ratio. It works great with the standard MGA speedo cable. The speedometer will have to be calibrated but it does run in the same direction. The adapter was installed without drilling any holes in the tunnel or removing the tunnel. I has some very close clearances.|
Search the archives and you will find a lot of information on the angle drive including information on ordering from the manufacturer and different ratios.
|Grant I ordered my angle drive for the Sierra box from Speedograph Richfield, in Nottingham, so on your side of the pond. Great service and cheaper than Hi Gear. I calculated what the ratio should be and ordered on with a ratio of 1:1.4 and it works great and the speedo reads the correct speed without any other device. The 1:1 ratio will read slow. I also ordered a longer speedo cable from them, 4" longer than the original which fits great. |
It's possible to calcualte the difference between the original gearbox drive shaft revolutions to the speedo drive revolutions against the Sierra T9 and order an angle drive which will correct the speedo calibration. According to my research on the original MGA gearbox, in fourth gear (direct drive) there are 12 driveshaft revs to 5 speedo drive revs a ratio of 2.4 driveshaft revs/speedo rev. On the T9 there are 7 driveshaft revs to 2 speedo drive revs, a ratio of 3.5 driveshaft revs/speedo drive rev. Therefore with the T9 the speedo will show a slow speed. If you divide 3.5/2.4=1.46 you should get the correct ratio for the angle drive. Speedograph Richfield make an angle drive with a 1:1.5 ratio that should work. However on my car I'm using a radial tire, 185/65R 15 which has a smaller diameter and rolling circumference than the origianl crossplys. The origianl tires were 25.5" dia and my new ones are 24.4" dia. This is a reductioin of 0.96 which changes the ratio to 1.46x0.96=1.4. Therefore I ordered an angle drive with a 1:1.4 ratio, part # RGB1030-09A 1:1.4 NR. You can find all the differnet ratios on their website.
I was talking to a speedo cable recalibration outfit here in Washington State. They said something like: if it is accurate at 60 mph then it is good enough.
With the right angle drive of 1:1.4, is your speedometer accurate all the way up from, lets say 10 mph to 90 mph?
|Ray, I checked out my speedo yesterday with the 1:1.4 ratio angle drive and used a pace car with an accurate speedo. The speedo was accurate between 30 - 60 mph. I didn't go any faster, but I'd say it's just the same.|
Sounds like this would be a less expensive route to go.
I've looked into having a speedo shop install a inline recalibration gearing in the speedo cable, however at about $125.00 and the need to have six inches of straight line in the speedo cable, your way is cheaper and seems the way to go.
You have all the good advice above so I will not repeat. However, I did not share Jim Ferguson's experience when fitting the adapter. I found it was not possible to install it without cutting a sizeable hole in the tunnel wall. When fitted, the top edge of the adapter is barely a few millimetres from the wall, so there was not enough clearance to push the male adapter shaft into the gearbox without interference from the wall.
The alternative is to remove the tunnel wall to fit the adapter, then you will not need to cut a hole.
There again, you may be lucky as Jim appears to have been. I guess it depends how you line up your gearbox during the original installation.
thank you for your responses. As there seems to be a bit of disparity between the ratio, I'll probably plumb for a 1:1, as I need to get my speedo recalibrated and restored.
Steve, not a problem about fitting it, as the tunnel isn't on the car yet, but thanks for pointing that out - great pic!
As I am a man of my word, here's the links that I found, prices from £54, as it also appears that Caterhams and Westfields have the same issue:
and one for those in the USA:
|PS forgot to mention that apparantly Speedy Cables do one too.|
When you do get one I think you will be most impressed with the smoothness of the speedometer. Gone will be the erratic needle swings and oscillations. Incidentally, you can always use sat nav to check instrument accuracy, no need for a pace car.
being that I bought my a as a box of bits, and the first time I run it properly will be with the adaptor, I almost feel like I'm missing out on the eratic needle swings ;-)
As long as it's close enough around 60/70mph I'll be happy, as it's built for accelleration, not top end, which should be fun! :-)
PS I might just have copied your rather good idea using the MGB header tank :-)
|Grant, as Steve mentioned it's very tight between the angle drive and the trans tunnel. I'd say impossible to install without cutting a hole in the tunnel. Like yourself I installed mine when the car was in pieces and the tunnel was off the car. Een then I'd guess there's only 1/8" clearance.|
This thread was discussed between 09/04/2009 and 15/04/2009
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