Early Griff Speedo
Discussion
I’m sure that this subject has been flogged to death in other threads, however for those Griff owners with the early (‘92/’93) models I though that I’d bring everything together in a single posting. A couple of weeks ago my speedo started playing up (speed readings jumping and on occasion failing totally) and from other PH’s experiences I surmised that the problem was the sensor. So I phoned around my local TVR dealerships to find that one of them had a sensor fitting the description of the one that I’d by now removed.
I was aware that there is a 8 pulse sensor and a 4 pulse sensor, however I wasn’t sure which one I required. When I arrived at the TVR dealership, they looked at the sensor and said, “yep, we’ve got one of those”. When I asked whether it was an 8 or 4 pulse (they really are identical in appearance) they said that they didn’t know, but that their engineer knew everything about these sensors and that he could answer my question. So I waited around for 25 minutes for him to return from a test drive and when he came back he said that you have to test the sensor on an oscilloscope and… yeah you’ve guessed it, they didn’t have one. “So how do I test it?” I asked, knowing what was coming. “You’ll have to fit it and if the speedo reads true, you’ve got the right one”.
So off I trundled and spent the next 60 minutes fitting it and of course it was the wrong one
– they’d given me a 4 pulse sensor and the car takes an 8 pulse (the speedo was reading half the true speed - no defense in law I'm afraid 
). Apparently TVR switched from the 8 pulse to 4 pulse after they realised that the 8 pulse was unreliable. The early Griff owners have to shop around for an 8 pulse sensor or buy a 4 pulse with a new speedo! Fortunately for me my local dealership were very resourceful and managed to source me an 8 pulse sensor which is now fitted and working perfectly 
.
Here are the details – my speedo has 0mph at 1 o’clock and goes around clockwise. The sensor slots into the back end of the gearbox and can only be accessed by lowering the exhaust (undo 8 bolts and 4 nuts, simple). The sensor is retained by a simple bracket held in place by a single 10mm bolt, which is a bit awkward to access. The sensor has a two pin plug which is easy to connect - like shelling peas.
>>> Edited by griff4.0 on Saturday 25th September 18:56
I was aware that there is a 8 pulse sensor and a 4 pulse sensor, however I wasn’t sure which one I required. When I arrived at the TVR dealership, they looked at the sensor and said, “yep, we’ve got one of those”. When I asked whether it was an 8 or 4 pulse (they really are identical in appearance) they said that they didn’t know, but that their engineer knew everything about these sensors and that he could answer my question. So I waited around for 25 minutes for him to return from a test drive and when he came back he said that you have to test the sensor on an oscilloscope and… yeah you’ve guessed it, they didn’t have one. “So how do I test it?” I asked, knowing what was coming. “You’ll have to fit it and if the speedo reads true, you’ve got the right one”.
So off I trundled and spent the next 60 minutes fitting it and of course it was the wrong one
– they’d given me a 4 pulse sensor and the car takes an 8 pulse (the speedo was reading half the true speed - no defense in law I'm afraid ). Apparently TVR switched from the 8 pulse to 4 pulse after they realised that the 8 pulse was unreliable. The early Griff owners have to shop around for an 8 pulse sensor or buy a 4 pulse with a new speedo! Fortunately for me my local dealership were very resourceful and managed to source me an 8 pulse sensor which is now fitted and working perfectly . Here are the details – my speedo has 0mph at 1 o’clock and goes around clockwise. The sensor slots into the back end of the gearbox and can only be accessed by lowering the exhaust (undo 8 bolts and 4 nuts, simple). The sensor is retained by a simple bracket held in place by a single 10mm bolt, which is a bit awkward to access. The sensor has a two pin plug which is easy to connect - like shelling peas.
