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MG TD TF 1500 - Speedometer 4.3 conversion

Recently there was a discussion regarding a speedometer gearbox conversion that attached to the transmission to correct for a differential change from a 4.875 to a 4.3.
I recently made the change for my 1250 mgtf and want to make the speedometer more accurate. Can anyone recommend an outfit that does this work? Also while I am at it I want to send my speedometer and clock to a repair shop. The clock does not work and the speedometer needle swings back and forth during speed. Does anyone know of a shop that does this work?

Bill
Bill Schroeder

Bill - Butch Taras mgyowner@yahoo.com for the converter box

Hal Kramer halandjoan@aol.com for the clock

Nisonger instruments www.nisonger.com
John Wolfe Co. www.tempman.qpg.com
APT INstruments http://www.gaugeguys.com/ for speedometer
Cheers - Dave
David DuBois

Bill, I read the following article in a back issue of The Sacred Octagon. Can't help you with the 4.3 problem, however I am interested myself as I've gone from a 5.125 to a 4.3. But the following may solve your whiplash issue.

"THE SPEED0 NEEDLE WHIPLASH SYNDROME
The Sacred Octagon VOl 15 No 3 June 1979.

Prior to the introduction of the Y-Type Saloons almost all M.G.s used chronometric speedometers and tachometers, so-called because the internal mechanism of this type is quite similar to the inner workings of a clock. On these instruments the needle moves up and down the scale in a series of short jerks, much like the movement of the second hand of a watch. It's supposed to move like that, so don't try to "fix" it. The late TD, TF and all Y Saloons use magnetic instruments, as do most modern cars. These are not necessarily any more accurate than the chronometric units, but under normal conditions they do provide a very smooth needle movement which seems to be more reassuring to most American motorists. Unfortunately, there comes a time in the life of most magnetic instruments when the old chronometric jerk begins to look pretty good.
The syndrome is characterized by a wild whipping back and forth of the needle, even though road speed and engine speed are actually steady.
The worst example I have ever seen was, unfortunately,
on the way home from the Natter & Noggin this February. According to the speedometer in Len Renkenberger's Mercedes I was going 60 mph, but the speedo needle in my YA was whipping back and forth between 50 and 75. Three hundred miles of watching a speedo needle with St. Vitus's dance was made all the more annoying by the fact that it was my own fault.

Barring a breakdown in the instrument itself, this condition is usually brought about by lack of lubricant in the drive cable. There's a lot of space between the inner cable and its housing, and when the lubricant dries up the inner cable is able to whip around quite a bit inside the housing. Although the rotational speed at the driven end of the cable is uniform, all that whipping around causes the instrument end of the cable to go through rapid cycles of acceleration and deceleration. The needle tries to follow the antics of the cable, so it whips back and forth. This problem also exists with the older chronometric instruments, but it isn't so noticeable at the needle because the chronometric mechanism tends to average out readings which change very rapidly.
The cure is simply to lubricate the cable. The thin graphited fluid sold by most auto supply stores as speedometer cable lubricant is useless, as it doesn't fill the void between the inner cable and the casing. It does lubricate the cable, but it doesn't stop it from whipping around. What is needed is lots of nice, thick chassis grease. Disconnect the cable at one end and pull out the inner cable. On some cables the ends are prevented from sliding back into the casing by circlips. If you have this type, you will have to disconnect both ends, remove the circlip from
one end, and withdraw the inner cable from the other end. Soak the cable in solvent to remove any dirt and old grease which may be present. When the inner cable is clean and dry, coat the first three or four inches with a thick layer of grease and push it into the housing. Then coat the next few inches, push it in, then coat the next few inches, and so on until the inner cable is all back where it belongs. Tight spots can usually be gotten past by rotating the cable as you push it in. At the very last you will have to rotate the cable slightly to line up the squared end with the corresponding fitting in the gearbox or instrument, depending on which end you are working from.
This will cure the needle's whiplash problems 99% of the time, and it should be done every five or six thousand miles. The grease helps to prevent the inner cable from whipping around, and also acts as a damper to smooth out the speed fluctuations at the instrument end of the cable. If you are on the road and can't stop to lubricate the cable, a cure suggested by Len is effective as a temporary
measure. Reach up under the facia and bend the cable
casing into a "U" as close as possible to the instrument, and anchor it in that position. The resulting extra friction on the inner cable tends to dampen out some fluctuations in cable speed, so the needle won't whip back and forth quite so violently. This is pretty hard on the cable, though, so straighten it out and lubricate it as soon as you get
home. If you bend the casing far enough to kink it or break it, then you will need a new cable, so be careful.
The Technical Editor."
P Hehir

