series 2A erratic speedo

[para]

my 2A is fitted with a nissan 2.8 6cyl diesel, the gear box is a series 3 full syncro.The speedo is the original, main scale kms ph inner scale mph. when i travel at a 100kms ph the speedo actually registers 60 kms ph, i know this cos i have followed another vehicle at various speeds so i could mark the speedo accordingly. when i travel at 100kms ph the speedo needle throws a wobbly and jumps up and down and i have no idea what speed i,m doing even if i slow down.if i stop the vehicle for a while and start off again the speedo works normal again until i reach just over a 100 again. Any clues? i wonder how many people will say dont go over a 100???????

[hodgo]

The speedo has counter waits that keep the needle steady at all speeds your is out of balance and will have to be repaired by an instrument repair shop as the speedo will have to be recalibrate.
Its not a real expencive job, last time I had work done about 5 years ago I think it was about $60 and if you remover the speedo from the dash your self you will make a big saving

hodgo

[foz.in.oz]

The speedo has counter waits that keep the needle steady at all speeds your is out of balance and will have to be repaired by an instrument repair shop as the speedo will have to be recalibrate.
Its not a real expencive job, last time I had work done about 5 years ago I think it was about $60 and if you remover the speedo from the dash your self you will make a big saving

hodgo

is a bla at wht a do dah.

Try oiling the cable first.

[Mick_Marsh]

I have had what you described in several vehicles. It is usually before the cable breaks, although, once it was just before the speedo output drive in the gearbox **** itself.
Yes, remove and lubricate (or replace) the cable and inspect the speedo output shaft from the gearbox for wear or damage. If it was me, I'd replace the cable with a new inner and outer. (A spare Speedo cable is one of those things that's handy to have hanging on the garage wall.)
In my experience, from what you have described, it won't be too long before something breaks (cable or output), then you'll have your answer.

Just reading your post further, I noticed you mentioned the speedo error. Go to a speedo repairers and get an in-line ratio box made up. With that you will probably require two new cables anyway (one for gearbox to ratio box and one from ratio box to speedo). The speedo repairer will measure how many revs per km the gearbox puts out and note how many revs per km the speedo requires and make up a ratio box of the right ratio. I had one made up years ago and found it to be excellent. They're not cheap though.

regards
Mick

[JDNSW]

The problem is most likely to be the speedo drive gear slipping on the transfer case output shaft. The gear is not keyed to the shaft but is clamped by the nut holding the output flange on. I would check this first, although the other suggestions may be the problem. Note that this problem is likely to be exacerbated if the speedo cable is hard to turn, for example if it is kinked or has loose strands and is about to break.

Disconnect the front of the rear prop shaft and tighten the large nut on the end of the shaft that this uncovered. Reassemble. Cost $0.

John

[para]

thanx to JDNSW,MICK MARSH,HODGO and FOZ in OZ for your replies.When i had the 2.25p engine in and the original speedo cable there was not a problem, it wodn,t do more than a 100 kms ph so the needle never jumped.its since i put the diesel engine (2.8) that its started.i have repaced speedo cables twice, in the last 2 mon ths the gearbox has been stripped and rebuilt.when i had series lanys in the u.k i always remember the the end of the speedo cable had a square end, the ones here (SA) have flat ends which fit into the gearbox???.every speedo cable i put in has done exactly the same, jumped.am i right in assuming that no matter what engine you have and speedo dial that if you do a 100 kmsph the speedo will read 100 if it was working properly?
Para

[Mick_Marsh]

If you have only changed the motor, and the original gearbox for that model car has only been rebuilt, I would be looking at the speedo. It could be worn or clagged up with dust and old grease.

Yes you are "right in assuming that no matter what engine you have the speedo will read 100 if you are doing 100 if it was working properly". It's only when you change gearboxes, diffs and wheels does the speedo read incorrectly provided it is in good working order.

I'm not so sure about Landrovers but in some cars if you change the differential ratio, you must change the speedo output drive in the gearbox to keep the speedo accurate. In other cars if you change the differential ratio, you must change the speedo to keep the speedo accurate.
If I had cable ends that didn't match up and an inaccurate speedo, I would (and have done) go to a speedo repairers and get an in-line ratio box made up. I would (and have done) have two new cables made up (one for gearbox to ratio box and one from ratio box to speedo).
As previously mentioned, the speedo repairer will measure how many revs per km the gearbox puts out and note how many revs per km the speedo requires and make up a ratio box of the right ratio.

regards

[para]

thanks everybody for your suggestions. well it has been sorted out now and the speedo no longer jumps. i stripped the speedo and cleaned it, but putting it back together i lost some essential bits! so i went the whole hog and got a old speedo, new cable and gear for the gearbox so i had all the bits. the problem was with the speedo itself, when i fitted the new speedo and tested it it worked first time with no trouble, that sorted. as for the calibration of the speedo, a few years ago i fitted defender 3.5 diffs, so to know what speed i was actually doing i followed the wife in another vehicle to note the speed so i could mark the speedo, maybe a ratio box some time in the future. once again thanks very much.

[p38arover]

The speedo has counter waits that keep the needle steady at all speeds

You'd be waiting a long time for a Series to reach 100km/h!

However, I doubt that the counterweight would affect the speedo.

My experience has been that the problem is mainly caused by a worn cable or lack of lube in the cable.

[vnx205]

Even the wrong lubrication can cause an erratic speedo.

When I fitted a new cable to my Series III, the closest tin of grease was some old wheel bearing grease, so I used that to lubricate the cable.

The speedo, which had been quite steady with the old cable fluctuated at all speeds.

Wiping off as much of the wheel bearing grease as possible reduced the problem.