Is my gap too big?

[bhpjon]

That's got your attention! Fairly mundane question though! After having a bouncing speedo for the last year and a milometer that was clocking up well over double the quantity of miles i was actually doing! i got round to fitting a new sensor (over the propshaft) i left a gap of 8 thou (the old one looked like a milling machine had been at it!) and turned it several times to make sure none of the teeth were fouling it (adjusting one or two teeth in the process). When i drove it home the bouncing needle had disappeared (phew) but i did seem to be registering rather higher speeds than i felt i was doing eg i was doing 100-120mph on the clock but i wasn't rushing past everthing else on the road (normal 'a' road)especially as i am bedding the engine in i am certainly not 'hoofing it', the only thing i can think is maybe my gap is still too large or it's missing the occasional tooth out from it's calculations, all contributions gratefully recieved!

By the way can you buy new toothed wheels?

Edited by Big Al. on Sunday 30th September 13:41

[That Daddy]

Any up and down movement in that flange,where the prop bolts to?

[spend]

If you have ETB clocks they are adjustable - so you can calibrate the speedo. Should be quite easy if you take it out, extend the wiring & let a willing passenger tinker with a GPS running at the same time.

If it is the sensor wheel that looks like a crown on the front of the diff I wouldn't have thought a new one would make much difference - its quite a big chunky signal (unlike the fine ABS type wheels). I can wind my sensor out to 10mm & in to 1mm & it makes no difference to the operation. The bracketry on the nose of the diff is pretty substantial on mine BTW, cant see that flexing - its must be as strong as the chassis itself The GKN nose sensor seems pretty bomb-proof to me which is a good thing as its pretty tough to get at.

Dave

[bhpjon]

spend said:

If you have ETB clocks they are adjustable - so you can calibrate the speedo. Should be quite easy if you take it out, extend the wiring & let a willing passenger tinker with a GPS running at the same time.

If it is the sensor wheel that looks like a crown on the front of the diff I wouldn't have thought a new one would make much difference - its quite a big chunky signal (unlike the fine ABS type wheels). I can wind my sensor out to 10mm & in to 1mm & it makes no difference to the operation. The bracketry on the nose of the diff is pretty substantial on mine BTW, cant see that flexing - its must be as strong as the chassis itself The GKN nose sensor seems pretty bomb-proof to me which is a good thing as its pretty tough to get at.

Dave

How do i know if i have ETB clocks Dave?

[spend]

It says 'ETB' on the label behind the clocks

I think typically they are the black rimmed ones, with a recessed bevelled profile, not the ally rounded ones. They are also slightly larger IIRC (that might be the minor gauges tho) - no warnings in the speedo/rev, low fuel warning in the fuel gauge, no odometer & the noisy mileometer . Generally fitted in the early cars, with the GKN diff & speed sensor at the front + LT77 box drive feeding the EFi ECU roadspeed.

Dave

[bhpjon]

spend said:

It says 'ETB' on the label behind the clocks

I think typically they are the black rimmed ones, with a recessed bevelled profile, not the ally rounded ones. They are also slightly larger IIRC (that might be the minor gauges tho) - no warnings in the speedo/rev, low fuel warning in the fuel gauge, no odometer & the noisy mileometer . Generally fitted in the early cars, with the GKN diff & speed sensor at the front + LT77 box drive feeding the EFi ECU roadspeed.

Dave

I'm pretty sure i don't have ETB's then Dave! I have the t-5 box and i believe btr or gkn diff (must check in the book!)Also i have oil and alternator warnings in my speedo, does this mean i can't tweak it myself?

[spend]

Unlikely, they sound like the later CAI ones. If you have the T5 box it is more than likely that the 'black box' which splits the signal to feed the ECU and the speedo is the root of your problem. The earlier split system seems to be have proved much more reliable IMO

Dave

[That Daddy]

spend said:

Unlikely, they sound like the later CAI ones. If you have the T5 box it is more than likely that the 'black box' which splits the signal to feed the ECU and the speedo is the root of your problem. The earlier split system seems to be have proved much more reliable IMO

Dave

Dave,out of curiosity do you know where said black box is situated,mine dont indicate until 15 minutes into my journey(then it indicates fine)its not a major thing because i use the speedo on the Sat Nav,and it keeps the mileage down

Edited by That Daddy on Tuesday 2nd October 09:29

[spend]

Somewhere under the dash?

Dave

[That Daddy]

Thanks

[Ozstyle]

Hi,
just a point to mention the gap is important and depends on the type of speed sensor you have (using T5 gearbox). The later long thin brass version with wiring plug needs about 6 thou of an inch (from all the threads I have read). The earlier shorter aluminium type (no wiring plug just two prongs for wire connections) needs about 1 - 2 mm gap, found out by trial and error with car up on axle stands (and confirmed by one thread I found).

[bhpjon]

Ozstyle said:

Hi,
just a point to mention the gap is important and depends on the type of speed sensor you have (using T5 gearbox). The later long thin brass version with wiring plug needs about 6 thou of an inch (from all the threads I have read). The earlier shorter aluminium type (no wiring plug just two prongs for wire connections) needs about 1 - 2 mm gap, found out by trial and error with car up on axle stands (and confirmed by one thread I found).

Thanks for that, do you know if you can buy new toothed wheels?

[Ozstyle]

no idea on the toothed wheels, best to try Clevor Trevor, TVR Power etc, or if no luck one of the TVR breakers