Bill
I made the 4.3 conversion and went through this same process on my speedo. I communicated with Butch Taras, but he really did not have the item to do the job. I sent my speedo to Nisonger and they recalibrated it nicely. Not overly expensive.
A new cable took care of my swinging needle.

I believe Hal Kramer passed away this year. Forgive me Hal if I am in error!

Tom
'54 TF
T Norby

Wait! Hal Kramer is alive and quite well. I spoke with him just last week.
-David
D. Sander

And, his email is hkramer(at)nycap.rr.com Bud
Bud Krueger

And make sure you route, or reroute, the cable with bends as gentle as possible. Pay specific note to the cable as it leaves the gearbox.
John Quilter (TD8986)

I am testing my gearboxes at present and so far so good. I have run them for hours on end with a speedo cable and the speedo in the lathe. They sit on the rear of the speedo.
I am also doing replacement clocks-see next post.
Regards
Declan




Declan Burns

Another photo


Declan Burns

Prototype clock

Regards
Declan


Declan Burns

Details 1


Declan Burns

Details 2


Declan Burns

Details 3
Different clock


Declan Burns

Beautiful work. I really like the second clock (details 3, different clock). The face and nomerals appear to be closer to the '50s period.

Thanks for the pictures.

Jud
J K Chapin

Fellas,

Thank you all for your very helpful suggestions and advice. I have talked with Nisonger and as Tom Norby stated they can do the job along with repairing the clock which has never worked. I have also purchased a new cable. By the way, I am very happy with the conversion from 4.875 to 4.3 ring and pinion. I feel more comfortable cruising at 60 mph and it did not affect the acceleration from standstill as much as I thought it might.

Bill
Bill Schroeder

Thanks Jud,
The second clock is the one everybody likes although the first one is closer to the original it does look a tad too modern.
Regards
Declan
Declan Burns

...have only had my clock running for about a minute or two when I first got the car on the road... frustrated, I did the same as Declan... Quick trip to a discount watch place got me something that worked for the time being (???)
I put a bead of clear silicon seal around the edge of the face and low and behold the tach light bulb lights up the face...



gblawson(gordon- TD27667)

Gordon, do you have a shot of the back showing how you attached the clock?

Thanks.

Jud
J K Chapin

Gordon,
I like the idea of the silicon seal. I think I'll try fitting an acrylic / perspex glass ring to light up the watch face.

Jud,
The clock is fitted with the original 4.2mm self tapping screws which sit 50mm apart. The clock sits at a slight angle to the speedo rear housing ~2°. It is not flush.This is compensated by a thin layer of glue between the mounting bracket and clock holder. The glue is allowed to set after the clock has been centred. The mounting bracket has elongated holes to correct the centring.

Regards
Declan
Declan Burns

J.K.
Mine is exactly the same (great minds)...only the little 'block' that holds the actual watch is closed cell foam... (think I used some packaging material...) carved it to match the real clock and carved out a little depression for the watch....
I used a little aluminum strap drilled to match the bolt/screw holes....
Easy to get out when I have to change the battery...once a year or so....


gblawson(gordon- TD27667)

Neat. Thanks.

Jud
J K Chapin

This thread has become more about clocks. Should rename it.
The TF clock is a different set-up than the TD. Has anyone inserted a modern dial/clock in their TF?
I had Hal work on mine a few years ago, but it still works only occasionally.

Tom
'54 TF
T Norby

Declan;

Your gear drive for the 4.3 conversion is so simple that it is elegant. I have to do the same thing to get my speedo reading closer. I like the idea of having the conversion gearing under the dash instead of under the car. Are you planning to either making up some units or providing plans?

C.R. Tyrell

C.R.
Both options are open at the moment.
Regards
Declan
Declan Burns

This thread was discussed between 26/12/2013 and 02/01/2014

MG TD TF 1500 index

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