>>> Edited by griff4.0 on Saturday 25th September 18:56
I'm doing exactly the same at the moment, I've sent both my speedo and transducer to Speedy Cables and they have said that both are busted. They are opening up the transducer and replacing the innards, it will be back early next week and I will post reply.
www.pistonheads.co.uk/gassing/topic.asp?t=123608&f=9&h=0
Prior to this I went to a Rover dealer who said they could get me the part, their criterior was how many teeth the drive cog had (I think it was 20, I've got a pic somewhere) and came up with this part number DRC 8007A @ £93.00 inc VAT. from an SD1 gearbox.
www.pistonheads.co.uk/gassing/topic.asp?t=123608&f=9&h=0
Prior to this I went to a Rover dealer who said they could get me the part, their criterior was how many teeth the drive cog had (I think it was 20, I've got a pic somewhere) and came up with this part number DRC 8007A @ £93.00 inc VAT. from an SD1 gearbox.
antonyj said:
I already had a scope connected to my sensor ( via the connectSo just a quick question, is a car over pit jobbie . Or will axle stands suffice?
ions to the speedo) and got no signals. So I need to get mine out soon.
Sounds like you've scoped it at the speedo and no pulses. You want to get the transducer off and test it on the bench, a pit would be easier as you've got to either take the exhaust off or loosen as above. I've got mine on car ramps under the back wheels.
Look for a black plasic connector tie-wrapped onto an O/S chassis upright in the 'tunnel' and take the transducer out by un-doing the 10mm 'clamp' bolt (easy).
I'm not 100% sure what voltage you should 'feed' the transducer with, I measured 12v from the speedo but as I've now found out my speedo is also busted, but you could measure this at the back of the speedo before taking it out.
Would be good if you post your findings so that we know what to look for next time we have to do this
Reading what has been posted so far on this topic, I have a few questions.
Does the gear box actually drive this transducer, or does the gear box drive some sort of flag disc which switches the transducers.?
I ( as a maintenance tech) expected the latter, however reading that there are " 4 or 8 pulse " versions of the transducer think I am wrong. Does this mean the transducer gives either 4 or 8 pulses to the speedo for every one of its own revolutions?
Think I will try and get mine back off and borrow the scope again. ( Quite a neat one which works via laptop)
Northern Paul could you post these pics you have?
Does the gear box actually drive this transducer, or does the gear box drive some sort of flag disc which switches the transducers.?
I ( as a maintenance tech) expected the latter, however reading that there are " 4 or 8 pulse " versions of the transducer think I am wrong. Does this mean the transducer gives either 4 or 8 pulses to the speedo for every one of its own revolutions?
Think I will try and get mine back off and borrow the scope again. ( Quite a neat one which works via laptop)
Northern Paul could you post these pics you have?
Los Angeles said:
Morning, Northern Paul. I'm amazed anyone would post at the back of seven ay-em on a Sunday morning. Have you nothing better to do, like sleep! (It's almost midnight here.)
Sorry Dude - I missed you this morning. I had got up to watch the Grand Prix and couldn't resist a quick post mid race, then it was back to the GP. Button was looking good for a while!
antonyj said:
Northern Paul could you post these pics you have?
[pic]
http://photos.fotango.com/p/eba00471475f00000001.jpg [/pic]
After reading the bible I was expecting to find a toothed cog and an adjustable plate but I think that for later cars, on my '92 I found the above, this is driven directly from the SD1 gearbox and has no adjustment.
It would be good to get Griff4.0 to qualify that is what he got from his dealer and then you may have to deal with the 4 or 8 pulse problem.
My pre-cat speedo has just started playing up too. It works fine for quite a while but after about 30-40 mins when things get hot it starts to fail. Even when hot it works ok upto about 60 or 70mph but then starts to fluctuate and under-read. I think I remember reading something in the bible about heatsoak eventually knacking the sensor after a while. Need a new sensor? Anyone know how much they are?
jam1et said:
Anyone know how much they are?
If you look further up this post 'Saturday' from me you will find a part number and price from Rover. I thought that was high and as I also had a speedo problem I sent both off to Speedy Cables. They are attempting to repair the transducer for £35.00 + VAT, should get them back soon so I will post results.
To answer the questions. My sensor looked exactly the same as the one in Paul's piccie - the only difference was that I seperated mine at the connector (the black thing with two wires coming out of it) - the piccie shows both halves of the connector.
As for cost, the sensor was £73+vat!
As for cost, the sensor was £73+vat!
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