WTF?? Bouncing tacho and plunging speedo....

[Nosh]

Had a great weekend driving the TVR, but both the tacho and speedo are exhibiting strange behaviours.

The tacho seems to be 'bouncing' although the engine 'sounds' normal. The needle is certainly NOT steady.....

...and to top that, the speedo drops to 0 mph when I put my foot hard down, but as I lift the throttle off gently, the speedo goes straight up to the speed I am doing.

Mine is a 93 Chim 4L with a Serp engine ant LT77 box.

Anyone got any ideas?

Thanks in advance
Nosh

[SpecB]

Diff mount bush. Hard acceleration makes the gap between diff and sensor too large for the sensor to pick up the reading. Don't know about the rev counter though.

[blitzracing]

Magnecores?

[PRTVR]

Have heard of problems with the taco from low resistance HT leads, what type of leads are you running?

edit to add must type faster.....

[Nosh]

SpecB said:

Diff mount bush. Hard acceleration makes the gap between diff and sensor too large for the sensor to pick up the reading. Don't know about the rev counter though.

I thought the speed sensor was on the gearbox on a Lt77 ?

[SpecB]

Just had a look in the manual and indeed it should be. Sorry, should read before posting.

[loud430]

mine is a 94 car, it has the rover box with speedo sensor on it & also has a sensor above the diff!

[Nosh]

loud430 said:

mine is a 94 car, it has the rover box with speedo sensor on it & also has a sensor above the diff!

Interesting....I will take a look tomorrow night.

Ta

Nosh

[loud430]

no probs, hope it helps. i had my car in at henley heritage for a none working speedo & sent the speedo head off to speedy cables for a refurb only for them to send it back saying it was fine, then had new speedo drive on gearbox & wiring checked before they realised there was a sensor tucked up on top of the diff. they said it was unusual to have both?
cheers. paul.

[TV8]

Mine has the Rover box and a diff sensor. Haven't checked if it has one on the box as well though!