thor64
Rover Fanatic
Posts: 138
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Post by thor64 on Jul 3, 2023 18:35:11 GMT
Has anyone had dealings with the Speedometer drive housing attached to the 3 litre DG auto box? Having a good working speedometer, prior to having my DG auto box rebuilt, I now find it is not. The needle is going further than the speed I am doing so when travelling at 40 the needle is zooming up to 60. The needle returns reluctantly on deceleration but on acceleration insists I am going 60 miles an hour when doing only 40. I'm thinking the Speedometer drive housing is the culprit and was planning on taking it out and having a look. Thank goodness for iPhone speed apps.
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Post by dmaxwell on Jul 4, 2023 18:35:48 GMT
I had a similar problem that I was able to fix by lubing the speedometer with some mineral oil (also used as sewing machine oil in the US). I'm told that this kind of oil does not have any additives that can cause the moving parts to gum up over time. It's been about a year and my speedometer is still working fine.
David
California
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thor64
Rover Fanatic
Posts: 138
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Post by thor64 on Jul 6, 2023 19:14:46 GMT
Hi David, thanks for the reply, it's wonderful to be talking with someone in California. I have never been but do envy you the sunshine.
So you think it could be at the dial end of the cable. I have read the posts on refurbing the speedo dial and I would prefer to work on that than taking the drive housing off the gear box.
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Post by dmaxwell on Jul 6, 2023 19:38:23 GMT
Well, the description you gave sounded a lot like the problem I had. Though my P5 had been sitting in the garage on jackstands for over 20 years so that may have played a part in the speedometer acting up for me!
David
California
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Post by djm16 on Jul 10, 2023 4:52:20 GMT
The bronze gear wheel inside the speedometer housing is an interference fit in the alloy casting and can get cold welded to it in the absence of lubrication.
I had to gently tap mine out with a hammer and relieve it slightly with 600 grit W&D.
The speedo needle not returning suggests that some dirt has got into the jewel bearing, and / or the bearing is adjusted tight. A quick and gentle spray of the jewel bearing with brake cleaner should do it. Check that there is a trace of end-play in the speedo needle shaft, if not, then adjust it so there is.
Worth checking the route of the speedo cable so that it has the least bends in it, and take out the cable from the casing to clean and (slightly) lubricate.
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thor64
Rover Fanatic
Posts: 138
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Post by thor64 on Jul 13, 2023 17:58:57 GMT
Hi thanks for that very useful information. It gives me a number of avenues which I will pursue to find out the cause.
Have you ever removed the speedometer drive housing from the gearbox? The manual says the whole gearbox needs to be taken out. I have had the gear box out and repaired/refurbished and don't wish to do it again. There seems to be some room to remove the bolts but I was wondering if it is worth attempting to remove the housing in situ?
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