MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Speedometer cable and working under the dash

Got a new speedometer cable to put in my 73B roadster. Crawled under the dash and found the knurled nut on the back of the speedometer. Got my left hand up and in to remove the nut with some minor knicks and bruises, but got it off.

Haynes says to next remove the cable from a heater unit clip and pull the rubber bushing out the firewall.

Yes........how! I take it this has to take place from under the dash. No way can I get my hand to the bushing on the firewall !!!????!!! And it is not accessible from under the hood either.

This type of underdash work is something that has mystified me from the beginning. How do you get to this stuff??????????????????????

Thanks,
BH
BH Davis

Mr B,

I recently replaced my speedo cable. I simply removed the engine and then access was easy!!!

Seriously, even with the engine out it was a fiddly job. The cable gets pushed out of the cockpit into the transmition tunnel. My new cable had a slightly larger head on the cable and I had to file the hole in order to refit.

Good luck!

Iain
67 BGT
I D Cameron

Put down the book and take a few steps back.

My '71 B/GT never had the aforementioned
heater unit clip.

The cable should run horizontally behind the
dash, above the vent flap, and route it's way
into the engine compartment through the
passenger legwell bulkhead (that's where
the rubber grommet is located).

After the cable has been disconnected from
the speedo, you should be able to tug the
cable out from the passenger legwell

Of course, you'll have to remove the lower dash
panel (passenger side) before doing this.
Daniel Wong

Boy,

These things are apparently routed all over the place.

On my 73 roadster it goest from the back of the speedometer straight towards the front of the car. It passes through the firewall and then turns towards the passenger side of the car.

Next it travels in front of the bottom of the heater box and then down into the transmission tunnel, and straight to the trans. mounting point.

I have discovered that my car has the right angle gear box that allows the cable to go in straight.....no tight bend.

I also found the knurled nut on the trans. end was REALLY loose. I tightend it up after removing and taking a look at a pretty clean and easy to turn cable.

The knurled nut on the speedometer end was a little loose. After tightening both I've gotten rid of about 80% of the wobble in the needle. I think I'm going to live with that and and call the project completed. Good thing Moss has a good return policy for the new cable I bought!

Any other thoughts on getting under the dash sans multi-jointed gremlins let me know though.

Thanks,
BH
BH Davis

Daniel, that is correct for a 71. They also had an angle drive on the rear of the speedometer. Sometime around 73 at car #282419 the angle drive was dropped and the cable exit was changed to go through the driver side of the firewall as BH mentions. My 74 is like his. I don't think it had a grommet when I changed the cable after installing the overdrive. As I recall I had to push the knurled nut through from the engine bay with a long screwdriver. I didn't worry about a grommet. You could tape the knurled nut to the cable to keep it in place when pushing the cable through. I have owned a 68 and a 71 and their cables were as Daniel describes.

Clifton
Clifton Gordon

Oh well.......the needle is still bouncing at 60mph even though it is noticeably more stable at 30 after tightening the knurled nuts.

As far as I could tell the cable ends looked okay....although anything could be happening internally along the run. Since I have the right angle adaptor at the trans. I have to wonder if swapping out the cable is worth the effort. It'd be a drag to go to that trouble and find I still have the jumping needle.

Seems the problem could be the speedo, the cable or the right angle adaptor.

With getting under the dash to free up the cable from some possible heater clip such a nightmare I'm uncertain how I should proceed.

BH
BH Davis

I just reread some of the replys to my post last week on diagnosing this problem.

The 2 main (relatively easy) suggestions seem to be to try a touch of oil at the cable connection on the back of the speedometer. This is easy enough to do.

The other one that I found interesting was suggesting to pull the cable out of the cable housing to check it. I find this intriguing as I could then leave the old cable housing in place and thread the new cable in (leaving the new cable housing unused). Is this a viable alternative?

Thanks,
BH
BH Davis

Working under the dash is always a time to wish for smaller hands.

I forgrt how or why, but I run my speedo cable straight out of the meter, then down through the hole in the tunnel for checking transmission oil, then to the connection to the transmission.

And just a side note that probably doesnot deserve a thread of its own, if you find you're using a lot of oil for your transmission, replace the O ring in the speedometer pinion -- it's on the bottom with all the oil above, so it's a mighty fine spot for an oil leak.
glg

I'm fairly certain that MG used some of those 'House-elves' from Harry Potter. Tiny strange stunted creatures with incredibly long thin powerful fingers and magic powers.
make sure the cable is centred at the screw on end at the transmission. First loosen it a little and jiggle the cable about as you retighten
If you've got a choice then run the cable straight to the engine bulkhead and then in a big gentle curve to the right angle drive.
The English cars had the speedo cable go out and down through a hole in the tunnel a little to the left of the steering column, because of the asymetric location of the heater fan primarily. I have an American style dash in a RHD car which places the speedo up a little, which causes an excessive bend if I try the English route. I solved this problem by swapping the speedo and the tacho over so the speedo cable goes straight out through the big rubber bung. I still get slight bouncing at 5KPH but think this is due to damage caused in the begining when it bounced around by about 10MPH.
Given the variety of routing of the cable, it must always have been a problem since they changed the speedos from the Mark 1. These were bigger and consequently positioned lower than the later cars.
Peter

It's tasks like this that renew my wish that when
the factory was originally designing the "Abington
Pillow" dash - the oval instrument cluster should
have been made as a separate and fully
detachable sub-panel module.
Daniel Wong

This thread was discussed between 05/07/2007 and 06/07/2007

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.