Speedo problem. 1972 P6B Auto

edward1

New Member
Driving off recently, I heard a tick, tick, tick which developed into a clack, clack clack. A glance at the speedo revealed no reading.
Back home I removed the fascia binnacle and withdrew the inner speedo cable expecting to find a break. It was intact!
I replaced it and placed a 1" square of cardboard on the end. A quick drive down the road revealed no turning of the cable.

Wadhams supplied me with an angled drive for the gearbox which I duly fitted. On the original, the short cable on the gearbox side was in two halves so that was obviously the cause of the speedo failure.

With everything reassembled I did another road test. Still no speedo! I have known even brand new parts to fail so I tested again with the cardboard which tuned.
This left the angle drive behind the speedo as the culprit. When tested it turned but was sticky in its action.
It was replaced with a "new old stock" item with identical part number.
Duly installed, a road test revealed still no speedo.

In desperation, a s/h speedo was bought from Wins Int. I checked that it was working and popped it in. Still no speedo.

I have now run out of ideas as to where the fault lies. Can anyone help me please?
 
If all the parts you have mentioned are in good condition and are fitted correctly, then I would make sure that the rear flange bolt on the gearbox is tight.
 
Hi Harvey.
Thanks for your response. I have taken everything apart and checked for faults and reassembled, as you do when desperation sets in!
By "rear flange bolt" , do you mean the bolt holding the part that the gearbox rightangle fits into?
 
Harvey means the nut holding the output flange at the back of the gearbox. You have to remove the prop shaft to get at it.

Yoours
Vern
 
No, I mean the bolt that holds the rear flange which the front end of the propshaft bolts to. The speedo drive gear is clamped by the rear flange, and if the flange is loose it allows the gear to spin on the shaft, which normally gives speedo needle waver, but in the extreme could cause loss of drive to the driven gear altogether. Both the drive gear and the driven gear are steel so they don't normally strip the teeth as plastic driven gears tend to do, and as you would appear to have changed pretty much everything else, I'd be looking at the rear flange bolt.
 
Hi I had a similar problem when I first got mine. The previous owner had a new angle drive fitted. Speedo stopped like you I checked the cable all was fine. It turned out the new angle drive hadn't been fitted properly and hadn't seated. This ruined the drive. I sourced a new one from a Stag specialist (they were cheaper) I made sure it fitted correctly. Its easier if you do it through the transmission tunnel as I was advised on here.
 
Many thanks to each of you for such helpful information provided so quickly.

I will call upon my local Classic friendly garage next week to put the P6 on the hoist and investigate the matter further.

I'll report back with the findings.
 
At last, the vehicle has now been checked over and the flange is tight.

Another road test reveals that the speedo cable behind the fascia only turns momentarily on starting off and then stops turning completely.

I have removed and checked the new angle drive at the gearbox and this functions perfectly. It is correctly fitted to the gearbox i.e fully inserted and securing ring screwed up tight. (Incidentally, which side should the copper packing washer which came with the drive be positioned?)

The cable is likewise fully inserted and screwed up tight.

I can only deduce that the plastic gear on the little shaft which goes into the box must be worn down (part no. 556609). Where can I source a replacement please or alternatively, can anyone confirm the diameter so that I can check its condition.
 
I think (unlesss I dreamt it) that both the drive and driven gears are steel so they are unlikely to strip and if somehow something was to get jammed in between them it would damage both. Best thing would be to get the driven gear out and inspect it, and while you're at it have a look down the hole at the drive gear.

If it comes to it I should definitely have the drive gear, and may have a driven gear as well.
 
So today out came the driven gear which is in fact plastic. The photo shows that its diameter is 23mm and there is no sign of damage. Obviously, I don't know the as new diameter but the drive with a screwdriver inserted in the square turned freely as it was eased back into position and stopped during the last part of its travel when it engaged with the gear on the output shaft.

The new right angle has been checked again and this functions without fault.

This was reconnected to the gearbox and speedo cable and both ends inserted and securing rings fully tightened.

On inspecting the speedo cable at the top end there is no constant drive. The inner turns initially but soon stops. When withdrawn the inner is completely intact. The squared end at the gearbox I can feel locating itself in the right angle output and the square top end protrudes sufficiently for it to go into the right angle behind the speedo. So, therefore, there is no break in it

Before I reinserted to driven gear I examined the splines on the shaft in the box and they are in good condition and they did engage with the plastic driven gear. See photo.

The way things are going I think my Sat Nav will be in service for some time to come as a substitute speedo!
 

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Just going over the thread again from the start......
It appears your speedo was working well until you heard the clicking sound ( which is something rotating ) then your speedo stopped working.
Your speedo cable was found to be broken?
So you replaced your cable? Still no speedo?
You replaced your angle drive? Still no speedo?
So you need to look at the parts you have replaced so far as the speedo worked fine up to that point.
If the cable snapped? Then chances are it would jam and break the angle drive ( hence the new angle drive? )

The replacement angle drive looks aftermarket to me, sadly aftermarket products are just not well made, this is more to do with the fact we like things that cost less.
Try a good used or NOS angle drive.
 
Many thanks "ghce" for the thought. I did try turning the cog while holding the shaft with a pair of grips. There is no way that it is able to move. It's just as if it's made in one piece.
Thanks also to "eight of them". Just a slight alteration to your recap. The speedo cable to my surprise was intact and I thought it the most likely culprit. I later found that the right angle at the speedo end had jammed and that caused the short drive shaft between gearbox the gearbox right angle to shear. So I have a NOS right angle by the speedo and an intact inner cable so I agree with you that the fault must lie with the new g/b right angle which came from a major Rover parts' supplier.
Has anybody any idea where I can source a good used g/b right angle drive?
 
Personally just looking at the picture of the angle drive I would say it is an aftermarket one, the originals did not have a circlip holding in the plate, they were spiked closed.
I would return it to the supplier if found to be the culprit.

I have a used one here, send me a PM if you are still in need.
 
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